Why 5 fingers

Or more? Or just four? Here's why. By Jack Scanlan. Not quite enough fingers there, Grampa Simpson. Dinosaurs may have gone extinct millions of years ago, but their evolutionary offspring still walk amongst us. Koala thumbs! In Social. And the first tetrapods four-legged animals to invade the land had anywhere up to eight toes per foot.

But the common ancestor of all mammals, birds, reptiles and amphibians had five, and we have stuck with that number. Many groups have lost digits, but five is still the basic number. A horse has a single toe on each foot but if you look at an early horse embryo, its limb buds have five little stripes of Sox9, just like ours.

Pandas have adapted a wrist bone into a pseudo-thumb to help them grasp bamboo; they effectively have six fingers. Mutations that give you more fingers might also screw up your heart or spine. So, why five? No one really knows. Bmp-Sox9-Wnt Turing network modulated by morphogen gradients. All rights reserved. Share Tweet Email. Go Further. Animals Wild Cities This wild African cat has adapted to life in a big city.

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