by Brian Switek
Even more perplexing was that Eoanthropus was in the wrong place to be a human ancestor. Latent racism made many anthropologists balk at the notion that our species had evolved in Africa, and many scientists believed that Asia was a more suitable place for our kind to have emerged. The American Museum of Natural History launched several expeditions to Mongolia during the 1920s to dig up evidence for this hypothesis, but all they found were ancient mammals and dinosaurs. A different team working in China had better luck.
In 1921, the Austrian paleontologist Otto Zdanksy, working with Swedish geologist John Gunnar Andersson, American paleontologist Walter Granger, and Canadian anatomist Davidson Black, discovered a humanlike tooth at Dragon Bone Hill in Zhoukoudian, China. It was not much to go on, but Black wrote a short communication to Nature suggesting that “man or a very closely related anthropoid [ape] did exist in eastern Asia” at the same time that Pithecanthropus lived in Indonesia. This tooth was matched by two others found in 1926, and Black used them to establish a new kind of fossil human at the site, Sinanthropus pekinensis, even though the rest of the skeleton proved elusive.
Three more years passed without further sign of Sinanthropus, but in November 1929 the team found a 130-foot-deep hollow they dubbed “Ape-Man Cave.” The onset of harsh winter weather forced many of the experts to end their field season, but Chinese scientist Pei Wenzhong and a few workers stayed on to fight the frozen ground for fossils. On December 2, their efforts were rewarded with the first “Peking Man” skullcap. It would not be the last. By 1937, numerous Sinanthropus bones had been recovered, including six low-domed and heavy-browed skulls. Some scientists, like Franz Weidenreich, thought the skeletons represented a type of human more primitive than Pithecanthropus, but more discoveries were needed to determine the exact relationship between the two.
Research halted when the Japanese army began its occupation of China. The looming prospect of war threatened the safety of the bones, and it was decided that the Sinanthropus fossils would be sent to the United States for safekeeping. In early December of 1941, the fragile cargo was readied for its journey and placed in the care of a group of American marines—but on December 7 war broke out between the United States and Japan when Japanese forces attacked the American naval base at Pearl Harbor, Hawaii. Military forces on both sides sprung into action, and the American soldiers charged with protecting the Sinanthropus bones were captured before they could leave China. What happened to their ancient cargo is unknown, and the precious collection of bones was never seen again.78
The loss of these relics was devastating, but by this time a neglected set of fossils from Africa would turn out to be even more important to understanding human origins. While teaching anatomy at the University of the Witwaters, and in Johannesburg, South Africa, in 1924, the Australian-born anatomist Raymond Dart told his students to keep a sharp eye out for interesting fossils. When his student Josephine Salmons told him she had spotted a fossil baboon skull in the living room of the director of the Northern Lime Company, Dart wondered if the nearby lime quarry might contain other rare fossils, and he arranged to have two crates worth of bone-bearing limestone that had already been excavated delivered to his home.
When the crates arrived, Dart was playing host to a friend’s wedding in which he was also filling the role of best man. He was supposed to be getting dressed, but the arrival of the fossils was just too exciting. He decided to at least have a peek before carrying out his duties. The first crate contained little of interest, just a few fossil turtles and miscellaneous bone fragments, but he was shocked by what he saw when he opened the second. When he took off the lid he saw the fossilized cast of a primate brain, and a large one at that, with the rest of the skull present in another chunk of rock. Dart was astonished; no one had ever found such a thing before.
With the groom plaintively tugging at this sleeve, Dart returned the fossils to their packaging and performed his ceremonial duties, but for him the wedding could not have ended soon enough. As soon as the last of the guests left he went back to have another look at the fossil. It was an extraordinary specimen, but Dart had few resources to help him prepare his treasure. He whittled away at the limestone with a hammer, chisel, and one of his wife’s knitting needles, and on December 23 the visage of the primate came into view.
The ancient face was flatter than expected for an ape, and it lacked the heavy brow ridges of the Neanderthals and Pithecanthropus. More surprising, though, was that the foramen magnum, the hole in the bottom of the skull through which the spinal cord exits, was oriented downward. In quadrupedal animals, like dogs, the foramen magnum is oriented backward, while in our species it is situated underneath so that the skull sits on top of the spinal column. The skull Dart was examining had an opening oriented further forward than that seen in chimpanzees, and this suggested that it had been a bipedal animal. Combined with the exceptionally large brain size, these features linked his fossil closely to our ancestry. Dart rushed a manuscript to Nature in which he named the fossil Australopithecus africanus, the “southern ape from Africa.”
Other physical anthropologists were not very impressed. Like Tyson’s “Pygmie,” juvenile apes were known to show similarities to human skeletons that disappeared as the apes aged. Many anthropologists felt that Dart had simply found a fossil ape that was of little relevance for human evolution. The general consensus of anthropologists was made clear when Dart brought his “Taung child” (named for the quarry from which it was found) to London to show the scientific elite. Following a well-received presentation on the discoveries at Dragon Bone Hill illustrated with lantern slides, Dart simply stood in front of his audience and spoke about the miniscule skull in his hand. He felt overwhelmed and underprepared, and he had failed to change the opinion of many of his colleagues that Australopithecus was a backwater genus of ape made irrelevant by the exciting work being done in Asia.79
Yet Dart had a strong ally in the Scottish paleontologist Robert Broom. While Dart returned to his specialty of neuroanatomy, Broom visited numerous South African caves and quarries in search of more Australopithecus fossils. He found them in abundance, including the skulls and brain casts of adults. This led Broom to name a number of new genera and species that were later absorbed into existing categories. Among the new fossils was a second, more robust type of australopithecine with massive jaws and crushing teeth he named Paranthropus robustus in 1938. These were impressive finds, but many experts still thought these creatures were just aberrant apes. They were not ancestral to humans, many anthropologists agreed, and so were only of passing interest.
Other fossil apes seemed to have more potential to fit into our pedigree. On Rusinga Island in Kenya’s Lake Victoria, the English anthropologist Arthur Hopwood found a fossil ape he named Proconsul in 1933. The next year, G. Edward Lewis announced another fossil ape, Ramapithecus, from the Siwalik Hills of India. These apes were old enough and generalized enough to possibly have given rise to the earliest humans, but there still remained a wide gap between them and Homo erectus (the new name for the “Sinanthropus” and “Pithecanthropus” fossils). Could the australopithecines of Dart and Broom have fit in the void between fossil human and fossil ape? Most of the pronouncements about them had been based upon casts and photographs, so when the Kenyan-born anthropologist Louis Leakey organized a conference on human prehistory in Nairobi in 1947, his English colleague W. E. Le Gros Clark took the opportunity to travel further afield to have a closer look at the “southern apes.”80
Armed with copious notes on ape anatomy Le Gros Clark examined the original australopithecine fossils and visited the sites where they had been found. He was certain that australopithecines were non-human apes when he arrived, but the evidence he saw forced him to reject this conclusion. Now it was “hardly possible to overemphasize their significance,” for their anatomy clearly showed that “there must be a real zoological relationship between the Australopithecinae and the Hominidae [humans].”
There were several f
eatures that strengthened this relationship between the australopithecines and humans. One important observation was that the end of the humerus (upper arm bone) of Paranthropus was not as flared and robust at the elbow joint as in chimpanzees. Instead, it resembled a human humerus and suggested that the australopithecines were probably not walking on their knuckles. This was confirmed by the orientation of a bone in the foot, the astragalus, which articulates with the leg to form the ankle joint. Its shape is a vital clue in determining posture, and the australopithecine astragalus more closely resembled the same bone in our skeleton than its counterpart in chimpanzees or gorillas. This matched the orientation of the end of the femur that formed the knee joint. It was directed inwards like ours—another trait associated with human bipedalism.
Combined with other similarities, these features allowed Le Gros Clark to demonstrate that the australopithecines were bipedal creatures more closely related to us than living apes, and he deemed them the “little modified survivors of the ancestral stock from which, at a still earlier date, the line of human evolution originated.” He wasted no time relaying these findings to the conference attendees in Kenya, and he reiterated his statements in print when he returned home to England. Many of his colleagues who had spurned the australopithecines, like Arthur Keith, changed their mind on the subject. Perhaps Africa held clues to our evolution, after all.
Le Gros Clark’s conclusions signaled a turning point in paleoanthropology and it was underscored by a lecture the vertebrate paleontologist G. G. Simpson delivered at the Cold Spring Harbor symposium on human origins in 1950. Despite their interest in evolutionary questions, he said, paleoanthropologists had largely ignored the development of the modern evolutionary synthesis. Many were still cooking up almost fanciful stories and appealing to internally driven mechanisms of evolution that other paleontologists, Simpson foremost among them, had cast out. Simpson’s criticisms cut deep, but they were essential to give paleoanthropologists a more solid evolutionary framework in which to interpret their finds.
The revitalization of paleoanthropology coupled with the intriguing discoveries made in Africa precipitated a conference on African hominids held in England in 1953. All the major extinct human fossils were discussed, save for one: Piltdown Man.
As discoveries were made elsewhere, the Piltdown fossils became more of an anomaly that did not fit in with the rest of the human evolutionary picture. This change perplexed one of the conference attendees, Joseph Weiner. Even though he found the idea repugnant, Weiner thought it possible that someone had planted the bones in the countryside gravel pits nearly half a century earlier. He reinvestigated what was known about the fossils, and the more he dug the more suspicious the evidence became. After expressing his concerns to colleagues W. E. Le Gros Clark and Kenneth Oakley, the three confirmed their fears: “Piltdown Man” was a hoax.81
As it turned out, Piltdown Man was a chimera. The jaw came from an ape and the skull was Homo sapiens, and the forgery extended beyond the “Eoanthropus” fossils alone. Nearly everything of scientific significance, from the stone tools to the bones of extinct mammals from the site, had been artificially manipulated and deposited.82
The Piltdown fiasco had given anthropology a black eye. No paleontologist had suspected that one of their own colleagues held such a capacity for deceit. Still, work carried on, and with the reputation of the australopithecines rehabilitated, Raymond Dart returned to paleoanthropology to paint a horrifying picture of our past. The depravity of our own species had been put on full display during World War II. For Dart, these were just echoes of the violent birth of humanity. Vast accumulations of battered bones in South African caves led Dart to think that australopithecines had an “osteodontokeratic” culture in which they used bones, teeth, and horns as tools to kill prey. Even more horrific was the prospect that the smashed skulls of some australopithecines represented the birth of our kind:The blood-bespattered, slaughter-gutted archives of human history from the earliest Sumerian records to the most recent atrocities of the Second World War accord with early universal cannibalism, with animal and human sacrificial practices or their substitutes in formalized religions and with the worldwide scalping, head-hunting, body-mutilating, and necrophilic practices of mankind in proclaiming this common bloodlust differentiator, this predaceous habit, this mark of Cain that separates man directly from his anthropoidal relatives and allies him directly with the deadliest of Carnivora.
The remains in the hollows were clues to ancient crime scenes where murderous man-apes clubbed each other to death and feasted on the flesh of the fallen. Blood flowed freely across the plains as australopithecines hunted not only game animals, but each other. Perhaps they even became the prey of later, more advanced hominids. Homo habilis, described in 1964 by Louis Leakey, Philip Tobias, and John Napier, was such a contender.
The story of Homo habilis actually began several years before, with the description of an entirely different kind of human. In the summer of 1959, Louis and Mary Leakey were searching Olduvai Gorge in Tanzania for early human fossils when Mary spotted the fragments of a skull weathering out of the hillside. They worked through August to collect all the pieces they could find, and as they picked over the site they found stone tools and the shattered bones of other mammals. For Louis, the implications of this association were clear. Whatever this human was, it had been a toolmaker that processed the carcasses of mammals for meat, and since it used tools it was most certainly ancestral to our own species.
Louis remained steadfast in this interpretation, even as the skull Mary pieced together did not look anything like one of our direct ancestors. The heavy brow ridge, low-domed skull, flaring cheek bones, and enormous teeth identified the human as a species of Paranthropus , similar to the humans Robert Broom had found in South Africa, but Louis could not accept this. He had a habit of thinking of his fossils as true ancestors of Homo sapiens and those of everyone else as dead-end side branches less relevant to our ancestry. He asserted that there were subtle differences between his new fossil and Paranthropus that placed it closer to our ancestry, and he decided to name it Zinjanthropus boisei (though he informally called it the “Dear Boy”).
FIGURE 90 - The skull of Paranthropus boisei recovered by Louis and Mary Leakey at Olduvai Gorge.
This identification created some new problems. At the time of its discovery it was thought that the deposits from which the skull came were only 600,000 years old, which would make “Zinj” a creature of the ice age. (Repeated testing with absolute dating techniques would later show that the skull was about 1.75 million years old.) This was not very much time for something as distinct as Zinj to evolve into Homo sapiens, so Leakey had to come up with a way to speed up the evolutionary process to span the gap. The stone tools seemed to point at an adequate solution. In a lecture given to the South African Archaeological Society in 1960, he proposed that the use of stone tools had greatly accelerated the evolution of something like Zinj into us. We had domesticated ourselves in less than 400,000 years.
Leakey abandoned this view almost as quickly as he had proposed it. That same year, his son Richard and his wife, Mary, began to find bones from a prehistoric human that was anatomically more similar to us than Zinj was. Louis quickly became convinced that these fossils were the remains of the true toolmakers, perhaps the earliest members of Homo yet found, and he kicked Zinj off to a sidebranch. (It was later grouped with the robust australopithecines as Paranthropus boisei.) Yet he could not publicly state his new opinions. The discovery of the “Dear Boy” had brought with it fame and fortune, and if he quickly shifted his ideas again his impetuous nature would again embarrass him. Instead he waited for more evidence, but by 1963 he was itching to announce the new humans to the world.
If the job of describing the fossils sat with Louis alone, he could have published them, but he had brought in Philip Tobias and John Napier to help with the description. Tobias, in particular, thought the bones were from some kind of australopithecine, not, as
Leakey thought, an early member of the genus Homo, but Leaky eventually convinced him otherwise. Though cultural evidence was not technically acceptable in determining the relationship of fossil humans, Louis, at least, was certain that any human that made tools had to be ancestral to us, and so in 1964 the three published the description of the earliest known member of our genus, Homo habilis. The fact that it was found at Olduvai with Zinj had chilling implications. The human that had once been heralded as our proud, tool-making ancestor was now an unfortunate victim of our early relatives:While it is possible that Zinjanthropus and Homo habilis both made stone tools, it is probably that the latter was the more advanced tool maker and that the Zinjanthropus skull represents an intruder (or a victim) on a Homo habilis living site.
But were humans really such savage competitors in the “struggle for existence”? Although popularized in books like Robert Ardrey’s African Genesis and the introduction to the film 2001: A Space Odyssey, Dart’s “blood-bespattered” view of our origins was so ludicrously graphic that it failed to gain traction among other paleoanthropologists. Still, it was not far from the consensus that meat eating, tool using, and hunting were what made us human. These were the traits that had allowed our ancestors to rise above the apes. Indeed, the tool making and inferred carnivorous habits of Homo habilis fit well within the “Man the Hunter” model of human origins. The acquisition of meat not only provided protein for brain expansion, but it provided selective advantages for hominids to work cooperatively and make increasingly advanced weaponry. As Sherwood Washburn and C. S. Lancaster wrote in a paper presented, appropriately enough, at the “Man the Hunter” conference in 1966, “In a very real sense our intellect, interests, emotions, and basic social life—all are evolutionary products of the success of the hunting adaptation.”
