Each person has a smell of his or her own. Such characteristic odors are detectable even before birth, according to a study published in the March 28 Proceedings of the National Academy of Sciences. Trained rats can distinguish between samples of a woman's urine taken before and after she gives birth, Gary K. Beauchamp of the Monell Chemical Senses Center in Philadelphia found.
But Beauchamp and his colleagues were unsure how the rats made this distinction. So the researchers tested the rats with samples of the mother's urine during pregnancy and postpartum urine mixed with urine from her child. In fact, the rats could not distinguish between these samples 73 percent of the time.
Yet the rats could simply have been picking up on a general odor
characteristic of any fetus, says Beauchamp. So the researchers also tested the rats using a mixture of urine from a woman and an infant that was not her own. The rats responded to this mixture about 44 percent of the time.
This indicates that the odor type and pertinent genotype of the fetus is present in the mother's urine, says Beauchamp, although a more general fetal smell may also be detectable.
A genetic basis for individual odor types was first discovered in mice, Beauchamp says. …