Humans provided the animals with food and protection in exchange for which the animals provided the humans their milk, eggs, and—yes—their flesh. Both parties were transformed by the new relationship: The animals grew tame and lost their ability to fend for themselves in the wild (natural selection tends to dispense with unneeded traits) and the humans traded their hunter-gatherer ways for the settled lives of agriculturists. (Humans changed biologically, too, evolving such new traits as the ability to digest lactose as adults.)
