The Next Species: The Future of Evolution in the Aftermath of Man (8 page)

The project was interested in the effects animals in this ecosystem had on the hominids who were once here with them. At one time the Olduvai Gorge area was a place where animals interacted with man in a balanced community. We saw that some of this balance still exists today, since this area is surrounded by national parks.

We continued traveling along the ridge of the gorge until we came to a plateau where the team parked its vehicles and the men and women aboard prepared to go to work. As you looked out over the gorge, you could see the layers of earth in the sides of the canyon. We were fortunate enough to have these well-defined layers, which Hlusko said made it possible to determine the era of a fossil by the stratigraphy of the soil. The group of scientists and Maasai helpers spread out over the sloping side of one section of the canyon. I learned to avoid those climbing precipices after I followed one group up a pinnacle and had trouble getting down.

That morning, we found the lower jaw of an ancient mastodon, and Hlusko spent more than an hour extracting it from the ground, carefully packing it into a plaster mold to take back to camp. She explained that she normally avoided hippo and elephant bones because they don’t appear to evolve as much as man or some of the other carnivores. But this elephant jaw was so intact that she just
couldn’t resist.

Later that week the project’s codirector, Jackson Njau, took me to his study site in Serengeti National Park along the Grumeti River. Like Hlusko, Njau was interested in how animals related to early man, but he had chosen to focus specifically on
crocodiles and their possible effect on hominid intelligence. Trees and brush lined the river, though savanna grasslands dominated the greater landscape. Njau was born in Tanzania and got his BA there at the University of Dar Es Salaam and his PhD at Rutgers University before taking a position at Indiana University. He and Hlusko had worked together at other sites in northern Africa.

We arrived on a cloudy day at the Grumeti River, where more than twenty hippos weighing 3,000 to 10,000 pounds (1,600 to 4,500 kilograms) glistened in the sun as they jostled with each other for a place in the water. Along the shores lurked four or five crocodiles, their rough, bumpy skin and long, toothy jaws blending eerily into the landscape. Though the hippos were not to be ignored, it was the crocodiles that drew the most attention from Njau.

According to Njau, crocodiles are the most dangerous predators in Africa, causing far more deaths than lions or leopards. Crocodiles have killed more than five hundred people in Tanzania alone since 1985. Njau explained the inevitability of these occurrences: “Victims know where they are, how to avoid them, yet they still keep getting caught and killed.” Njau warned me that for every crocodile you see above the water, there can be several others below waiting. I stayed far back from the river.

The reason for this caution was that crocodiles frequented the water where men or animals came to drink or bathe, and these secretive reptiles were very, very patient. At just the right time, when its prey, man or beast, came forward, convinced there was no danger, the crocodile would lunge out of the water with extraordinary speed and grab its victim. The crocodile locks its jaws on the head, shoulder, arms, or front legs of its prey, then drags its spoils back into the pool
to be held down to drown.

During his thesis study, Njau came to the Grumeti River in the early summer to observe how the crocodiles overtook other animals. He visited a few months later in the dry season when the river had vanished and the crocodiles and hippos had moved on. He studied the bones left in the middle of the pool where the river had dried out and compared the tooth marks left by crocodiles to those of other carnivores. He wanted to know what marks the different predators made so he could study fossils and better know what was happening back then.

Crocodiles had rows of as many as sixty-six teeth along powerful jaws that were ideal for gripping prey. The crocodile would often grab a victim and beat it against a rock, or it would sometimes go into a death spiral and roll over and over, or two crocodiles would grab the victim and roll over in opposite directions. The crocodile tried to disarticulate a substantial chunk of meat and then swallow it whole, allowing the reptile’s stomach acids to do most of the digesting.

Crocodiles left puncture wounds where their jaws locked on a victim. But they weren’t able to move their jaws from side to side. This meant they actually made fewer marks on the bones of prey than other predators, although in some instances they left dense concentrations of bites on bones they were unable to swallow. A crocodile would tend to rip a large piece of meat and bone from a victim, swallow it whole, and then leave the rest. Lions, leopards, and even hyenas would gnaw on the ends of the bones to get the meat off, and even break the bone to get at the marrow. Thus most of the bones of
crocodile victims would show fewer tooth marks than the bones of lion or leopard victims, and lacked gnawing damage on the ends. Crocodiles would take only right-size chunks of meat—not too big to catch in its throat, but not too small not to warrant the effort of the hunt. Bones that didn’t fit either of these categories were left in the water to settle to the bottom of the pond, along with leftover crocodile teeth.

Back at Olduvai on a day when the sun was beating hard, we revisited the high ridge of the gorge, parked our cars near a cliff, and hiked
down the cliff face to a wide bend in the dry creek, a site surveyed by the Leakeys in the 1960s and more recently by the current crew.

Codirector Njau used his work in the Serengeti on living animals and their prey to understand how crocodiles might have affected early man in Olduvai. Njau told me that the entire gorge area had been through a series of drastic climate changes since two million years ago, when
Homo habilis
first occupied it. He said it was much more humid then, and that there was a lake not too far downstream from where we stood into which the river flowed. Today, the area was very dry with the exception of a few months of the rainy season when the Olduvai River floods briefly.

Homo habilis
took meat here, but not as a hunter. “Most people think, ‘Oh, here comes man, he must have been a hunter,’ ” said Njau, “but no,
Homo habilis
was only about three or four feet tall, and weighed less than one hundred pounds. There was no way he could have brought down wildebeest-or gazelle-sized animals here. We think he lived here as a scavenger, feeding off the kills of lions and leopards.”

In order to survive like this, he had to be well aware of the terrain, and he had to forage in groups. One man alone was too much of a target for local predators. The Leakey family originally hypothesized that early man may have lived along the waters running through Olduvai, but Njau thought that the evidence for crocodiles, hyenas, leopards, and lions as well as hippos, elephants, and other wetland animals was too great and the result too dangerous for men to have stayed here on any type of permanent basis. He considered this space more as a puzzle that
H. habilis
had to learn to navigate, and that an ability to plan, to hunt cooperatively, and to anticipate predator movements would have provided selective pressure for early human intelligence. If you didn’t figure out the puzzle, you died and didn’t pass on your genes—the basic element of evolution.

Fossil evidence for tool use at Olduvai showed that
H. habilis
had instruments for cutting flesh away from bones, but not stone spear-or arrowheads that could kill fully grown animals or drive off lethal
predators. They may have had wooden spears, but they were scavengers, not hunters. Being smart here improved their chances of survival but also provided access to meat, which had the extra calories necessary to evolve bigger brains.

Studies of the lineage of man provide not only a look at the past but also insight into the future. It was only in 1856 that scientists found the fossilized bones of the first extinct human in the Neander Valley, Germany. Darwin mentioned nothing in
On the Origin of Species
about the evolution of man, though the book came out in 1859, three years after the first Neanderthal fossil was discovered. It was not until 1864 that these fossils were recognized as a separate species,
Homo neanderthalensis
.

Darwin later proposed that our early ancestors diverged from Old World monkeys in the early Miocene epoch, about 20 million years ago. In 1927, Dr. H. L. Gordon, a retired government medical officer, found in limestone deposits in western Kenya a specimen of one of the first primates to diverge from apes. Gordon named it
Proconsul africanus
, after a chimpanzee named Consul that performed in the
Folies Bergère
in Paris in the early 1900s. The
Folies
chimp wore a tux, played the piano, and smoked a cigar, before taking off his trousers, standing on his head, and somersaulting into bed. Mary Leakey found one of the most complete skulls of
Proconsul
in 1948 on Lake Victoria.

The discoveries of early primates leading up to man didn’t end with
Proconsul
. Africa had many more tales to tell.
Australopithecus afarensis
(better known as Lucy, which lived from 3.85 million to 2.95 million years ago) was discovered in 1974 by American paleontologist Donald Johanson and grad student Tom Gray. They found Lucy in Hadar, Ethiopia, and celebrated under a star-filled sky playing the Beatles song “Lucy in the Sky with Diamonds.” Lucy walked upright with a humanlike pelvis but had a small brain and primitive teeth. She had a powerful jaw, probably used more for stripping plant material
than eating meat.

Then meat eaters started to appear.
Homo habilis
, the scavenger, was the earliest of the genus
Homo
to which we belong.
Homo habilis
(2.33 million to 1.6 million years ago), the “handyman,” was so named from early tools found by the Leakey family at Olduvai. The males stood about 4 feet 3 inches (1.3 meters); the female stood about 3 feet 3 inches (1 meter).
Homo habilis
was short but had a significantly larger brain than Lucy’s family. Its carnivore diet provided the calories that enabled that growth.

Homo erectus
(1.8 million to 140,000 years ago) is thought to have evolved from
Homo habilis
in Africa. Its fossils follow
H. habilis
in the stratigraphy. The first findings were made at Trinil, Java, Indonesia. German evolutionist Ernst Haeckel had predicted that the origins of man would most likely be found in Southeast Asia. It was largely through the work of the Leakey family that scientists began to recognize Africa as the more likely birthplace of both
H. habilis
and
H. erectus
.

Still, if
Homo erectus
did evolve from
Homo habilis
, he did so in one amazing growth spurt. If you look at the life-size replicas of
Homo habilis
at the Smithsonian’s Hall of Human Origins,
habilis
is a little guy with not much heft.
Erectus
appears as if he’s ready for some early hominid basketball. Standing at 6 feet 1 inch (1.8 meters), he’s looking down, I must confess, at me. Fossil remains of
Homo erectus
are found predominantly from 1.8 million to 140,000 years ago. He was the first of the hominids to migrate to the Far East and to Europe.

Homo sapiens
evolved in Africa about 200,000 years ago from
Homo erectus
via one or two intermediate species.
Homo neanderthalensis
evolved via its own intermediaries in Europe. About 120,000 years ago, early
Homo sapiens
migrated out of Africa to the southeastern Mediterranean coast, infringing for a while on Neanderthal territory before a cold phase ensued and
Homo sapiens
pulled back into Africa. The next time they appeared they were better equipped and more
numerous.

Back at Olduvai, Tomos Proffitt, a graduate student at University College London’s Institute of Archaeology, sat on a bench outside the field house trying to simulate what it must have been like for early man to make stone tools. He held a single round rock, or “hammerstone,” in his right hand and a larger piece of rock cradled in his left hand resting on his knee. He took careful aim with his hammerstone before bringing it down at an angle on the larger rock with sufficient force to break off chips and extend the sharp edge around the larger stone. A pile of rounded rock chips surrounded his feet.

Proffitt’s hammerstone was made of quartzite and the large stone, the eventual hand ax, was made of phonolite, a fine-grained lava rock.
Homo erectus
, the tall guy, used similar tools to butcher meat and possibly to sharpen wooden spears.

Simple flakes, small pieces of sharp rocks used for cutting, are thought to be a part of the
Homo habilis
tool kit. Bifacial tools, like the hand axes Proffitt spent hours each day crafting, are part of the
Homo erectus
tool kit. It was in the 1970s that the first tools were recognized in Olduvai Gorge, dating back to 2.5 million years ago. Their creation shows that early man had the mental capacity, the dexterity, and the fine motor skills to craft tools as well as use them.

The
tool technology of early man plays a determining role in why Neanderthals ended up on the losing end of their mortal competition with
Homo sapiens
. Neanderthals, our closest relatives, dominated Eurasia for the better part of 500,000 years, spreading over Europe, Britain, Greece, Russia, and Mongolia. Despite the broad reach, their population is thought to have been from 10,000 to 100,000 total individuals at its apex.
Examinations of Neanderthal bones reveal that adult males had greater strength in their right arm as opposed to their left, indicating that they carried heavy, hand-held spears, which they probably used for thrusting rather than throwing. Males had solidly built bodies, standing only about 5 feet 5 inches (1.7 meters) but weighing around 185 pounds (84 kilograms). They needed 5,000 calories a day to do their job, an amount approximately equal to what a typical cyclist needs to compete for
a day in the Tour de France.