WASHINGTON, July 22 (Xinhua) -- A study of 13 mammalian species ' genome showed that elephants are truly "superior smellers" because the large animals have the most genes related to sense of smell.
The study, published Tuesday in the U.S. journal Genome Research, examined the olfactory receptor (OR) repertoire encoded in 13 placental mammals, including humans, chimpanzees, horses, cows, dogs, rats, mice, guinea pigs and rabbits, and identified over 10,000 OR genes in total.
The repertoire of OR genes found in any given species was highly unique as only three OR genes were shared and evolutionarily conserved amongst all 13 mammals, the study showed.
Surprisingly, African elephants have the most extensive olfactory repertoire, with almost 2,000 OR genes, more than twice that found in dogs and five times more than in human. The previous record-holder was rats, which have about 1,200 OR genes.
"Apparently, an elephant's nose is not only long but also superior," study author Yoshihito Niimura of the University of Tokyo said in a statement.
"The functions of these genes are not well known, but they are likely important for the living environment of African elephants," Niimura said.
Conversely, humans, along with our primate relatives, have much fewer numbers of OR genes compared to all other species examined. This is possibly due to our diminished reliance on smell as our visual acuity improved, the researchers said.
Olfaction is essential for the survival of most mammals, as it is used for finding foods, avoiding dangers, identifying mates and offspring, and identifying marked territory.