There is also accumulating evidence indicating men react differently to women when they are on birth control. A 2004 study in the journal in Behavioral Ecology used the T-shirt study methodology but instead put the shirts on 81 women. A panel of 31 men, smelling the T-shirts, experienced the greatest attraction for the non-pill-using women when they were ovulating. Twelve women on the panel didn't detect any difference.
A study on primates appears to support the idea that hormonal contraceptives change mating preferences. Duke University researchers studied hormones secreted by female lemurs before and after the animals received a hormonal contraceptive. They also studied males' preferences for these scents.
The findings, published in the journal Proceedings of the Royal Society, Biological Sciences this year, showed that the injection of Depo-Prevara, a long-lasting contraceptive that is approved for use in humans, dramatically altered the chemicals that female lemurs give off to indicate their identity and how genetically healthy they are.
The females given the contraceptive became overall less appealing to the males than before getting the injection, says Christine Drea, a professor in Duke's evolutionary anthropology department and senior author on the study. The contraceptive erased all the normal information the odor signals conveyed, she says.
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