Abrupt shifts in the evolution of animals -- short periods of time when an organism rapidly changes size or form -- have long been a challenge for theorists including Darwin. Now a newly published ...

The Indigenous peoples of the Bolivian highlands are survivors. For thousands of years they have lived at altitudes of more than two miles, where oxygen is about 35 percent lower than at sea level.

Why does natural selection appear to happen slowly on long timescales and quickly on short ones? A multigenerational study of four lizard species addresses biology’s “paradox of stasis.” James Stroud ...