figure 7. Chinook salmon cluster analysis using characters associated with body shape, meristics, biochemistry, and life history. Clustering strategy is correlation. See Table 2 for key to stock names.




http://www.nytimes.com/2009/02/10/science/10evolution.html?em

Darwin drew the first evolutionary tree when he was 28. He had recently returned to England from his five-year voyage around the world aboard the Beagle, and his theory of evolution was still in an embryonic state. It occurred to him that evolution could explain the similarities and differences between species. The descendants of an ancestral species might have evolved into different forms, splitting into separate lineages “like the branching of a great tree from a single stem,” as he would later write in “On the Origin of Species.”

Darwin’s first tree is now a familiar sight in books, museum exhibits and, of course, on Wikipedia. But David Kohn, the director of the Darwin Digital Library at the American Museum of Natural History, has recently discovered 10 other trees that Darwin drew in later years. “It’s a long-term preoccupation,” Dr. Kohn said. “It feels like he’s using it to think.” While pondering how humans evolved, Darwin drew a cluster of branches to represent our common ancestry with apes and monkeys.