Primates with bigger testicles cheat more, researchers say

Maybe size does matter, at least when it comes to primates being faithful to their partners. A study by Norwegian researchers found the larger the testicles of a primate, the more likely he is to cheat on his significant female other. The cheating heart cuts both ways as University of Oslo researchers found female partners also cheated more if the male had big testicles because she feared his being unfaithful would harm her reproductive chances.

Professor Petter Bockman spoke for researchers saying the less faithful the female in species like bonobos and lions were, the larger male counterpart’s testicles seemed to be. This was explained by adding that testicles had to be large to ensure enough sperm could fertilize the female ahead of competitor semen.

Animals with short lifespans had exceptionally large testicles, Bockman said testicles accounted for half of some grasshopper’s body mass and sea urchins were almost all-testicle with a small shell. For the record, human testicles were, on average, 1 1/2 times larger than gorilla testicles. That’s because gorilla males control harems and don’t need an abundant semen flow to do the job, Bockman said.

The Norwegian study was released as part of the fanfare leading up to February’s new anniversary exhibit at Oslo University’s Natural History Museum. The museum is hosting a year-long Sexus exhibit exploring the correlation between sex, sperm, and fidelity.

The Oslo research was related to another recent study of primate testicle size. A few months ago a study by Emory University in Atlanta researchers found men with smaller testicles had a greater parental role than those with bigger testicles.

Research from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany found that 15 percent of non-human primates were monogamous with just 17 percent of 560 separate human societies featuring monogamy.

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Large testicles mean greater infidelity, research finds
http://www.telegraph.co.uk/science/10603957/Large-testicles-mean-greater-infidelity-research-finds.html