Ep 47: The Origin of Us: Human Evolution (with Kate Wong)
Where, when, and how did Homo sapiens appear? What do we know about the complex set of ancestral hominins that preceded us? How recently did other hominin lineages live and what happened to them?
On this episode, we talk with Kate Wong (@katewong), a senior editor at Scientific American, about her latest article, The Origin of Us. Our understanding of hominin evolution over the past several million years has been transformed by exciting new fossil finds and new DNA sequence data. We talk with Kate about the biggest news, the luxuriant evolutionary bush from which our ancestors emerged in Africa, and her favorite fossil species.
Find more articles from Kate here: Stories by Kate Wong
Cover photo: Comparison of Modern Human and Neanderthal skulls from the Cleveland Museum of Natural History via Wikimedia Commons. hairymuseummatt (original photo), DrMikeBaxter (derivative work) (CC BY-SA 2.0)
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Art Woods 00:09
In 1965, in a book about the evolution of humans, the media company Time Life published an image often called The March of Progress. I'm sure you've seen it. Left to right, it shows our ancestors transforming gradually from chimps into modern humans.
Marty Martin 00:24
That image has stuck with us even though it doesn't reflect much about our actual evolutionary trajectory. These days, the image is used to satirize almost any kind of progress.
Art Woods 00:33
Our actual story is much messier. Today, we're the only living member of our genus, the Homo in Homo sapiens, but many of our human-like ancestors lived alongside other species of hominids. We emerged as the sole living branch of what journalist Kate Wong called a luxuriant evolutionary bush.
Marty Martin 00:51
Kate is a senior editor at Scientific American, and has covered the field of biological anthropology for more than two decades. She wrote a recent article to commemorate the magazine's 175th anniversary, which coincides roughly with the genesis of the field she covers.
Art Woods 01:04
In the early days of biological anthropology, scientists seemed to find all kinds of evidence pointing to our special status. Our ancestors fashioned stone tools, hunted in sophisticated groups, spoke languages and painted stories on cave walls. More recently, though, scientists have discovered evidence that other hominid species also could do many of these things. The origins of key human traits keep getting pushed back further in time.
Marty Martin 01:28
In the article, Kate also discusses the influence of racism on biological anthropology. In the early 20th century, some European scientists were reluctant to recognize Africa as the birthplace of humanity, and they sometimes cherry picked evidence to fit their beliefs,
Art Woods 01:42
Or even invented evidence outright. In one early episode, an amateur archaeologist named Charles Dawson found what appeared to be a human-like skull with the jaw of an orangutan near Piltdown in England.
Marty Martin 01:54
It caused a sensation, evidence that early homo originated in England. Until it was revealed to have been a fraudulent pairing in the 1950s. The crazy thing is that during this time, actual hominid fossils were turning up all over Africa and Asia.
Art Woods 02:10
For example, in 1925, Raymond Dart discovered a fossil with an ape-like braincase and human-like teeth from South Africa, a real missing link from 2.8 million years ago connecting African apes to humans, which is now known as Australopithecus africanus. But it took years for the scientific establishment to recognize it as such.
Marty Martin 02:31
On this episode, Kate explains how spectacular new fossil finds and rapid advances in DNA sequencing and analysis have washed away many preconceived notions and led us, or forced us, into a modern, more nuanced view.
Art Woods 02:43
We talked with her about some of the most important traits that humans evolved and the fuzzy line that separates us from our ancestors.
Marty Martin 02:50
I'm Marty Martin.
Art Woods 02:51
And I'm Art Woods.
Marty Martin 02:51
And you're listening to Big Biology. I guess let's kick off the chat today with this new article that you have coming out in the September issue of Scientific American, that's called The Origins of Us. And as I read it, and I think your goal was to sort of focus on how our views of evolution have changed since Darwin first speculated about human origins more than 150 years ago. So can you sort of just walk us through the history of ideas about human origins, and especially what I understood to be mostly a linear progression, you know, thinking going from something simple to something like us, the more more of a traditional way of thinking about things versus the kind of tangled bush mindset concept that that's around now.
Kate Wong 03:48
Yeah. So what was really amazing to me, when I started this, this project, working on this article, was just kind of thinking about how, in the entire span of the sort of lifetime of Scientific American, that's the birth of biological anthropology and the study of human origins. And, you know, it doesn't really kick off until you have Darwin writing his famous On the Origin of Species in 1859. I should back up for a second and say that Scientific American was founded in 1845. So it takes 14 years before we even get to Darwin. And the funny thing about On the Origin of Species is that he talks about all kinds of organisms, ants and armadillos, and you know, birds and a zillion other things, and he doesn't talk about the origin of humans until the very end of the book. And he has this like, it's like a throwaway line. He just says light will be shed on the origin of humans and their history or something like that. And that's it, a total tease, right? Because that's, of course, the thing that is like everybody wants to know. And, you know, I think the thinking is that he was being strategic here, he knew that, for Victorian society, in which, you know, the evolution of all species, every species is created, specially by God, and humans, of course, are the specialest of all. If he were to come out in his argument, you know, for evolution by natural selection, that, if he had thrown humans into the mix, people would have just been like, too freaked out. So I, you know, he's deliberately holding back from from talking about how humans evolved in that book. But it's not until 1871, that he comes out with some more concrete thoughts on on human origins in his book, The Descent of Man. And even then, though, when you get to the Descent of Man, you know, he's focusing in that book, which is really kind of all over the place, on just like making the case that humans have evolved, like all the other organisms. But the thing is, he doesn't really talk about earlier stages of humanity, because there's not really any evidence for him to talk about. Now, he believes it's out there, but it just hasn't been discovered yet. So I think by 1871, you know, there's, you know, there's some Neanderthal remains, there's some earlyish homosapien remains, but there's nothing that really sort of takes us back closer to our common ancestor with with the great apes. And, you know, he could see from, from his comparisons, his anatomical comparisons, that we have a lot in common with the African great apes, the gorillas and chimps. But, you know, there weren't nearly any, any sort of fossils that that showed those ape-like characteristics, Neanderthals were just too modern, to show that.
Art Woods 04:58
What a tease, right?
Kate Wong 05:24
It's interesting to think about those fossils, you know, just just Neanderthal fossils, that they even had access to them, because they surely had no idea about the timing of those right in, in history. And it seems like without timing information, too, it'd be really hard to interpret what what they mean. Yeah, it took a while for, for geologists to come up with the right sort of information to inform how old life on Earth is, and, and, and for human fossils to surface, it took a really long time. And, you know, it's not until the the early 1900s, that you start getting stuff coming out of South Africa, in particular, that really starts to look like, okay, here are things that we can see, they're a kind of intermediate between apes and humans, they have a combination of those traits. And, and even at that time, it was hard for people to kind of accept that, because I think specifically of the link to Africa, which a lot of scholars, European scholars, weren't comfortable with. And, you know, they, I think they also just needed more fossils to persuade them.
Art Woods 08:22
So if we just sort of fast forward to, you know, this more modern conception that we have of this luxuriant bush of, you know, hominids, hominins. So, did that view just evolve gradually among anthropologist as we gathered more and more specimens of different kinds? Or was there a kind of singular moment when people realized that, oh, you know, it's not this linear thing? It really is a complicated bush, you know, which, at some points in time had many species coexisting in different parts of the world.
Kate Wong 08:55
I think, you know, for a long time, anthropologists recognized that later on in human evolution, you have multiple hominid species coexisting, like the Neanderthals coexisting with Homosapiens. But they kind of thought that the earlier stages were pretty much that straight line. And, you know, where like everything that was found and there wasn't a whole, there weren't like tons and tons of new species being announced, but the ones that were found, you know, seemed like they could maybe be slotted together into this into this, this line. And then they started finding stuff that was clearly different and that lived at the same time stuff that you know, like Paranthropus, which is just another genus. So Homo's our genus, Paranthropus was another genus. And we now know that Paranthropus coexisted with the early members of our own genus for a really long time. and this was a totally different kind of animal, you would have looked at it and thought this was like an alien, you know, I mean, it had this huge crest on its head, great big teeth and jaws. This is like Cuisinart this thing. And it's, you know. And so while our own sort of branch of the tree, Homo, was, you know, inventing all sorts of technology, to kind of pursue a really broad diet, Paranthropus seems to have evolved a number of adaptations to, to eating really tough foods, things like grasses and sedges. And so it's just a totally different kind of human, and one that doesn't make sense as an ancestor for us, but that really showed quite clearly that it's that there are multiple branches of humanity, farther back in time, not just at the time of Homo sapiens and the Neanderthals.
Art Woods 11:01
I think Marty and I were using the word hominid and hominin interchangeably. And I think you were using these more carefully. Can you just tell us real quick what the difference is between hominid and hominid?
Kate Wong 11:12
Yeah, the the closest living relatives of of Homo sapiens are chimpanzees and bonobos, they're there in the genus Pan. And so we have a common ancestor with them that would have lived somewhere in the order of, you know, 8 to 12 million years ago, I think, is the current estimate. Now, everything that is on our line, you know, going from the divergence point between chimps and humans at that at that last common ancestor, everything that's more closely related to us is called a hominin. And once upon a time, for a very long time, the term that was used was hominid. And then I don't know, I want to say a decade ago, but I'm not really totally sure about that, people started using this other word hominin. So, you know, I, it's basically humans and all of their extinct relatives going back to the last common ancestor with chimpanzees.
Art Woods 12:22
Well, I think what we want to do is circle back to some of these diversity issues and talk later in the conversation about, you know, multiple species coexisting, and how they might have interacted. But for now, maybe let's focus on on the emergence of what we call modern Homo sapiens. And so if we just if you just had to say, what's the modern consensus on on where and when modern Homo sapiens emerged? What is it? And then maybe we could talk a little later about, like, what it even means to be modern?
Kate Wong 12:55
Sure. So modern Homo sapiens makes its first appearance in, in Africa. And we've seen this date get pushed back farther and farther in time, and right now, the the sort of oldest Homosapiens fossils on record are around 315,000 years old. They're from Morocco, so Northern Africa.
Art Woods 13:22
I used to teach it was like 200,000 years, but now now, you know, I feel like, the dates keep getting pushed back.
Kate Wong 13:29
They keep getting pushed back. And, you know, but the thing is, I mean, you were asking earlier, like, what, you know, what, what is modern Homo sapiens? And this is a really complicated question, actually. And in the case of the the Moroccan fossils that I just mentioned, you know, there actually is a little bit of debate, like, how modern are they? So, you know, modern Homo sapiens is, you know, is defined by having a really large brain on average, I think it's about 1400 cubic centimeters. We have a really round skull like a, like a basketball, with a flat forehead and, and a smooth brow. And we have a prominent chin. We have a pretty lightly built skeleton. But you kind of have to compare that contrast that with all of the extinct relatives in the tree, and those guys tend to have a sort of elongated skull like a football as opposed to our basketball. They've got these like big brow ridges, and low foreheads, and their their bones that encase the brain are really thick. And, and their bodies are just kind of they're just beefier, stockier, or sturdier. And so those are some of the traits and when you look at the fossils from Morocco, they don't have that full suite of of traits that, you know that people today have, you know, their, their their brain case isn't quite as basketball like.
Art Woods 15:12
So they're kind of somewhere around that fuzzy line between not modern and modern right and, at some level, it's got to be an arbitrary judgment call about, you know, whether it's wholly modern or not.
Kate Wong 15:21
Exactly. You know, there's been a sort of long history of debate about, you know, a lot of times when people talk about modern Homo sapiens, also, they're talking about behavior, right. So for a long time, there was this idea that Homo sapiens, the sort of anatomical package, came together really early in Africa, originated in Africa. But it wasn't until much, much later that you get this sort of full suite of behavioral characteristics that characterize modern humans. So then people would talk about behaviorally modern humans, as opposed to the earliest ones who maybe weren't doing a lot of the things that we think makes make people modern. So things for example, like, using symbols, that's like one of the main main things. And for a long time, people thought, well, you know, actually Homo sapiens for a long time, you know, is making the same kinds of tools that Neanderthals are making in other places. And there's not a whole lot to distinguish them, and it's not until, you know, maybe 40,000 years ago or so, give or take a few 1000, that you start seeing Homo sapiens doing extra stuff, making more complicated tools, making art. And, you know, art in particular, is is often used as in as a proxy for language. In the archaeological record, we can't actually see language fossilized, but we can see paintings, we can see the use of jewelry, of pigments for decorating your body, all the kinds of things that indicate that you have a type of human that that is capable of coming up with and using symbols to communicate.
Art Woods 17:18
So how old is the oldest art that's known?
Kate Wong 17:20
So it depends on like, what kind of art you're talking about, but.
Art Woods 17:24
Another fuzzy line, huh?
Kate Wong 17:26
Yeah, another fuzzy line. You know, the very oldest, it's, it's a it's a shell, from Indonesia. And it's got this engraving on it and an engraved design. It's like a simple geometric sort of zigzag design on it, clearly intentionally made, and pretty securely dated to about 500,000 years ago, which makes it, you know, and it's it's, you know, the sort of context there would be that you would assume that this is the something that Homo erectus made. Homo erectus was not supposed to do this. So this is like, this is this is crazy.
Art Woods 18:08
Big shock.
Kate Wong 18:08
Yeah. And then, so, you know, not only do we have Neandertals, also making making complex tools, and we're learning more and more about about the sort of artistic endeavors they undertook, they seem to have made jewelry, they used pigments, to, in some cases, paint their jewelry, maybe to paint their bodies. And there's some evidence now that they've also made cave paintings, which was kind of seen as like the last, the last thing separating Neanderthals from, from Homo sapiens was the creation of art on cave walls. And, you know, a few years ago, a team who was, that was working to date images in a series of caves in Spain found, you know, found evidence that some of the, the images, and these are like, these are sort of geometric images, they're not figurative art, like you might associate with a sort of ice age, the French caves, like Lascaux, with the beautiful horses, that kind of stuff.
Art Woods 19:22
Spears going into the woolly mammoths.
Kate Wong 19:24
Yeah, exactly. It's not that it's these, it's these more like, symbolic shapes. And they're so old that they predate the arrival of Homo sapiens in Europe. So the assumption is they have to have been Neandertal creations. Now, who knows? Like maybe somebody's going to find the evidence that Homo sapiens was in Western Europe long enough ago that it could be the creator of these images, maybe that'll happen down the road, but for now, the assumption by many archaeologists is that Neandertals must have made it. So it's no, you know, it's just, I think all of this is just to kind of underscore what you said, Art, about the fuzziness, you know, we used to have these sort of hard lines in the sand. These are things we know Homo sapiens does that nobody else does. Oh, wait, Neandertals did that. Oh, even Homo erectus did this little shell engraving, one, at least one Homo erectus did this.
Art Woods 20:29
It's like the only special thing we have left is smartphones. And you know, maybe we're gonna find smartphones in some layer of sediment in these caves in Spain, right?
Marty Martin 20:38
Give it time. So Kate, can I can I circle back to the sort of behavioral elements of modern humans? And where where did that happen? And did it happen, sort of in one place? Or was this sort of an emergence in a tiny window of time of these innovations across human populations?
Kate Wong 20:59
You know, it doesn't seem to have all emerged at once as like a part of a single, you know, adaptive package, sort of a great cognitive leap. That was an idea for a while that maybe there was some kind of gene that cropped up in the Homo sapiens gene pool that all of a sudden imparted us with the ability to make art and have language and have huge social networks, and that has really fallen out of favor, because it just looks like, you know, you've got different kinds of top technology popping up at different times and in different places. There's increasingly this, folks embracing this idea that that that early on with Homo sapiens, you've got a bunch of sort of little populations that are scattered around the continent. And periodically, the climate conditions, either bring them together, or push them apart, like when there's a sort of a drying of the climate, deserts expand, and these little populations are pushed out to the peripheries, pushed away from each other. And then when it gets wetter, and the climate is more favorable, they are more easily able to sort of connect and interbreed and exchange culture and technology. And, you know, this kind of comes out of the observations that when people have found early Homo sapiens fossils, and the, and the cultural materials that are associated with them, they don't all look the same, there's a lot of variability from one group to the next. And so that's kind of given rise to, to this idea of having these sort of scattered, smaller populations that kind of come together and go their separate ways and come together and go their separate ways over time.
Art Woods 23:03
That's, that's super interesting, and I just, I just flashed on something, as you were talking about that, made a connection of something I never thought of, which is about, so when I've talked about human evolution in the past, and my my biology courses, I've sometimes talked about this contrast between the out of Africa hypothesis and the multiregional evolution hypothesis. And just to sort of lay those two out super briefly, you know, out of Africa says, modern Homo sapiens evolved in Africa, spread out across the world, and displaced all other hominids that were there. Multiregional evolution says, you know, modern Homo sapiens, more or less evolved in Africa, and then interacted a lot with these other hominids living elsewhere in the world, and interbred with them and incorporated lots of their traits into our own modern genomes now. And it sounds almost like what you just said is that there's a kind of within-Africa version of that, right? So, you know, maybe the point is not to say, you know, here, here in Africa is where modern Homo sapiens evolved, but rather, there's this kind of complex network of populations that are merging and splitting over many tens of 1000s or hundreds of 1000s of years. And it's out of that, that kind of mess that modern Homo sapiens emerged. Is that, is that a fair comparison to draw?
Kate Wong 24:27
That's a, yeah, that's a great way of putting it. I think, if you go back a little bit sort of farther in time maybe to like the, the 80s or so, the sort of classic out of Africa scenario versus the the multiregional evolution scenario that multiregional evolution wasn't quite emphasizing that that African contribution in the way that you just described, it was more kind of like, okay.
Art Woods 24:55
They emerged everywhere?
Kate Wong 24:56
Homo sapiens emerges from archaic populations that are found around throughout the Old World, and but, you know, they're all sort of interconnected through through gene flow and kind of all end up in this from roughly the same place, but with some regional variation. And what has become clear, you know, largely through genetic work, but also but also through the fossils and archaeological evidence, is that you definitely get Homo sapiens appearing first in Africa that's it's indisputable.
Art Woods 25:36
So sort of pure, multiregional evolutions have been excluded as an idea.
Kate Wong 25:40
I think so. Well, I think both pure multiregional evolution, and, and the sort of strictest out of Africa scenario, which involves Homo sapiens evolving in Africa and then replacing every other archaic, human species around the globe, without interbreeding with them in any sort of substantive way. I think both of those are really not supported at this point and it's more intermediate.
Art Woods 26:12
I see. So the consensus is some kind of hybrid. Yeah.
Kate Wong 26:15
Some kind of hybrid, and then what you were talking about when you talked about the multiregional evolution within Africa, that is, that is a sort of newer idea that's, that's being embraced. And, and yeah, that's really talking about this idea that I was alluding to before of having multiple sort of populations of Homo sapiens that split apart, kind of evolve along their own trajectories behaviorally and anatomically, and then come together, and, you know, the sort of the stuff that makes us who we are today sort of coalesces, from all of that diversity.
Art Woods 26:52
You sort of mix and match traits from these different formerly separate populations, and you know, get get presumably the best out of all of them. Right?
Kate Wong 26:59
Exactly. Yeah, yeah.
Art Woods 27:13
Let's, let's turn and talk about another trait that I find particularly fascinating. And that's the origins of language, the ability to speak. And what what do we know now about the timing of that, and which lineages had it and how it happened?
Kate Wong 27:30
Yeah, so this is, it's a fascinating question. That's certainly one of our maybe our most distinctive behavioral characteristic as a species.
Art Woods 27:41
We don't stop talking.
Kate Wong 27:42
And, you know, I kind of, we don't stop talking, we cannot stop talking. And, you know, other other animals communicate, but but human language is uniquely rich and complex. And so I alluded to earlier in our conversation, this idea that, that archaeologists, you know, because language doesn't preserve, in the archaeological record, they have to kind of look for other clues to its existence, and the use of symbols is their best sort of proxy for language ability in, in our, in our extinct predecessors. And so, I mean, I think if you look at the sum total of what's been found for Neandertals, you know, culturally, they, we now know, they were doing things like decorating their bodies with with bird feathers, with with pigment. There's a really, some really interesting evidence from I think it's from Spain, that they were mixing pigments together and adding a sort of sparkly element to it. And that's sort of believed to have been a kind of really blingy body paint. Early carnival. They, they made jewelry from animal teeth, from shells, there's an amazing discovery in Croatia, of of eagle talons that have been modified so that they could have been strung together to be worn as a as a bracelet or a necklace. This is Neandertals doing this stuff. And these are all the kinds of things that with that for a long time, people thought that only Homo sapiens did. And then there was there's the evidence for cave paintings and there's a there's a site in Gibraltar, a sort of late Neandertal cave site where they've kind of they've, they found a an engraved sort of hashtag symbol in the cave.
Art Woods 29:59
An early hashtag, yeah.
Kate Wong 30:04
So Neanderthals probably had language is what I'm trying to say.
Art Woods 30:08
But, you know, I guess I guess one question is, why did these sorts of decorations and paintings necessarily indicate language per se? Right? So you can think of other species that do lots of decorating, like, you know, bowerbirds, they have they do elaborate decorations of their nest, and yet they're not talking to each other. And so why does that necessarily indicate language?
Kate Wong 30:30
That's a good point. Um, I think, well, there's one way to sort of look at it. I mean, this example, I think, is a little more concrete, although it doesn't, it's, it's an example from early Homo sapiens. This was a, a cave painting that was discovered just last year, I believe, of a painting that that really, that shows a scene. So it shows some kind of part human part animal figures, and they look like they're hunting some local kind of wild, bovid, you know, cow-like animal. And there, you're getting the depiction of a story. Okay. And you're also seeing elements of fantasy, you know, with the the sort of animal human hybrid figures that are that are often in, in sort of modern recent societies, like religious figures. So that, you know, that's more explicit, I think there's a more explicit connection to, to language in that kind of discovery.
Marty Martin 31:40
So I want to shift gears just a little bit, and we have touched on it. But there's a there's a portion, talking about language, it's made me sort of want to ask you about this piece, Kate. Because when I first started learning about human evolution, besides language, the thing that was always put forward as this is what differentiates humans is tool use. And probably one of the biggest things that I've learned in the ensuing 25, 30 years has been yeah, not so much. We have Lars Chittka, he's going to be our first guest, or has been depending on people that are listening to this, who's done an enormous amount of work with tool use in insects. And then of course, we've got lots and lots of tool use for a lot of different species. But in some of the things that you've written, one of the totally new things about tool use that I didn't know is how old they are in our ancestors. I mean, it was well before right, there's evidence now that well before Homo sapiens used tools, other hominids, were using tools. Do you want to tell us something about that?
Kate Wong 32:37
Sure. So I mean, for a long time, you know, there was this idea that the tools are basically a defining trait of our branch of the family tree, Homo, our genus. And it you know, it was kind of how, how people explained our success, and we talked a little bit earlier about when we had Homo and this other really different genus of hominin called Paranthropus around at the same time, Paranthropus, kind of, you know, this is at a time when, you know, the climate and environment are changing pretty dramatically in Africa, to drier conditions. And so, you know, as, as that happened, Paranthropus evolves this sort of package of traits in its skull and jaws that make it really good at eating really tough foods, whereas Homo seems to go in a different direction, and, you know, pursue a really broad diet, including meat, and that as part of its strategy for doing that, not intentionally, but this is just kind of how its, its trajectory goes, it develops tools that allow it to, you know, capture and process animals and, and, you know, butcher them for food. That's sort of the simple take on it. But then there comes out of the blue, this discovery a few years ago, from a place called Lomekwi, in Kenya. And it's on the western shores of Lake Turkana where people have been looking for hominin fossils for a long time and have made several discoveries. And this team goes out there, they're trying to go back to one of their old sites, or a site that that was already kind of on their on their radar that they wanted to explore. They take a wrong turn, they kind of get lost. They decide, well, this kind of looks interesting, like the kind of place that maybe could have something interesting, let's get out and survey. And they start finding tools, and the tools seem like they're coming out of deposits that are really old. And you know, then they undertake more prospecting, and they start taking geological samples, they tried, they all, to start trying to work together work out, you know, where in the sort of layer cake of rocks, in this area, the tools are, are coming from how old those layers are. And ultimately, they determined that the tools are about a little more than 3.3 million years old. So previously, it's a little over 2 million. And, and it's all, every tool that you find is associated with with Homo. And now you've got them back as far as you know, 3.3, 3 million, at Lomekwi. And when you're at that depth of time, that's way older than any evidence for the genus Homo. That puts us into the realm of Australopithecus, things like Lucy, for example, but some some other sort of Australopithecine species. And those are those are different creatures from us, those are, their, their body proportions are different, much more ape-like they have brains that are a third of the size of our own. And, you know, definitely smaller, still smaller than then the earliest members of of our own genus, Homo. And it shifts it back to a time where we don't really know yet exactly what's going on climate-wise, but it doesn't, it's not, you know, part of the sort of drying trend that was thought to be driving tool evolution in the genus Homo. So it just kind of explodes everything that people thought they knew about the origin of tools and how it affected hominin evolution.
Marty Martin 36:51
S, so Kate, I mean, to back back to the reason that I was asking the question, I mean, what does this say about the role of tools in the sort of specialness and the origins of Homo sapiens in particular? There's a really neat part of your article that, maybe if you can relate these two things would be useful. You talk about the difference between low and high fidelity behavioral transmission. And so is it something about the diff, it's not just a mechanical difficulty, as we've been talking about of making the tools, it's the you know, how well you can pass on the, you know, the best the best made tool? Were Homo sapiens better at that part? Or what's the current thinking?
Kate Wong 37:31
Yeah, that's a really good question. I mean, so a couple things. I think, as we get farther back in time, and we and we see, okay, well, in at least one place at 3.3 plus million years ago, hominins are making stone tools. Okay. So now, that probably means we need to be looking, archaeologists need to be looking a lot more, you know, in deposits that are that old to see, whether they find more of this. If they find more of it, that might suggest one thing, if they aren't finding a lot of it, that maybe suggests that this is a sort of ephemeral behavior. It's not something that sticks and becomes integral to the survival of hominins at that point in time. It's, it's an experiment. And, and that could be for any number of reasons, maybe it just isn't helping them out that much. Or maybe they just don't have as an effective means of transmitting those those behaviors to their next generation. You know, one of the things that some archaeologists have talked about is that, you know, when, you know, to learn how to make a stone tool, you you really need someone to show you. It's kind of a.
Art Woods 38:48
You don't just stumble onto it, yeah.
Kate Wong 38:49
You don't just like go out in the yard and like start smashing rocks together and then like, create a beautiful like, stone knife. And one of the things that makes it easier to be taught how to make a sophisticated stone tool is language. Somebody telling you, not just showing you, like showing is, that's important, but also being able to tell you and correct you. And then to have you know, a hominin that is, you know, living in a probably a bigger social group, and that has survival of, you know, overlapping generations for a period of time, there's been really interesting work done showing that, you know, Homo sapiens is kind of unique in having a lifespan that allows us to kind of overlap with our grandparents. And that can impact our ability to transmit skills across generations and retain, you know, somebody figures out a really awesome way to make a stone tool like that has a better chance of actually staying in the sort of knowledge ether of the the species. So yeah, that that sort of fidelity of transmission of of knowledge is really important.
Art Woods 40:16
Well, can we step back right here, and I want to think about these traits altogether that we've been talking about. So we've, we've identified a bunch of things about, you know, the origin and timing of different traits that we historically thought of as sort of exclusively a Homo trait. So big brains, language, tool use, sociality, art. If you think about the emergence of that complex of traits, there's the question of whether they all emerged together, or separately. And I think there's also an interesting question about what, what came first, and what potentially drove the evolution of the other traits? So, so what, what drove what?
Kate Wong 41:03
That's a really good question. And it's so hard to answer because I feel like at every turn, there's a chicken and egg situation, right? So I mean, so we know the brain is really energetically expensive, it consumes like 20% of your energy requirements, like it accounts for 20% of them, which is disproportionate to how much it weighs, you know, compared to the rest of your body. So the fact that we have large brains, the fact that you see a trend toward large brains over the course of human evolution, and we go from having like a chimp-sized brain, which is like, you know, the size of a grapefruit to something three times that size. So having a large brain must have conferred some pretty significant advantages. And, and I think a lot of a lot of it boils down to giving us greater behavioral flexibility, you know, just just more of a buffer against the onslaught of hard times that that, that our species and our, and our lineage faced over millions of years. And I mean, I think, you know, there are a few different models for, for what sort of like, is driving this, you know, one of them is the social brain hypothesis. So this idea that, you know, that we need large brains, because our form of sociality is so complex, and we need to maintain our our vast social networks, another model sort of focuses on the environmental challenges of being able to find food and just kind of like, stay safe, suddenly that drove the evolution of large brains. And then there's this idea that cultural intelligence was the driving factor, you know, that, because, you know, we, we learn all of our sort of life skills socially, from other people, as opposed to having like most of our behaviors hardwired, like they are in other species. And that's that sort of need to acquire those skills, you know, to, you know, to, to go out and find enough food in the world to subsist on, and to learn those through social learning that maybe that was the driver. So you've got these models, I don't know. I mean, I think that they're not like mutually exclusive models, and that there's ways for like, all these things to kind of feed into it.
Art Woods 43:50
Yeah, and maybe my question, you know, is poorly posed, right? Maybe it's not like one thing drove the other, but that there was just sort of reciprocal relationships among all of these, all of these traits that were kind of self reinforcing over time.
Kate Wong 44:03
Yeah, I think that maybe is a little closer to my sort of read on it. You know, it's like, you know, if we try to ask the question, is brain evolution, like a cause or a consequence of something like language? You know, it's, I mean, it's really hard to unpack it. But if you see it as like, Tom Schuneman, who who's a sort of brain evolution expert, an American brain evolution expert, has kind of described it as like, you get an increase in brain size, and that paves the way for the evolution of language by allowing the brain to evolve different sort of regions that has specializations. And then it also, you know, paved the way for us to have like this more complex sociality and that that, like that, that sort of a heightened complexity of sociality, in turn, makes language a very useful thing to have. And so you know, that ultimately you have a scenario where the brain and language kind of like, coevolve and adapt to each other. And that that I mean, that makes sense to me. But you know, it's really, it's like I said, it's really tough, because because of all this chicken and egg business.
Art Woods 45:27
Sure. And lack of evidence.
Kate Wong 45:28
But you know, I think if you, lack of evidence, yeah.
Marty Martin 45:31
And difficulty to ever get evidence.
Kate Wong 45:33
Well, but there is one sort of thing that you can look at which I think is interesting, which is, at what point do we see hominins having potentially access to a diet that is high enough and quality by which I mean, like, provides enough calories to fuel our larger brain? Because it it can't be bigger if you can't, like, put the gas in the tank, right?
Marty Martin 45:59
Can't pay for it, right.
Art Woods 46:00
And by this, you mean like discovery of fire and sort of extensive use of fire to break down your food before you eat it?
Kate Wong 46:00
Yeah. So, you know, there's indications that, that that's happening, you know, like, around 2 million years ago, things are things are changing, and you're getting this, like an uptick in in brain size. And you're seeing that humans are exploiting more animal foods. There's an argument that Richard Wrangham at Harvard has put forth, which is that cooking becomes a thing that we do that makes, it gives us access to, to more calories from food, it kind of unlocks their potential a little bit more, you don't lose everything, to roughage. Yeah. Exactly. Exactly. Yep. So those are like fun ways of getting it that, just kind of trying to establish when in time we might have been able to pay for that bigger brain. But it doesn't, you know, can't tell you the whole story.
Art Woods 47:00
Yeah, sure.
Marty Martin 47:02
Okay, so everything that we've been talking to over the last few minutes in conjunction with some of the things that we discussed before, it's a little bit weird to me, because in one sense, we're sort of saying that this constellation of traits that rolls up under something called behavioral flexibility, is what probably had some value to allowing Homo sapiens to be so successful. And yet, we talked about 3.3 million year old tools, we talked about Neandertals with probably language, and definitely art. So are we really special? Or were we ridiculously lucky? Or both? What's the current consensus or what's Kate Wong's thoughts?
Kate Wong 47:44
There's never a consensus.
Marty Martin 47:47
Of course, not in science. It's what we do.
Kate Wong 47:51
I think it's, I think it's kind of both I mean, you know, it just seems to me, like, there's so many experiments happening over a really long period of time. And by the time you get to homosapiens, you've got the Neandertals, you've got Denisovans, you've got other creatures running around in different parts of the world. And some of them, we're not the only ones who are developing bigger brains and better technology and, you know, artistic expression, symbolic expression. And so, you know, what I've had several paleoanthropologists say to me, is, well, maybe Homo sapiens is just a little bit better, just it gets to that, you know, whatever that sort of line is, over which you become like, the most successful one. They just, they just get there faster. And, you know, and that, you know, that makes a certain amount of sense to me. But I think, you know, if we get back to this idea of, of African multiregionalism, and this idea of, of interbreeding, you know, Homo sapiens, in that sense, could be considered lucky, because, you know, they've got their circumstances in Africa that are kind of creating all sorts of opportunities to, for adaptation to a bunch of different kinds of circumstances. And then they they start spreading out of Africa, and they meet up with these other, these archaic humans that are already out in these other parts of the world. So the Neanderthals in Europe, the Denisovans in Asia, and probably other things that we don't even know about yet, other creatures. And we know that they were interbreeding right, because like we were saying at the beginning of the episode, we carry today people today carry DNA from, from ancient interbreeding between early Homo sapiens and Neanderthals and Denisovans, and other archaic humans. So maybe, you know, as Homo sapiens is moving out and interbreeding, they're actually picking up beneficial genes and potentially technology from these other humans that are already really well adapted to Europe in the case of Neanderthals in Asia, in the case of Denisovans. And that introduces, you know, very quickly into the Homo sapiens, gene pool, and into their behavioral repertoire, potentially, ways of being able to cope with this, this new world that they're entering. So they have the advantage, both of everything that they've kind of gleaned from their time in, in Africa, and this, this new sort of influx of genes and, and cultural practices when they get to the rest the world, and maybe that's the sort of magic combination that helps them succeed. Maybe we are, where we are today, the last hominins standing, because of those encounters with our archaic relatives.
Marty Martin 51:36
We wanted to talk briefly about your writing process? And just, you know, how did you get interested in this area broadly? And then how do you approach your choice of topics, I mean it must take an enormously long time to put together one of these articles, so I know that's not a lightly made decision.
Kate Wong 51:53
You know, when I was when I was in college, I started off on a on a pre-med track. And I really messed up. And at some point, you know, halfway into it, I was like, acing all of my biology classes and failing, literally failing chemistry and physics. And things got so bad that I actually got kicked out of school. And I looked at, you know, I had to, like, sit down and really kind of think hard about what to do. And I, I finally realized, like, I didn't really want to be a doctor, and I really did love biology, and there had to be something else I could do that was, you know, going to involve getting, doing a major in the stuff I really loved. And I realized I could get a degree in biological anthropology, and zoology, which were things I adored. And so I went back, I finished up, I got my degree in in that area. And when I was done, I was so in love with that, I thought, wow, maybe I want to do a PhD. Like that would be amazing. But that's going to be a pretty big commitment. So maybe I better think that through. And so I, you know, went and I had to get a job while I thought things through, and that job turned out to be as a fact checker and photo researcher at Scientific American 23 years ago, and, you know, a few months into that, I thought, gosh, I would really like to write about something, you know, like human origins-ish. And I'd heard that was a conference coming up the American Association of Physical Anthropologists. And I had always wanted to go to that as an undergraduate and never, never did. And I thought, well, why don't I go into that and see if I can find a story. And so I went, and I came back with a story on a Miocene ape called Morotopithecus. And I pitched it to the news editor and he said, okay, and I wrote it in my spare time, because that's not what they were paying me to do. I spent a month of nights and weekends like interviewing a thousand people and writing up so many notes, it's kind of crazy. I could have written a book about Morotopithecus. And by the end of it, you know, I had a little news story on it. And that was kind of the beginning. And I really, you know, that was, that's when the bug bit me. I was like, oh, like writing, which was a thing that I had always kind of been told I was good at, but didn't think I wanted to do anything with professionally, when I realized that I could actually do that and combine it with my interests my, you know, in this particular field of science, you know, that that's, that's the light went off, and, oh, I can do this. Yeah, yeah. And there wasn't anyone at the magazine covering that at that time, so I was able to kind of make a little niche for myself.
Art Woods 54:41
But how do you write your articles now? Like, what, what's the process and, you know, how extensive is it? How long does it take? What do you do?
Kate Wong 54:49
I mean, so the the first part is just finding something that I think is absolutely fascinating, and that's new and that I can convince my colleagues, you know, we should be doing a big article on. And then once that's kind of in the bag, then I go through the really fun part, which is the reporting and talking to lots of people, you know, sometimes getting to go and hang out in the field or visit a lab and like see them in action. And, you know, just gather all the string I can. And, and then, and then like, there's the hell phase that is fueled entirely by self loathing and involves lots of like, you know, procrasti-baking, and, like swearing and crying.
Art Woods 55:34
Put the brain nucleus to work, yeah.
Kate Wong 55:36
It's ugly. It's not a great process, my process, but you know, I mean, ultimately, I get there, so I guess it's okay. But it's kind of chaotic. And I, you know, I tend to be somebody who, I don't spend a lot of time like, on the front end, developing outlines and that kind of thing, I really just kind of get all the information, stew on it for a while and freak out that I'm not like writing anything. And then it all just kind of comes out. And I write it through, like, all the way through.
Art Woods 56:09
So just from, say, conception, conception of an article to the end, how long does it take?
Kate Wong 56:14
Well, it really depends. Sometimes I can do something really fast. You know, when I'm writing something for the print magazine, we're, you know, we're working, those deadlines are just, it's a different kind of schedule. So we tend to choose those stories pretty far out, it might be a year between when I propose it, and when it actually runs in the magazine. But you know, sometimes I'm writing stories that that are just for online or that would go online first, and then get put into the magazine. And those can be really fast turnaround. You know, that might be a week or two, that where I do those, so it really kind of depends, I really run the gamut.
Marty Martin 57:06
Human evolution isn't only about deep history. A 2010 study in the journal Science found evidence that a gene helpful for living at high altitudes spread rapidly since people colonized the Tibetan plateau in the last 3000 years.
Art Woods 57:17
And a 2006 study in Nature Genetics found that a mutation allowing adults to digest milk sugars swept through European populations starting about 7000 years ago.
Marty Martin 57:27
Radical changes of the past several 100 years in where we live, what we eat and how we interact with our surroundings means that human populations are still evolving.
Art Woods 57:39
Thanks for listening to this episode of Big Biology. If you love the podcast, we encourage you to make a donation to the show through our Patreon page patreon.com/bigbio, you can make a one time contribution at bigbiology.org.
Marty Martin 57:52
You can also help the podcast by telling your friends about us over social media. Tag us on your Twitter, Instagram or Facebook feeds.
Art Woods 57:58
On the next episode of Big Biology, we talk with Greta Binford, a biologist at Lewis and Clark College who studies the evolution of spider venoms.
Greta Binford 58:06
We basically started with the brown recluse and tried to walk our way out the tree of life to find the closest relatives that didn't have that toxin in their venom to try and figure out okay, you know, we know the brown recluse can cause these these types of damage when they bite, but not all spiders do, so somewhere in the history of spiders, there was this evolutionary event that turned on this toxin as a venom toxin.
Marty Martin 58:33
Thanks to Matt Bloise for producing this episode. Big Bio interns Ajinkya Dahake, Dana Baxter, Jordan Greer and Ruth Demree manage our social media accounts and help us produce the show. And thanks to Steve Lane as always for help with the website.
Art Woods 58:44
Thanks to the College of Public Health at the University of South Florida. The College of Humanities and Sciences at the University of Montana and the National Science Foundation for support.
Marty Martin 58:53
Music on this episode is from Podington Bear.