What's the currency for all life on Earth? Carbon. Every living thing needs a source of carbon to grow and reproduce. In the form of organic molecules, carbon contains chemical energy that is transferred between organisms when one eats the other.

Even biologists only capture a glimpse of the lives of whales. There are still many species whose lives are largely a mystery, particularly the deep diving whales.

In mammals—including us humans—sperm are surprisingly picky about temperature, thriving best in conditions a few degrees cooler than normal body temperature. But, given that the female reproductive tract is warmer than normal body temperature, how do these heat-sensitive swimmers manage to fertilize an egg in such a toasty environment?