Why are there equal number of males and female people?

Perhaps, but that article, without any hint of a citation, isn’t evidence for the claim.

(BTW, apparently the paper’s author, Roy F. Baumeister, found some MSWordDocDoc-to-Text convertor that selectively deletes spaces.)

I’m not sure you’re thinking this through correctly. The human species collectively has more female ancestors than male ancestors, but that doesn’t imply that every (or any) individual human does. If you and I each had 50% female and 50% male ancestors, but more shared ancestors who were male, we’d have more female ancestors between the two of us.

It depends what you mean by “evidence.” If an authoritative person makes a statement, it’s evidence that the statement is true.

I think what you are saying is that the claim does not carry a lot of weight without a citation. I see your point, but when you think about the claim carefully, it actually makes a lot of sense. Even in 2012 in the United States, based on general observation, it seems that a higher percentage of women than men reproduce.

And when you look at old sources, for example the Bible, you definitely get a sense that polygamy was pretty common back in the day.

So I am willing to (tentatively) accept what this professor says without a citation because the claim is so sensible.

I’m not sure I see your point, but here is a thought experiment. Go back 15 generations in your family tree – there are about 30,000 slots to fill. Write down the names of each person for each of the 30,000 slots. Of course there will be people whose names occur more than once. Cross out those names. You will be left with a list of your distinct 15th generation ancestors. I assert that the list will be significantly more than half female. And that if you go back far enough, you will end up with a list that is about (perhaps?) two thirds female one third male.

Agreed?

Yes, that seems likely.

I guarantee you that at least one human has more female ancestors - just by himself - than male ancestors. Me. My great grandfather married his half-first-cousin. That is, a man impregnated two wives, who bore half-siblings. Those people had kids, who married each other, and had one of my grandparents.