GAINESVILLE ---A University of Florida anthropologist is part of an international research team whose new findings could change the way human evolution theory is taught in some classrooms.
The team that includes UF anthropology professor Susan Anton used a relatively new dating technique to show that the remains of a modern-human ancestor are thousands -- and perhaps hundreds of thousands -- of years younger than previously thought.
The new evidence may alter opinions that have been held for more than 60 years.
"As modern-human-origins debates go, this is the debate of the `90s," Anton said.
The project, to be featured in today's issue of the journal Science, deals with the age of the youngest remains of Homo erectus, the predecessor of Homo sapiens, or modern humans. The Homo erectus remains were discovered by Dutch researchers in 1931 along the Solo River on Java, Indonesia.
Initial estimates placed the remains at between 100,000 and 400,000 years old. "Among other things, they used morphological dating, which means they looked at the (remains) and said, `They must be old,'" Anton said.
But Anton and her colleagues, led by Carl C. Swisher, a geochronologist at the Berkeley Geochronology Center in Berkeley, Calif., used two modern dating techniques, one of which -- electron spin resonance (ESR) -- is considered state-of-the-art. Because the remains are not available for samples to be taken from them, Anton's team dated water buffalo teeth dug from the same area from which the Homo erectus remains came.
The new age: 27,000 to 53,000 years old.
That bolsters one prevailing hypothesis of modern human origins, known as the Out of Africa model, but contradicts the other: Multiregionalism.
Multiregionalists say Neandertals evolved into modern humans in Europe, with the latest Neandertal remains being about 30,000 years old. About the same time, they say, Homo erectus evolved into modern humans in Asia and Southeast Asia. Those who subscribe to the Out of Africa theory believe Homo sapiens arose in Africa and then spread throughout the world, replacing Neandertals and Homo erectus with little or no gene flow.
The new, younger age of the latest Indonesian Homo erectus remains indicates they coexisted with modern humans in Southeast Asia, Anton said. That would mean current versions of the Multiregional theory no longer are chronologically possible.
"If we're right ... then at that time period you actually have three hominids -- Homo erectus, Homo sapiens and Neandertals" walking the earth at the same time, Anton said. By today's measure, with only modern humans on the scene, that may seem like an odd notion.
In the big-picture scheme of things, it may not be so strange after all.
"It actually turns out we're probably the exception rather than the rule," said Anton.
Anton doesn't expect her team's new information to be accepted by everyone. While anthropologists are about evenly divided between Out-of-Africa followers and Multiregionalists, she said, the former generally enjoy more prominence.
"Out-of-Africa folks will pick it up sooner," she said.
Indeed, the team's work likely will spark new debate between the two schools of thought, said Philip Rightmire, an anthropology professor at the State University of New York at Binghamton, N.Y., who is familiar with the team's work and thinks highly of it.
Rightmire said he doesn't expect the findings to show up in textbooks for at least a couple years, but he believes they eventually will enjoy widespread acceptance.
"I think they've done a good job, and most people will end up accepting the ESR dates," he said. "If what they say is true, the Multiregional people will have to do some fast talking."
The project is funded by grants from the U.S. National Science Foundation and the Leakey Foundation. It is an ongoing collaborative study by UF; the Berkeley Geochronology Center; McMaster University in Hamilton, Ontario, Canada; and Gadjah Mada University in Java, Indonesia.
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