Female First

 Here are five evidences that females were the original genotype, and males evolved later from them: 1) As mentioned here, if no SRY gene is activated on the Y chromosome, all mammalian embryos will BY DEFAULT continue on as females. 2) Still today, many amphibians, fish, insects and reptiles are all-female breeding colonies (ants, bees, termites), giving birth to genetic clone females via parthenogenesis and engaging in pseudo-coitus ( Whip-tailed lizards). To date, there is no known all-male breeding colony discovered in any species. 3) The female genotype is homologous XX, the male is a deletion mutation of one of the Xs to become a much shorter Y chromosome, to make it XY later in evolution. 4) The Mitochondrial Eve is 200,000 years old from East Africa, the Genetic Adam is only 60,000 years old, from the same region. 5) All juvenile skeletons, both for male and female children, look female-like till they approach puberty. Then, due to testosterone surge, the skeleton undergoes sexual dimorphism. The default set up again, is female.