for National Geographic News
It may be the dream of many parents to have their children skip the teenage years altogether. But it was a major step forward in human evolution, and scientists have long been intrigued by when the change first took place.
A prolonged pattern of growth and maturation—during infancy and adolescence—is significant because it allows extra time for learning.
An international team of researchers has found that taking a longer time to reach adulthood is a fairly recent development in human evolution. They have concluded that it occurred sometime between 800,000 years ago and the appearance of the larger-brained Neandertals about 300,000 years ago—a finding that surprised them.
"We were quite shocked, really," said Alan Walker, a paleoanthropologist at Pennsylvania State University and a co-author of a report on the research published in the December 6 issue of the journal Nature. "We expected it to have occurred much earlier, in Homo erectus," he added. "But that was just a guess, really, based on the fact that Homo erectus looked like humans with small brains."
Homo erectus lived from about 1.9 to 0.8 million years ago.
"Our study shows that it wasn't until much later, perhaps contemporaneous with the Neandertals, that the prolonged pattern of growth first appeared. Earlier members of the genus Homo, in particular Homo erectus, don't have it," said Gary T. Schwartz, a paleoanthropologist at George Washington University and the Smithsonian Institution. Schwartz is also a co-author of the study.
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