Animal penises’ amazing evolution

Barbara Natterson-Horowitz and Kathryn Bowers in Salon:

The earliest single-celled organisms on Earth simply cloned themselves. Some of their descendants still do. But as complex multicelled organisms evolved and eventually “discovered” the ability to mix their gametes, they gained a giant genetic advantage. Since these ancient creatures lived in the sea, the earliest sex was a straightforward process of spraying sperm and eggs into the water. The lucky few connected.

In that massive free-for-all, the fittest sperm reached the eggs and were rewarded with the prize of bringing their DNA into natural selection’s next round. Sometimes the fittest sperm were the strongest swimmers. Sometimes they were the ones deposited nearest the eggs. Others developed ways to follow molecular scent pathways to find the eggs. Or they bundled together in teams to improve their timing and accuracy. As sperm perfected ingenious rudders, tails, chemical markers and swimming strategies, the genital hardware that ejected them was evolving, too.

More here.