Why Human Penises Lost Their SpinesWhy Human Penises Lost Their SpinesDNA study offers clues to "impenetrable mystery" of evolution, expert says. Men have lost the DNA code that once made human penises spiny, according to a new analysis of the human genome. Penile spines, which are still present in several modern animals, are usually small barbs of keratin—a type of hard tissue—that line the outside of the organ. The prehistoric ma
