Waterfowl wage genital warfare

A sexual arms race waged with twisted genitals has been discovered in waterfowl.

The genitalia of the females of these species have at times apparently evolved to make it harder for males to successfully impregnate them, according to new findings that shed light on the eternal war of the sexes.

Most birds lack phalluses, organs like human penises. Waterfowl are among the just 3 percent of all living bird species that retain the grooved phallus found in their reptilian ancestors.

Male waterfowl are especially unusual in that their phallus length varies greatly among different species, ranging from a half-inch to more than 15 inches long. They also display a remarkable level of diversity how elaborate they are, ranging from smooth to covered with spines and grooves.

Scientists had speculated that male waterfowl evolved longer phalluses to give them a competitive edge over those not as well-endowed when it came to successfully fertilizing females...

--MSNBC