Hands and feet
When you were an embryo, your hands and feet were webbed at first. Scientists do not know why most animals develop in this way, but to make fingers and toes, cells between them have to die. Unwanted cells switch on a 'suicide program' that neatly removes them without damaging their neighbours. This process is called programmed cell death, or apoptosis. In animals with webbed feet, such as ducks, there is less cell death.
