Humans, mice, narwhals — most mammals rely on ancient genes to produce teeth and tusks. But the tuskless elephants of Africa show that nature can quickly alter the code.
As scientists learn more about milk’s evolution and compositional variations, they are redefining what used to be a signature characteristic of mammals.
Five hundred million years ago, soft-bodied sea animals used phosphate to build elaborate, protective armor. Then their resource dried up, and evolution moved on.
The birds are widely reviled for their carrion-eating ways. But an evolutionary history of scavenging has forged a creative, cunning and wide-ranging mind.