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The Search for Our Earliest Ancestors: Signals in the Noise

Homo_neanderthalensis_adult_male_-_head_model_-_Smithsonian_Museum_of_Natural_History_-_2012-05-17.jpg

Our modern naturalist quest for our ancestors has featured recent setbacks. It features something else too, whose significance is rarely considered: When we find our ancestors, they will not be human.

Science-Fictions-square.gifNaturalism commands us to believe that mud somehow produced mind. Therefore, our ancestors are not gods or heroes but half human or less. Our long-vanished cousins were not human. We don't experience the discovery as a profound problem mainly because we've never found them.

Not for want of trying. Paleontologists have long hungered for a species halfway between human and ape, to cast in the world's face as irrefutable evidence for mud at work. Indeed, a little publicized assumption of Darwin's theory was that future humans would eventually separate into different species:

The break between man and his nearest allies will then be wider, for it will intervene between man in a more civilised state, as we may hope, even than the Caucasian, and some ape as low as a baboon, instead of as now between the negro or Australian and the gorilla.
Darwin didn't think this out of bad will or bigotry; it is merely the logic of a theory that encompasses all of life. The human future took very different turns, it seems, but the quest for a non-human past survived them. Here are a few things we think we know:

We are told that our ancestors lived on African grasslands for six million years, and that they started to walk upright four million years ago. They originated in Africa, but at various times, most left. A case has been made for an Arabian stopover. But some researchers believe, on the contrary, that the human race originated in Asia and got to Africa on naturally occurring rafts of vegetation.

One thing we know for sure is that early human cultures were generally more sophisticated than the Ooga! Ooga! narrative. They led a hard and busy life. The popular picture suggests that our ancestors mostly ate flesh meat from large animals. Indeed, there is evidence for elephant hunting 420,000 years ago. But many also ate vegetables, nuts, cereal grasses, and fish. Some think, from studying fossil teeth, that there was a turning point in the diet toward a greater variety of plant foods around 3.5 million years ago. Deep sea fishing dates back at least 42,000 years. Evidence for fishing in general goes back at least 750,000 years, to the time of Homo erectus. As does evidence for complex social behavior around work:

At the prehistoric Gesher Benot Ya'aqov site in northern Israel, researchers have found the earliest known evidence of social organization, communication, and divided living and working spaces -- all considered hallmarks of modern human behavior.
A study of the DNA of body lice suggests that humans wore clothes at least 170,000 years ago. Bedding consisting of plant materials known to repel insects has been found from 77,000 years ago.

Tools have also been found from very remote antiquity. Stone flakes, resulting from (probably) Homo erectus knapping rocks to create tools for butchering animals have been found in sediments almost 1.85 million years old. Axes unearthed in Kenya are estimated to be around 1.76 million years old. There is evidence of sophisticated tool production 200,000-400,000 years ago, with a cave organized into sections, according to task. Stone-tipped (hafted) weapons have been found from 280,000 years ago and 500,000 years ago. The earliest evidence of a human hit by a projectile, under unknown circumstances, dates from 150,000-200,000 years ago.

And prehistoric life was not devoid of culture. The earliest known musical instruments are well over 40,000 years old. Wall art has been discovered from 37,000 years ago, and prehistoric hunters were quite accurate in their drawings of moving animals. An artists' paint factory has recently been found from 100,000 years ago, which suggests that art in the Stone Age was a more organized affair than we have supposed. Mysterious, too, in some ways. Cave art may actually have gone downhill over the millennia. The oldest art was some of the most elaborate, "challenging our current knowledge of human cognitive evolution."

Some interpretations of ancient human life are under fundamental dispute. One group of researchers offers evidence for humans using fire one million years ago. Others argue that people were cooking nearly two million years ago. A third group dissents, noting that the earliest known European hearths date back only 300,000-400,000 years.

Similarly, one recent study suggests that a switch to farming spurred innovation. Probably, but other research has found the benefits of farming to be surprisingly mixed: Farming made us shorter and sicker, and farm life, we are told, also led to shorter and broader jaws, resulting in an increase in tooth problems. Of course, the advantage of a more regular source of food from cereal grains may have outweighed the identified health disadvantages.

One clear pattern emerges: The further we get from physical evidence as above, the more (possibly irresolvable) contradiction or uncertainty we encounter. For example, there is much dispute about sex and family life. Two computer simulations have reached opposing conclusions about why monogamy evolved in primates in general, and researchers were understandably reluctant to extend their conclusions to humans. Bolder authorities tell us that language change came about when new immigrant men arrived at prehistoric settlements. But others say, based on skulls and teeth, that "ancient hominid males stayed home while females roamed." Predictably, "Some scientists believe that ancestors of humans had chimp-like patterns of mating and child-rearing." We also hear that at Çatalhöyük in Turkey, people did not appear to live in families. This assertion rests on the fact that people buried beneath the floors of houses were not closely related. Trouble is, we don't know how certain individuals were chosen for floor burial in various homes. The decision may have been based on factors we can never discover at this date (They were thought to intercede with the gods? Drive away bad luck?).

Now and then, a signal rises above the noise. From surprisingly early periods, we encounter special respect for the dead and a sense of the divine. Meanwhile, because we keep finding artifacts and organized activities from earlier periods than "expected," the half human creature we were originally seeking continues to elude us.

Editor's note: Here are links to the whole "Science Fictions Human Evolution" series to date.

Image: Model of an adult Neanderthal male, Smithsonian Museum of Natural History/Wikipedia.