Once upon a time, there was an animal called a pilosa that caught insects with its trunk. Some pilosas had wide trunks. Others had skinny trunks. When habitat changes caused their dinners to tunnel underground, pilosas with wide trunks began to starve and die. The pilosas with thin trunks could still reach the bugs. So they stayed healthy and had babies that also had thin trunks. Eventually, all pilosas had skinny trunks and they lived happily ever after. Or they might have, if they were real.
Read the whole story: Scientific American