Episode 47: Adam Rutherford on Humans, Animals, and Life in General

0:00:00 Sean Carroll: Hello, everybody, and welcome to The Mindscape Podcast. I'm your host, Sean Carroll.

0:00:03 SC: Today we have Adam Rutherford, all the way from the United Kingdom. Adam is a geneticist by training, but he's become also an extremely successful science communicator. It seems to me sometimes like every professor of science in England or the rest of the United Kingdom, also has a column in The Guardian, a radio show on the BBC, etcetera. At least Adam does all of those things. And he's also the author of a number of very interesting books. He has a brand new book out, which I tease him a little bit on the program. I don't love the title of the book, which is called Humanimal. The idea behind the book is to relate human beings and how we are and how we behave, to other animals, right? Human beings are animals just like everyone else. We think we're special.

0:00:49 SC: There are ways in which human beings are different from other animals. For example, other animals don't have podcasts, at least they don't host podcasts, as far as I know. Someone in the comments, I'm sure is gonna correct me on that misimpression. But it turns out, maybe it shouldn't be surprising, that it's actually very difficult to pinpoint what it is about human beings that make us special. Our brains are big but other animals have big brains. We use fire but guess what? There are birds that use fire for purposes of their own. Other animals use tools. Other animals use versions of language. So we learn a lot about human beings in our relationship to the rest of the world by looking and studying the behavior of animals.

0:01:31 SC: And of course, Adam is also a geneticist, so we don't just study behavior, but also where human beings came from. And perhaps because he's a professor, perhaps because he's a science communicator, perhaps because he's written books on other topics as well, such as synthetic biology and the origin of life, Adam is a great talker. He's someone who has a lot of opinions about lots of different things. So compared to other episodes of Mindscape, this one is not as focused on the original theme that I had in mind, but I think that's a feature, not a bug. I think it's a good, wide-ranging, rambling conversation where we talk about what life really is, how genetics works, how genetics is misunderstood in the public, the role of the Second Law of Thermodynamics, to what it means to be alive, all sorts of interesting things come up in this. So this is a more synthetic than focused episode of Mindscape, but that's good. We should cleanse the palate every once in a while with something exactly like that.

0:02:26 SC: And Adam's certainly a lot of fun to listen to. I think this is gonna be an entertaining, as well as insightful podcast. So let's go.

[music]

0:02:51 SC: Adam Rutherford. Welcome to The Mindscape Podcast.

0:02:54 Adam Rutherford: It's lovely to talk to you, Sean.

0:02:55 SC: So you're a geneticist by training. The most recent book, though, has to do with more the intellectual/cultural evolution of the human species. But I know that you did write a previous book that was more biological, strictly speaking, is that right?

0:03:10 AR: Yeah, that's exactly right, in fact. So the last book, which was called A Brief History of Everyone Who Ever lived, was the application of genetics to human prehistory and human history. So, the whole premise was that we've suddenly given ourselves access to this new historical source which is our DNA, and the book is about... Well, the first half is about some sort of re-figuring human evolution through pre-history and how that has revolutionized our understanding of our trajectory to here from there. And the second half of that book is about using DNA as a sort of historical source to sit alongside the more traditional ways of knowing the past, which is archeology and paleontology, and the paper trail, and just the things of history.

0:04:01 AR: So it's very much a book about genetics, genetics as a historical source. A historical source which is different to those other ones, because it's one that everyone has. It is the story of all humanity. The slightly bombastic title [chuckle] is... It's sort of metaphorically true because within every cell of your body, you contain the entire history, not just of your family, but of our species, of our greater family groups within the evolutionary tree and ultimately, all life on earth.

0:04:37 AR: So that was a brief history. And there was a single line in the final chapter of Brief History which sorta triggered me thinking about what the next book was gonna be. And you know this as a writer, that sometimes you just get something, a seed gets planted and you can't shake it. And it was, it was a line from... [chuckle] Well, you know, we've talked about films before. We both love pop culture, and I quote films all the time in my work, mostly for my own amusement. I occasionally...

0:05:09 SC: The author must keep the author's self amused, otherwise what's the point of writing a book?

0:05:13 AR: Exactly, exactly. But it has got to the stage, a sort of disease-like stage for me where I'm quoting things without necessarily realizing when I'm doing it. So, I wrote this line, which was, "Everyone is special, which is another way of saying that no one is." And I sent it off to my editor, and when I got the feedback from the first draft, she said, "I like the way you quoted that film in the last chapter." [chuckle] And I hadn't even realized I'd done it. Do you know what film it is?

0:05:42 SC: I do, but only because I have watched your video.

0:05:44 AR: [laughter] Yeah, so it's from The Incredibles.

0:05:45 SC: Where you revealed this. Yeah.

0:05:47 AR: I'm sort of slightly pleased and slightly embarrassed that I've done this. But anyway, the point is that it was that idea of human essentialism, of human uniqueness, of our incredibly anthropocentric view of the universe. Where do we position ourselves now with this new-found information about genetics, about our cultural evolution, about the evolution of our minds? This whole trajectory of science over the last several hundred years has been to inch ourselves back into nature, having spent a long time thinking of ourselves as separate from nature. You know this as a cosmologist. The first steps were heliocentrism rather than thinking of...

0:06:33 SC: Yeah. The Copernican revolution happens in every sub-field of science at some point.

0:06:38 AR: Exactly. And that's... For us, for the biologists, it was just a concept of evolution, which of course was solidified by Darwin in 1859. And that was the key step, that was the Copernican version for biology, that puts us in nature, part of nature. Everything we've done since then has cemented our position in nature. And yet, we're a paradox. We do have this sort of conundrum position, which is that we accept that we are part of nature. We're an animal. We have the same DNA, the same cell structure, blah, blah, blah. And yet, the two of us are talking 7,000 miles away over the internet. I've just managed to get this to work.

0:07:23 SC: And it worked flawlessly the first time, because we're such advanced creatures, yes. [laughter]

0:07:28 AR: Listener, it really didn't. [laughter]

0:07:32 SC: But good. So I love the idea of the most recent book. I'll confess, I don't love the title. And I know that the title went back and forth, and it ended somewhere unfortunate in my point of view, Humanimal, right?

0:07:45 AR: Yeah.

0:07:45 SC: Is the title of the most recent book? Stated out here.

0:07:47 AR: In the UK, it's called The Book of Humans. And the...

0:07:51 SC: That makes sense.

0:07:52 AR: Sure. So my American publishers, The Experiment, which is a great little publishing house based in New York, they wanted to try something different. And then they suggested this to me, very late in the process. So it's very shortly before publication, and my initial response was, "Yeah, no." [chuckle] I'm not really into neologisms. It just didn't jell with me. And the first thing was the cover, they showed me the cover with this design on it. And it did make sense because it was a sort of blending of the words. But the second thing, it was a single word argument that my editor said, which was, "Freakonomics." [chuckle] And I went, "Oh, yeah, yeah, yeah. I see what you've done there." So I went with it, I've gone with it.

[laughter]

0:08:37 SC: I will mention... I mostly want to say good things about your book. I will mention one other thing about the American version which is that you're British, you write as a British person does with all these funny spellings that you folks use. [chuckle] And someone clearly did a global search and replace, turning color, C-O-L-O-U-R, into color, C-O-L-O-R, which is too bad, because at one point, you were contrasting the British and American ways of spelling things but they're both the American way in the book.

0:09:08 AR: We spotted that, that is corrected now. [laughter]

0:09:11 SC: Okay, good. Not just my hallucination. Anyway, so it's a wonderful sort of puzzle of a book, because on the one hand, yeah, obviously, we human beings are different in some way. And the book does a wonderful job of pointing out how hard it is exactly to identify that way because we have so many similarities with animals. But before we get there, I do wanna give some chance to talk about the previous book or at least the content therein, in the sense that let's lay the ground work for understanding who we are in the animal kingdom by talking about our genes, our DNA, what we've learned, how we've diverged from other primates, and so forth. So what is the big, big picture story of humanity over evolutionary time?

0:09:55 AR: Right. So that's a great question because... Well, it's a great question at any point in time. It's a particularly great question right now, because the whole field has gone through a massive, a huge revolution which is ongoing. So a revolution that we didn't really anticipate was gonna happen and it's all predicated on two things. The first is that we simply understand genetics better now than at any point in history, and that's just the progress of science. The way the code translates into a lived life, our fundamental biology, we know that better than at any other time. And that's all post-Human Genome Project, which was sort of nominally complete in 2001-2003. So, that's step one. But the second thing is that we invented the technology, the ability to extract DNA, not just from you and me, from living people, but from people who have been dead for thousands, hundreds of thousands, tens of thousands of years. And that gave us access to this historical source in people who, in the past, we had scarce remains of and most of our understanding of evolution was based on paleontology, so old bones.

0:11:08 AR: And they are still valid. They are very, very useful pieces of evidence in understanding the story of how we got from there to here. But they're limited. And the genome is the richest source of data, is the richest data set that we're aware of in the universe. And so having access to that, unlocking that, meant that all of a sudden, we just suddenly had this amazingly rich data set. It started with Neanderthals in 2008, '09, '10. Soon after that, we had discovered in a cave in Siberia, just a little finger bone of a teenage girl and a single molar tooth, which is not enough to say this is a different type of human, it's enough to say it's a Hominin.

0:11:56 SC: Are these the Denosovians? Denisovans?

0:12:00 AR: Denisovans. Exactly, yeah. Denisovans.

0:12:01 SC: Denisovans. By the way, when you say Neanderthals, what do you mean is we got their DNA. Is that right?

0:12:08 AR: Yeah. Yeah. So Neanderthals' first discovered in the 1820s, first named in the 1860s, always identified as a separate species from us. They do look a bit different to us, big barrel chests, much more muscular, slightly flattened brows, heavier eyebrows, bigger nasal capacity. So they were legitimately classes of different species to us during the era of morphology being the primary determinate, which we're still in. Back in 2009, Svante Pääbo's group managed to get the full genome out of a Neanderthal specimen. And in doing so, we suddenly went, well, okay. Not only do we have the whole genome but we can tell immediately a big outstanding question from human evolution, which is, what is the relationship between Homo sapiens and Homo neanderthalensis?

0:13:05 AR: We can calculate using DNA when our species diverged in time, which we now think is around 600,000 years ago, which roughly fits with what the bones told us as well and what the trajectory from Africa or into Europe. Neanderthals are primarily European or Eurasian species, whereas Homo sapiens started in Africa. And, but crucially, and this is the really exciting thing, the evidence is unequivocal that there was what geneticists euphemistically referred to as gene flow events between...

0:13:41 SC: Such a sexy term.

0:13:43 AR: I know. [chuckle] Yeah. It's not really a great chat-up line that, is it? But you know, genetics is fundamentally about sex and families, but we introduce all of these terms to make it sound so boring, it's unbelievable. But, yeah. So when we got the Neanderthal genome in 2009, we then have unequivocal evidence that there were gene flow events between Homo sapiens and Homo neanderthalensis, and we then... We could identify bits of the genome in living people, which we now know are derived from Neanderthals. And so I know you and I can tell from looking at you that you have European ancestry, as do I, basically all people of recent European ancestry have approximately 1% to 2% Neanderthal DNA, which we can only tell by having the full Neanderthal genome.

0:14:31 AR: Now, this throws the whole field of sort of species definitions of taxonomy into disarray. And this appeals to me because I'm sort of opposed to taxonomy in many ways. Dawkins' phrase, which I think is very elegant and very accurate, is that we suffer as a species from the tyranny of the discontinuous mind. We obsessively try to put things in neat boxes and... Listen, with apologies to you and I say this in public, but never to actually a physicist that I'm talking to. [laughter] Biology is... I get physics envy, because in general, I think of physics as being quite reductionist and that your boxes are quite neat. Biology is just a science of exceptions. It's incredibly messy. Every time we come up with a rule, the first thing you do is look for exceptions to it and there always are.

0:15:27 SC: Yeah.

0:15:27 AR: Is Homo neanderthalensis a different species from Homo sapiens? Well, yes, because we decided it was. The species definition says that two separate species are organisms that cannot reproduce and make fertile offspring.

0:15:46 SC: That's what I was taught.

0:15:47 AR: Right. But I'm looking at you now...

0:15:48 SC: But they did that. Yeah, here we are.

0:15:50 AR: I'm looking at the fertile offspring of a Neanderthal and Homo sapiens mating, admittedly 40,000 to 50,000 years ago. And that says well, either the species definition is wrong, Homo neanderthalensis and Homo sapiens are not separate species. Or what I think, I'm not sure it matters.

0:16:10 SC: Yeah.

0:16:10 AR: Because I think that it doesn't inform the experiment that you have to ask which is fundamental to the scientific process. Are we wedded to a definition to such an extent that it stops you asking what these creatures did rather than what they are? And I think that a lot of science is slightly paralyzed by that obsession with holding on to what a thing is. I suppose, in planetary physics that the equivalent is the Pluto story.

0:16:44 SC: Pluto, yeah. Yeah, exactly. And there's... My mind was changed by reading Mike Brown's book about it. Mike was a previous podcast guest, and my attitude was, "Look. You know Pluto's been a planet. It's in the text books. Let's just keep it... Who gets hurt by calling it a planet?" And his response was, "It helps organize our understanding of the world. We're gonna go out there and look at other stars and the planets around them, and it will be useful to future generations to have a definition for what's a planet and what's not." And in his mind, there are no definitions of planets which would include Pluto without also including thousands of other things. So I think that made sense to me. The question is, what is the usefulness to us as scientists?

0:17:25 AR: I think that is exactly right. But it is how it informs the question that you're asking. There's another example which I wrote about in an earlier book, when I was writing about the origin of life. And our historical obsession we're trying to define what life is I argue has actually fundamentally hampered the experiments to determine what the origin of... What occurred during a biogenesis when chemistry became biochemistry. And the reason for that is because for a long time since the beginning of the 20th century, people have been thinking about what life is rather than what life does. And as soon as you start looking for the fundamental bases of what life does rather than trying to pin it down and say, this is the sort of platonic ideal of a living thing or a planet, if it's Pluto, or a species, if we're talking about Homo sapiens or Homo neanderthalensis, as soon as you sort of release yourself from the shackles, you can just ask a much more interesting question which is, what is the common behavior of a cell, of every single cell which says, this is what a living system is rather than this is what a living system does. I do think... Go on.

0:18:48 SC: This is deep philosophical waters that we could potentially wade into here. I'm not sure how I feel about this attitude, to be honest, because I look at people who have argued about the definition of life, and I don't agree with any of them. And one of the reasons I don't agree with any of them is because they almost always include the fact of natural selection and biological evolution. And my attitude as a physicist is like if I took a bunch of atoms, and one by one made a cat out of them, a sterile cat, that it could not possibly reproduce. I've made that and it's walking around and it's meowing and it's never gonna reproduce, there is no biological evolution and natural selection involved, but you can't possibly tell me the cat's not alive.

0:19:28 SC: And so I think that there is a, even though it's frustrating and occasionally unhelpful, there's nevertheless value in having these debates about how we should draw the lines, knowing that they could always be adjusted and we could always learn new things and we could always do it better.

0:19:47 AR: I think that's right, but I'm gonna... I'm not just playing to the audience here or playing to the interviewer here. I think there is a better understanding of what life does rather than what life is, and it is a basic physics principle. And I think that biologists have really misunderstood or haven't paid attention to basic physics. And it is the Second Law of Thermodynamics, because what life does is that it temporarily contravenes... No, it doesn't contravene. I have to get my language exactly right here. I don't... I'm just gonna ignore...

0:20:16 SC: Yeah, you're gonna hit my other hot buttons here.

[laughter]

0:20:20 AR: No, it doesn't contravene 'cause your laws...

0:20:22 SC: You can't.

0:20:22 AR: Especially thermodynamics are non-negotiable. They are non-negotiable.

0:20:23 SC: We have laws. That's right.

0:20:26 AR: But the analogy I used in that book and I've used in lectures and TV programs is life is the only thing that has sat at the table in the casino continuously for the last four billion years. We reduce negative entropy, that is what living systems do. We... And until our cells are ordered states, until we die and then they submit to the will of the universe. How's that work with you?

0:20:53 SC: You know, it's all true. But the process of keeping our bodies in homeostatic order, I also have Antonio Damasio coming up on the podcast, overall increases the entropy of the universe. The way that I like to put it is that, it's not that life either contravenes or even temporarily resists the Second Law of Thermodynamics, life is an expression of the Second Law of Thermodynamics. It relies on the Second Law of Thermodynamics 'cause if we were in thermal equilibrium, there wouldn't be any life. Life is one of the ways in which entropy increases.

0:21:27 AR: Right. Well, I can't deny that and I would be foolish to deny that in conversation with a physicist. But what that sort of slightly philosophy of science context says in a metabolic way and this is where I think it's important for informing your experiments as a biological researcher at the lab, at the bench, is that it says that life is a process of extracting energy from its environment and utilizing that energy and that is a manifestation of... I mean, this is all from Schrödinger, right, this all comes...

0:22:02 SC: Yeah. And I completely agree with what you just said, I think it is important. I think the biologists don't always take it very seriously.

0:22:07 AR: You see, I'm a Darwinian to my core. I think it is probably the most powerful idea that anyone's ever come up with. It is difficult to conceive of life in the rest of the universe that doesn't work in a Darwinian process. That's not just say that that is not the case, but it's just I can't... My imagination is not rich enough to imagine a non-Darwinian process. But further than that, I think what underlies Darwinian processes is, especially when you're considering the origin of life, is a metabolic process, is extracting useful energy from the environment. And we're talking about this because we were thinking about taxonomy and categorization. I think it's inherently important in this regard, because you've gotta think about what an organism is doing at the origin of life, which then puts you in a particular position on earth.

0:23:07 AR: So you say, well, one of the classic questions is is a flame a living organism because it behaves in a very similar way in terms of extracting energy from the environment as a source it needs, it can be continuous if you feed it. Is that a living thing? Is a crystal a living thing? And this is an idea that Schrödinger investigated, because it's capable of reproduction? No, I don't think so. It looks a bit like it has characteristics of natural selection, the information that is being transferred from generation to generation that isn't modified, though. And so piling those things on top of each other, if we need a sort of framework in order to understand what life does rather than what life is, I think you have to start with the basics, which is energy extraction from the environment. Natural selection comes after that.

0:24:00 AR: Why this is important is because biology is so ridiculously complicated that we try and break down the processes of genetics and cellular mechanics and metabolic pathways and stuff like that. And it's very hard to break the circle, because you've got DNA which encodes RNA, which makes proteins, and proteins do stuff and the proteins, many proteins are involved in making DNA in order to continue this cycle. So how do you break that deadlock?

0:24:32 SC: How could it possibly have started also, right?

0:24:34 AR: Exactly. Now, we've got a reasonable model of how the information process started. Well, actually, it probably it looks like it started with RNA rather than DNA which is a simpler but less robust molecule and can store information. The concept of the original gene, which is simply a replicating thing, a unit of replication. But no one ever thought to say, that process doesn't occur unless you have metabolic input.

0:25:01 AR: The whole concept of the primordial soup or the primeval soup which was first formulated in the first couple of decades of the 20th century by two independent... By Haldane and by Oparin in Russia. It's a very sticky name for it which I think is part of its successes as an idea in the 1950s, in 1953, there is the classic Urey-Miller experiment where Miller was a PhD student who asked to do this experiment where he sealed a bunch of simple chemicals, water, carbon dioxide, methane in a sealed tube, put 10,000 volts across it and just let it stew. And his supervisor Urey, said, "I'll give you two weeks". After four days, the whole clear liquid goes brown. They extract it and it's full of amino acids, amino acids being the building blocks of life, and everyone goes, "You've created life."

0:26:01 AR: It's a really important and interesting experiment, that, but it doesn't do what life does. The thermodynamics of that chemistry is over once that is reacted. There is no incentive for that reaction to continue. And what life is, is a continuous chemical reaction, a chemical reaction which is sustained and has been sustained for four billion years without break. So the concepts of the primordial soup and the Urey-Miller experiment, they're interesting. They don't tell you where life came from because they don't replicate what life does.

0:26:47 AR: So concepts, like people say we need a bolt of lightning, so we need some energy source. Well, we're not powered by lightning. Some people say... Darwin talked about the warm little pond, and if you got the chemistry right on the surface of the earth heated by the sun or whatever, then that is a possible way to think about how simple chemicals become more complex chemicals or, in modern parlance, how chemistry becomes biochemistry, except we're not powered by the sun. No one thought to say, "Well, what does life actually do?" There are no organism... Well, there are ponds powered by the sun but they're a later development in evolution. We're powered by metabolism. We're powered by proton gradients, by extracting energy, by putting energy on, by putting high energy things on one side of a barrier and low energy on the other side and letting it run from one to the other, and that's how all life is powered.

0:27:45 SC: So the audience should know, in case they haven't figured it out already, that you've also written a book about the origin of life.

[laughter]

0:27:51 AR: Yeah, we didn't plan this conversation at all, but this is...

0:27:54 SC: We're not very good at planning, but that's okay. We adapt to our environment.

[overlapping conversation]

0:27:58 AR: I think interaction of physics and biology is perfect.

0:28:02 SC: It is. In fact we could go on about nothing but this, but I really... There's some interesting stuff about humanity that I wanna get to.

0:28:09 AR: Yeah.

0:28:10 SC: So yeah. We're the end point of these billions of years of biological evolution, but at some point, regardless of one's opinions about the usefulness of categorizations and taxonomy, there's something that we call Homo sapiens. So for the non-biologist out there, just give us the rough guide to when did human beings... When did we first have Homo sapiens and what made us different from the other great apes that we're related to, like what is the distinction there?

0:28:40 AR: Okay. So having dissed taxonomy, I'm gonna adhere to it now for the useful purposes of this conversation.

0:28:48 SC: There you go.

0:28:48 AR: So anything in the genus homo, we refer to as human. So this is a genus that emerged a couple of million years ago. The oldest is Homo habilis, which literally means handyman. So we wanna come... Why we call it that, and there have been a few, maybe somewhere between 5 and 10 depending on how you define them, versions of humans over the last couple of million years. We are the last remaining member of that family. We're the last remaining humans. You go back 100,000 years, and we've got Homo neanderthalensis, which is the Neanderthals. We've got the Denisovans, which don't have a designation as a separate species but almost certainly were as much as Homo neanderthalensis was.

0:29:39 AR: And then there's earlier versions, such as Homo erectus, Homo antecessor, Homo heidelbergensis, and they all have different characteristics, some derived, some new. They all reflect adaptations to local environments, which is how evolution works. And then there's oddities like Homo floresiensis, so the funny little Hobbit creatures, the small meter-high humans that have only been found on Flores so far, but just last week, another possibly new species of dwarf humans was found nearby, another island near there. And so all of those are categorized as humans because we put them into the genus Homo.

0:30:30 AR: Now, Homo sapiens itself, the earliest versions of Homo sapiens until about two years ago came from the Rift Valley and were about 200,000 years old, so particularly from Ethiopia, and we always thought of East Africa being the nursery of humankind in that sense. Late 2017, it was, some fossils that had been found in the 20th century in Morocco in a place called Jebel Irhoud were re-dated and they came out as a minimum of 300,000 years old, and they are also Homo sapiens. So we're now beginning to think of Homo sapiens as being a sort of a pan-African species, so a species possibly made up of multiple locations of slightly different versions of Homo sapiens from around Africa.

0:31:22 AR: Now, so we are fundamentally an African species, and then something significant happens between 150,000 years ago, probably around 70,000 years ago, which is a small band of them migrate out of Africa, and that is the population from which the rest of Homo sapiens is derived. The language, as with the taxonomy, is deeply problematic here because we talk about migrations, and we think... Generally, we think about migrations in modern terms, people going from here to there or deciding that we're gonna move from this place to another place. In evolutionary times, we're talking about migrations that have taken thousands of years. So we talk about... The out of Africa event is an event that takes thousands of years. They're migrating at the rate of a mile per year.1.

0:32:13 AR: It's a slow diffusion more than picking up states and moving thousands of miles away.

0:32:17 AR: Yeah, exactly. So one of my lectures is about time scales in science in general and how people like you think about time scales as billions of years as a heart beat. People like me think of 10,000 years as being a flash in the pan. I'm much happier with hundreds of thousands or millions. And then you've got the quantum physicists who are talking about time scales which are unimaginable, unimaginably small. So there's that scale of thing. I find that one of the biggest problems in the sort of popular discourse of human evolution is recognizing the rate of change, which is immensely slow in terms of human appreciation.

0:33:01 AR: So there was the out of Africa event, taking tens of thousands of years. Homo sapiens then spreads around the world. So we move out of Africa, some go east towards Europe, sorry, west towards Europe, those are the ones that have the gene flow events with the Neanderthals. Some go further east and they have gene flow events with the Denisovans, and generally, we spread all over the world and by 40,000 years ago, we are everywhere apart from the Americas...

[overlapping conversation]

0:33:36 AR: Yeah. That doesn't really happen until about 20,000 years ago when during the last Ice Age, so much of the waters of the oceans are sucked up into glaciers, and so sea level is much lower. What is now the Bering Straits was just land, continuous land between Siberia and what is now Alaska, and there is a movement of people across from what is now Siberia into what is now Alaska. And then the seas rise 11,000 years ago, and that population is cut off and they are the founding indigenous people of the Americas. We now know with great certainty because of genetics, that all the pre-European colonization populations of North and South America are derived from that original founding population around about 20,000 years ago. Yeah. So that's the basic story. That's how we got there.

0:34:29 SC: And one of the things I just don't wanna... It doesn't sort of chronologically belong here, but I don't wanna forget it. One of the things I learned from your book is this transition from 24 pairs of chromosomes to 23 pairs of chromosomes and how that separates humanity, genus Homo, from the other great apes. And could you just explain to the audience what that is and maybe speculate a little bit about what that meant for why we're special.

0:34:55 AR: Yeah, yeah. It's a really good point and it's a point that comes up and it's quite useful in having arguments with creationists, to the extent that the Pope John Paul II used this as part of his argument as to why evolution was correct. And it's a sort of basic facet of biology. Our genes are organized into chromosomes, which are long stretches of DNA, which arranged during a certain point in the cell cycle in those iconic structures which look a little bit like, I don't know, Xs or... I talk about them as being like pinched socks. So if you take a pair of socks and pinch the middle, that's kind of a lot what chromosomes look like. And they are discrete packages of DNA which vary in size. The ones we are most familiar with are the X and the Y. So me and you have one X and one Y, the Y is the smallest and that sort of shriveled piece of stunted chromosome, whereas the X is a sort of magnificent beast of a chromosome, women have two Xs and we have an X and a Y in general.

0:36:06 AR: We have humans... Homo sapiens have 23 pairs of chromosomes. You get one set from your father via the sperm and one set via your mother from her egg. So we have 46 in total, 23 pairs. So you got two pairs of 1, two pairs of chromosome 2, two pairs of chromosome 3, blah, blah, blah, blah, all the way up to 22. And then you either have an X and an X or an X and a Y, if you are genetically typical.

0:36:36 AR: All of the other great apes, of which there are four, so that's gorillas, bonobos, chimpanzees, orangutans... Was that four? Yes. And there's sub-species of all of them. All of those have 24 pairs of chromosome, so 48 in total. And a few years ago, we worked out how that changed. So our common ancestor, with chimpanzees and all the other great apes, had 24 pairs, 48. But at some point, probably 7 or 8 million years ago, there was an enormous chromosomal disruption during probably an individual, and normally chromosomal disruptions like this are fatal, but this one wasn't. And two bits, two chromosomes in our ancestors fused together and made chromosome 2 for us. So our chromosome 2 is the fusion of two ape chromosomes that have stuck together at some point, and instead of killing that individual, which is typical in situations like that, it gave birth to the the rest of humankind.

0:37:44 SC: We're crazy to even imagine that it wouldn't kill that offspring. It was such a large disruption of how your DNA was organized.

0:37:51 AR: Yeah, there are very few chromosomal abnormalities of that sort of scale which are non-lethal. Down's syndrome is one example. So having three chromosome 21s, mostly those are what they call translocations. Mostly those translocations either result in profound serious diseases like cancers or they're just lethal early on during development, soon after conception. But for reasons that we don't understand, this was a massive chromosomal translocation and fusion, which resulted not in lethality but in the birth of our genus.

0:38:30 AR: The reason this is important biologically is because there's basic high school level biology, which teaches us about how sperm and eggs are made and how the process of the shuffling of our genes as we have sexual reproduction occurs, and it requires the two individuals to have the same number of chromosomes, because the chromosomes line up and they swap it over with each other. If you've got a different number of chromosomes, then you've got a massive disjuncture. You can't swap evenly, which... And that's a lot of the reason why we think that having different numbers of chromosomes or why we wouldn't be able to reproduce with chimpanzees.

0:39:15 AR: Having said that, and this is a reference to what I was saying earlier about biology being a science of exceptions, a paper published a couple of years ago described successful hybrids between species of equids, so horses, horse to horse type species, who had chromosomal ranges of between 60 and 31. And I remember this paper landing on my desk because it was, I looked at it and it was one of those moments where the first reaction is, "What?" And the second reaction is, "Ah, so annoying," because this is one of our basic rules.

0:39:52 SC: You can't say anything with definitiveness in this whole field.

0:39:55 AR: No, no, you can't, you can't. And we don't know how that works. So there isn't a current model of how that could possibly be the case.

0:40:04 SC: I mean, it seems that that first offspring to have 23 chromosomes had to mate with somebody, probably somebody with 24 and the 23 won out, at least in some subset of the offspring.

0:40:17 AR: Yeah. So we don't... This is another aspect of the sort of language that we use because we have sort of such a personal association with things like sex and reproduction and to a certain extent the basic mechanisms of biology. I think sometimes we make generalizations, which make a lot of sense, but actually don't necessarily reflect the time scales involved. So yes, that mutation had to happen once, but it's more that we have to think about it conceptually as an event rather than a sort of singular event. At the same, I mean, I struggle with this. I struggle with this on the grounds that it did have to have, I mean, it happened once. But at the same time, can we draw a trajectory back to that individual? Well, probably not. But what we then begin to look at is the population within that mutation occurred and how that was transferred within a population and it becomes a sort of ancestral pool.

0:41:11 AR: There's another example of this, which is one that many of the listeners will be familiar with, which is the birth of eukaryotic life. So life is divided into, in our taxonomy, three domains, which are bacteria, archaea, which are very similar to bacteria, but different enough to be sort of a different category, different domain, and then there's everything else and everything else is eukaryotes and eukaryotes includes us and blue whales and fungus and all plants. The fundamental difference between the bacteria and the archaea and the eukaryotes is that we have this subcellular unit called the mitochondria. And they're the energy-generating, that's where all the electron transfer chain that we were talking about earlier in terms of energy generation occurs. Now, what we now know, and sort of a deeply heretical thinker called Lynn Margulis came up with this as a theory in the 1960s and it is unequivocally correct now.

0:42:10 SC: We now know it's right. Yeah.

0:42:11 AR: Exactly. Was that it was... This was an event where one cell got inside another cell, which happens a lot, but normally the cell that gets inside the other cell gets consumed as food, but somehow this resulted in the stable transfer of one cell becoming inside another cell, and that resulted in the single birthplace of the origin of all life that isn't bacteria, that isn't archaea. Again, the evidence says, this is an extraordinarily unlikely event, and it may have happened many times, but it only appears to have survived once. And again, it becomes a sort of singular node on the evolutionary tree of life and a node from which 2 billion years later, it's me and you having a conversation. I find this conceptually hard, problematic.

[chuckle]

0:43:10 SC: Well, yeah, it did take a long time and exactly because it's rare, and I'm sure that the 23-chromosomes thing was also rare. It seems likely to me that it only happened that once. Once it happens, if it's gonna be evolutionarily adaptive, if it's gonna be good, then it's gonna spread and that seems to be what happened rather than it happening separately all over the place. So it doesn't seem that crazy to me.

0:43:38 AR: Yeah, but evolution is incredibly creative over long time periods, but it's also incredibly conservative. And so, we notice just from the way that the genetic code is constructed. So without getting too technical about this, we have four letters of genetic code, but in genes they're arranged in triplets and the triplets encode individual amino acids, of which we have 20, and all proteins are made of those 20 amino acids in different orders. The three letters of the genetic code are not evenly, they're not equally weighted. And there's a good evolutionary reason for that. So the first one sort of determines what type of amino acid it is gonna be. Is it gonna be hydrophilic or hydrophobic? The second one is more specific than that, and the third one has some redundancy in there. So you have in the genetic code, in the way that we arrange those four letters into triplets, there are 64 versions, but there's only 20 amino acids. So there's redundancy in the code which allows this third letter of a triplet codon to change without fundamentally screwing up the amino acid. If you change the first one, right, if you take a standard protein, and change one amino acid from being hydrophilic to hydrophobic, the chances are you've broken your protein.

0:44:56 SC: Yeah.

0:44:57 AR: But if you take the same amino acid and change the third codon from an A to a T or whatever, then you may be just the difference, you may be just encoding the difference between blue eyes and brown eyes or the subtle differences between me and you. And so evolution is... The genetic code is conservative in that sense, it has this, it has this built-in mechanism which is that it doesn't allow, it allows experimentation, but it doesn't allow experimentation which is sort of radical. But what we're talking about are the great transitions in evolution and they do appear to be radical things. Things that are sort of insanely radical, like huge chromosomal shifts or like one organism swallowing another and not eating it, but instead taking some of its behaviors.

0:45:50 SC: Creating a life together, yeah, and making it matter.

0:45:53 AR: Yeah.

0:45:54 SC: Yeah, no, no, I get that. And I think this actually, remarkably enough, reminds me of the conversation I had with Edward Watts who was a historian of Ancient Rome, and history is the same way as you described evolution. There's long periods where it's more or less not much happening, and then suddenly, something dramatic changes, 'cause I was asking about the well-known great man theory of history. Should we give so much credit to these individuals when obviously many more people we don't know about also played a role? And his answer, which I thought was very insightful, was most of the time the great individuals don't matter. The same thing would have happened. But at these crucial periods where things are on a precipice, when you're near a transition, then there could be a huge impact to a very small number of people acting in the right way, and I think that the same story could probably be told genetically rather than historically.

0:46:47 AR: I think that's right. And I've spent a lot of time thinking about this and wrangling with my desire to tell the true story of how science evolves and how, what we commonly refer to as a scientech revolution in the last four or five centuries. And of course that view, the Whiggish view of history, that you can draw a line, a straight line as we've historically taught science between, I don't know, Aristotle all the way to, through Darwin, through Faraday, through Einstein, and to Hawking. And those things are easy to do. Do they represent how science and how knowledge is actually transferred? Well, probably not. At the same time, and I think about these as nodes as well. Darwin is my man, right? And that was a nodal event. Stuff was different on the 25th of November, 1859 than it was the day before. There was a radical shift, well, a post hoc radical shift between the publication, before, pre-publication of the Origin of Species and afterwards. Was the idea in the air? Well, definitely. He didn't conceive of evolution, I mean, people were talking about evolution.

0:47:56 AR: His grandfather, Erasmus Darwin, was a key proponent of thinking about evolution. Lamarck, who in the UK at least, we kind of mock for getting his theory of evolution wrong, acquired characteristics. The whole idea that giraffes have long necks, because during their lives they stretch to reach the tallest branches and that characteristic is passed on to the next generation. Well, you know, he was a good scientist, he had a theory, and it was a theory that was based on observations, and it was wrong. And it's really unfair to mock him for that. In France they don't mock him. They have a Lamarck day. And I think that's right.

0:48:35 SC: I actually while reading your book was wondering if we could imagine the alien species which did evolve through Lamarckian means, like going to work out would make their children stronger as well as themselves.

0:48:45 AR: Yeah, well, I think that is perfectly plausible. I don't think it would take much imagination to come up with that. And actually, a Darwinian-Lamarckian process. And we mustn't forget, I didn't write about it in the last book, but Darwin didn't answer all the questions of evolution in 1859. He got the ground work revolutionarily right, and we've spent the next 160 years trying to disprove him, and basically failing at every juncture. He was pretty Lamarckian about many aspects. He didn't know genetics, he didn't know about genes, he didn't know what the unit of selection was. That didn't come until the 1930s, and what we refer to as neo-Darwinism, and he thought that there was evidence for acquired characteristics being passed on at least in plants from generation to generation. And again, it's a sign of a good scientist to come up with ideas, which subsequently turn out to be incorrect.

0:49:44 SC: We're pro-Darwin here on the Mindscape Podcast as a matter of official doctrine. [chuckle] And so, even pro-Lamarck he was a good scientist. Scientists should be allowed to be wrong, but all this talk of turning points and phase transitions brings up something I wanted to ask about, because we have clearly a turning point when Homo sapiens comes on the scene roughly 300,000 years ago. Is that a fair number?

0:50:05 AR: Yeah.

0:50:05 SC: But then there is this even more mysterious turning point 40,000 or 50,000 years ago.

0:50:10 AR: Yeah.

0:50:11 SC: Where we didn't change that much biologically. You make the point in the book that if you brought a 200,000 year old Homo sapiens up and gave them a shave and put them in nice clothes, you wouldn't maybe even tell on the streets, certainly not the streets of Los Angeles, that they were in any way unusual. But there is this more cultural, intellectual, cognitive shift. I'm not sure how to put it, just 40,000 years ago.

0:50:37 AR: Yeah, no, that's exactly right. And this is the paradox. This is the subtitle of the book is how Homo Sapiens became Nature's Most Paradoxical Creature. And I think that's a useful way to think about it, because we do have this weird stasis between 300,000 years ago and let's say, 50,000, 40,000 years ago where we don't change physically, we don't really change genetically very significantly. There's none of those big chromosomal shifts that we just talked about in terms of going from 23 to 24 chromosomes or whatever. None of that happens. There is definite genetic change, but not so much that we're all quite clearly the same species and clearly capable of inter-breeding. But then there is this sudden emergence, and evolutionary timescales we're talking about, so sudden meaning tens of thousands of years, of what we might refer to as behavioral modernity. So the things, the characteristics that we recognize in ourselves. And so they are things like high levels of skill in terms of tool making, in terms of manual dexterity, and that's manifested in the archeological remains, in the way that tools became much more sophisticated, in the way that we are clearly in control of manipulating fire, which is a very important step in our evolution, something that Darwin thought was sort of quintessential to humans.

0:52:07 AR: But also we see the emergence of things like abstract thought, and that's manifested... That manifests as art. So we have the cave paintings. We have the earliest examples of figurative art, so things like the Löwenmensch, the Lion-man of Hohlenstein-Stadel, which is this just beautiful 12-inch statue carved out of a tusk of a man with seven stripes down his left arm, which we think might be tattoos 'cause we think that they had tattooing kits at that time, but it has the head of a cave lion. Now, it's beautiful. It's a work of art. It's beautiful in whatever manifestation you're thinking about it, but it also shows aspects of behavioral modernity. It shows that the mind behind it was not substantively different from our minds today. It shows creativity. It shows the ability to imagine a chimera, a beast that does not exist. It can't exist in isolation. So it must be part of a series, so it shows immense manual dexterity, the selection of the tools required, the selection of the material required. It shows some sort of totemic importance of lions at that stage.

0:53:25 AR: We can only guess as to what those things meant, but the important thing is it shows that the person behind the creation of that thing was fundamentally no different in terms of their cognitive abilities to us, and we don't see that earlier. We don't see the continuous... We see flashes of this, flashes of things that you might call art or abstract displays of thought. But from about 40,000 years ago, we see it continuously and we see it all over the world. And so people have referred to this as the cognitive revolution. I'm not keen on that phrase 'cause I think revolution should take short... I think they should take 24 hours or a week or something rather than 10,000 years. [chuckle] But we see the Lion-man and then we see these Venus figurines all over Europe, which they tend to be smaller, little amulets of the female form often with very exaggerated sexual characteristics. So people have speculated that they are to do with sexuality or reproduction. I sort of don't care, because we don't know the mind of someone else. The joke I make in lectures is it's hard enough to know the mind of someone you're actually married to, let alone someone who died [laughter] 40,000 years ago. So they might have been toys. They might have been dolls. Maybe they were totemic reproductive symbols. We don't know.

0:54:56 SC: To me, I think we actually under-appreciate maybe the appearance of these artistic figures in the following sense, not only the carved figures but the cave paintings. We are so used to doing this. This is very human, making art, but there had to be a first time that it happened and that's kind of amazing. We don't think of even our closest relatives in the great apes as making representations of themselves. I don't think that's ever happened. So is there any idea of what caused it, do you know? There doesn't seem to be as we said any physiological change going on.

0:55:33 AR: No, and that's exactly right. We don't see any manifestations of this creative process in any other organism apart from Homo sapiens, with one caveat, which we can talk about in just a minute, and that is weird. So why would that be? And the truthful answer is, well, we don't know.

0:55:54 SC: Right.

0:55:56 AR: So the speculation on why the cognitive revolution... I'm not gonna call it that, the transition to behavioral modernity is important as a concept is because it represents a big shift in our evolutionary trajectory which doesn't appear to be modulated by genetics, by physiological or genetic change, but in fact is an evolution which is predicated on social interaction. And so one analogy which I quite like is that if we think about our biology as being hardware and our culture as being software, then what we have gone through in that transitionary period is we've shifted so much of the emphasis of our biological makeup from hardware to software. So the hardware doesn't fundamentally change, but it is in the interaction of software in the cultural domain, how we interact with other organisms in the same species as us that has fundamentally changed and formulated the basis for all of the creation of these things. We can speculate reasonably that, I don't know, being able to carve a flute or make the best possible tools or paint a megalosaurus on a cave wall, we can speculate that that is an attractive characteristic because that is something that other members of your tribe will look at and say, "Hey, he's the guy who does the megalosaurus cave paintings, and therefore, he's a successful person, and therefore, from a reproductive sense, we might wanna reproduce with him more."

0:57:37 AR: And so that's a characteristic which is gonna be passed on through the generations. The fact that it's not necessarily genetically encoded, I think, is really important, and this is really the key idea in the book. The emergence of social behaviors, the transfer from hardware to software, we've talked about that for a few years now. It's stuff that Jared Diamond has written extensively about, and Darwin talks about it in 1871 in the Descent of Man. Why it happened and the mechanism by which it happened in terms of how our populations were structured, well, that's brand new, and that's an idea which emerges out of... Well, two research centers, so basically, UCL, which is where I'm affiliated, and also Harvard, so a guy called Joseph Heinrich at Harvard. And it's kind of remarkably un-sexy in its genesis.

0:58:31 AR: It seems to be determined by population size. So when we model these things mathematically, and this corresponds with what the archeological record looks like, it appears to be the case that, as population sizes increase, you see a simultaneous expansion in these sort of creative artifacts. What it looks like is we see this sudden expansion in the complexity of the archeological record and what the mathematical model suggests is that this coincides with, our population is suddenly increasing in size. And so this is kind of the key idea, demographic transition is how we talk about it, and it's all to do with information transfer.

0:59:16 SC: Right.

0:59:17 AR: So we have very uneven distribution of expertise in humans, unlike all other species. You know physics, I know biology. If you need to get your car fixed, you take it to the shop. If you wanna know how to do a thing that you don't know how to do, what do you do? You ask someone who knows how to do it. The mathematical model suggests that, if a population size is above a certain threshold, then the transmission of that information occurs with great efficiency, and when your population is below a certain size threshold, then it occurs with great inefficiency. And so...

0:59:58 SC: Is it population size or density?

1:00:02 AR: It's probably a combination of both of those things. So the way I described it, it sounds very academic and very mathematical, but it actually kind of makes a lot of sense. In an age before writing stuff down where you can record things and therefore pass on that information on Wikipedia or in a book, the ability to... If I'm the guy in the village who makes the flutes, if you wanna know how to make a flute, you come to me, right? But if there's only 10 people, then you're all gonna learn how to make the flute from me and you've all got to learn it really accurately in order to pass that unit of information flute-making into the next generation. If the population is very large, it means that inefficient transfer of flute-making skills can pass to many, many people and that can be passed on, and that can be a continuous unit, which can transfer both horizontally and vertically through the generations. And that coincides, that population expansion, that transfer of information about whatever the unit of information, that appears to coincide with the sudden emergence of things like figurative art, of great complexity and tools. And it happens all over the world.

1:01:23 AR: We've only talked about Europe and the sort of cave paintings 'cause we have a very Eurocentric view of evolution, that's changed in the last couple of years. The earliest figurative art was the Lion-man. It's now a banteng painting in Borneo and that was only published last year and it's about the same date, but the overlap, the error bars point to Borneo being older. We see it in African populations. We see it in the Middle East. And as populations grow, we see a sudden expansions in the indicators of behavioral modernity.

1:01:57 AR: We also see the opposite. In one particular example, which has some cultural sensitivity, and that is Tasmania. So until the last glacial maximum 10,000 or 11,000 years ago, Tasmania is attached to mainland Australia and there were people, indigenous people are throughout those joint islands. The seas rise as the glaciers melt. Tasmania become separated, becomes an island. We've got no evidence that they were sea-going people... Indigenous people of Tasmania was seagoing and that there's transfer between Tasmania and mainland Australia. So they're an isolated population for the last 10,000 years.

1:02:39 AR: Now, what we see in the archeological record is very interesting because at a time, 12,000 years ago, we see a sort of standard level of complexities of tools, a tool set, which is in the few dozen. By the time European colonizers arrive in the 17th-18th century on mainland Australia, the tool sets for indigenous people of the Australias has gone up at a standard rate and is now in the hundreds. But the tool set of the indigenous people of Tasmania has dropped to below 20. We see specific examples of this, which is the loss of things like fine-tooth bone harpoons, and it looks like the people of Tasmania had returned to being foragers on the sea front rather than hunting for fish beyond the barrier using harpoons. And we've got records of that from history, such as James Cook's men, as they were arriving in places like Tasmania said that the indigenous people expressed shock that they were hunting for cartilaginous fish. We see the disappearance of cartilaginous fish bones in the archeological record.

1:04:00 AR: Talking about this, it does have cultural sensitivities. It's not saying that there's any... We're not making any judgement about the people, the indigenous people of Tasmania during that evolutionary trajectory, just the fact that they did not continue to develop technologically in the same way that mainland, in Australia, indigenous people did which was based on constant interaction with other groups, travel, sharing of information rather than a very isolated population.

1:04:32 SC: It's very consistent with the point that Geoffrey West made on an earlier podcast that innovation happens not linearly with population but with some higher power. You innovate more and more quickly as the density of interactions gets more and more vivid and vibrant. And I think that it also speaks to this question of whether or not scientific, technological, intellectual progress is a story of a few geniuses or something more collective, because certainly, if you just listed the great breakthroughs, there would be a few geniuses who get the credit, but only in retrospect, only because they were embedded in these larger communities of thought and that most human beings lived before the Industrial Revolution and yet most good ideas in some sense happened afterward. And I think that this is not that we human beings have gotten better, but the environments that we're in have changed dramatically.

1:05:26 AR: I think that's exactly right. And so we do legitimately say that Darwin was a genius and Newton was a genius and Rosalind Franklin was a genius. And those people in which changes pivoted those nodal events in the history of science or the history of thought. The environment in which they're in is the stew from which they are allowed to emerge, though. I think there's a difference between the myth of the genius and the myth of the sort of heretical lone genius. Those two things are slightly different. I do think, for example, that Darwin had both the... Well, 99% grit, facilitated by being extremely wealthy, and therefore, not having to work.

1:06:10 SC: It helps.

1:06:12 AR: It certainly does. But he carved out that theory over 20 or 30 years after being on the Beagle. So he didn't go to the Galapagos and see the finches and go, "Holy shit, that's evolution." [chuckle] He went back home and spent years working on pigeon bones, and writing to literally hundreds of people to ask for bits of information where he was carving out his one big argument. It was that intellectual environment that enabled him to see further, to have that 1% which pushes him from being one of the great scientists into what I argue is the greatest scientist. And we mustn't forget that Alfred Wallace came up with exactly the same idea in far less detail at exactly the same time, wrote to Darwin and said, "Here's my idea, 'cause I'm out in Indonesia at the time." And Darwin, "Yep, yep. You've got it too."

1:07:11 SC: There's my idea. Yeah. [chuckle]

1:07:14 AR: And in 1858, they announced it together. So a year before... So Darwin was ill and Wallace was absent, but it was presented at the Linnean Society together as... Which I think befits the quality of the idea, and it also reflects the nature that this is an idea that is in the air. Right?

1:07:37 SC: Right. Exactly. And I think that's part of the lesson of how these developments happen. But I don't want to... We're gonna have to come to a close pretty soon, so I don't want to go too far. In the spirit of your book, we've just been talking about things that make human beings special. Much of the point of your book is to say that many of the things that we think make us special are in fact found there in other species of animals. So we talked about tool use and art and so forth, but tool use in particular, you just have a wonderful selection of examples of tools being used by non-human animals that takes us down just a little bit of a path.

1:08:13 AR: Yeah, yeah, sure. Yeah. So one of the themes of all of my work, and I think it's particularly exemplified in this last book in Humanimal is that I'm not really into uniqueness theories. I'm not really into triggers. We've talked about nodes, these events where things flow into them, and then the world blossoms out of it, or new knowledge blossoms out of it. I like to revel in the complexity and the sophistication that is actually how science works, and actually how evolution works. And one of the things that we are really prone to do, is to suggest that there are individual things. This is the thing that made us human. And people for hundreds, thousands of years, and continue to this day to have successful careers saying, "It was this." Darwin said, "It was fire, tools and speech." Other people have said... Serious people have said that it was... There's the pyrophilic ape theory that it is fire that is the determining factor in switching us from being the earlier versions of ourselves into the versions that we recognize today. Other people have suggested hallucinogenic drugs.

1:09:29 AR: It is all of those things and none of the above. And I think what's important is to recognize that having the biological framework to manipulate fire or speak as we're doing, or the physical capability and the neural capability to carve a stone, something that dolphins will never be able to do because they need their four limbs to paddle, so they're fused together. They can't hold things. They will never carve a hand axe. They will never carve a flute. Dolphins will never be able to manipulate fire, mostly because they live in the sea. [chuckle] And that means that their evolutionary trajectory is fundamentally different to ours.

1:10:13 SC: Yeah.

1:10:14 AR: I don't think we're very good at recognizing the sort of cosmic happenstance, the environment in which evolution happens. And I think we're very attracted to looking at behaviors that look familiar to us because we do them, and then we see an animal doing it, and then just automatically saying, "Well, the chimpanzee does this. We are closely related to chimpanzees. Therefore, this is an evolutionary behavior which we have inherited from our common ancestors, the chimpanzees." We just don't know that.

1:10:44 SC: Yeah.

1:10:44 AR: They're often very hard things to test. Tool use used to be thought of as uniquely human. We now know, because we watch nature documentaries, that loads of... Well, all the great apes and loads of other primates use tools, sticks, wooden and stone tools. We now know that the corvids and other birds are sophisticated tool users. In fact, tool use is... We are obligate tool users, which means we can't function without tools, and we now think that around about 1% of animals are obligate tool users, which doesn't sound like a lot. It's 1 in 100, but that is literally thousands of species. What's more interesting than the number, is the range. So lots of mammals do it. We do it. Other primates do it.

1:11:27 SC: In fact, dolphins do it. You mentioned dolphins.

1:11:30 AR: Yeah, dolphins... There's ne example of dolphins using tools, which I think is of fundamental interest because the mechanism by which the transfer of that tool skill looks more like the way that we do it, which is that we talk to each other and we... And what we're doing now, we're sharing ideas. The example in dolphins is wonderful. A pod of bottlenose dolphins in Australia, in Shark Bay in Australia, have been studied for decades, were observed doing something peculiar. A proportion of them, about 50% of them were observed doing something peculiar, which is that they would swim down to the sea floor, and sort of work a sponge onto their rostrum, which is their beak. Well, initially the researchers didn't know why they did this. [chuckle] But then when they went diving with them, it was observed that they were using these sponges as protection for when they were foraging on the sea floor, because it's rocky, and you don't wanna scratch up your beak because that can get infected and that's bad.

1:12:35 AR: So this is an example of one animal using another animal to hunt for a third animal. That's relatively rare. We kinda do that sometimes, but that is unusual in itself. The story gets much more interesting in the 2010s when it was worked out why only a proportion of the dolphins were doing this, which is only females do it. So no males have ever been observed sponging like this, and that is difficult to explain. You don't see any differential sexual success between the males and the females who are sponging and who don't. But it's hard to understand why something which clearly has benefit is only being done by females. There are lots of obvious jokes to make at this point, [laughter] but it may be the males are idiots. [chuckle] That's rude to male dolphins.

[laughter]

1:13:26 AR: But there's a second... On top of that, when the genetics of the dolphins that are doing the sponging behavior was looked at, they're not particularly closely related. So all the females that are doing this, they're not mother and daughter, they're not sisters. So this looks like a behavior which is spread laterally that is being either learnt or taught and there is a sort of academic distinction between those two, which I'm a bit fuzzy on and I'm not that keen on what the distinction is, but one of the ways I frame the book is that we are... Lots of animals learn but only humans teach, which is not quite... There's nuance within that. It looks like this behavior within the sponging dolphins... It's definitely a learnt behavior. It may be a taught behavior. We have to remember that most organisms spend almost all of their time unobserved by us.

1:14:19 AR: And there's a third thing that emerges from this, which I just think is wonderful. You can look at the pattern of behavior, of the sponging behavior in the dolphins that do this, and we can check their relatedness via DNA, which also means we can sort of trace back through time an evolutionary pedigree of where that behavior actually started, and it starts with a single origin. We're talking about single origins again. It looks like it was six generations ago, generational time in a dolphin, in a bottlenose dolphin is around about 25 years, so that puts it to an individual female in the mid-19th century who we refer to as Sponging Eve, who, I don't know, one morning, got up, put a sponge on its nose. It seemed like a good thing to do.

1:15:02 SC: A lone dolphin genius.

1:15:04 AR: I know. 150 years later, they're all... Well, not all of them. All of the females are doing it and the males have yet to catch on. It's a wonderful example. It demonstrates so many things about the cognitive abilities of different animals, the transfer of information between individuals within that group. But I think more than anything, it tells us something terribly important, which is the best thing a scientist can ever say about anything, which is, "We don't really know."

1:15:34 SC: Right. [laughter] And it's also a good thing to contrast not only with human beings, but with other tool-using animals. I mean, you have the wonderful example in your book of the birds that spread wildfires intentionally. Darwin and others thought of us human beings as the animals that use fire, but that's clearly not true.

1:15:54 AR: That's right. It turns out a few animals are dependent on fire and utilize fire in various capacities. Chimpanzees in Fongoli in Senegal have a sophisticated understanding of the regular, the annual wildfires. They will stay near fires which are very dangerous and capricious. They will cruise in as soon as the fires have gone out and foraged for semi-cooked organisms. There are beetles that head towards fire with infrared detectors on their bodies because they will plant their eggs in recently burnt logs.

1:16:32 AR: So there are plenty of animals, lots more plants, that understand that fire is part of their natural ecology. But the idea that it's essential for humans is very powerful for a number of obvious reasons. One, it allows us to keep warm as we migrate away from the equator, so that facilitates us moving around the world. Two, it has social importance to this day that is... I'm sitting two meters from our fire...

1:17:00 SC: There you go.

1:17:00 AR: On which half an hour ago, my children were sitting watching Independence Day. Now they've gone to bed. [chuckle] But also it's an external stomach. Eating is a risky business because our mouths are very close to our... They're on our faces in general, and so near to our eyes. If you've got your head down in some food, you're spending a lot of time eating, which increases the risk of you being eaten. So if you can spend less time eating, then that potentially increases your survival. So we pre-digest our food by cooking it. We spend less time chewing, we spend less time eating because it is semi-digested before we even put it in our mouth. So all of these things are essential parts of our development. We are obligate fire users. So this notion that we are the only organism that can create fire anew is different from saying that there are lots of organisms that are dependent on fire.

1:18:04 SC: Yeah.

1:18:04 AR: Now, that was a robust and good and interesting important theory until about, I think it was December 2017. So my editors hate me for constantly updating books after the deadline has passed.

[overlapping conversation]

1:18:20 SC: Not gonna stop, yeah.

1:18:22 AR: I just need them to stop for a year so we can catch up. They just don't do it. But it was the publication in the scientific literature of the description of three types of Australian raptors, so hawks, that hang around on the edges of savanna fires in Western Australia, pick up burning twigs, fly over natural or man-made fire barriers and drop them in dry areas of brush, and then they go and settle up in a tree. And all of the little critters, the mammals and the lizards that run away from being burnt to death, run away from these bush fires and into the mouths of the raptors who have basically flushed them out. Now, the raptors do this. They flock. There are hundreds of birds in three different species so far that we've identified that do this, and it, in fact, explains a lot of spontaneous fires that occur over man-made or natural fire barriers.

1:19:20 SC: Yeah. [chuckle] They're natural, but they're not unintentional.

1:19:25 AR: They're not bird-proof is what they are.

1:19:26 SC: Yeah. [chuckle]

1:19:28 AR: I think there's another really interesting point within this which is that... This is published in the scientific literature in 2017, Aboriginal Australians have known about this for maybe thousands of years. Fire raptors, fire birds, form part of various dream time ceremonies. Some people have even speculated that this is a behavior that humans might have learned from the birds. I think that's speculation.

1:19:55 SC: That's very poetic, I like it, but yeah, I don't buy it.

[chuckle]

1:19:58 AR: I'm the same. If it were true, this is an example of cultural transmission between species, which is relatively rare, but it's a lovely idea. I don't think it's supportable using the evidence at hand. But what it does show very clearly is what is referred to as Indigenous Expertise Knowledge, IEK. This is something which has been known for generations, maybe hundreds, maybe thousands of years amongst one population for which it's incredibly important. It gets written up in the scientific literature in 2017, and we all sort of gulp at it, because it is an incredibly cool thing.

1:20:40 SC: Yes.

1:20:40 AR: It's a ridiculously cool thing. But it just shows that proper engagement, this is work done by Bob Gosford in Australia, proper engagement with people with indigenous expertise results in much richer science.

1:20:55 SC: Right. And I think one other example I wanna get on the table while we're listing ways in which we're not as unique compared to the rest of the animal kingdom, not just using tools that we find on the ground, but there's examples, you're gonna correct me, I hope, but in your book, I think it's a kind of chimpanzee that not only uses spears, but sharpens them when they go hunting, or even going to war with each other?

1:21:18 AR: Yeah, sure, so a lot of the great apes do this, we know that some orangutans sharpen a straight stick, they'll select a stick. So it's another example of the thought process involved in choosing the right stick, which also corvids do as well, they've got a way of identifying good stick for making a tool rather than a bad one. And in fact, there's a good experiment, which shows that if you put, so the Caledonian crows in particular, if you put a good-looking, hooked stick just out of reach behind a bar, but you put a not so attractive stick in reach, the corvids, the Caledonian crows will use the first stick to fish the second stick out. So that's sort of meta tool use. And that shows too, that is complex cognition required to do that. The Fongoli chimps, the same ones I was talking about a minute ago in Senegal, they will take sticks and they will create spears out of them, sharpen them with their teeth, they'll strip them. And they do this for a specific, slightly grim reason, but then again, nature doesn't care what we think, which is that they like to eat bush babies and bush babies are nocturnal.

1:22:24 SC: Bush babies, by the way, are not human babies that are sleeping in bushes, they are a form of animal, a tiny little mammal.

1:22:33 AR: Yes.

1:22:33 SC: Just so the audience knows.

1:22:35 AR: It's an important clarification. They are no less cute than...

1:22:39 SC: They have the big eyes, yeah.

1:22:40 AR: They've got the big eyes, because they're nocturnal. They often sleep in holes in trees, hollowed out holes in trees. And this has been observed many times. If you strip away, if you reach in and pull away the bark in order to get to the bush babies, they wake up and they run away and they're much lighter than chimpanzees, they scamper off to the top of the trees and the chimps can't get them.

1:23:03 AR: The Fongoli chimps take spears and what they do is they sneak up in the trees and they will jam the spear through the bark, having been sharpened with their teeth, and they basically kebab them and they will remove a bush baby on the stick and they will eat it straight off the bone. It's grim but effective.

1:23:25 SC: Nature.

1:23:27 AR: Exactly, nature does not care what you think. It's a really good example of tool use for specific purposes, for hunting. Again, we have taken this to extraordinary extreme levels in terms of our sophistication and tool use. There's a Darwinian phrase, which I talk about a lot in the book, it's a lovely phrase, which is, he talks about humans differing by degree and not by kind.

1:23:56 AR: Now, it's such an important phrase, but it's one that I can test in some circumstances. I think there's cultural reasons for that. Darwin was right in the 1870s where the question of whether humans had evolved from earlier apes was still very much being debated. And so, he uses this phrase to say, well, there is continuity in whatever we look at between humans and earlier organisms, so we differ by a degree and not by kind. I think that sometimes that's true in the contemporary age where we're no longer debating that with other scientists and most sensible people. Now that we are established as evolved creatures, we can be more honest about the fact that there are some things which differ by degree and there are some things which just are so fundamentally different that they look like they are different by kind. The best example is what we're doing right now, speech, communication.

1:25:04 SC: Symbolic manipulation of ideas, representations.

1:25:08 AR: We don't see that in any serious degree, in any other organism. Attempts to teach great apes particularly Coco in California, died last year, I think are slightly absurd experiment and say much more about us than they about gorillas. But even so, Coco had, I don't know, a few thousand words, but I couldn't do what a three-year-old does naturally, which is to construct a syntactical grammatical sentence.

1:25:43 SC: Had no grammar, yeah.

1:25:44 AR: Yeah, and I use the example of the fact that grammar is a rules-based system that we continually violate the rules, and kids say cute things all the time because they learn these rules and they apply these rules to other words which actually turn out to be incorrect because we don't follow the rules. The example I used in the book is my daughter says, "We swimmed," rather than we swam.

1:26:09 SC: Can't blame her for that. Can't really punish her, yeah.

1:26:11 AR: No, you can't. English is a stupid language. It's a ridiculous non-rules-based language, but the fact that she does that intuitively means that there is an innate grammatical framework which is part of the complexities of the physiology, the mechanics, the anatomy of being able to speak combined with an enormous mainframe of processing power in which language is an in-built facility. I think that is not different by degree. I think that is different by kind.

1:26:44 SC: Right. And so just to wrap up here, you've mentioned a couple of times that some of these transitions that we point to as revolutionary cusps or turning points or whatever actually spread out over thousands or tens of thousands of years. Presumably, a million years from now, future historians are gonna be saying the same thing about our ongoing symbolic revolution in the use of language and information that we're in the middle of right now. We're not at the end of it. Would you even dare to speculate a little bit about the future and where we're going, given that we're still lifting ourselves up by our bootstraps, with this newfangled technique?

1:27:21 AR: Yeah. Well, no is the answer to that, and it's to do with the time scale question. So it is singularly the question that I get asked most in public talks, are we still evolving. Now, there's two ways to answer this. The first is, yes we are, because evolution simply means change over time, and as long as we keep having children by sexual reproduction, our children are genetically different to us, and that it is the constraints of difference and natural human variation. The question I think most people are really asking is, are we evolving under the constraints of natural selection. Now, the answer to that is, there are two ways to answer that. The answer in evolutionary time scales is yes, because we've got really clear examples over the last 10,000 years, if you want, which is a blink of an eye in evolutionary time scales, of natural selection occurring measurably in human populations all over the world. There are regional adaptations in human populations which have allowed us to become so globally successful.

1:28:32 AR: A really fun example we always talk about is milk-drinking. Most Europeans can process milk after weaning, after they've been nursed, but most people in history and most people on earth can't, because the enzyme that processes a particular sugar in milk called lactose, the enzyme's called lactase, basically switches off by age five in most people. About 7,000 years ago, 7,000 or 8,000 years ago, a population in Europe who were pastoralists already developed a mutation, a random mutation, which meant that they could continue to process lactose into adulthood, and that is why me and you can drink tea. There's an interesting sideline to this, which is that in the last couple of years, and my next book is about race and genetics, which is now finished and will be out next year. Neo-Nazis and white supremacists have taken this genetic truism as an example of their own superiority, of European superiority...

1:29:38 SC: Of milk-drinking?

1:29:39 AR: Yeah, milk chugging is a thing. And so you go on YouTube and you look at milk-chugging Nazis, and they've all got their tops up and they're quite drunk and they're pouring gallons of milk all over their faces, which is just... Well, it's a weird thing to do. Almost all Europeans are lactose-persistent, which is the condition that we're talking... The evolved, the derived condition that we're talking about. They have failed to notice that lactose persistence also has independently emerged in pretty much every population that has had pastoralism as part of its evolutionary trajectory, and that includes the Tutsi in Rwanda, the Khoisan in South Africa, Southern Africa, Middle Eastern camel farmers. It's a semi-serious point that I like to make, but then again, we don't look to white supremacists for contemporary understanding.

1:30:34 SC: It's not the only thing they have failed to notice, so yeah.

1:30:37 AR: That is true, that is true. Why did I mention that? What were we talking about?

[laughter]

1:30:44 SC: We were talking about the future and it's hard. The time scales are hard to get right.

1:30:47 AR: Oh, yeah, yeah. Right. So the milk-drinking thing is a really good example of recent evolution and local adaptation, which is... Natural selection isn't quite the right way to think about it. It is selection but it's more... It's what we refer to as gene culture coevolution. So our cultural behavior, which is farming, pastoralism, has influenced the selection of a random mutation in our genes. So it's those two things happening at the same time or roughly the same time, which has caused that ability.

1:31:21 SC: And it seems like that is the future in the sense that now that we can not only store information in words and books and so forth and use that to manipulate ourselves and hand it down to other people, and now we can even manipulate our genomes. The future evolution of our genome will necessarily involve co-evolution of what happens through natural selection and what happens through our external information processing and gathering and sharing systems.

1:31:53 AR: Yes, definitely true, but what I think is apparent is how unevenly distributed these things are. So the main drivers of evolution are how many children you have and how young they die. What we know very clearly is that since records were first taken about infant mortality in the 19th century, there were very clear patterns about lowest levels of infant mortality were in Northern Europe, mostly Scandinavia, and the highest levels were in Western Africa. Now 200 years later or 150 years later, the infant mortality has dropped all over the world at pretty much the same rate. The highest levels of infant mortality are still in West Africa, and the lowest levels are still in Scandinavia, and America and the UK, surprisingly, are somewhere in the middle, which is... I always find that a weird stat.

1:32:52 AR: So that uneven distribution of this main driver of evolution around the world may mean that there is selection in those areas, but it's not universal. We do see glimpses of natural selection or forms of selection in different populations that have been studied. The technological question I think is really interesting. People have asked me if the advent of in vitro fertilization has shifted our trajectory. The estimates are about 5 million babies since 19... Since Louise Brown in 1979-1980 was born have been the result of in vitro fertilization. And that seems like... That's a decent chunk of people, 5 million people. If you saw them at a festival you'd think that's a lot of people. It's less than a thousandth of the global population, so relatively small, but it's also massively, unevenly distributed. It's a very, very Western technologically-based process. And so I think the answer is probably no, probably not a significant contributor.

1:34:00 AR: Another example is we've begun to manipulate the germ line of a very few diseases that have been approved. So, this is pre-CRISPR technology, which is this new gene-editing kit, which I think is gonna prompt a revolution if it hasn't done already. But we've actually chosen to eradicate a particular type of disease, a mitochondrial disease where they have a separate genome. We take donor mitochondria from a third individual, a third adult, and replace the mitochondria in children who are gonna have this otherwise lethal disease. Now, again, we have eradicated, we have changed the direction. Those children would not have made it to adulthood. They would not have reproduced and that mutation would have died with them. We have replaced that using technology.

1:34:52 SC: Yeah.

1:34:52 AR: Has it changed evolution? Almost certainly not, because it's a tiny proportion of people for whom this has been applied, and it will never be very many people, because it is a mercifully rare disease. From an ethical point of view I think we're at the point where we... The question is not whether we should do it, it's whether we shouldn't do it, right? If we are capable of doing this, then you have to ask yourself questions about why you wouldn't wanna do this rather than why you would. CRISPR may change that. We saw just before Christmas, what I think is probably the greatest violation of biological ethics that I have experienced in my lifetime, which was the announcement of the birth of two girls in China who had been genetically edited via CRISPR by a Chinese, not really a reproductive scientist at all, to at an attempt to make them immune to HIV.

1:35:52 SC: Right.

1:35:55 AR: It wasn't the right mutation. They checked, he checked that it was the right mutation before it was implanted into the mother, and knew that it wasn't the right mutation, but implanted them anyway. It is an ethical and moral violation, the likes of which I haven't seen I don't think in my lifetime.

1:36:13 SC: It won't be the last one.

1:36:15 AR: It won't be the last one. I think it may have had the effect of unifying the community, including China, which is traditionally not as accessible in terms of openness about what they're actually doing. He was a rogue element, and I think will spend the rest of his life either in jail or the rest of his life isn't gonna be that long. You're right, he won't be the only one, but well, at least we're talking about it.

1:36:49 SC: Yeah, yeah.

1:36:50 AR: Is it gonna change our future history? I don't think we're anywhere near understanding the genome well enough to actually say, "Yeah."

1:37:00 SC: We'll check back in 500 years and see what new things we've learned.

1:37:03 AR: I would love to know where we've got, how we got from here to there.

1:37:08 SC: I will let the audience know one last thing, which is that Adam's new book contains a long and highly entertaining section about sex that we didn't get to talk about here. Lots of the... I think the motto is there's plenty of non-reproductive sex going on everywhere in the animal kingdom. So the idea that sex is just for reproduction is not a very good one. We didn't get to talk about it here, but I want people to know it's in the book.

1:37:32 AR: Yeah, like I say in the lectures, I didn't set out to write a book about weird animal sex. It just is a book that contains a lot of weird animal sex.

1:37:39 SC: What can you do? It's determined. Alright, Adam Rutherford, thanks so much for being on the podcast.

1:37:45 AR: Sean, thank you for talking to me today. It was a complete pleasure. I love having these long-form conversations where we can really get stuck in.

1:37:51 SC: Alright, good luck with the book.

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