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Search all BMC articles Search. All articles are available free of charge, according to BioMed Central's open access policy. It's also of great scientific and evolutionary importance. The authors are not sure why this ability has evolved, but they speculate that if females can recognize the sex of sperm and change in response, they might be able to create an environment that favors boys or girls. That on its own is amazing. If we understand how they can do that, this can revolutionize the field. They found that genes consistently produced proteins in differing amounts depending on whether X or Y sperm was present.

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