Chapter Content
**Chapter 42: Footprints in Time**
In the period leading up to Christmas of 1887, a young Dutch physician with a decidedly un-Dutch surname, Eugène Dubois, set sail for Sumatra in the Dutch East Indies. His quest: to unearth the fossilized remains of the earliest humans to have walked the Earth. (Note: Despite his Dutch nationality, Dubois was born in the small town of Eijsden, nestled on the border of the French-speaking region of Belgium.)
Several factors made Dubois' undertaking remarkably unconventional. Firstly, no one had previously embarked on a deliberate hunt for the bones of ancient humans. Prior discoveries had been purely accidental, and Dubois, with his training as an anatomist, seemed an unlikely candidate to spearhead such a global endeavor. He lacked any real background in paleontology. Furthermore, there was no compelling reason to suspect the presence of early human fossils in the East Indies. Logically, the search for such remains should have focused on the vast continents, cradles of ancient human activity, rather than the relatively contained archipelago. Dubois was driven to the East Indies by a mix of intuition, the prospect of securing employment, and the prevalence of caves in Sumatra – the very environments where most significant hominid fossils had been unearthed to date. What defied all expectation was that he actually located what he sought. It was nothing short of miraculous.
By the time Dubois conceived his plan to find the missing link between apes and humans, the known fossil record of humankind was sparse: five incomplete Neanderthal skeletons, a small, dubiously sourced jawbone, and six Cro-Magnon skeletons from the Ice Age, freshly unearthed by railway workers in a cave near Les Eyzies, France. The most complete of the Neanderthal remains, later placed on a shelf in London, languished in obscurity. Its survival was a marvel, considering it had been blasted out of rock in a Gibraltar quarry by workers in 1848; alas, no one at the time recognized its importance. It received a cursory mention at a meeting of the Gibraltar Scientific Society, then was dispatched to the Hunterian Museum in London, where it gathered dust for over half a century, only occasionally being wiped down. It wasn't until 1907 that it underwent its first formal description by William Sollas, a geologist with "only the sketchiest qualifications in anatomy."
Thus, the Neander Valley in Germany inadvertently became the birthplace and namesake of the first identified early human fossils – an odd coincidence given that “Neander” loosely translates to “new man” in ancient Greek. In 1856, workers in another quarry along the Düssel River unearthed some peculiar bones. Recognizing his interest in all things natural, they presented them to the local schoolteacher. To his credit, Johann Carl Fuhlrott realized he might have discovered a novel form of humanity, but the nature and significance of this discovery would be debated for years to come.
Many refused to accept the Neanderthal remains as fossils of ancient humans. The influential Professor August Mayer of Bonn University proposed they were the remains of a Mongolian Cossack soldier who, wounded during the fighting in Germany in 1814, had crawled into the cave to die. Responding to this, the British T.H. Huxley sarcastically noted that the soldier must have been remarkably agile to climb a 60-foot cliff while gravely injured, then strip off his clothes, discard all his personal belongings, seal the cave entrance, and bury himself under two feet of soil. Another anthropologist, after extensive study of Neanderthal brow ridges, suggested they resulted from prolonged frowning caused by a poorly healed forearm fracture. (In their eagerness to dismiss evidence of early humans, authorities often readily embraced improbable scenarios. Around the time Dubois departed for Sumatra, a skeleton was found near Périgueux and confidently declared to be an Eskimo fossil. The question of what an ancient Eskimo was doing in southwestern France remained conveniently unanswered. It was, in fact, an early Cro-Magnon.)
It was against this backdrop of skepticism and nascent knowledge that Dubois embarked on his quest for ancient human fossils. He did not, however, wield the pickaxe himself. Instead, he employed 50 convicts, loaned to him by the Dutch authorities. These men toiled first in Sumatra for a year before being transferred to Java. It was there, in 1891, that Dubois – or rather, his team, as he rarely visited the site – unearthed a small fragment of an ancient human skull, now known as the Trinil skullcap. Though incomplete, it revealed a braincase significantly larger than that of any ape, yet lacking the pronounced features of modern humans. Dubois christened his find *Pithecanthropus erectus* (later renamed *Homo erectus* for technical reasons), proclaiming it the missing link between ape and man. He soon became known as Java Man. Today we call him *Homo erectus*.
The following year, Dubois' workers discovered an almost complete femur, strikingly similar to that of modern humans. Indeed, many anthropologists argued it was a modern human bone, unrelated to Java Man. Even as a *Homo erectus* bone, it didn't match others discovered. Dubois deduced – correctly, as it turned out – that apes walked upright. Based on a mere skullcap and a tooth, Dubois even constructed a full skull model, which proved remarkably accurate.
Dubois returned to Europe in 1895, expecting a hero's welcome. He received the near opposite. Most scientists rejected his conclusions and disliked his aloof demeanor. They considered the skullcap apelike, possibly belonging to a gibbon, and certainly not an early human. In 1897, he enlisted the support of Gustav Schwalbe, a respected anatomist at the University of Strasbourg, to create a skull model to bolster his case. Schwalbe's subsequent publication garnered far more support and attention than anything Dubois had produced. Schwalbe even embarked on a series of well-received lectures, as if he himself had made the discovery. Consumed by resentment and bitterness, Dubois retreated to a mundane post as a geology professor at the University of Amsterdam, where, for the next two decades, he barred anyone from examining his prized fossils. He died in 1940, a disappointed man.
Meanwhile, on the opposite side of the world, Raymond Dart, the Australian-born head of anatomy at the University of Witwatersrand in Johannesburg, South Africa, received in 1924 a remarkably complete child's skull, complete with face, jaw, and an endocast – a natural brain cast. It had been unearthed from a limestone quarry at Taung, on the edge of the Kalahari Desert. Dart immediately recognized that this was not a *Homo erectus* like Dubois' Java Man, but a more apelike ancestor. He estimated its age at around two million years and named it *Australopithecus africanus*, or "southern ape of Africa." In his report published in *Nature*, Dart claimed the Taung fossil bore "striking resemblances to man" and suggested a new family be established for his find: the Hominidae ("man-ape" family).
Dart faced even more resistance from the establishment than Dubois had. Almost everything about Dart's theory – indeed, almost everything about Dart himself – seemed to displease them. He had, firstly, conducted the analysis himself, without seeking the guidance of more seasoned experts, betraying a lack of deference. Even the name he had chosen for the fossil, *Australopithecus* – a hybrid of Greek and Latin roots – revealed his academic shortcomings. Most damagingly, his ideas ran counter to prevailing theories. It was universally believed that humans and apes had diverged at least 15 million years ago in Asia. If humans had originated in Africa, heaven forbid, would that not make us all, essentially, Negroes? It was akin to a present-day office worker claiming to have discovered the fossil of a human ancestor in, say, Missouri. It simply did not fit with established knowledge.
Dart's sole notable supporter was Robert Broom, a brilliant but eccentric Scottish physician and paleontologist. Broom, for example, had a habit of conducting fieldwork stark naked when the weather was warm, which it often was. He was also known to have performed questionable anatomical experiments on poor and docile patients, burying their bodies – which sometimes resulted from his experiments – in his backyard for later study.
Broom, as an accomplished paleontologist residing in South Africa, had the opportunity to examine the Taung skull firsthand. He immediately recognized its significance, championed Dart's cause relentlessly, but to little avail. For the next 50 years, the consensus remained that the Taung child was nothing more than an ape. Most textbooks didn't even mention it. Dart spent five years writing a paper on his find but could find no publisher. Eventually, he gave up on seeking publication (though he continued his fossil hunting). The skull – today considered one of anthropology's most precious artifacts – served as a paperweight on a colleague's desk for years.
By 1924, when Dart announced his discovery, only four types of ancient humans were known: Heidelberg Man, Rhodesian Man, Neanderthal, and Dubois' Java Man – but this was about to change dramatically.
First, in China, Davidson Black, a Canadian amateur archaeologist, began excavations at a site known as Dragon Bone Hill. The hill was known locally for its ancient fossils. Unfortunately, locals weren't preserving the fossils for scientific study, but grinding them into powder for medicinal purposes. We can only speculate how many priceless *Homo erectus* fossils were consumed by locals as ingredients in Chinese medicine. By the time Black arrived, the site was already heavily depleted, but he still discovered a molar. From this, he astutely concluded that he had discovered a new type of fossil human: *Sinanthropus pekinensis*, soon known as Peking Man.
At Black's urging, more sustained excavations were conducted, yielding numerous other fossils. Sadly, these were lost on the day after the attack on Pearl Harbor in 1941. As a U.S. Marine detachment attempted to evacuate the fossils from China, they were intercepted and detained by Japanese soldiers. Inspecting the boxes, the soldiers found nothing but bones. They left them by the roadside, and they have never been seen since.
Meanwhile, back at the same sites in Java where Dubois had found Java Man, an expedition led by Ralph von Koenigswald discovered another group of early human fossils along the Solo River in the Ngandong region, later named Solo Man after their findspot. Koenigswald's discovery could have been even more significant had he not made a tactical error. He had promised the locals 10 cents for every human fossil discovered. To his horror, he discovered they were smashing larger fossils into smaller pieces to maximize their earnings.
In subsequent years, as more and more fossils were unearthed and identified, a proliferation of new names emerged: Aurignacian, *Australopithecus transvaalensis*, *Paranthropus robustus*, *Australopithecus boisei*, and dozens of others, each seemingly warranting a new genus or species. By the 1950s, over 100 hominid names had been assigned. To add to the chaos, many names were subsequently reassigned a succession of others as paleoanthropologists refined, revised, and endlessly debated the classifications. Solo Man, for instance, was variously classified as *Homo soloensis*, *Javanthropus*, *Homo neanderthalensis soloensis*, *Homo sapiens soloensis*, *Homo erectus soloensis* – and eventually simply as *Homo erectus*.
In 1960, in an attempt to streamline the chaotic hominid nomenclature, Clark Howell of the University of Chicago, following suggestions made by Ernst Mayr and others over the preceding decade, proposed a reduction to two major genera – *Australopithecus* and *Homo* – and rationalized many of the species classifications. Java Man and Peking Man were both classified as *Homo erectus*. For a time, this classification enjoyed some popularity within the hominid community, but not for long. (Note: Humans are classified within the subfamily Homininae, whose members are traditionally called hominids, encompassing any animal, extinct or extant, more closely related to us than to chimpanzees. Apes and hominids together form the superfamily Hominoidea. Many authorities now believe chimpanzees, gorillas, and orangutans should also be included in this family, with humans and chimpanzees in a subfamily called Hominini. According to this view, all animals traditionally called hominids become hominoids. [Leakey and others support this.] Hominoidea is the superfamily name for apes, and includes us.)
After a decade or so of relative quiet, paleoanthropology entered a period of unparalleled discovery that continues unabated to this day. *Homo habilis*, discovered in the 1960s, was seen by some as filling a gap between ape and human, while others argued it was not a separate species at all. Then came (among many others) *Homo ergaster*, *Kenyanthropus platyops*, *Homo rudolfensis*, *Homo antecessor*, and the *Australopithecines* proliferated: *Australopithecus afarensis*, *Walkeri*, *Australopithecus anamensis*, *Australopithecus walkeri*, *Australopithecus lacustris*, etc. To date, nearly 20 documented species of hominids exist, but no two experts agree on which 20.
Some experts continued to follow Howell's 1960 two-genus system, while others singled out certain *Australopithecines*, placing them in the genus *Paranthropus*, and still others added the earlier genus *Ardipithecus*. Some classified *praegens* within *Australopithecus*, others within a new genus, *Praehomo*. Most, however, simply dismissed *praegens* as not being a separate species. No consensus authority emerged to arbitrate, and the only way a name became widely accepted was if no one objected, which was rare.
To a greater degree, the crux of the problem was the scarcity of evidence. A paradox, in a way. Over the history of humanity, billions of people (or near-people) have lived, each passing on slightly different genes. Yet, from this vast population, our understanding of prehistory hinges on the often fragmented remains of just 5,000 individuals. When I asked Ian Tattersall, a curator at the American Museum of Natural History in New York, how many hominid and early human fossils had been found in the world, the affable, bearded curator replied, "If you didn't mind having a dreadful mess, you could fit them all into the back of a pickup truck."
The scarcity would be less troublesome if the fossils were evenly distributed in time and space. They are not. They are found here and there, often tantalizingly out of reach. *Homo erectus* roamed the Earth for over a million years, ranging from the Atlantic coast of Europe to the Pacific coast of China, yet if you resurrected every *Homo erectus* found, they wouldn't fill a school bus. *Homo habilis* fossils are even rarer: two incomplete skeletons and a few scattered limb bones. Some events, lasting no longer than our own civilizations, are almost certainly beyond retrieval based solely on the fossil record.
To illustrate, Tattersall said, "In Europe, you find a hominid skull in Georgia dating back roughly 1.7 million years; then, at the other end of the continent in Spain, a fossil from nearly a million years later; then, in Germany, a Heidelberg Man fossil from 300,000 years after that. There's hardly any similarity between them." He smiled and added, "You're trying to reconstruct the whole history of humanity from these fragmented pieces. It's very difficult. We really know very little about how the various ancient species relate to each other – which ones evolved into us, which ones were evolutionary dead ends. Some probably shouldn't even be considered separate species."
The incompleteness of the record makes each new discovery appear abrupt, vastly different from all others: if myriad fossils were distributed evenly in time, subtle variations would become apparent. As the fossil record shows, all new species didn't simply spring into existence. The closer one gets to the demarcation points, the more apparent the similarities. Thus, distinguishing between late *Homo sapiens* and early *Homo erectus* is difficult, sometimes impossible, because they were so similar. Similar problems plague fragmented fossil identifications – for example, whether a bone belonged to a female *Australopithecus boisei* or a male *Homo habilis* is hard to determine.
The study of ancient human fossils is rife with such uncertainty that scientists must make assumptions based on other evidence found nearby, assumptions that are sometimes little more than wild guesses. As Alan Walker and Pat Shipman observed, with characteristic understatement, if you associate tools with the fossils often found nearby, you'd have to conclude that early toolmaking was largely the province of antelopes.
Perhaps the most puzzling phenomenon involves the contradictions found within the fragmented fossils of *Homo habilis*. In isolation, the *Homo habilis* fossils are meaningless. But when arranged in sequence, they reveal significant differences between males and females in terms of the speed and direction of evolution – with time, males became more distinct from apes, acquiring more human characteristics, whereas females seemed to evolve in the opposite direction, becoming more apelike. Some authorities argue that there's no reason to classify *Homo habilis* separately. Tattersall and his colleague Jeffrey Schwartz believe it belongs in the "wastebasket species" – a kind into which unrelated fossils can be haphazardly tossed. Even those who regard *Homo habilis* as a distinct species cannot agree on whether it is in the same genus as us or belongs to a different, long-vanished lineage.
Finally, perhaps the most important element in all this is the human factor. Scientists naturally lean towards interpreting their findings in ways that best secure their reputations. Few paleontologists, upon claiming to have found a set of bones, announce that their discovery is insignificant. As John Reader aptly noted in his book *Missing Links*, "Discoverers often interpret new evidence to confirm their preconceived ideas, which is of interest."
All of this certainly leaves ample room for argument, and no one loves argument more than paleoanthropologists. "Of all scientists, paleoanthropologists are perhaps the most self-aggrandizing," stated the authors of the recent book *Java Man*. One of its notable features is the lengthy, undisguised criticism of others, particularly former friends and colleagues, like Donald Johanson. A small segment is below:
While we were working together at the institute, he (Johanson) unfortunately contracted a habit of volatile and loud reprimands, at times accompanied by the dramatic throwing of books or whatever was at hand.
Therefore, please keep in mind that, regarding the history of prehistoric humanity, one can scarcely say that there is anything about which someone somewhere will not argue. The most we can say with any assurance about what we believe we know, who we are, and where we come from is this:
As biological entities, we shared a family tree with African chimpanzees for 99.99999% of history. We know almost nothing about prehistoric African chimpanzees, but whatever their situation, it was no different than our ancestors. Then, about seven million years ago, something decisive occurred. A new group of animals emerged from the African rainforest and started roaming the vast savanna.
The *Australopithecines* appeared. For over five million years, they were the dominant hominids on Earth. (Austral is derived from the Latin word for "southern," with no connection to Australia.) *Australopithecines* branched into several species, some slender like Raymond Dart's Taung child, others robust, but they were all capable of walking upright. Some of these species lasted for over a million years, others for only a few hundred thousand years. What must be understood is that even the shortest lived of these species had a history many times longer than our own.
The most famous hominid remains are the 3.18 million-year-old *Australopithecus afarensis* fossils discovered in 1974 by an archaeological team led by Donald Johanson in Hadar, Ethiopia. Its number is A.L. (meaning "Afar region") 288-1. Later, it was affectionately named Lucy, after a melodious song by The Beatles, "Lucy in the Sky with Diamonds." Johanson never doubted her importance. He said: "Our earliest ancestor. The missing link between ape and man."
Lucy was short – only a meter tall. She could walk, though how well is debated. She was clearly skilled at climbing. Other aspects of her are guesswork. Her skull was mostly gone, so it's hard to determine her brain capacity with certainty, but the remaining fragments suggest a small brain. Many books state that 40% of Lucy's skeleton was complete. Some state nearing 50%, a book by the American Museum of Natural History says two-thirds were complete, and the narration for the BBC television series *Ape Man* even stated "a complete skeleton." However, the image shown on television wasn't even close to this.
A person has 206 bones, but many are duplicates. If you have a left femur, you know the size of the right femur without looking for it. Remove all the duplicates and you are left with 120 bones – the so-called hemiskeleton. Even using this method, and even if the smallest fragments are counted as complete bones, Lucy was found to have 28% of her hemiskeleton (20% of a full skeleton).
In *Wisdom of the Bones*, Alan Walker recounts asking Johanson how he reached 40%. Johanson answered, with a smile, that he didn't include the 106 bones in her hands and feet. You might think that the bones in hands and feet make up almost half of the bones in the human skeleton, and they are a vital half, given that Lucy was Lucy because she used her hands and feet to cope with a changing world. In any case, for Lucy, our conjectures far outweigh our knowledge. In fact, we don't even know if she was a woman; her sex is surmised based only on her smaller frame.
Two years after Lucy's discovery, in Laetoli, Tanzania, Mary Leakey discovered what are thought to be footprints from the same family, left by two hominids. The footprints were left after a volcanic eruption, as the hominids walked through the muddy volcanic ash. The ash hardened, preserving their footprints for over 23 meters.
The American Museum of Natural History has a fascinating display documenting their passing. Life-size models show a man and a woman walking through the ancient African plains, shoulder to shoulder. Their entire bodies are hairy, and they are about the same height as chimpanzees. However, their facial expressions and gait are human. The model is touching because the man has his left arm around the woman's shoulder, guarding her. Such a kind gesture implies their close relationship.
The scene is so believable that it's easy to overlook that almost everything surrounding the footprints comes from imagination. All of the creatures' external features – hair length, facial features (how much did their noses resemble humans, and how much gorillas?), expressions, skin tone, the size and shape of the woman's breasts – are purely imagined. We can't even be certain if they were a couple. The woman may have actually been a child. We are also unsure whether they were *Australopithecines*. They are presumed to be *Australopithecines* because we don't know of any other candidates.
I was told that they were arranged that way because the female model kept falling over. However, Ian Tattersall insists, with a smile, that this isn't true. "We obviously don't know whether the man had his arm around the woman, but by measuring their footsteps, we can determine that they walked shoulder to shoulder. They were very close – close enough to touch each other. It was a very open space, so they were likely in danger, which is why we made them look a little worried."
I asked Tattersall if he met with any problems when he made the model, and attempted to gain people's approval. He answered, without hesitation, "You always meet with problems when you are recreating something. You might not believe how much discussion there was on details, such as whether the Neanderthals had eyebrows. The situation with the Laetoli statue is much the same. We don't really know what they looked like, but we can surmise their height, posture, and give reasonable guesses at their appearance. If I was recreating the model, I think I would make them look slightly more like apes. They weren't human, but bipedal apes."
Until recently, it was thought that we were descendents of Lucy and the Laetoli animals, but today many authorities aren't so certain. Although some physical characteristics (such as teeth) suggest a connection between *Australopithecines* and us, other aspects of the *Australopithecines*' anatomy tell a different story. Tattersall and Schwartz point out in *Extinct Humans* that the upper femur of humans is very similar to that of apes, but very different from the *Australopithecines*. If Lucy is in the direct lineage between ape and humans, it would mean that we had femurs similar to *Australopithecines* for one million years, and then reverted to the femur shape of apes as we evolved. They argue that, in fact, not only is Lucy not our ancestor, but she may not have even walked upright.
"Lucy and her relatives didn't walk like modern humans," Tattersall insists. "These hominids only walked on two feet when they had to travel between two trees. Due to the structure of their bones, they were ‘forced’ to do so." Johanson disagrees, writing "Given the traits in Lucy's hips and the formation of her pelvic muscles, she would have had as much trouble climbing as modern humans."
The matter grew even more confusing between 2001 and 2002, as four strange new fossils were unearthed. One, found near Lake Turkana in Kenya by Meave Leakey (whose family is renowned for finding fossils), was later dubbed *Kenyanthropus platyops* (Flat-Faced Man of Kenya). Living around the same time as Lucy, it raised the possibility that he was our ancestor and Lucy belonged to a species that died off. Also discovered in 2001 was *Ardipithecus ramidus kadabba*, who lived from 5.8 million to 5.2 million years ago, and *Orrorin tugenensis*, who may have lived 6 million years ago. The latter was the earliest hominid – but it only held this title for a short time. In the summer of 2002, a French archaeological team discovered a 7 million-year-old hominid, *Sahelanthropus tchadensis*, in the Djurab desert of Chad (an area where no ancient fossils had been found before). Some believe this isn't a hominid, but an early ape, and should be called *Sahelpithecus*. All of these animals are ancient and primitive, but could walk upright. They did so for much longer than previously thought.
Bipedalism was a risky, skilled transition. It meant altering the construction of the pelvis so that it could bear the entire weight of the body. In order to keep the body as strong as possible, the female birth canal had to be relatively narrow. This had three results, two of which were quickly apparent, and one that would be apparent later. Firstly, it meant that childbirth became more painful and that the likelihood of death for both mother and infant was greater. Secondly, in order to make their way through the narrow birth canal, infants had to be born with smaller brains. Therefore, infants needed parental care from birth. This meant that their upbringing took longer, which implied that relationships between men and women had to be strong.
This is a major issue even today, when humans are the most intellectually advanced creatures on the planet. To short, vulnerable *Australopithecines*, giving birth to a baby with a brain about the size of a clementine (Note: Certainly, the absolute size of the brain does not say everything – maybe not even a lot. The brains of elephants and whales are larger than our own, but you are clearly smarter than they are. The size of the brain is relatively important, often not important at all. As Gould pointed out, the brain of *Australopithecus africanus* was 450 cubic centimeters, smaller than a gorilla. A typical *Australopithecus africanus* weighed less than 45kg, with females weighing even less, while gorillas weigh 150+ kg) would have been very dangerous.
Why, then, did Lucy and her relatives leave the trees and venture into the African jungle? They likely had no choice. The slow rising of the Isthmus of Panama blocked Pacific sea water from entering the Atlantic. The change altered the northward direction of warm currents, creating very cold ice ages in northern latitudes. In Africa, seasonal dryness and cold caused forests to turn into grasslands. "It's not that Lucy and her relatives left the forest," John Gribbin wrote. "The forest left them."
But walking into the open savanna clearly exposed early hominids. Hominids standing upright could see more clearly, but were also seen more easily. As a species, we are almost absurdly vulnerable in the wild. Almost every large animal we can name is stronger, faster, and has sharper teeth than we do. In the face of attack, modern humans have two advantages. We have a well-developed brain that can come up with solutions, and we have hands that are skilled at throwing or brandishing deadly objects. We are the only animal capable of killing an enemy from a distance, and therefore are the only animal that isn't afraid of attack.
Every factor seemed to favor the quick evolution of the brain, but this didn't happen. For over three million years, Lucy and her fellow *Australopithecines* barely changed at all. The size of their brains didn't increase, and there isn't any evidence that they used even the simplest tools. Even stranger, we now know that other hominids who lived with them for almost a million years used tools, while *Australopithecines* never used the technology around them.
Sometime between three and two million years ago, an estimated six groups of hominids coexisted in Africa. Only one of them was destined to survive, *Homo*. Their origin is uncertain, but they originated roughly two million years ago. No one is entirely sure what the relationship was between the *Australopithecines* and *Homo*, other than they lived together for almost a million years. Then, roughly a million years ago, all of the *Australopithecines*, both robust and slender, mysteriously, or perhaps suddenly, vanished. No one is sure why. "Perhaps," Matt Ridley said, "we ate them."
It is generally thought that *Homo* started with *Homo habilis*, an animal about which we know almost nothing. *Homo habilis* eventually evolved into *Homo sapiens* (literally "thinking man"). There are another six *Homo* in between, depending on whose opinion you value: *Homo ergaster*, Neanderthal, *Homo rudolfensis*, *Homo heidelbergensis*, *Homo erectus*, and *Homo antecessor*.
*Homo habilis* ("skilled man") was named by Louis Leakey and his colleagues in 1964. The reason for this name was because he was the first hominid to use tools, however simple. He was rather primitive and apelike, but about 50% more brain mass than Lucy (which translates to proportionately more) – the Einstein of that period. There is no good reason for why the hominid brain started increasing in size two million years ago. It was believed, for a long time, that brain development was related to walking upright – ancient humans who left the jungle had to come up with complex plans, which aided the evolution of the brain. Thus, it was shocking to repeatedly find dimwitted bipedal animals, as it made people aware that there wasn't a clear relation between the two.
"We don't have any evidence that conclusively explains why the brain started increasing in size," Tattersall says. The giant brain is an energy-intensive organ. It accounts for 2% of a human's total mass, but 20% of the energy used. It is even picky about the energy used. The brain won't complain if you don't eat grease, as it has no interest in this. Instead, it loves glucose, and wants more and more, even if it means skimping on other organs. As Guy Brown described it, "The gluttonous brain often puts the body in danger of exhaustion, but also doesn't dare let the brain starve, as that can quickly lead to death." The larger your brain, the more you eat; the more you eat, the greater the danger.
Tattersall thinks that the increase in brain mass may have been an evolutionary coincidence. He subscribes to Stephen Jay Gould's argument that if the evolution of life were replayed, even if it started with the hominids, the possibility of a modern human, or a similar animal, remaining until this day is "very small."
"One of the hardest concepts for people to accept," he said, "is that we aren't the pinnacle of everything. We live here, and everything is not inevitable. Partly because of human vanity, we often interpret evolution as being designed to create humans. Until the 1970s, even anthropologists thought this way. Until 1991, C. Loring Brace still persistently held the linear evolution concept, in his popular textbook *The Stages of Human Evolution*. He only acknowledged one evolutionary end point, the extinction of the *Australopithecus robustus*. Every other species represented a linear process of evolution. Each group passed the baton to the group that followed. It now seems certain that many of these early groups went off the beaten path and died out.
We were lucky. A tool-using hominid suddenly appeared, existing simultaneously with the ambiguous *Homo habilis*. This was *Homo erectus*, the species found by Eugene Dubois in 1891. Depending on the material you read, they existed from 1.8 million to 200,000 years ago.
According to the authors of *Java Man*, *Homo erectus* was a dividing line. Those before him were apelike. Those after him were human. *Homo erectus* was the first to hunt, use fire, make complex tools, leave evidence of encampments, and care for the weak. Compared to all of the other species, *Homo erectus* looked and behaved more like humans. Their limbs were long, their bodies slim, and they were incredibly strong (much stronger than modern humans). They were energetic and smart enough to migrate successfully over a wide area. Compared to the other hominids, *Homo erectus* must have appeared big, strong, nimble, and gifted. Their brains were the most advanced in the world.
According to Alan Walker of Pennsylvania State University, the world's leading scholar, *Homo erectus* was "a raptor of his time." *Homo erectus* appeared to be human on the surface, but "you wouldn't want to talk to him, you'd become his prey." Walker said that he had a grown man's body, and an infant's brain.
Although *Homo erectus* was discovered almost a century ago, our understanding of him remains based on scant fossil evidence – never enough to put together a complete skeleton. It wasn't until an unusual discovery in Africa in the 1980s that his importance as the forerunner of modern humans – or perhaps his possible importance – became fully understood. The remote Kenyan Lake Turkana region (formerly the Lake Rudolf region) is now one of the world's richest for early hominid fossils, but for a long time, no one had ever thought to look for them. It was only when a plane went off course and flew over the lake region that Richard Leakey realized that it might be more fruitful than originally thought. An archaeological team was sent to the area, but at first found nothing. Then, late one afternoon, Kamoya Kimeu, Leakey's most famous fossil digger, found a small piece of a hominid's eyebrow ridge on a hill a short distance from the lake. Such a place wouldn't likely have had any major finds, but out of respect for Kimeu's intuition, excavation was started. Surprisingly, a nearly complete *Homo erectus* skeleton was unearthed. It was of a boy of 9-12 years of age, who had died 1.54 million years ago. Tattersall thought the skeleton possessed "all of the body structures of modern humans." In some ways, it was unprecedented. "The Turkana boy was obviously one of us."
Kimeu also discovered a 1.7 million-year-old female skeleton in Lake Turkana, catalogued as KNM-ER1800. It was the first time that scientists had learned anything about *Homo erectus* that made them realize the creature was more interesting and complex than they had thought. The woman's skeleton was deformed and spotted, showing that she had a chronic illness known as hypervitaminosis A. Such a disease could only be gotten by eating the liver of a carnivore. For the first time, this showed that *Homo erectus* was a carnivorous *Homo*. It was even more amazing that she had survived for weeks or months without dying, with that many spots on her skeleton. Someone must have taken care of her. This was the first sign of tenderness discovered in hominid evolution.
Studies have also shown that the skulls of *Homo erectus* contained (or, in the opinion of some, possibly contained) Broca's convolution, an area in the front left part of the brain relating to speech. Chimpanzees lack this feature. Alan Walker thinks that even with this feature, *Homo erectus*' brains were not large or complex enough to learn to speak, so they may have been able to communicate with each other as much as modern chimpanzees. Others, like Richard Leakey, are certain that they could speak.
For a time, *Homo erectus* was the only