After I'd come to understand evolution and know a little about history and farming, I saw that the thick white animals I laughed at for following each other around and getting caught in bushes were the product of generations of farmers as much as generations of sheep; we made them, we moulded them from the wild, smart survivors that were their ancestors so that they would become docile, frightened, stupid, tasty wool producers. We didn't want them to be smart, and to some extent their aggressiveness and their intelligence went together. Of course, the rams are brighter, but even they are demeaned by the idiotic females they have to associate with and inseminate.
The same principle applies to chickens and cows and almost anything we've been able to get our greedy, hungry hands on for long enough. It occasionally occurs to me that something the same might have happened to women but, attractive though the theory might be, I suspect I'm wrong.
Iain Banks, "The Wasp Factory"