Do we have more female than male ancestors?


I have read a claim in several sources, including a New York Times article by John Tierney, that we have more female ancestors than male ancestors.

"Citing recent DNA research, Dr. Baumeister explained that today’s human population is descended from twice as many women as men. Maybe 80 percent of women reproduced, whereas only 40 percent of men did."

While this may seem unintuitive, it is possible due to pedigree collapse and a lower rate of male repoductive success. A lower rate of male repoductive success (i.e. males were less likely to survive to reproductive maturity) in combination with pedigree collapse may mean that our total number of female ancestors can exceed the total number of male ancestors.

Is this true for a person with predominantly European ancestry? I would particularly like to see genetic or demographic evidence that supports or refutes this idea. If true, it would also be useful to quantify the ratio of male to female ancestors at a given generation level - in other words, roughly how significant is this effect on a genealogical timescale?

Harry Vervet

Posted 2015-10-21T00:33:13.590

Reputation: 17 763

@vervet I might add rather than it be more open ended for 'any' studies.. seeking a summation of mathematical studies might help refine the question to be more specific and digestable by others so it doesn't become commentary discussion like NYTimes comments in the source article. – CRSouser – 2015-10-21T16:50:09.577

1@CRSouser I didn't originally add a source for the claim because I didn't want the question to be centred around one article. There are many others I could have included as alternatives. I'm also not particularly interested mathematical studies, because I understand how theoretically this might occur; mathematical models can only take you so far. I'm more interested in seeing a synthesis of the evidence for this in the population of interest, and understanding the significance of this effect on a genealogical timescale. – Harry Vervet – 2015-10-21T17:00:55.413



This article is not talking at all about pedigree collapse or male reproductive rates.

What Baumeister states in his book Is There Anything Good About Men is that "DNA studies, notably those by Jason Wilder and his colleagues ... concluded that among the ancestors of today's human population, women outnumbered men about two to one." He then states this means that "humanity's ancestors were about 67% female and 33% male."

He then gives an example of a desert island with 4 people, two male and two female. One male has a child with both females. The other male does not. We now have two children. They are descended from two females and one male. 67%, 33%. John Tierney, in the article you refer to, expands this to a Gilligan's Island example going one more generation and showing a grandchild with 3 female ancestors and 2 male: 60% to 40%.

What this is doing is going back to the very first ancestors. The work by Jason Wilder (e.g. Genetic Evidence for Unequal Effective Population Sizes of Human Females and Males) was related to finding the Y-chromosomal Adam and Mitochondrial Eve.

The Y-chromosomal Adam article explains that there was a discrepancy in time depths with mt-MRCA most recent common ancestor living 150,000-200,000 years ago, but the Y-MRCA living 84,000 years ago. It states: "One explanation given for this discrepancy in the time depths of patrilineal vs. matrilineal lineages was that females have a better chance of reproducing than males due to the practice of polygyny. When a male individual has several wives, he has effectively prevented other males in the community from reproducing and passing on their Y chromosomes to subsequent generations."

So Baumeister is not stating anything about generational levels. It is not in any way trying to state that the total number of female ancestors someone will have will be twice as many as the number of male ancestors they have. It is only referring to humanity's set of most recent common ancestors, and it is only "one explanation" for a discrepancy in the MRCA depths.

Polygyny was common in primitive and biblical times, but became rarely practised after that. And even if you had some polygyny, the practise is no longer widespread enough to prevent the other males from finding a partner. So that practise will not be a cause of misbalance in the number of your male versus female ancestors in your genealogical research.


Posted 2015-10-21T00:33:13.590

Reputation: 16 148

We now have two children. They are descended from two females and one male. This is wrong : Each kid has exactly one male and one female ancestor, and the male ancestor just happens to be the same (in this particular case). Only if those kid's descendants get children together, those children would have more female ancestors than male, and most certainly not by 67%/33% difference. – Bregalad – 2015-10-22T08:22:13.603

Polygyny was only ever common among riches, and the majority of your ancestors are typically poor. Polygyny is only one of the reasons there could be more female ancestors than males, the other reason is a husband dying and the women remarrying another man, although the opposite also happened so you'd have to prove that this happened more than men remarrying to another woman. – Bregalad – 2015-10-22T08:26:29.507

A male doesn't need to be married in order to impregnate a lot of females. – pxc3110 – 2019-10-17T17:54:41.613

very high male mortality rate due to dangerous hunting is the primary explanation. No hunters could afford 2 wives, hence monogamy was the norm. But even then, humans weren't sexually monogamous. Many women were impregnated without being married. The concept of marriage probably wasn't popular back then. – pxc3110 – 2019-10-18T19:17:23.533