Too many girls

Living on Earth: Arctic Gender Imbalance:
[Via Living On Earth]
Here is the lede of the report:

Only girls are being born in a village in Greenland. Host Steve Curwood turns to Lars Otto Reiersen, of the Arctic Monitoring and Assessment Program, to find out what may be behind a growing gender imbalance in babies born around the Arctic Circle.

The study looked at inhabitants of Greenland because the blubber of marine mammals, the main diet of these people, is very high in PCBs.

The normal ratio of boys to girls is about 1.1 to 1. But it appears that PCB concentrations may alter this ratio. Here is what happens in this population with increasing PCB levels in the mother’s serum:

birth rates

As you can see, increasing PCB levels initially results in an increase in male births. But at high PCB levels, the ratio turns and there are almost 2.5 girls born for every boy. This is pretty disturbing.

There is, as yet, no good biological explanation for this. While there does not appear to be an increase in spontaneous abortions, there is an increase in stillbirths and birth defects as PCB levels increase.

Substantially altering the sex ratio of the human population would have huge effects on our ability to survive. It will be worth keeping an eye on this research as it tries to determine what is the biological cause for this effect.

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