Dogs are Evolved from Wolves Through Artificial Selection

Take the domestic dog (Canis lupus familiaris), a single species that comes in all shapes, sizes, colors, and temperaments. Every single one, purebred or mutt, descends from a single ancestral species—most likely the Eurasian gray wolf—that humans began to select about 10,000 years ago. The American Kennel Club recognizes 150 different breeds, and you’ve seen many of them: the tiny, nervous Chihuahua, perhaps bred as a food animal by the Toltec of Mexico; the robust Saint Bernard, thick...

 Skeletal Similarities in Mammals

What a piece of work is the mammalian skeleton. I don't mean it is beautiful in itself, although I think it is. I mean the fact that we can talk about 'the' mammalian skeleton at all: the fact that such a complicatedly interlocking thing is so gloriously different across the mammals, in all its parts, while simultaneously being so obviously the same thing throughout the mammals. Our own skeleton is familiar enough to need no picture, but look at this skeleton of a bat. Isn't it fascinating ho...