Human Origins

Article excerpt

Paleoanthropology, the study of human origins, is of intense interest to us because it deals with the subject of where we came from and how we got here. For thousands of years every society devised its own particular creation myth to explain human origins. Now, however, paleoanthropologists, through the discoveries of fossilized remains of our ancestors, are presenting scientific explanations for how humans have evolved to become the most influential species on planet Earth today.

When Charles Darwin and his colleague Thomas Henry Huxley, in the nineteenth century predicted that humans and the extant African apes had a common ancestor, few embraced the idea Huxley and Darwin based this prediction on the many similarities in anatomy among humans, chimps, and gorillas. Today, careful field observations of African ape behavior, particularly that of the chimpanzee, substantially strengthen those close ties. These apes demonstrate a wide range of behaviors and emotions suggestive of our own. Furthermore, detailed comparisons of human and chimpanzee DNA confirm our remarkable closeness to each other. Humans and chimps are roughly 98 percent identical in our DNA sequences. What could be more convincing proof for Huxley and Darwin's ideas?

If humans and African apes shared a common ancestry, then the fossil records must contain examples of more ancient, more primitive hominids that, by a combination of ape and human features, bridge the distance we see between ourselves and the African apes. Darwin made a brave prediction in 1871 in The Descent of Man, when he wrote:

In each great region of the world the living mammals are closely related to the extinct species of the same region. It is, therefore, probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere.

This suggestion was incredibly insightful because fossil evidence for human evolution in 1871 consisted of a few poorly understood and inadequately dated Neanderthal remains from Europe. Discovery of an ancient hominid fossil in Africa did not come until half a century after Darwin's death.

Important Fossil Finds

It was Raymond Dart's announcement of the species Australopithecus africanus in 1925 that vindicated Darwin and ignited the search for more hominid fossils in Africa. Using his observations of a child's skull from the Taung site, Dart proposed that he had found a small-brained, upright walking creature that he saw as intermediate between human and ape.

Scientists were initially skeptical of Dart's claims, but the discovery of hundreds of additional hominid fossils from several cave sites in South Africa eventually convinced most scientists that Australopithecus represented an ancient human ancestor. In addition to more Taung-like fossils, skulls of another, geologically more recent species were found. Dubbed A. robustus, these creatures possessed large, flat faces, enormous chewing teeth, and sometimes a crest on top of the skull for anchoring massive chewing muscles. Widely viewed as specialized vegetarians, these forms of Australopithecus eventually faced extinction about 1 million years ago, 1.5 million years after the first appearance of this lineage.

In 1959, after attention had long been focused on South Africa, Mary and Louis Leakey startled the world with the discover of a skull from Olduvai Gorge in Tanzania, dated to approximately 1.8 million years ago. This find, initially called Zinjanthropus (East Africa Man), and now assigned to Australopithecus boisei, dramatically shifted the arena of field exploration from southern to eastern Africa. Expeditions were sent to East Africa in the hope that additional hominid sites would be located in the Great Rift Valley.

The New Paleoanthropology

The discovery of "Zinj" also heralded the beginnings of the New Paleoanthropology. …