There has been a lot of discussion in the blogosphere as of late as to whether the “cads”—i.e., low paternal investment, promiscuous (and often low-IQ) men were siring more children than “dads”—high paternal investment, monogamous, high-IQ men. While I and others have produced some evidence (primarily from the GSS) that tenuously indicates that this is not the case, it may be impossible to know for sure, due to the potential unreliability of self-report promiscuity and fecundity.

The finding that motivates these observations is the fact that the age of the onset of puberty seems to be decreasing. While the primary cause of the decrease is likely better nutrition (mirroring secular increases in height, BMI, and IQ), the change is not so dramatic that genotypic change, i.e., evolution, cannot account for a large share of it. Peter Frost and Heartiste have posited that this may be because cads now have a reproductive edge over higher investment men. They certainly appear to have a mating edge, but thanks to modern contraception, it’s unclear if that translates into an increased number of descendants.

However, I’ve realized that we’re looking at this the wrong way. If the “r-strategists” (low-IQ, low future time orientation, higher sex drive, earlier maturing individuals) are breeding more, it may have little to do with dads. It may be about the moms.

The Audacious Epigone and myself have discovered that when compared by IQ, for men, reproduction is pretty even. That is, men reproduce roughly equally at all levels of IQ. However, for women, this is not the case; low IQ women appear to be considerably more fecund than their high-IQ sisters:

Women on the low end of the IQ bell curve, where many of the r-strategist behaviors are to be found, pass on their traits to both their daughters and sons, which could explain the decreasing age of puberty (beyond whatever is explained by better nutrition).

Low-IQ women likely didn’t have a reproductive edge in the past. Back in the day, people—especially women—were far more variable in their reproductive success than they are today. Indeed, my own look into the GSS found that back at the beginning of the 20th century, a sizable portion of women (nearly 20%) failed to leave any offspring:

As well, nearly another 30% percent had four or more offspring, 10% having 8 or more. One can imagine that this process was likely eugenic in several respects. As has been the case for Europeans since prehistoric times (on and off), women were dependent on breadwinner husbands to survive—or at least to successfully raise a family—thus the mating market for eligible bachelors was in men’s favor. One would imagine that such a situation allowed women to be somewhat selected for traits such as beauty, work ethic, faithfulness, and, quite likely, intelligence—in other words, K-selected traits.

Today, women are far more even in their reproductive success, with most women having between 1-3 children. Further, the existence of the social safety net and other developments, such as women gaining entry into the work place and welfare, have allowed women who leaned more towards the r-side of things to be more successful than they once were. This would translated into more r-selected traits—earlier puberty, increased promiscuity, and lower IQ—becoming more prevalent in the population, even if men of all walks were about as reproductively successful today as they were in the past.

Now I’m sure certain voices will use these data to advocate certain social agendas, particularly trying to roll back the modern age of the sexually liberated, working woman. Whatever merits this might have (and to be fair, there would be some), this is simply not going to happen in the foreseeable future. The best way to address the apparent issue of dysgenic breeding among women is to promote more and better family planning and to adopt conditional welfare measures.

I will add that the above GSS data that this post is based on may come with a caveat: it may be that it’s not that lower IQ men have the same number of children as their smarter counterparts, but that they are less able to keep track of the number of children they sire. After all, a woman always knows exactly how many children she’s had. This is not necessarily the case for men.

Edit, 12/29/12: Because of the issue mentioned above—that men may be under-reporting the number of children they’ve fathered—I checked the GSS data. I compared the CHILDS variable for men to that reported by women, by decade of birth, beginning in the 1880s. Since the average number of children born to women should approximately equal the average number of children born to men, if there is a disagreement, it would suggest misreporting. I found that except for a discrepancy in the 1930s cohorts, the average number children born to men and women agree across all decades. This indicates that men in the GSS aren’t largely under-reporting (either intentionally or via ignorance) the number of children they sire (or at least no more so than are the women). I checked both Whites only and with all races. The 1930s group seemed to have an excess of 0.4 children born to women, for reasons unknown.

Overall, this does indicate that dysgenic fertility is primarily occurring in the form of excess births to low-IQ women (and/or deficient births to high-IQ women, thanks primarily to lengthy educations). This may be the legacy of reduced competition between females for mates, as was the case in sub-Saharan Africa, producing similar evolutionary pressures.