lunes, 4 de abril de 2011
Menstruation and the Origins Of Culture
By 40,000 years ago, the effects of a symbolic explosion - an efflorescence of human art, song, dance and ritual - were rippling across the globe. The bearers of symbolic culture were recent immigrants from Africa, dispersing so rapidly to encompass the globe that the process has become known as 'the human revolution'. Enough data and sophisticated neo-Darwinian theory now exists to begin to explain this most momentous revolution in history.
Simplistic, sexist stereotypes on the model of 'Man the Hunter' or 'Man the Toolmaker' contravene Darwinian theory. Females are not appendages; they pursue their own independent reproductive strategies, which typically diverge from those of males.
Primate societies are systems of alliances through which individuals pursue their fitness interests. Group-living places a premium on social intelligence, setting up selection pressures for large brains. But among primates, this process is constrained by the very high thermoregulatory, metabolic and obstetric costs of such brains. The exponential increase in brain size characterising the evolution of Homo sapiens indicates that, in some radical way, these constraints were overcome.
The costs of brain growth fall over-whelmingly on the female. In the human case, not only did mothers have to secure more and better quality food, they had to accomplish it whilst weighed down by heavily dependent infants. The problem is: how did they cope?
We now know the basic answer. Evolving women succeeded in gaining unprecedented levels of energetic investment from their mates. Success went to mothers who could reward more attentive, heavily investing partners at the expense of would-be philanderers.
A philandering male maximises his reproductive fitness by fertilising as many females as possible. He achieves this by reducing the time spent searching for each fertilisable female, and the time spent with her to ensure impregnation. The human female appears well-designed by evolution to waste the time of any philanderer by witholcling information about her true fertility state. Concealment of ovulation and loss of oestrus with continuous receptivity deprives the male of information on whether his mate is likely to have been impregnated. The longer a male takes to impregnate anyone female, the smaller his chances of being able to fertilise another.
A further means of thwarting philanderers is reproductive cycle synchrony. If females synchronise their fertile moments, no single male can cope with guarding and impregnating a whole group. He must concentrate on one at a time. The effect is to maximise the number of males in the breeding system, and hence the amount of male investment available.
Ovulatory synchrony in local populations drives the ratio of sexually active males to females in groups towards one-to-one. Sustained male/female bonds on this basis mean greater paternity confidence, hence greater inclination on the part of males to invest in offspring. The evolutionary effect is to discriminate against philanderers in favour of more committed males.
Once ovulation was concealed and oestrus lost in the human lineage, menstruation acquired new significance as a cue. This, however, threatened the stability of the female strategy of withholding information from philanderers. Menstruation in the human case is particularly profuse. It is not something a female can easily hide. In fact it is a complete give-away. It signals a female's imminent fertility - and hence by contrast the infertility of neighbouring females who, whilst pregnant and nursing, are not displaying such blood. Males would have been drawn towards any such
fertile female within the local area, competing to bond with her at the expense of pregnant or nursing females. Mothers with heavy childcare burdens, lacking the menstrual signal, would then have lost out just when they most needed help.
Cosmetics, according to recent research, were the answer. If there is a menstruating female in the neighbourhood, why not join her? Why not appear to be as fertile, painting up with blood-red colours? Ethnographic and historical records show how hunter-gathere"r women across southern Africa prevented any young menstruant in their midst from being perceived as an isolable individual. Conjoining with her in a ritual dance, they used red ochre body-paint not only to signal menstruation and fertility, but simultaneously to indicate inviolability or taboo, their basic message being: 'No meat, no sex!'. We know that in Africa, anatomically modern humans
were intensively mining, preparing and liberally applying red ochre bodypaint
110,000 years ago.
Human symbolic culture emerged out of struggle. Its rituals and myths were expressions of 'counterdominance' - signals for thwarting exploitation by males. The signallers were females, allied with their male kin; their targets were their mates." Culture, in short, was a female invention for the provisioning of babies. Through it, womankind resisted and brought to an end the male's time-honoured biological status as the leisured sex.
C. Knight Blood Relations. Menstruation and the origins of culture.