I'm having trouble to understand how this can be true. It seems like every human should have equal numbers of male and female ancestors, e.g. by induction on how many generations back you look.
Taking an average human generation time of 25 years, you would theoretically have 2^30 = roughly a billion ancestors 30 generations back, or 750 years ago. But the population of the Earth in 1300 was... maybe 400 million. (e.g. https://www.census.gov/data/tables/time-series/demo/internat... for world population estimates)
And your ancestors in 1300 aren't drawn from the entire population of the world; they're drawn from a tightly restricted subset of that.
And if you think that's ridiculous, imagine how many ancestors you'd have thirty-one generations back!