A publication of the Archaeological Institute of America
New dates for Homo erectus fossils from Ngandong, Java, suggest this hominid lived as recently as 53,000
to 27,000 years ago. The dates, obtained by Carl Swisher of the Berkeley
Geochronology Center and colleagues, add to the debate between those who
favor an out-of-Africa model and those who adhere to a multiregional one.
The former believe modern humans developed in Africa 150,000 to 100,000
years ago, then dispersed into the Middle East and Europe, where they replaced
Neandertals by 30,000 years ago, and into Asia, where they replaced H.
erectus. The alternative is that modern humans evolved from predecessors
in various regions. Multiregional proponent Milford Wolpoff of the University
of Michigan holds, for example, that modern Australians owe certain characteristics
to H. erectus forebears. The models, when first presented, were thought
to be mutually exclusive.
If confirmed, the new dates for H. erectus contradict the multiregional model in its original version and support the replacement one. Some scholars, including Jean-Jaques Hublin of the Musée de l'Homme, Paris, support a milder version of the replacement model in which different scenarios could have occurred in different regions. Some areas, such as Western Europe, would have experienced a total or almost total replacement. In other places, and possibly in the Far East, some level of gene flow could have occurred between local archaic populations and modern humans.
The Ngandong crania are widely accepted as H. erectus but have higher vaults than earlier H. erectus from Java or China. This is consistent with their late age. Wolpoff would simply consider them intermediate between local H. erectus and modern Australian, which the new dates make difficult to accept. In the replacement model, however, one must still explain the Ngandong cranial features, either as some degree of convergent evolution in Asian H. erectus and H. sapiens or some gene flow between them.
"It is rather striking to see that this overlap between long-lasting archaic populations and modern humans is documented only at the two extremities of the Old World, in the two culs-de-sac which are Western Europe and Indonesia," says Hublin. "In both places, each year brings new evidence of the possible interaction between contemporary but different groups of humans.