Chew On This

Monday, March 29th, 2004

Chew On This discusses the recently discovered MYH16 mutation — and another similar mutation that probably dates to the same period in our evolutionary history:

For one thing, a hominid with a weak jaw can’t grind up tough foods the ways its ancestors did; it needs new foods. The oldest tools, interestingly enough, date back to about the same time as the MYH16 mutation. Scientists suspect that hominids were using these simple stone axes to hack meat off of carcasses and dig up tubers. This new diet might have meant that a mutation to MYH16 wouldn’t have mattered much. The new diet may have been just as important as the missing jaw muscles to letting the hominid brain expand. For one thing, a big brain requires lots of energy. One way to make more energy available is to shrink the size of other organs, and it turns out that we humans have one particulary small organ: our intestines. Other primates use their long bowels to digest tough foods poor in nutrients; we can survive on our abbreviated bowels because we eat better grub.

So here’s a prediction: scientists will eventually discover genes that control the development of intestines in humans. When they compare them to ape genes, they’ll discover that they underwent an evolutionary change around the same time that MYH16 shut down. Our brains did not evolve in a vacuum; they coevolved with the rest of our bodies in a complicated dance of tradeoffs and feedbacks.

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