Of all the primates, humans have the largest brain. In fact, brain size has tripled over the past 2 million years, much faster than any other mammal's brain. The question has been why the human brain is so large, proportionally. Was it a response to climate change? Did ecological demands, or a lack thereof, lead to the growth? Or did social factors necessitate a larger brain size?
A recent study suggests that the primary motive for the evolution of larger brain size was coping and competing with other humans. Researchers analyzed over 150 fossil hominids from around the world, looking at the climate, the presence of parasites, and the estimated population density. The skulls with the largest brain cases were part of the largest population groups, suggesting that brain size helped attain necessities and social status in these early social groups.
Despite this new evidence, though, the large size of the human brain is a peculiarity. The brain is a very energy-intensive organ. Having a large brain size would need to provide a significant advantage to evolve, because it requires so much energy to grow and maintain. Why only humans have discovered this advantage, to our knowledge, is still a mystery.
Credit: Science Daily