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 4 billion years of our ...

Dominant male lemurs flexibly grow their testicles when other males are around, putting them in a better position to successfully mate. In many species, dominant males have larger testes than ...

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 ...