for National Geographic News
Two archaeologists are challenging what many experts consider to be the basic assumption of human migrationthat humankind arose in Africa and spread over the globe from there.
The pair proposes an alternative explanation for human origins: arising in and spreading out of Asia.
Robin Dennell, of the University of Sheffield in England, and Wil Roebroeks, of Leiden University in the Netherlands, describe their ideas in the December 22 issue of Nature.
They believe that early-human fossil discoveries over the past ten years suggest very different conclusions about where humans, or humanlike beings, first walked the Earth.
New Asian finds are significant, they say, especially the 1.75 million-year-old small-brained early-human fossils found in Dmanisi, Georgia, and the 18,000-year-old "hobbit" fossils (Homo floresiensis) discovered on the island of Flores in Indonesia.
Such finds suggest that Asia's earliest human ancestors may be older by hundreds of thousands of years than previously believed, the scientists say.
"What seems reasonably clear now," Dennell said, "is that the earliest hominins in Asia did not need large brains or bodies." These attributes are usually thought to be prerequisites for migration.
The authors maintain that, although there is no absolute proof, putting all the evidence together requires an open mind about other geographical origins of the first humans.
The First Asians?
The authors point out that there is very little solid information about the first early humans in Asia, and paleontologists are left with assumptions that are too often treated as historical facts.
There is no archaeological or fossil evidence to prove that early humans moved from southern Africa to the Nile Valley in the early Pleistocene (1.8 million years ago to 11,500 years ago), they say.
The earliest evidence of a human ancestor in Asia appears to be the 1.8-million-year-old cranium found in Mojokerto, Indonesia. But, the authors note, the fact that no older specimens have been found in Asia does not prove that they didn't exist.
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