Bio Extra Credit
Two weeks before Charles Darwin died he wrote a short paper about a clam clamped to a water beetle in a pond in the English Midlands. The man's son that sent him the beetle worked together with his son and discovered that what Darwin said about evolution was correct. The vindication came from a book that said every organism has a certain chemical code called DNA.
Darwin surmised that all Galapagos finches were close cousins and he explained this in his book The Voyage of the Beagle. Scientist today can confirm that his thoughts were correct and they can prove that with their DNA findings. Darwins greatest idea was that natural selection is largely responsible for the variety of traits one sees among related species. He says this is visible with the different sizes, shapes, and lengths of their beaks.
In The Origin of Species, Darwin tactfully left unspoken how his theory would extend that commonality to include humankind. A decade later he confronted the issue in his book The Descent of Man.
He wrote to the American botanist Asa Gray that "The sight of a feather in a peacock's tail, whenever i gaze at it, makes me sick!" Even biologists became obsessed with arguing that traits evolve to suit the species, rather the individual. Darwin did not speculate much on why a female would choose any certain male. It is a question that still excites biologists, because they have two equally good answers to it. One example is fashion such as when females are choosing males, other females must follow suit or risk having sons that do not attract females. The other is more subtle. The tail of a peacock is an exhausting and dangerous thing for the bird to grow. It can only be done well by the healthiest males: parasites, starvation, and careless preening will result in duller plumage. So bright plumage constitutes what evolutionary biologists call an "honest indicator of fitness." Substandard peacocks cannot fake it. And peahens,...