The side effects of the cold..

Nature is an incredible thing. Evolution demands that organisms are fine tuned into these wonderful machines, every part serving a purpose, the pointless bits culled out over millions of years.

For example, when you're cold, vasoconstriction occurs (ie blood vessels narrow in size to prevent heat loss), you hair stands up to create an insulating layer of air over your body, your metabolism goes up.. etc etc..

And when you're cold, you nipples go hard. What possible evolutionary or biological purpose could this serve...?

hmmmmmm......