We’ve learned from Jurassic Park how survival of the fittest can include the changing of one species’ sex. Amphibians do it when numbers of the opposite sex are low. But what happens when they aren’t in charge of their own sex-changing? Scientists have tested the impact of this by adding synthetic estrogen to municipal wastewaters where a variety of fish live.Why synthetic estrogen? Because excessive estrogen that comes from birth control pills are having adverse effects on fish in which the males are now producing eggs.

The results of this study?

clipped from news.nationalgeographic.com The result was an impaired ability of the minnows to reproduce, which caused the population to collapse in the second year of the study, the researchers found. The population even failed to recover in the two years after the researchers stopped adding estrogen, indicating the effects were quite persistent, according to Kidd.

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