evolution of humans

By Alan G. Thorne and Milford H. Wolpoff

Both fossil and genetic evidence argues that ancient ancestors ofvarious human groups lived where they are found today

Three decades ago the pa-leoanthropological community was locked in a debate about the origin of the earliest humans. The disagreement centered on whether the fossil Ramapithecus was an early human ancestor or ancestral to both human and ape lineages. Molecular biologists entered that discussion and supported the minority position held by one of us (Wolpoff) and his students that Ramapithecus was not a fossil human, as was then commonly believed. Their evidence, however, depended on a date for the chimpanzee-human divergence that was based on a flawed "molecular clock." We therefore had to reject their support.

Paleoanthropologists are again engaged in a debate, this time about how, when and where modern humans originated. On one side stand some researchers, such as ourselves, who maintain there is no single home for modern humanity—the idea that humans originated in Africa and then developed their modern forms in every area of the Old World. On the other side are researchers who claim that Africa alone gave birth to a new species of modern humans within the past 200,000 years. Once again the molecular geneticists have entered the fray, attempting to resolve it in favor of the African hypothesis with a molecular clock. Once again their help must be rejected because their reasoning is flawed.

Genetic research has undeniably provided one of the great insights of 20th-century biology: that all living people are extremely closely related. Our DNA similarities are far greater than the disparate anatomical variations of humanity might suggest. Studies of the DNA carried by the cell organelles called mitochondria, which are inherited exclusively from one's mother and are markers for maternal lineages, now play a role in the development of theories about the origin

POINT-COUNTERPOINT: For an opposing view of how humankind arose around the globe, see "The Recent African Genesis of Humans," on page 54.

of modern humans across the globe.

Nevertheless, mitochondrial DNA is not the only source of information we have on the subject. Fossil remains and artifacts also represent a monumental body of evidence—and, we maintain, a considerably more reliable one. The singular importance of the DNA studies is that they show that one of the origin theories discussed by paleontologists must be incorrect.

With Wu Xinzhi of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, we developed an explanation for the pattern of human evolution that we described as multiregional evolution. We learned that some of the features that distinguish major human groups, such as Asians, Australian Aborigines and Europeans, evolved over a long period, roughly where these peoples are found today, whereas others spread throughout the human species because they were adaptive.

Multiregional evolution traces all modern populations back to when humans first left Africa almost two million

Qafzeh 9

(Upper Pleistocene)

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