Gorillas make a splash, Science Online,.Big bottomed baboons make better mates, Science Online,.Grunters not guffawers get the girl, Science Online,.In other words, the arousal previously elicited in the male by the sight of the female's pendulous buttocks bisected by a central cleavage was now elicited by the mimicking breast arrangement on the front.
According to Desmond Morris in The Naked Ape (McGraw Hill, 1987) this development coincided with the switch over from front-to-rear to front-to-front mating. Much of the human breast size is accounted for by fat, not milk glands, and human breast size is not explained by the need to nurse infants.Įvolutionary psychologists explain the large female breast as a secondary sexual characteristic that evolved to attract mates. Relative to body size, it is much bigger than the breast of the female gorilla and significantly bigger than the breast of the female chimp. Therefore, according to evolutionary theory, humans should be intermediate between gorillas and chimpanzees in respect both of promiscuity and polygamy.Īnother aspect of human anatomy in need of explanation is the size of the female breast. Relative to his body size, his penis and testicles are much larger than the gorilla's but not as large as those of the chimpanzee. The human male is slightly larger than the female. Under these circumstances natural selection would produce males with large penises and testicles. The male who inserts the most sperm in the female has the best chance of fertilising the egg in a situation where several males often copulate in quick succession with the same female. Male chimps therefore rely largely on their sperm rather than on physical strength and ferocity in order to compete with other chimps in the race to father offspring. Dominant males have more frequent, but not exclusive, access to females. Chimpanzee societies also have power pyramids, but they are more complex and "political" than with gorillas and orangutans. The male and female chimpanzee are of similar size. In his case a little penis and small testicles go a long way - surely the ultimate demonstration that size doesn't matter. The dominant ape, so the argument goes, doesn't need large genitalia producing lots of sperm in order to compete with the sperm coming from other apes. This evolutionary "arms race" escalated over time, producing massive males equipped with huge canines and prominent secondary sexual characteristics to attract mates.īut when you reach the top of the gorilla community-power ladder you have a relatively quiet life and pretty much uncontested access to all the females. The massive size of the male gorilla is interpreted to have resulted from competition among males for access to limited females, with natural selection favouring the evolutionary success of the largest, most powerful males. The male gorilla is much larger than the female, which is common across the animal kingdom in species that practice polygamy, i.e., where dominant males mate with multiple females. So how does evolutionary biology explain such marked differences in penis and testicle size? Let us look more closely at some arguments commonly used. The gorilla's flaccid penis is so demure that it is not readily visible. Testicle size, and the conspicuousness of the penis varies correspondingly. It measures 1.5 in an orangutan, three inches in a chimpanzee, and five inches in a man.
To move on to some specific measurements, the average length of an erect penis in a gorilla is 1.25 in.
But the truth is that, relative to his mass, the gorilla has a very small penis and small testicles compared to the male human.Īll of which prompts the question, posed in one publication in stark and vulgar form: "If the male gorilla is so big and tough, why are his balls so small?" Although not a matter that I ever pondered, I would have assumed the male gorilla to be handsomely endowed in genitalia.
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