THE more we learn about our evolutionary journey from ape to human, the more astonishing it seems. Around 3.5 million years ago, a gene involved in brain development duplicated itself in one of our ancestors. Around a million years later it did it again. The duplicate genes now play a crucial role in the design of our big, powerful brains (see 鈥�The humanity switch: How one gene made us brainier鈥�).
The double duplication joins a handful of other mutations 鈥� notably in FOXP2, also known as the 鈥渓anguage gene鈥� 鈥� that appear to have endowed us with uniquely human traits. It is no exaggeration to say they are the genes that make us human.
On one level that is not hugely surprising. The differences between humans and chimps are obviously encoded in DNA, most likely in genes that determine brain architecture.
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But on another it brings home the sheer improbability of our existence. The essence of humanity largely boils down to a bunch of random mutations, every one of them happening by chance.
Richard Dawkins once described evolution as 鈥渃limbing mount improbable鈥�. It is always worth remembering that humans have climbed the highest.
