Modern Humans May Need Redefining

Article excerpt

Modern Humans May Need Redefining

Many paleoanthropologists contend that fragmentary fossils found in caves at the mouth of South Africa's Klasies River represent anatomically modern humans who lived in Africa more than 80,000 years ago. Thus, the Klasies River Mouth specimens--consisting of several partial lower and upper jaw bones, about a dozen cranial fragments, a number of isolated teeth and four lower-body bones -- provide critical support for the theory that modern human populations originated in Africa around 200,000 years ago and then spread throughout the Old World, replacing groups such as the Neanderthals.

But two scientists at the University of Michigan in Ann Arbor argue that the Klasies folk were probably a transitional form of Homo sapiens preceding anatomically modern humans. In a controversial presentation at the meeting of the American Association of Physical Anthropologists last week in Miami, Rachel Caspari and Milford H. Wolpoff reported that the South African remains differ in important ways from anatomically modern humans living in southern Africa several thousand years ago.

Anatomical variation is apparently the rule both in the Klasies fossils and in today's human populations, the researchers assert. They note that the thickness and breadth of the lower jaws and the size of molar teeth vary markedly in the Klasies finds, and that modern people living in some regions, such as Asia, have smaller, lighter cranial bones than those living elsewhere, although Asians are not necessarily more anatomically modern.

"It's hard to say what 'anatomically modern human' really means because of geographic variations in modern human anatomy," Wolpoff says.

These variations often obscure trends toward modern human anatomy in the fossil record, Caspari adds.

Despite this confusion, the new analysis of the Klasies River Mouth bones adds fuel to the theory, championed by Wolpoff, that modern humans evolved simultaneously in several parts of the world (SN: 2/27/88, p.138). In this scenario, ancestral populations of Homo erectus independently evolved into archaic Homo sapiens and then into fully modern humans.

Caspari and Wolpoff compared the Klasies River Mouth skull remains with 36 human crania from a nearby site dating to between 1,000 and 9,000 years ago. …