Virtually all calico cats are females and my techs think that most of them are ornery and difficult to handle. The family of Mitten, the cat who modeled for this week's cartoon, lent some support to this observation when they told me that their daughter Laura is the only one in the family that can reliably handle Mitten on visits to the vet clinic. The many differences between men and women begin with the Y chromosome, which is much smaller than it's pair, the X chromosome. In Reptiles, who have been around for a really long time, the equivalent of the X and Y chromosomes are pretty much equal. But then, during the last 300 million years, things pretty much went downhill.
Chromosomes carry genes and genes make proteins.
Something had to be done to make up for the puny Y chromosome's lack of protein production. The female X chromosome came to the rescue. X chromosomes began to work twice as hard and produce twice as much protein. Sort of like a woman who raises children, runs the household, and also has a full time job. But women do not need the doubled output from two X chromosomes, so early in the development of the female fetus one of the X chromosomes in each cell shuts down.