I've recently read the "Sperm wars" book by Robert Baker. It deals with human sexuality and infidelity. The main premise of the book is that human male has different kinds of sperm:

  • Regular sperm for fertilization
  • Toxic sperm that kill competitor sperm (similar in concept to white blood cells)
  • Slow, inactive sperm to block channels in female cervical filter

According to the author, when a female engages in infidelity or group sex, the sperm actually "goes to war" killing competition and preventing passage through cervical filter.

Are there are indeed different kinds of functional sperm in humans, and are their functions involved in sperm competition / warfare? In other words, does human sperm not only fertilize the egg, but also to block passage of competitor sperm and even kill it?

  • $\begingroup$ This guy seems to have reasonable credentials. Next step would be to search academic journals for this research and see whether peer reviewed. $\endgroup$
    – bpedit
    Jan 29, 2017 at 17:19
  • $\begingroup$ The logical conclusion to this claim seems to be that a woman could not get pregnant (or would be much less likely to do so) while engaging in "infidelity" or group sex. I'm pretty sure that this is contradicted by experimental evidence. $\endgroup$
    – jamesqf
    Jan 29, 2017 at 19:38

2 Answers 2


I wanted to respond to your question because while I don't know very much about this particular subject myself, I did have the pleasure of attending a talk by Robert Martin, author of How We Do It (https://www.amazon.com/How-We-Do-Evolution-Reproduction/dp/0465030157/ref=sr_1_2?ie=UTF8&qid=1492260860&sr=8-2&keywords=how+we+do+it). In the talk and in his book he does address this topic (and the book Sperm Wars) and basically says that while it was a highly influential idea, the underlying science isn't reliable. He argues that evidence suggests that humans have not evolved under multi-male types of mating systems. There is a lot of evidence to back this up, and revoke the idea of "killer sperms." Check it out and see what you think! If anything it is an interesting read.


Not in humans

Sperm competition is supported in humans (multiple sperm from multiple partners can be present in the same female)

Specialized sperm is not supported.

Specialized sperm is however confirmed in non-human non-vertebrate animals which was surprising, although what the different types of sperm do in these animals is not understood.


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