Sometimes boys are worth more, sometimes girls are worth more. In an evolutionary sense. Or, more correctly, the value of a certain sex … as an offspring … can be measured in fitness terms. Fisher noted this and hypothesized this was the explanation for the 50-50 sex ratio we usually see. As one sex becomes more rare, it becomes more valuable, and thus parents (mothers, perhaps, usually) bias towards that sex. Then the disparity goes away and thus the differential value goes away.
Of course, the truth is that we don’t actually see the 50-50 sex ratio all the time … many species of organisms have a highly biased sex ratio. Many have a highly biased ratio in adults, much more biased than in offspring. This sort of thing varies quite a bit. But what about humans, and what about the report that Indian girl-boy ratios at ‘all-time low’ …
The anthropological theory on this is pretty well established, and is based on Trivers’ model of differential investment (known in this case as the “Trivers/Willard hypothesis.”) It is a long story which I will not go into here (but see this)
Essentially, there are conditions under which parents should bias their investment towards a particular sex, and this is what happens in middle and upper castes in India, where people practice the caste system and the related hypergynous marriage.
In this system, a female must always marry up, and a dowry must be paid. This means that a girl requires investment in a dowry which will go away at marriage. A boy, on the other hand, will garner a dowry. And, if you are in the top caste, there is no “up” to marry to!
The solution to this is of course to get rid of the girl babies. Abortion is one way, starving them off is another. The details vary by the result is always the same: A very biased sex ratio.
“In a country with a long history of discrimination against women, the preference for sons over daughters has led to the number of girls under the age of six hitting an all-time low,” said ActionAid in a report.
Ratios of boys to girls aged 0-6 in sites in four out of five states it studied in north and northwest India were now lower than at the time of the last nationwide census in 2001 — and the gap was widening, the report said.
Both rural and urban areas showed similar declines and the phenomenon cut across class and wealth lines, added the report, which is titled “Disappearing Daughters”.
The report called on the Indian government for tougher enforcement of laws banning pre-natal sex detection and sex-selective abortion, describing their efforts to implement the legisation so far as “woefully inadequate”.
Attitudes towards girls as financial burdens for families because of dowry pressures also need to be challenged, while the quality of and access to public health care and state-run schools had to improved, it added.
“It is clear that without sustained action on many fronts, millions more women will go missing in India,” it said, citing figures from medical journal The Lancet that more than 500,000 female foetuses are being aborted per year.
Members of ActionAid and Canada’s International Development Research Centre interviewed families in more than 6,000 households and compared statistics with national census data.
The researchers said that normally, there should be about 950 girls born for every 1,000 boys, but found that already low ratios of girls to boys from 2001 in the sites surveyed were now even lower, except for Rajasthan.