Jul 2, 2021 07:50 PM
(This post was last modified: Jul 3, 2021 01:46 PM by C C.)
https://nautil.us/issue/102/hidden-truth...mans-smart
INTRO: Talking to Jeremy DeSilva about human evolution was so fun. As was reading his recent book, First Steps: How Upright Walking Made Us Human. I learned something new and fascinating on every page. Do you picture our hominin ancestors as hunters? I did. Not so much. “They were the hunted,” DeSilva writes. Let’s take another look, as modern paleoanthropologists have, at the Taung child’s skull, one of paleontology’s most famous fossils, the remains of a child from the species, Australopithecus africanus, discovered in 1924. A reanalysis of the Taung child, DeSilva tells us, showed talon marks in its eye sockets. “A bird of prey, probably a crowned eagle, must have plucked the Taung child from the ground and carried it off to be eaten.” See, I told you. Fun!
I might summarize DeSilva’s book and our interview as, “Everything I thought I knew about why humans walk upright is wrong.” And DeSilva, a paleoanthropologist at Dartmouth College, is an insightful and genial guide. I told him I was moved by his admission in First Steps that “for the first few minutes of every visit with a new fossil, my calipers, camera, and scanner remain idle. I just sit, alone, with the remains of my ancestors.” He smiled. “I love fossils,” he said. “When I first sit with a batch of fossils, I think of them as individuals. I think, ‘Hey, a million years from now, if I’m lucky enough to be a fossil, and there’s some paleontologist standing over me, I hope they take a moment to think about me as an individual, and apply everything that they can possibly think of scientifically to squeeze information out of my bones, to retell the story of what my life was like.’ That’s what we do as paleoanthropologists.”
I began our interview by asking about the misperception that lingers to this day in his field and specialty.
What are the most popular wrong scientific explanations for why humans walk upright?
As new evidence is discovered, we always can change our minds, right? But one wrong idea that’s still with us—the basis of 2001: A Space Odyssey—is we were a violent species from the get-go and evolved bipedalism to free our hands for weaponry. It was based on a misinterpretation of fossils discovered at a site called Makapansgat in South Africa. The bones were supposedly butchered at the hands of Australopithecus. But it turns out they were remains that had been consumed by hyenas. There’s another popular idea that we evolved bipedalism to see over tall grass. But honestly, if you’re looking over tall grass and see a predator, the worst thing you could do is run away on two legs. We’re too slow. It would make sense that you run away on all fours, when you could gallop at twice the speed of a typical human, or not even a typical human, an exceptional human.
So even Usain Bolt would be toast?
Yes, he would. Even the fastest human being that we can possibly imagine, probably the fastest human who’s ever lived, is pathetically slow compared to your typical quadrupedal animal on an African savanna. Usain Bolt tops out at about 28 miles an hour. That’s half the speed of a galloping zebra or antelope or leopard or lion.
To me, the greatest revelation of your research is we didn’t evolve from hominins that walked on all fours. We evolved from ones who already walked upright.
This is a really hot topic in our field right now, and the field is divided on this, and I might be completely wrong; we’ll see as we find more fossils. But my interpretation from the key time periods when bipedalism was emerging, is that apes are not moving on their knuckles. They’re not adapted for life on the ground. Instead, they’re up in the trees, moving with hand-assisted bipedalism, much like an orangutan, gibbon, and siamang do now. We call them “lesser apes,” and they moved bipedally a lot. What’s interesting is the knuckle-walkers, gorillas and chimpanzees, don’t move bipedally very frequently.
We have fossils, mostly from Southern Europe, where apes appear to have a body posture that’s a little more upright. What’s fun is the possibility that knuckle-walking might actually be the more recently evolved locomotion. The image of a chimpanzee slowly turning into a human that we see on T-shirts and coffee cups and bumper stickers may not be how this all unfolded. It could very well be that the common ancestor was more upright, and that chimpanzees and gorillas evolved knuckle-walking independently.
That famous image is called “March of Progress.” Tell us about it.
“March of Progress” was an illustration done by a Russian artist, Rudolph Zallinger, in a 1965 Time-Life book called Early Man. It’s this beautiful foldout that shows ancient apes down on all fours, and it has them slowly rising up to modern humans. At the time, with the fossils we had, you could create a narrative like that. But in the last half century we’ve made so many amazing discoveries that show the human family tree is much more diverse. The pace of evolutionary change is quite different and it turns out that upright walking is the earliest of these evolutionary changes. The earliest bipeds on the ground were evolving from things that were upright to begin with in trees. Really all that happened was an ecological change. These hominins were living in environments that had fewer and fewer trees. To continue to get from point A to point B to get your fruit and other food resources, you already are pre-adapted for an upright posture and moving on two legs. In that case, bipedalism wouldn’t be a new locomotion, it’d be an old locomotion. It was just in a new setting on the ground, rather than in trees.
If bipedalism makes us slow, easy prey, why didn’t our ancestors go extinct? Why are we here?
It’s a great question. What are the advantages in freeing the hands? We could carry objects—food and babies. There are also thermo-regulatory adaptations. By being on two legs rather than four, you can disperse heat better. Maybe those things became factors that allowed us to survive.
What’s the most beneficially adaptive trait for early hominins to walk upright?
I don’t know. I would disagree with any characterization that said there was one reason. If there was one reason, we’d know it. It’d be obvious. In fact, bipedalism could have evolved independently in different hominins in Africa. With the fossils we have, there’s the tantalizing possibility that it didn’t just happen once... (MORE, rest of lengthy interview)
INTRO: Talking to Jeremy DeSilva about human evolution was so fun. As was reading his recent book, First Steps: How Upright Walking Made Us Human. I learned something new and fascinating on every page. Do you picture our hominin ancestors as hunters? I did. Not so much. “They were the hunted,” DeSilva writes. Let’s take another look, as modern paleoanthropologists have, at the Taung child’s skull, one of paleontology’s most famous fossils, the remains of a child from the species, Australopithecus africanus, discovered in 1924. A reanalysis of the Taung child, DeSilva tells us, showed talon marks in its eye sockets. “A bird of prey, probably a crowned eagle, must have plucked the Taung child from the ground and carried it off to be eaten.” See, I told you. Fun!
I might summarize DeSilva’s book and our interview as, “Everything I thought I knew about why humans walk upright is wrong.” And DeSilva, a paleoanthropologist at Dartmouth College, is an insightful and genial guide. I told him I was moved by his admission in First Steps that “for the first few minutes of every visit with a new fossil, my calipers, camera, and scanner remain idle. I just sit, alone, with the remains of my ancestors.” He smiled. “I love fossils,” he said. “When I first sit with a batch of fossils, I think of them as individuals. I think, ‘Hey, a million years from now, if I’m lucky enough to be a fossil, and there’s some paleontologist standing over me, I hope they take a moment to think about me as an individual, and apply everything that they can possibly think of scientifically to squeeze information out of my bones, to retell the story of what my life was like.’ That’s what we do as paleoanthropologists.”
I began our interview by asking about the misperception that lingers to this day in his field and specialty.
What are the most popular wrong scientific explanations for why humans walk upright?
As new evidence is discovered, we always can change our minds, right? But one wrong idea that’s still with us—the basis of 2001: A Space Odyssey—is we were a violent species from the get-go and evolved bipedalism to free our hands for weaponry. It was based on a misinterpretation of fossils discovered at a site called Makapansgat in South Africa. The bones were supposedly butchered at the hands of Australopithecus. But it turns out they were remains that had been consumed by hyenas. There’s another popular idea that we evolved bipedalism to see over tall grass. But honestly, if you’re looking over tall grass and see a predator, the worst thing you could do is run away on two legs. We’re too slow. It would make sense that you run away on all fours, when you could gallop at twice the speed of a typical human, or not even a typical human, an exceptional human.
So even Usain Bolt would be toast?
Yes, he would. Even the fastest human being that we can possibly imagine, probably the fastest human who’s ever lived, is pathetically slow compared to your typical quadrupedal animal on an African savanna. Usain Bolt tops out at about 28 miles an hour. That’s half the speed of a galloping zebra or antelope or leopard or lion.
To me, the greatest revelation of your research is we didn’t evolve from hominins that walked on all fours. We evolved from ones who already walked upright.
This is a really hot topic in our field right now, and the field is divided on this, and I might be completely wrong; we’ll see as we find more fossils. But my interpretation from the key time periods when bipedalism was emerging, is that apes are not moving on their knuckles. They’re not adapted for life on the ground. Instead, they’re up in the trees, moving with hand-assisted bipedalism, much like an orangutan, gibbon, and siamang do now. We call them “lesser apes,” and they moved bipedally a lot. What’s interesting is the knuckle-walkers, gorillas and chimpanzees, don’t move bipedally very frequently.
We have fossils, mostly from Southern Europe, where apes appear to have a body posture that’s a little more upright. What’s fun is the possibility that knuckle-walking might actually be the more recently evolved locomotion. The image of a chimpanzee slowly turning into a human that we see on T-shirts and coffee cups and bumper stickers may not be how this all unfolded. It could very well be that the common ancestor was more upright, and that chimpanzees and gorillas evolved knuckle-walking independently.
That famous image is called “March of Progress.” Tell us about it.
“March of Progress” was an illustration done by a Russian artist, Rudolph Zallinger, in a 1965 Time-Life book called Early Man. It’s this beautiful foldout that shows ancient apes down on all fours, and it has them slowly rising up to modern humans. At the time, with the fossils we had, you could create a narrative like that. But in the last half century we’ve made so many amazing discoveries that show the human family tree is much more diverse. The pace of evolutionary change is quite different and it turns out that upright walking is the earliest of these evolutionary changes. The earliest bipeds on the ground were evolving from things that were upright to begin with in trees. Really all that happened was an ecological change. These hominins were living in environments that had fewer and fewer trees. To continue to get from point A to point B to get your fruit and other food resources, you already are pre-adapted for an upright posture and moving on two legs. In that case, bipedalism wouldn’t be a new locomotion, it’d be an old locomotion. It was just in a new setting on the ground, rather than in trees.
If bipedalism makes us slow, easy prey, why didn’t our ancestors go extinct? Why are we here?
It’s a great question. What are the advantages in freeing the hands? We could carry objects—food and babies. There are also thermo-regulatory adaptations. By being on two legs rather than four, you can disperse heat better. Maybe those things became factors that allowed us to survive.
What’s the most beneficially adaptive trait for early hominins to walk upright?
I don’t know. I would disagree with any characterization that said there was one reason. If there was one reason, we’d know it. It’d be obvious. In fact, bipedalism could have evolved independently in different hominins in Africa. With the fossils we have, there’s the tantalizing possibility that it didn’t just happen once... (MORE, rest of lengthy interview)
