An analysis of the growth patterns in fossil teeth has thrown new light on the recent origin of the extended growth and development pattern that sets human beings apart from their primate ancestors, according to an article in the issue of Nature.
Based on the analysis of the fossil teeth, researchers from University College, London and Penn State University determined that the relatively long 15 to 25 year development period of humans compared with 11 or 12 years for primates came about more recently in the evolutionary process than previously thought.
"Dental development is a good measure of overall growth and development," study author Alan Walker, professor of anthropology and biology at Penn State University, said in a news release. "Teeth grow in an incremental manner like trees or shells, preserving a record of their growth with daily marks along the prisms that make up the enamel."
By making thin sections of modern and fossil teeth, the researchers were able to count the daily incremental markings with the enamel of humans, apes and fossil "hominin" species to measure up the rates of tooth formation. Based on the dental validation, the human-like development period does not appear until the Neanderthal period about 100,000 years ago.
Previous theories placed this evolutionary milestone as far back as 1.5 million years ago, corresponding with the first evidence of modern human-like characteristics such as body proportions, body weight and small teeth and jaws.
"It seems our prolonged period of growth and development may be a more recent evolutionary acquisition that arose in step with our comparatively recent development of a larger, modern, human-sized brain," Dr. Walker said.