Chapter Content
Okay, so, like, picture this. About a million and a half years ago, some total, you know, rock star of an early human ancestor, and it was probably a woman, honestly, did something completely out of left field. She, like, picked up a rock and, like, really carefully started, you know, shaping another rock. And bam! She basically invented the teardrop hand axe. It was super primitive, yeah, but it was, like, the first advanced tool ever.
And, like, because it was way better than anything else around, pretty much everyone started copying her. They started making their own hand axes. I mean, seriously, it's like the only thing early humans were doing for a while. This guy, Ian Tattersall, he's a paleoanthropologist, right? He said, “They made, like, thousands of these things. You can literally walk around in parts of Africa and, like, trip over them.” He thinks it's kind of weird, because these axes took effort to make. So, basically they were making them just, like, for the heck of it.
So, Tattersall, in his, like, super bright office, he grabs this giant model off a shelf and shows it to me. It's huge, like, almost two feet long and maybe eight inches wide. Shaped, you know, kind of like an arrowhead, but, like, as big as a stepping stone. The model was fiberglass, only weighed a few ounces, but the real thing? The one they found in Tanzania? Weighed, like, twenty-five pounds. And, get this, Tattersall says, “It's completely useless as a tool.” It'd take two people just to lift it, and even then, you couldn’t, like, really hit anything with it.
I’m like, “So, what was it for then?”
And he just shrugs. He’s, like, clearly enjoying the mystery. He says, “I don't know, maybe it was symbolic. We can only guess.”
These hand axes, they're called Acheulean tools, named after Saint-Acheul in France, where they found the first ones. And that's to differentiate them from the older, simpler Oldowan tools. Now, the Oldowan stuff, they found those first in the Olduvai Gorge in Tanzania. You know, the textbooks used to show Oldowan tools as, like, these dull, rounded rocks you could hold in your hand. But these days, paleoanthropologists think they actually knocked flakes off bigger rocks to use for cutting.
So, here's where it gets interesting. When early modern humans, the ones who eventually became us, started leaving Africa, like, over a hundred thousand years ago, they loved these Acheulean tools. They were, like, the best things to bring along. These early *Homo sapiens* were super into them. They carried them all over the place, sometimes they even carried the rocks they hadn't even turned into tools yet, so they could make them later. They were seriously obsessed. But, like, even though they found these Acheulean tools all over Africa, Europe, the Middle East, Central Asia, they almost never find them in the Far East. It’s a total head-scratcher.
Back in the 1940s, this Harvard paleoanthropologist, Hallam Movius, he drew this line, the "Movius Line," that split the world into two: one area with Acheulean tools and one without. It runs southeast through Europe, the Middle East, down to around Calcutta and Bangladesh. Past that, so, basically, all of Southeast Asia, China, they only found older, simpler Oldowan tools. But we *know* humans went way past that area, so why did they just ditch their cool advanced stone tools right before they got to the Far East?
This Australian National University guy, Alan Thorne, he was like, “This bothered me for ages. The whole idea of modern anthropology is based on the idea that humans left Africa in two waves. First, *Homo erectus*, and, eventually, they became Java Man, Peking Man, you know, that kind of thing. Then, the later, more advanced *Homo sapiens* came along and replaced them.” But, he says, you can't, like, believe that and *also* believe that the *Homo sapiens* carried these modern tools all that way and then just, for some reason, threw them away. At the very least, he thinks it’s weird.
And it turns out there are a lot of other weird things. One of the weirdest happened in Australia, Alan Thorne's stomping ground. So, in 1968, this geologist named Jim Bowler was out in the middle of nowhere in New South Wales, looking around in this dried-up lake bed called Lake Mungo. And then, boom! He finds a human fossil just sticking out of the sand. At the time, people thought humans had only been in Australia for, like, eight thousand years max. But Lake Mungo dried up, like, twelve thousand years ago. So, what was someone doing out there?
Carbon dating shows that this fossil, the guy lived when Lake Mungo was still, like, a pretty nice place to live. A big lake, twenty kilometers long, full of fish, trees all around. And get this, the fossil was, like, twenty-three thousand years old. Then they found other fossils nearby that were, like, sixty thousand years old. It was completely out of the blue. I mean, Australia had been isolated since, like, forever. Anybody who got there had to go by sea, and they'd need a, you know, a decent-sized group to survive, and they had to cross a hundred kilometers of water, not knowing if there was even anything on the other side. And the Mungo people, they went from the north coast, where they probably landed, like, three thousand kilometers inland. A report from the Australian National Science Association, they said, this showed that “the first arrival must have been far earlier than sixty thousand years ago.”
So, how did they get there? Why did they go there? It's still a total mystery. Most of the books say there's no way people knew how to talk sixty thousand years ago, let alone work together to build boats and, you know, explore the ocean to find new places to live.
When I met Alan Thorne in Canberra, he said, “We just don't know nearly enough about prehistoric migration.” And he was like, “You know, when anthropologists first got to Papua New Guinea in the 19th century, they found people growing sweet potatoes way up in the highlands, some of the most remote places on Earth. Sweet potatoes came from South America. How did they get to Papua New Guinea? We have no idea. None whatsoever. But it's clear that people were moving around with confidence much earlier than we thought, and that they were almost certainly sharing not just genes, but information too.”
And as always, the problem is the fossil record. Thorne says, there just aren't that many places in the world where human remains can survive for long. He’s, you know, got these sharp eyes and a serious, but gentle, expression, and a grayish-white goatee. He says that, “If it weren't for the loads of fossils they found at Hadar and Olduvai in East Africa, we'd know almost nothing. Look at anywhere else, and we know almost nothing. There’s only one ancient human fossil they've found in the whole of India, and that's, like, three hundred thousand years old. Between Iraq and Vietnam, five thousand kilometers apart, there are only *two* fossils. One in India and a Neanderthal fossil they found in Uzbekistan.” He laughs and says, “There's just not much bloody stuff to study.” As a result, we've only got a couple of places with loads of fossils, like the East African Rift Valley and, then, Australia, like, Lake Mungo. And, between those two, there's almost nothing, so it's no wonder paleoanthropologists have a hard time putting the pieces together.
The traditional theory about how humans spread out, and most people in the field still believe this, is that there were two big waves into Eurasia. The first was *Homo erectus*, who, like, took off out of Africa incredibly fast. Pretty much as soon as they became a species. It started around two million years ago. They settled in different places, and these early *Homo erectus* evolved into their own thing. Like, Java Man and Peking Man in Asia, and the Heidelberg people, and then the Neanderthals in Europe.
Then, like, a hundred thousand years ago, this more skillful species, the ancestors of everyone alive today, they popped up on the African plains and started migrating, too, a second wave. The theory goes that these new *Homo sapiens* replaced their dimmer, less adaptable ancestors everywhere they went. But *how* they did it, nobody really agrees. There's no sign of, like, massacres, so most experts think that the later humans outcompeted the earlier ones, although other things might have played a role. Tattersall said, “Maybe we gave them smallpox. You really don't know. What's for sure is that we're here now, and they're not.”
And these first modern humans, we don’t know a whole lot about them. Which is funny, because we know less about ourselves than we do about almost any other branch on the human family tree. Tattersall says, “The most recent major event in human evolution, the appearance of our own species, is perhaps the most obscure.” Nobody's even sure where the earliest fossils of modern humans were found. A lot of books say it was the fossils from Klasies River Mouth in South Africa, from about a hundred and twenty thousand years ago. But not everyone agrees those were really modern humans. Tattersall and Schwartz, they think it’s, like, “Uncertain whether some, or all, of them represent our species.”
There's not really any arguing that *Homo sapiens* showed up first in the eastern Mediterranean, where Israel is today, somewhere around a hundred thousand years ago. But even *there*, Trinkaus and Shipman described them as, like, “fragmentary, poorly classifiable, and poorly known.” Neanderthals were already living there, using a tool called the Mousterian, which, apparently, the modern humans thought was pretty good. No Neanderthal fossils have ever been found in North Africa, but their tools are all over the place. Someone must have brought them there. And the modern humans are the only ones who could have done it. We also know that Neanderthals and modern humans lived alongside each other in the Middle East for, like, tens of thousands of years. Tattersall was saying, “We don’t know if they lived in the same place, or if they were just neighbors.” But the modern humans were happy to keep using Neanderthal tools. It’s just hard to say who had the upper hand. It's also strange that they've found Acheulean tools in the Middle East from a million years ago, but they only show up in Europe about three hundred thousand years ago. So, why didn't the people who knew how to make these tools bring them along?
For a long time, people thought that the Cro-Magnons, these early modern Europeans, pushed the Neanderthals to the western edge of the continent, and they either jumped into the sea or died out. But we know now that there were Cro-Magnons way out west *while* others were moving into the continent from the east. Tattersall says, “Europe was an empty place. They would hardly have run into each other, even when they were moving around.” One of the things that's confusing is that Europe was going through the Boutellier interglacial at the time, and the climate suddenly switched from relatively warm to another long, cold period. Whatever made the Cro-Magnons head to Europe, it wasn’t a warm climate.
Anyway, the idea that the Neanderthals were completely wiped out by the new Cro-Magnon competition, it doesn't quite match the evidence. Neanderthals were tough cookies. They lived for tens of thousands of years in environments that only a few Arctic scientists and explorers have ever experienced. During the worst parts of the Ice Age, blizzards and hurricane-force winds were common. The temperature often dropped to minus forty-five degrees Celsius, and polar bears wandered around in the valleys of southern England. The Neanderthals retreated during the worst periods. But even then, they had to deal with climates that were at least as bad as a Siberian winter today. They definitely had a hard time. Neanderthals were lucky to live past thirty, but as a species, they were adaptable and persistent. They survived for at least a hundred thousand years, maybe two hundred thousand, from Gibraltar to Uzbekistan. That's a huge success for any species.
Who they were, what they looked like, it's still a mystery. Up until the mid-20th century, everyone thought Neanderthals were, like, clumsy, hunched over, shuffling along, basically apes. And it was just an accident that made scientists rethink that. In 1947, this French-Algerian paleontologist named Camille Arambourg was out in the Sahara, taking a break under the wing of his light aircraft. While he was sitting there, a tire exploded because it was so hot, and the plane tilted and whacked him hard on the back of his neck. Later, he had an X-ray, and it turned out his spine was lined up just like a Neanderthal's, hunched and clumsy. Either he was physically similar to a caveman, or we were wrong about what Neanderthals looked like. It turns out it was the second one. The Neanderthal spine was completely different from an ape's. It changed everything about how we saw Neanderthals, but it, like, didn't last.
Even today, loads of people think Neanderthals were just not that bright, not as smart as the more flexible, bigger-brained *Homo sapiens* who came later. And then there's this argument, “Modern humans were able to beat this advantage [Neanderthal strength] with better clothes, better ways to light fires, and better shelters, while the Neanderthals were in a tough spot, needing more food to feed their big bodies.” So, in other words, the thing that helped them survive for a hundred thousand years suddenly became a disadvantage.
And what's important is that almost nobody ever deals with the fact that Neanderthal brains were noticeably *bigger* than modern human brains. They think Neanderthal brains were, like, 1.8 liters, and modern humans are more like 1.4 liters. It's a bigger difference than the difference between modern humans and late *Homo erectus*, who we don’t even really think of as human. The excuse is that, even though our brains were smaller, they were somehow more efficient. It’s pretty crazy because you don't really see that argument in any other case of human evolution.
So, you might be asking, if Neanderthals were so strong, so adaptable, and had bigger brains, then how come they're not around anymore? One answer, it’s definitely debated though, is, maybe they are. Alan Thorne is one of the biggest believers in the "multi-regional" hypothesis. The theory says that human evolution was a continuous process, *Australopithecus* evolving into *Homo habilis* and Heidelberg Man, then into Neanderthals, and then modern *Homo sapiens* coming from the older species. So, *Homo erectus* wasn't a separate species, but just a stage. So, modern Chinese people are descended from ancient Chinese *Homo erectus*, modern Europeans from ancient European *Homo erectus*, and so on. Thorne says, “As far as I'm concerned, there was no *Homo erectus*. I think the concept's gone. It seems to me *Homo erectus* was just an early stage of *Homo*. I think only one *Homo* species left Africa, and that was *Homo sapiens*.”
The people who are against this "multi-regional" idea, they just don't buy that ancient hominids evolved in a similar way all over the world, in Africa, China, Europe, the super remote Indonesian islands, and wherever else. Some people also think that the theory encourages racist ideas, which is what anthropologists have been trying to get rid of for ages.
Back in the early 1960s, Carleton Coon, a well-known anthropologist, he argued that some modern races had different origins, basically saying that some of us came from better stock than others. Which is an uncomfortable throwback to the old way of thinking, which was that some minority groups, like the African “Bushmen” (the San people), and Australian aborigines were just more primitive than other groups.
No matter what Carleton Coon really thought, a lot of people thought his theory meant that some people were born better, and some might even be completely different species. It’s a view that seems super awful today, but it was promoted in a lot of respectable places not too long ago. There's, like, this popular book, *The Epic of Man*, put out by Time-Life in 1961. It says this about the Rhodesian Man, that he “lived nearly 25,000 years ago and may have been an ancestor of the Negroes. His brain capacity approached that of *Homo sapiens*." So, in other words, the ancestors of black Africans only *approached* *Homo sapiens*.
Carleton Coon was really against, and I'm sure of this, his theory having any racist meanings. He thinks that all the back and forth exchange that’s happened between different cultures and areas proves that human evolution is one and the same. He says that, “There’s no reason to assume that humans only evolve in one direction, that humans migrated all over the world, and almost certainly mixed genes through interbreeding when they met. New people didn’t replace the natives, but they integrated into them, eventually becoming one.” And when explorers like Cook and Magellan first met people in remote areas, he said, “They didn’t meet different races, but only met members of the same race with somewhat different physical features.”
And Thorne says that the human fossil record that you can see is a smooth, constant change. There's this famous skeleton they found in Petralona in Greece, from about three hundred thousand years ago. He's kind of controversial because he seems to have features of *Homo erectus* and *Homo sapiens*. So what? We’re saying this is exactly what you'd expect to see in a species. They're evolving, not being replaced.
Something that would help solve the problem would be proof of interbreeding. But you can't really prove that one way or the other from fossils. In 1999, some Portuguese archaeologists found a skeleton of a four-year-old child who died twenty-four and a half thousand years ago. The skeleton was, overall, a modern human, but it had some features from earlier humans, maybe Neanderthals. The leg bones were super sturdy, the teeth stuck out a lot, and it had, though not everyone agrees on this, a jagged dip on the back of the skull, which is a Neanderthal thing. Erik Trinkaus at Washington University, he's a big expert on Neanderthals. He says this child was a hybrid. Proof of modern humans and Neanderthals interbreeding. Other people were confused that the Neanderthal and modern human features weren't mixed up enough on the child. As one critic pointed out, “If you look at a mule, it doesn’t look like a donkey from the front and a horse from the back.”
Ian Tattersall thinks the kid was just a "robust modern human child.” He admits there might have been a lot of "hybrids" between Neanderthals and modern humans, but he doesn't think they would have been able to have kids. [There's a possibility that Neanderthals and Cro-Magnons had different numbers of chromosomes, which often happens when species that are related, but not the same, mate. Like, horses have sixty-four chromosomes, and donkeys have sixty-two. You cross them, you get a mule with sixty-three, who can’t reproduce.]
He says, “I’ve never heard of two animals that are so different, and still the same species.”
Because the fossil record doesn't really help much, scientists are more and more turning to genetic research, particularly mitochondrial DNA. They found mitochondrial DNA in 1964, but in the 1980s, some scientists at Berkeley discovered that mitochondrial DNA had two things going for it that made it a good molecular clock. First, it only comes down the mother's side, so it doesn't get mixed up with the father's DNA. And second, it mutates about twenty times faster than regular DNA, which makes it easier to track. By tracking the mutations, you can figure out a person's genetic history, and how different genomes relate to each other.
In 1987, a team of Berkeley scientists led by Allan Wilson studied the mitochondrial DNA of one hundred and forty-seven people. They found that modern humans showed up in Africa over the last one hundred and forty thousand years. And that “everyone alive today is descended from that group." This was a major blow to the "multi-regional" theory. But, people took a closer look at the data. It turned out that the "Africans" in the study were actually African-Americans, whose genes had obviously gotten really mixed up in the last few hundred years. And people quickly doubted the assumed mutation rates.
By 1992, the study was mostly disproved, but the technology to analyze genes just kept getting better. In 1997, some scientists in Munich took DNA from the arm bone of a Neanderthal, and they looked at it. This time, the evidence was really convincing. The Munich researchers found that the Neanderthal DNA was different from any DNA ever found on Earth, which pretty much meant there wasn't any genetic connection between Neanderthals and modern humans. This was a real blow to the "multi-regional" theory.
Then, at the end of the year 2000, *Nature* and some other publications reported on a study by some Swedish scientists. They looked at the mitochondrial DNA of fifty-three people. They said that every modern human came from Africa within the last one hundred thousand years, and from a population no bigger than ten thousand people. Later, Eric Lander, the director of the Whitehead Institute at MIT, he said that modern Europeans, and maybe people in other places, descended from "just a few hundred Africans who left their homeland as recently as 25,000 years ago."
Modern humans have hardly any genetic variation at all. It says that we just didn't have enough time, or enough people, to develop a lot of genetic diversity, because we came from a small group of ancestors not long ago. Which seems like another big blow for the "multi-regional" theory. Researchers at Penn State told the *Washington Post* that, from then on, "People won’t pay much attention to the ‘multi-regional’ theory, because there's hardly any evidence for it.”
But, as all this was happening, the ancient people of Lake Mungo in New South Wales just kept giving information. In early 2001, Thorne and some colleagues said that they'd taken DNA from one of the oldest Mungo people, who had lived sixty-two thousand years ago. The research showed that this DNA "had unique genetic characteristics.”
According to the findings, the Mungo man was anatomically modern, but with an extinct genetic line. His mitochondrial DNA couldn't be found in living people, which it should have been if he were descended from the people who left Africa not too long ago.
Thorne says, “Once again, it turned everything upside down.”
Then, other weird exceptions started showing up. Rosalind Harding, a geneticist at the University of Oxford, she found two variations while studying hemoglobin genes in modern humans. These variations were common in Asians and Australian aborigines, but hardly existed in Africans. She's sure that the different genes came about two hundred thousand years ago, but not in Africa, in East Asia. That’s way before modern *Homo sapiens* even got there. The only possible explanation is that ancient hominids, like Java Man, are ancestors of modern Asians. And the same gene variation, a "Java Man gene," let's call it, also shows up in modern people in Oxfordshire in England.
I was a little confused, so I went to the University of Oxford to see Harding. Her office was in an old brick house. Harding was short, cheerful, and born in Brisbane in Australia. And she was serious, but also funny.
I asked her why people in Oxfordshire would have this hemoglobin gene that they shouldn't have. She smiles, then answers, “The genetic record mostly supports the ‘out of Africa’ hypothesis.” She says, “But you then find these exceptions that most geneticists don't want to mention. Even if we figure it all out, we need to get a whole load more information, but we haven't done that yet, we're just starting.” She just said that things were obviously complicated, and she didn't want to say anything about the ancient genes of Asians showing up in Oxfordshire. She says, “At this stage we can only say, it's very odd, but we really don't know why that's the case.”
This meeting was in early 2002. A scientist at Oxford, Bryan Sykes, had recently put out a popular book, *The Seven Daughters of Eve*. In the book, he says he could trace the ancestry of pretty much every European alive back to seven women. The women lived between forty-five thousand and ten thousand years ago. He even gave the women names, like Ursula, Xenia, Jasmine, and so on, and made up stories about their lives.
When I asked Harding about the book, she laughed and said, like, "I think you should give him some credit for trying to popularize obscure subjects.” She took a moment and then said, “There's a one in ten thousand chance that he's right." Then she laughed and then said, “Any single gene doesn't really say much. If you go up one line of mitochondrial DNA, it might take you to some place, Ursula, Jasmine, or anyone else. But if you pick any other line of mitochondrial DNA, and follow it, it might take you to a completely different place.”
I think it’s, like, taking any road out of London, and ending up way up in Scotland. So, you figure that everyone from London comes from northern Scotland. It's possible, but they could have come from hundreds of other places, too. Harding says that every gene is a different road, and we've just started to map them out. “No one gene reflects the whole picture,” she says.
So, does that mean genetic research can’t be trusted?
"Oh, you can generally trust those kinds of studies. What you can't trust is what people assume based on them."
She thinks that the "out of Africa" idea is, like, 95 percent right. But she says that, “I think it's unscientific for either side to stick to their guns like that. It's likely that things were never as simple as either side thinks. There's evidence that there were multiple human migrations and expansions in different directions in different parts of the world, and all these became part of the overall human gene pool. It's not going to be easy to sort them out."
There were also reports questioning the extraction of old DNA. One scholar said that he saw a paleontologist lick an ancient skull to see if it had been painted. And the article says, “In that process, loads of modern human DNA would have transferred to the skull." Which meant that the skull couldn't be studied anymore. I asked Harding about this. She said, “Oh yeah, it's almost certainly been contaminated. Just touching a bone contaminates it. Breathing on it contaminates it. The water in my lab contaminates it. We're surrounded by strange DNA. To get a good, clean sample, you have to dig them up in a sterile environment and test them right there. There's nothing harder to do than get samples that haven't been contaminated.”
So, should all these conclusions be doubted?
Harding nodded seriously and said, “Of course."
And if you want to know right away why we know so little about human origins, I can take you to a place. It's on the edge of the Ngong Hills in Kenya, southwest of Nairobi. If you drive east out of Nairobi, along the highway toward Uganda, and climb up a hill, you get this stunning view. You can see this never-ending green African plain.
This is the Great Rift Valley, stretching nearly three thousand miles. Africa's drifting away from Asia along that fault line. It's about forty miles from Nairobi, near the dry part of the valley. There's this old place called Olorgesailie. It used to be next to a giant lake. In 1919, after the lake had long dried up, a geologist named J.W. Gregory was looking for minerals there. He was walking across this open space when he saw these strange, black stones scattered on the ground, with obvious signs of being worked by humans. He'd found one of the most important sites for making Acheulean tools, that Ian Tattersall had told me about.
I got to visit this amazing place sort of by accident. I was in Kenya to check on some USAID projects, but my hosts knew I was gathering material for my book about human origins, so they added a visit to Olorgesailie to the schedule.
After Gregory the geologist found the place, nobody visited it for twenty years. Then a team led by Louis and Mary Leakey started digging there. They're still digging today. The Leakeys found an area of about forty thousand square meters where stone tools had been made for about a million years. From a million, two hundred thousand years ago to two hundred thousand years ago. Today, the area where the stones were made is covered by iron sheds and surrounded by fences to keep thieves away. Other than that, the stones are still where the makers left them, and where the Leakeys found them.
Gilani Angori, a great guy from the Kenya National Museum, was assigned to be my guide. He told me that there wasn't any of the quartz and obsidian that they used to make the hand axes. He said that the early humans had to carry the stones from there. He nodded toward two mountains on the other side of the valley, Olorgesailie and Ol Esakut. The mountains were about ten kilometers away. So that’s quite a distance to lug stones with your bare arms.
Of course, we have no idea why the early people of Olorgesailie went to all that trouble. They carried those heavy stones to the lakeside from far away, and what's even more incredible is how organized they were. The Leakeys found areas for making hand axes, and areas for sharpening them. In other words, Olorgesailie was a factory, that never stopped working for a million years.
The hand axes are pretty well made, and it took a lot of work to make them. Even a skilled person would spend hours making just one. And get this, nobody really knows what to use them for. For cutting, chopping, scraping, anything like that, it's not that useful. So it’s pretty weird that loads of early humans came to this place, and made loads of tools, for over a million years.
And who were those people? We don't know. We assume they were *Homo erectus*, because we don't know who else it could be. So, when things were good for them, these workers at Olorgesailie might have had brains like a modern baby. Even though they've been digging for over sixty years, they haven't found any human fossils at Olorgesailie or anywhere nearby. No matter how much time they spent making stones there, they went somewhere else to die.
Gilani Angori smiled and said, "All of this is a mystery.”
The people of Olorgesailie disappeared about two hundred thousand years ago, when the lake dried up, and the Great Rift Valley started getting as hot and tough as it is today. By that point, the Olorgesailie people were pretty much done. The world was about to see the first really dominant human species, *Homo sapiens*. And things would never be the same.