To anyone who has stared into the deep and unwavering blankness of a house cat's eyes, or has watched his beloved pet stand motionless in the center of a room, waiting for a thought to enter its plum-sized brain?to such a person, the news will be no surprise: compared with its wild ancestor, the domestic cat has about one-third fewer neurons (nerve cells). The cat's brain has shrunk during the course of evolution, and it has shrunk by losing neurons. The researchers compared the brain of Felis catus with that of the Spanish wildcat. Spanish wildcats are living fossils?rare survivors of the species that gave rise to domesticated cats 15,000 to 20,000 years ago. While the domestic cat's line has evolved rapidly since then, the Spanish wildcat has barely changed. Williams and his colleagues found that the domestic cat's brain is 20 to 30 percent lighter than a Spanish wildcat's brain. (Its whole body is about half the size of the wildcat's body). To find out whether the domestic cat had smaller neurons, more tightly packed neurons, or simply fewer neurons, the researchers decided to actually count the number of neurons in a small section of the feline brain?the visual pathway. They found that the Spanish wildcat had half again as many cone cells-the cells that allow for daytime and color vision-in the retina; 50 percent more signal transmitting axons in the optic nerve; and 50 percent more cells in the lateral geniculate nucleus, a clump of neurons in the brain that sorts the signals from the optic nerve. If one extrapolates these findings to the whole brain, says Williams, this means that domestic cats have lost about a third of their neurons during evolution. The intriguing thing is that each domestic cat seems to start out within all its ancestral neurons? A large umber of the domestic cat's cells, however, die as the fetus develops. The death of brain cells often happens in mammals, says Williams. "The human retina initially has 3.5 million ganglion cells, and then half are lost. But the domestic cat makes close to a million and keeps only 160,000." If you're going to evolve a smaller brain, he adds, the cat's strategy is probably a good one. "It has a built-in flexibility. If conditions were to change rapidly in a few thousand years, an animal could take advantage and stop losing as many cells." Why the domestic cat should want to lose brain cells in the fist place, however, the researchers can't say. But they warn against drawing facile conclusions concerning the animal's intelligence. "In some respects I'm sure a wildcat is a much more competent animal," says Williams. "But domestic cats are much smarter at coping with humans than are wildcats?so in that respect, a domestic cat is obviously a genius Whitch statement best summarizes the main point of the passage