Species Divisions are Complicated

Zoologists have traditionally divided the vertebrates into classes: major divisions with names like mammals, birds, reptiles and amphibians. Some zoologists, called 'cladists',* insist that a proper class must consist of animals all of whom share a common ancestor which belonged to that class and which has no descendants outside that group. The birds would be an example of a good class. All birds are descended from a single ancestor that would also have been called a bird and would have sha...

 Ways to Understand Male Sexuality

There are five ways to find out. One is to study modern people directly and describe what they do as the human mating system The answer is usually monogamous marriage. A second way is to look at human history and divine from our past what sexual arrangements are typical of our species. But history teaches a dismal lesson: A common arrangement from our past was that rich and powerful men enslaved concubines in large harems. A third way is to look at people living in simple societies with Ston...