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A new study reveals some of the crucial molecular steps on the path to bipedalism.

By Carl Zimmer

Charles Darwin unveiled his theory of evolution in 1859, in “On the Origin of Species.” But it took him another 12 years to work up the courage to declare that humans evolved, too.

In “The Descent of Man,” published in 1871, Darwin argued that humans arose from apes. And one of the most profound changes they underwent was turning into upright walkers.