Humans, apes use odor-detecting receptors differently

December 9th, 2009 - 3:42 pm ICT by ANI  

Washington, Dec 9 (ANI): Apes and humans have same receptors for detecting odours related to sex, but they are used in different ways in all the species which plays a major role in mate selection and prevents cross-species couplings, according to Duke University researchers.

All the species use odour receptors in different ways, stemming from the way the genes for these receptors have evolved over time.The researchers analysed the sequences and functions of the gene for the odorant receptor OR7D4 in terms of perceiving two steroid molecules related to testosterone, androstenone and androstadienone.

The study did not try to examine how the receptors and odour perception might relate to behaviour.

“There’s variation in sensitivity of the odorant receptor from this gene (all primates) have. Maybe these molecules operate in the process of reproduction. The fact that there is variation fits with this theory. Reproduction demands that an animal avoid attraction to other species, so variation in the receptor’s sensitivity to these odours may prevent any cross-species attraction,” said Dr. Hiroaki Matsunami.

Animals rely on olfactory signals to make all sorts of decisions about other animals, particularly in reproduction, said Dr. Christine Drea.

“Beyond identifying members of the same species, odours help identify kin or nonkin, members of the opposite sex, even whether individuals are fertile or genetically appropriate as mates. How they do so is still largely unknown. By deciphering evolutionary changes in receptor function across species, Dr. Matsunami and his colleagues have brought us another step closer to unravelling the mysteries of olfactory signalling,” she said.

The odorant receptor gene, which the paper traces back to the mongoose lemur, evolved differently within the various primate species.

Human receptors were found to be most closely related to the chimps and bonobo monkeys, as opposed to gorillas and other primates.

The findings support the evidence that primates have a common ancestor, but we are very different now.

“One of the differences is in how well we are able to sense odours, which is exemplified by changes in the function of this odour receptor,” said Matsunami.

Ultimately, the work will aim at discerning how smelling these chemicals might affect human social and sexual behaviour.

“We will begin working with a collaborator to examine chimpanzee behaviour with regard to odour perception,” said Matsunami.

However, the sense of smell also can vary from animal to animal and person to person, because of combinations of a number of odour receptors.

“The sex-steroid related odours act as pheromones in pigs. Pigs that are ovulating and that are exposed to the pheromones assume a mating posture. It’s debatable whether these chemicals act similarly in humans. But there is evidence that smelling these odours can affect the mood and physiological state of both men and women. We have a lot more studying to do, but this finding and others in the future will create a picture of how smell may relate to sexual reproduction,” said Matsunami.

The study was published online in the Early Edition of the Proceedings of the National Academy of Sciences. (ANI)

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