The Evolution of Ejaculation Strategies

According to a paper to be released in the September issue of the journal "American Naturalist", the number of sperm a male ejaculates may be correlated to his attractiveness as measured by the females in the population. The idea came forth after scientists at University College London and the Oxford University mathematically modeled the optimal "sperm load" to maximize daddiness across a range of mating patterns. The research, which took place late one Friday night at the corner bar, was one of several proposed ideas to "settle a bet" between two of the scientists.

The results suggest that males who attract more females may produce fewer sperm per mating than those who aren't so lucky. Essentially, the model shows that the optimal way to get lots of offspring is to mate with as many females as possible, even if those matings involve fewer sperm and, thus, a lower probability of conception per 'bow chicka bow wow'. Conversely, males with fewer opportunities to mate should put all their sperm in whatever baskets they can woo. This increases the probability of conception per mating, an advantage when you can't get much.

This idea is in contrast to the assumption that higher quality males are more fertile. The authors recognize that the pattern may not hold true for all species, given the diversity of mating strategies across taxa. They also state that it is difficult to know how these findings apply to humans and other primates. However, we all know that was just a CYA statement and, in actuality, they nailed it.

Future studies will focus on comparing sperm load in males that are similarly attractive but with differing access to prime sperm-making resources. The authors do not mention which species will have the joy of settling this bet, but the odds of the results being apt for Homo sapiens are about 100:1.

Fig. 1 A schematic representation of optimal sperm load by relative attractiveness


Mr. Sprinkles


Exxon Valdez

'The evolution of continuous variation in ejaculate expenditure strategy' by S. Tazzyman, T. Pizzari, R. Seymour, and A. Pomiankowski will be published in the September issue of the journal American Naturalist.

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It post-ejaculation strategies that are the real problem.

Unless you don't give your real name.

Hahahahahah, I'm glad you guys are back. You crack me up.

There are a number of fish species which have "sneaky males" in addition to regular males. The sneaky males look and act like females or juveniles. They generally join in on regular spawning activities. I recall one instance where the sneaky males were called "super males" because their testes where several times as large as the testes of regular males.

By Jim Thomerson (not verified) on 14 Jul 2009 #permalink

I'd be interested to know if perceived attractiveness also correlates with testes size. If less attractive males tend to produce larger loads per coupling, they may also have larger testes, on average, to support these larger loads.

Also, I love science articles that discuss things like ejaculation strategies.

you might want to check out this classic conversation starter:
Soler, C., Nunez, M., Gutierrez, R., Nunez, J., Medina, P., Sancho, M., et al. (2003). Facial attractiveness in men provides cues to semen quality. Evolution and Human Behavior, 24, 199â207.

Two studies show that rated attractiveness positively correlates with sperm morphology, motility and some kind of "sperm index", but interestingly, NOT with concentration.

Lol to the males putting all their sperm in whatever baskets they can woo.

I think they did the study with chickens, right? It all sounded a bit suss to me...

..,there are lots of option about the medications of pre ejacuation among men... with so many option how can i be able to know which one is suited for me??????