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In researching Robin Baker’s book Sperm Wars, I found a number of fascinating stories concerning the man himself, which I’ve collected together here.
It all starts at Manchester University, in 1972, when Dr Baker starts experimenting with the idea that everybody has some sort of inbuilt magnetic compass which helps them navigate. To test this theory, people were transported blindfolded around Manchester, and after reaching a pre-determined point unknown to the subjects, they were asked to indicate the direction of ‘home’. According to Dr Baker, people were actually able to do this. However, other scientists working in navigation research were unconvinced, and many sceptics attempting to reproduce the results failed. Undeterred, Dr Baker re-analysed all the information from the other studies saying the experiments had worked, combined them, and claimed it as additional evidence for his theory.[1]
The media, who loves this type of story, quickly picked up on the idea of people having magnets in their heads, and granted Dr Baker a lot of press coverage. Then, shortly afterwards, Dr Baker turned to sex research, and human sperm competition.
Robin Baker, and his collaborator Mark Bellis, revealed in the early 1990′s that their nationwide survey had shown high levels of polyandry in the population, and that sperm from competing males battled to the death (killing each other inside the female reproductive tract) and that females controlled this conflict, using their orgasms to regulate the uptake of sperm, and ultimately the fatherhood of their children.[2]
At the same time, Dr Baker proposed that men with bigger testicles would be most successful in the race to fertilise most eggs, and that the testis size of individual men could predict their success in sperm competition. Remarkably, Dr Baker had managed to persuade 14 of his male colleagues to measure the size of their left testicle, using callipers. He then asked 20 female colleagues to look at the men, and rank them according to whom they would most like to have an adulterous relationship with. As he predicted, there was a correlation between the big-balled males and the apparent likelihood that the men would engage in extra-pair copulation, if given the opportunity.
Dr Baker’s methodology was however flawed: When reporting testis size, he hadn’t expressed testis size in relation to the height of the male owner of the testicles. In the animal kingdom, it is obvious that larger animals have larger testes. Further, we don’t know the races of the men in Dr Baker’s sample. Racial differences can account for a large variation in testis size.[3] Also, a great many other variables could have caused this positive correlation, none of which were taken into account.
Then in 1994, the media took further interest in the work of Baker and Bellis, as Desmond Morris (of Naked Ape fame) based a portion of his TV series ‘The Human Animal‘ on Baker and Bellis’s theories. Telling viewers that men who suspected their sexual partner had been unfaithful could unconsciously release specialised ‘killer sperm’ in their ejaculate, which then went about destroying the rival male’s sperm, whilst their regular sperm concentrated on penetrating the egg. The programme even showed footage of what looked like one sperm battering another sperm to death. However, according to several Andrologists, this sperm looked like it was already dead. And, even if this really was one sperm killing another, because none of the sperm were labelled in any way, how could anybody know whether these were sperm from different males, or the same male?
The theory that different types of sperm within a human ejaculate each had a specific role in sperm competition formed the basis of what Baker and Bellis termed the ‘Kamikaze sperm hypothesis’. And at the time, the claims made were earth-shattering! Sperm warfare going on inside female bodies was given some initial credibility because of theories about sperm competition and sperm choice provided by other biologists, from studies in the animal kingdom. However, it’s very dangerous to anthropomorphize; and the Kamikaze sperm hypothesis has been disproved several times since then.
- Baker, R. R., The Evolutionary Ecology of Animal Migration (London: Hodder & Stoughton, 1978); Baker, R. R., ‘Human navigation and magnetoreception: the Manchester experiments do replicate‘, Animal Behaviour (1987), 35, 691-704
- Baker, R. R., and M. A. Bellis, Human Sperm competition (London: Chapman & Hall, 1995)
- Diamond, J. M, ‘Variation in human testis size‘, Nature (1986), 320, 488-9
You might also enjoy reading:-
- Sperm Wars: The Science of Sex – Reviewed and appraised
- Human penis size evolution
- Sperm competition and the Kamikaze Sperm Hypothesis
- Women ‘on heat’
- Why Do Women ‘Tease’?
Posted by Jonathan in Biology, History, Sociobiology