Actually, I don’t think this is quite right, although it was commonly accepted. It seems that more recent research indicates that sexual dimorphism (difference in size between the sexes within a species) is more correlated with male-male competition in access to breeding females, but this should not be confused directly with monogamy.
It is well established that early humans split from chimpanzees. Later, another group of chimps, bonobos, split from chimpanzees as well. Bonobos share many characteristics with humans that chimpanzees don’t. For example, bonobos are the only primate species besides humans that tend to have sexual activity unrelated to procreation (for pleasure, perhaps, but at least for bonding and agression/tension reduction). Bonobos are also the only other primate to mate “face-to-face” (missionary position). Bonobos are closest to humans in sexual dimorphism among primates (where males are about 1.1 to 1.2 times the size of females). Also, like humans, bonobo females do not show obvious physical signs when they enter estrus, unlike chimpanzees, and tend to have a sex drive throughout their fertility cycle.
But bonobos are anything but monogamous. Their sexual practices encompass an enormous range, including oral sex and bisexuality. Their societies are predominately matriarchal, but pair bonding is not the norm. Unlike chimpanzees, bonobos are a very peaceful species, and appear to replace aggression in their societies with sexual activity.
And btw, this research tends to refute edwino’s (or Robert Wright’s) assertion that males avoid being cuckolded, at least within our “closest primate cousins”. The topic of “sperm selection” and relative testes size among primates offers support here, as well as the more recent “killer sperm” research. And interestingly, this seems to also relate to infanticide:
Later on this same page, and relevent to the topic of cuckoldery in humans:
[quote]
[ol][li]If when making love a woman has no orgasm, or has one more than a minute before the man ejaculates, then very little of his sperm remains in her vagina. [/li][li]If her orgasm was less than one minute before or up to 45 minutes later than his ejaculation, then most of his sperm stays in. [/li][li]In addition, the longer it was since she had previously had an orgasm, then the more sperm she retains. [/li][li]Finally, the amount the man ejaculated related to whether the couple had been together during the day or apart. If they had been together, the amount was less than if they had been apart.[/ol]All very interesting, but so what? Well, Baker and Bellis also asked the couples in their study about their extramarital affairs. In faithful women, about 55% of orgasms were high retention. In unfaithful women, 40% were, with their regular partner, but 70% were with their lover. In addition, the extramarital intercourse generally occurred at the woman’s most fertile period. The result is that a woman in their study could have intercourse twice as often with her partner as with her lover, but still be more likely to conceive a child by her lover. Even though the women did not have access to this information, these are the consequences of their actions.[/li][/quote]
Within primates, large sexual dimorphism tends to result in polygynous societies, but even in these cases, females are not necessarily pair bonded with dominant males.
In the animal kingdom generally, it was first thought that sexual dimorphism was directly correlated with monogamy/polygyny. A prime example was birds, which have very little sexual dimorphism, and many species were thought to be monogamous.
More recent studies using DNA fingerprinting have shown that birds may tend to be “socially monogamous”, but sexually polygynous in practice.
Suffice it to say, the topic is more complex than initially thought.
And pravnik, one may be safe when defining “marriage” so broadly, but I was under the impression that there were numerous human societies where “pair-bonded” marriage simply did not apply (in either monogamous or polygamous models), but where the “family unit” was more tribal in nature. This mating system is described as “promiscuous”. At least in one case, marriage and mating were not directly related. For example, the Nayar tribe of southern India:
Promiscuous socities are referenced in this link.
On the nature/nurture topic, didn’t Gould put forward that our biology puts forth our various potentials, but that our environment determines which potentials are realized? That theory tends to have significant explanatory power - in this mating system topic, for example, in that humans are genetically capable of many different mating systems, and the environment determines which system actualizes. Also, culture can subvert the expected actualization based strictly on an analysis of the more primitive environment constraints.
