From the book Sperm Wars, by Robin Baker:

Very few (less than 1 per cent) of the sperm in a human ejaculate are the elite, fertile 'egg-getters'. The remainder are infertile 'kamikaze' sperm whose function has nothing to do with fertilisation as such but everything to do with preventing sperm from another man fertilising the egg.

I have read elsewhere (can't remember exactly where, but I don't think it was a creditable source) that Baker's 'kamikaze' sperm hypothesis has been found experimentally to be false. Is this true?

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    Are you planning to start a reality TV series on one of the Science networks? You can call it: "Sperm Survivor" ... Watch Kamikaze Sperm under the microscope as they brutally outwit, outlast, and outplay one another for the ultimate prize! ;-) Commented Dec 12, 2011 at 5:06
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    @RandolfRichardson I was going to make a "Hunger Game" followup wisecrack but it sounded too weird :)
    – user5341
    Commented Dec 12, 2011 at 20:01
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    @RandolRichardson: That's... that's just wrong.
    – Borror0
    Commented Dec 14, 2011 at 2:50
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    @RandolfRichardson: hmmm... not what I had in mind ;) But I was thinking that perhaps one could determine whether a significant fraction of the sperm was or not infertile. If it were, then Baker's would seem more plausible. But if someone finds that most of the sperm is fertile, then Baker's hypothesis would be proven wrong.
    – a06e
    Commented Dec 14, 2011 at 6:52

1 Answer 1


One study argues that it is unlikely based on the evidence available:


Quoting part of the abstract:

More specifically, their "kamikaze" sperm hypothesis proposes that deformed mammalian sperm are adapted to facilitate the formation and functioning of copulatory plugs (Baker and Bellis, 1988). Here I argue that most, maybe all, mammals are unlikely to produce nonfertilizing sperm. First, mammals might not be able to afford to evolve nonfertilizing sperm, given that a) fertilization is often unlikely despite the huge numbers of sperm produced; b) production of larger numbers of sperm is constrained, presumably because of metabolic costs, evidence for which includes the fact that in species in which sperm morphology and anatomy of the female reproductive tract increase the probability of fertilization, the numbers of sperm produced is lower than in others; and c) selection appears to act against the production of deformed sperm. Second, some of the evidence advanced for the existence of nonfertilizing sperm does not in fact support the idea. Third, accessory gland secretions are sufficient on their own to coagulate semen and produce fully functioning plugs; thus the male that used accessory gland secretions would be at a clear advantage over the male that diluted his fertilizing sperm with "kamikaze" sperm; and indeed, current evidence indicates selection on accessory glands, not sperm morphology, to enhance coagulation of semen. Fourth, predictions made on the basis of the "kamikaze" sperm hypothesis are not supported by quantitative comparisons of data from polyandrous and monandrous primates (i.e., those in which several males mate with a fertile female, and therefore in which sperm competition should be operating, and those in which only one male mates).

  • So here we have one study that refutes Baker's hypothesis. Baker's studies, on the other hand, support Baker's hypothesis. This kind of debate is normal and is of course not enough to prematurely rule out a hypothesis. What I would really like to know is if the majority of the scientific community today rejects or accepts this hypothesis, or if it is still debated.
    – a06e
    Commented Feb 25, 2012 at 1:04

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