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Some primates' brains have shrunk over the course of evolution

New findings have challenged the notion that primate brains have grown steadily over the course of evolution.

Scientists studying the primate family tree found that many species have actually seen brain mass decrease over time, bucking conventional thought that brain size across all primates - including humans - grows over time.

The study, published in the journal BMC Biology, found that although the majority of primate species have undergone varying degrees of brain size increase, most notably humans, other branches of the family tree have reversed the trend.

Mouse lemurs, marmosets and mangabey monkeys have all, at some point in their evolution, seen their brain size decrease.

The findings shed new light on the case of a population of Homo floresiensis, otherwise known as the "Hobbits of Flores", whose remains were found on the Indonesian island of Flores in 2003.

Scientists had concluded that their small heads and brains were as a result of disease rather than evolution. However, the new discovery could indicate that the hobbits were actually a branch of humans that had evolved to survive on limited food resources.

The study revealed wide ranging differences in the evolution of primates, with some species undergoing drastic changes in body mass but a reduction in brain size and, conversely an increase in brain size over physiological growth.

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