Various specimens of Africa's earliest coelacanth have been found in a 360-million-year-old fossil estuary near Grahamstown, in South Africa's Eastern Cape. There are two main methods determining a fossils age, relative dating and absolute dating."If the skeleton is indeed an Australopithecus, as we believe, the findings could mean that these hominids were present in the area far earlier than is generally accepted." The research appears in Friday's (4/25) issue of Science.
"But based on the evidence, we found that the fossil was even older than the initial estimate." Granger and Caffee, of Purdue's physics department, analyzed samples of the skeleton in Purdue's accelerator mass spectrometer, a device capable of detecting the infinitesimal quantities of radioactive aluminum and beryllium in the samples."We found that the skeleton was between 3.5 and 4.5 million years old," Granger said.The speed at which carbon-14 decays, called its half-life, is only 5,730 years.This means that after a few millennia, the isotope is no longer useful to mark a fossil's age.In a finding that could shed light on the earliest origins of mankind, fossil remains found in South Africa of an ancestral human species have proven far older than expected when evaluated by a Purdue University research team. - In a finding that could shed light on the earliest origins of mankind, fossil remains found in South Africa of an ancestral human species have proven far older than expected when evaluated by a Purdue University research team.
Purdue's Darryl Granger and Marc Caffee have determined the age of a fossilized skeleton thought to be an Australopithecus - a genus of African hominids from which humanity is thought to have developed - by measuring the radioactivity of the cave sediments in which the skeleton was buried millions of years ago.Rather than use carbon-14 to date his landscapes, he looked for isotopes with far longer half-lives - and found them in aluminum-26 and beryllium-10.These elements often form in common quartz when it is on the Earth's surface and exposed to cosmic rays."An earlier hominid find in southern Africa, whatever the species might be, could force a rethinking of what that base population might have been." Granger said he hesitated to speculate on the broader significance of the findings, but he hopes the technique will prove useful in other investigations into prehuman history.This research was funded in part by the National Science Foundation.Many such fossils have been found in eastern Africa's Rift Valley, a region that was geologically active when Australopithecus walked the Earth. The fossil was well preserved, but its age was uncertain.