I always read through the latest research on gifted topics to add to our research page. I have to admit that I was a little surprised to find an article researching whether IQ and ejaculate quality were related. I then spent WAY too much time diving into the literature on reproduction and intelligence...and it turns out that there is actually a lot of it out there!
Some of the early research in this area stems from a fear that those with lower IQ are having more children, which could impact the collective IQ of societies. Some research has been presented showing some declines in IQ, while other research has shown that IQ continues to increase each decade.
There is a hypothesis that there may be a phenotype-wide fitness factor, which basically means that some people think that human intelligence and evolutionary fitness should have some simple relationship. Surely, they think, there must be a link between IQ and evolutionary survival of the fittest!
Research findings on this potential relationship have been mixed. Some research found positive correlations between intelligence and semen quality, while others found no relationship. Population level data in Sweden found men with higher IQ were more likely to have higher fertility (in part because they were the ones who were likely to be married and employed). Other research in Scandinavian countries has yielded similar results.
However, research from other parts of the world has shown that individuals with higher IQ tend to choose to have children later in life as they first work toward other goals (e.g., education or employment). The decision to have children later in life then reduces the reproductive years available and thus lowers the overall reproduction rates. This has become known as the slow life-history behavioral trait, a term that comes from evolutionary psychology. Basically life history strategies develop from experienced environmental pressures (faster life history generally develops because of harsh environments and the species needs to reproduce quickly; slow life history generally is when the environment is less risky and humans are more future oriented).
The bottom line is that there is no "right" answer to whether intelligence and reproduction are linked. It appears that they are in some cases linked due to those with higher IQs delaying reproduction and choosing to have fewer children while in other places, those with higher IQ have more children.
So that's a brief review of the literature on this topic! What do you think about the potential linkage?