Many animals rely heavily on their sense of smell to avoid predators, find mates and locate food and water. A dogs sense of smell is 10,000 to 100,000 times as acute as that of humans, which is part of the reason people have relied on them since prehistory. However, a recent genetic study has shown that elephants have the most developed sense of smell among mammals.

Researchers examined the olfactory receptor (OR) repertoire encoded in the genes of 13 mammalian species. They found that african elephants had twice the OR genes of dogs and five times the number in humans. In total the elephants had 2,000 OR genes.

Each mammal examined showed unique OR development, with only 3 of the 10,000 genes related to smell that were examined were shared among all 13 animals.

“The functions of these genes are not well known, but they are likely important for the living environment of African elephants. Apparently, an elephant’s nose is not only long but also superior,” said author Yoshihito Niimura in a statement.

The number of genes does not, necessarily, correlate to accuracy when it comes to smell. According to NOVA, a dog’s sense of smell is between 10,000 and 100,000 times as acute as that of humans, although the number of genes involved in OR is only two and a half times greater.

“If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well,” said James Walker, former director of the Sensory Research Institute at Florida State University.

However, according to Seaworld, an elephant can detect water sources up to 12 miles away, purely by smell. An elephant’s olfactory sense includes a ‘Jacobson’s organ‘ on the roof of the mouth. This organ can accurately detect chemicals in a substance and can be used to determine, for example, the reproductive status of a female elephant.

The sense of smell may even play a key role in Elephant intelligence.

“Our research suggests that their sense of smell may play a more important role in their decision-making process than it does for other species, and that this may have important implications for the design of future studies of their intelligence,” said Joshua Plotnik, an animal behavior scientist from the University of Cambridge, U.K to National Geographic in 2013.

According to the latest study, published in the journal Genome Research, humans and other primates had the fewest OR genes of the animals that were examined.

The authors of the study examined the evolutionary history of OR genes using a computational tool used to deduce ancestral genes. They then examined the genes duplication or loss in each species in the context of evolutionary history.

The researchers found that some lineages of OR genes expanded. For example, one ancestral gene that exists in both elephants and humans has expanded to 84 distinct genes in elephants while humans retain only the single, original gene.

“Comparison of the repertoires of OR genes among mammals lets us know the commonalities and differences of olfactory perception, deepening our understanding of the sense of smell in humans,” said Niimura.

Over the last several years, studies have revealed that the sense of smell in humans is more important than previously thought. It is now believed that, despite its weakness compared to other species, smell plays a role in many areas of human cognition including language and memory.