As humans domesticated cows and other milk-producing animals, the genetic mutation that allowed for the digestion of lactose became advantageous, and was passed on to more and more offspring. As for why our brains are shrinking, scientists have multiple theories. One is that our brains are becoming more efficient, taking up less space while performing more work.
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Key Facts In This Video
Scientists predict that in the next few decades, computers will be developed that can reach the computational speed of the human brain. 00:36
There is a man with a genetic mutation that allows him to digest almost anything. 02:15
Artificial selection could lead to a lack of genetic diversity, and make us vulnerable to a new disease. 02:52