Team McCallum

R&D for Lifetime of Life

When did ‘human’ features evolve?

According to a study by Martin Garwicz and others, the time of onset of walking is shared across humans and mammals that diverged in separate species as far back as 100 million years ago.

The study looked at 24 mammal species that walk and found that adult brain mass predicts time of first walking, accounting for 94% of the result.

This ‘time of walking’ model starts from conception, not birth. Horses can walk almost immediately because of a relatively long gestation period. Rodents take a few days to a few weeks, but they fit the time from conception/brain size model. Non-human primates take months. Human babies take the longest at a year or so, due to the amount of brain development that occurs outside the womb.

Since the 24 mammals studied fit this predictor and since they diverged as far back as 100 million years ago, fundamental patterns of early human life history may have evolved before the evolution of primates (55 to 65 million years ago).

The study is reported in the Proceedings of the National Academy of Sciences of the United States of America.

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December 17, 2009 - Posted by | Evolution

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