‘Java Man’ takes age to extremes

ALBUQUERQUE — New age estimates for Homo erectus fossils on the Indonesian island of Java have physical anthropologists scratching their crania.

After convincing most of their colleagues that H. erectus may have persisted on the Indonesian island of Java as recently as 30,000 years ago — late enough to have coexisted in Asia with modern humans for more than 100,000 years — anthropologists presented new analyses April 14 suggesting the fossils in question may actually predate Homo sapiens by hundreds of thousands of years.

It all depends which radiometric method you use to assess the fossils’ age, New York University anthropologist Susan Antón reported at the annual meeting of the American Association of Physical Anthropologists.

Antón and an Indonesian colleague lead a team that first announced in 1996 that sediment at two H. erectus sites on Java dates to between 50,000 and 30,000 years ago. Those “remarkably young” dates, based on analyses of radioactive elements in fossil-bearing sediment, suggest that H. erectus survived well into the era dominated by modern humans, Antón said. Many researchers now accept those dates.

But a new analysis, based on measurements of radioactive argon’s decay in volcanic rock above and below the fossils, puts H. erectus’ age on Java at roughly 550,000 years. It’s not clear why these estimates differ so dramatically and which one is more accurate, Antón said.

“It’s confusing right now, but I suspect that Homo erectus’ age on Java is still relatively young,” said Christopher Stringer of London’s Natural History Museum. A new analysis of sediment on Java suggests that animal fossils on the island date to between 200,000 and 150,000 years ago, providing a possible framework for when H. erectus lived there, he added.