The reason we humans have fingers today may all be thanks to a fish's clacker.

New research into the origins of digit formation shows that the DNA switch controlling finger and toe development got its humble start regulating the formation of fish cloacas , 380 million years ago.

It's a beautiful illustration of nature's "waste not, want not" ethos in action: why build new genetic tools from scratch when existing ones can be repurposed for the job?

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"The fact that these genes are involved is a striking example of how evolution innovates, recycling the old to make the new," says developmental geneticist Denis Duboule of the University of Geneva in Switzerland.

"Rather than building a new regulatory system

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