Such modeling techniques, which are widely used in science and commerce, take into account more overall information than earlier processes used to estimate evolutionary history using just a few individual fossil dates, Martin said. It can give scientists a broader perspective for interpreting data.
One example is a skull fossil discovered in Chad (central Africa) earlier in this decade. The fossil, named Sahelanthropus tchadensis and nicknamed Touma (which means "hope of life" in the local Goran language), raised great interest because it has many human characteristics. But consensus on how to classify the discovery has been elusive particularly because the fossil is about 7 million years old, well beyond the accepted time frame for human evolution.
Under the new estimate, Touma would fall within the period after the human lineage split from chimpanzees, Martin said.
The new approach to dating evolutionary history builds on earlier work by Martin and colleagues. In 2002, they published a paper in Nature that argues the last common ancestor of today's primates lived some 85 million years ago.
This implies that for 20 million years before dinosaurs became extinct, early versions of primates also lived and evolved. It challenged the accepted theory that primates and other mammals didn't really thrive on the planet until dinosaurs were gone.
After that paper was published, Martin said he expected someone would apply the new statistical techniques to the question of human evolution, but when no one did, "We decided to do it ourselves."
|Contact: Nancy O'shea|