Family pets may be cuddly friends, but their gradual transition from the wilds to the hearth offers a sobering message: tampering with mother nature can have totally unexpected consequences.

Ever since that first wolf sheepishly sought the companionship of humans -- and their scraps from the dinner table -- people have selectively bred everything from pigs to horses to see if they could tailor the beast to be a better servant.

Those early experiments with genetic engineering created animals that are vastly different from their ancestors in the forests, and for more than a century scientists have been trying to figure out why.

Even Charles Darwin couldn't explain something he called "domestication syndrome," dogs, foxes, pigs, sheep, and many other animals change dramatically when they become partners in the human pageant.

The question is: "Why?"

Why do most dogs have floppy ears, while the only animal in the wild with floppy ears is an elephant, according to Darwin's research in the 1800s?
Why do so many domesticated animals have white patches of fur, called depigmentation?

Why do so many pets have smaller brains than their ancestors, and smaller jaws and shorter snouts and smaller teeth?

Darwin thought there had to be a common cause for all those changes, although they seem so unrelated. Down through the years scientists have offered a number of theories, but none have been universally accepted. Now, scientists in Germany, the United States, Austria and South Africa have zeroed in on a biological process that begins very early in the embryonic spinal column of vertebrates.