Humans don't usually think of the ability to smell as an important survival tool -- just a way to tell if the garbage needs to be taken out. But mammals use their noses for all kinds of vital activities: finding food, determining whether food is safe to eat (or rotten), locating mates, avoiding predators and so on.
And among mammals, nobody has a better sense of smell than an elephant. Researchers have known elephants possess some serious sniffing skills, but only recently did they nail down some hard evidence of the animal's superiority. The ability to differentiate between lots of different smells is determined by how many olfactory receptors are found in an organism's genome.
A group of researchers led by Yoshihito Niimura, a molecular evolutionist at the University of Tokyo, analyzed the olfactory genes of 13 mammalian species. The African elephant, with 2,000 receptors, had the most -- double the amount dogs have, and five times as many as humans.
Their analysis was also able to isolate older more stable genes and others that have evolved over time, spawning new genes specific to the African elephant's environment.
The findings lend credence to an array of previous research heralding the keen noses of African elephants. One study showed the species could differentiate between two ethnic groups in Kenya, the Maasai and the Kamba.
"Maasai men spear elephants to show their virility, while Kamba people are agricultural and give little threat to them; therefore, elephants are afraid of Maasai men," said Niimura, lead author of the new study, published this week online in the journal Genome Research.
As to why the elephant has developed such an impressive sense of smell, Niimura thinks part of the reason is that the animal's nose is essentially its first point of contact with the surrounding world -- it is its hand.
"Imagine having a nose on the palm of your hand," he said. "Every time you touch something, you smell it!"