Human evolution is often told as a tidy story of adaptation, yet some of our most familiar body parts still defy straightforward explanation. From the jut of the human chin to the curve of the outer ...

A new study theorizes that evolution ticks at different speeds, especially when a big group of organisms first appears.

The human body is a machine whose many parts – from the microscopic details of our cells to our limbs, eyes, liver and brain – have been assembled in fits and starts over the four billion years of our ...