An Irish scientist is trying to unravel the secrets of what we smell and how our noses evolved to aid survival. And she has come up with important answers by studying the sniffing skills of the bat.
Evolution has shaped what people are able to smell just as much as it delivered other survival advantages like feathers on a bird or fur on a cat. Prof Emma Teeling of University College Dublin is learning how the sense of smell in bats has evolved as a way to understand how our own sense of smell has evolved as it is today.
“Smell is very important for survival, but there is so much about it that we don’t understand. For example we still don’t know how odours bind to the smell receptors in the nose,” she said.
Certainly, nature understands how important smell is, given that up to six per cent of our genes are dedicated to making our noses work, said Prof Teeling who is director of the Centre for Irish Bat Research in the university's school of biology and environmental science.
Humans have a fairly unsophisticated sense of smell in that we have about 800 smell receptors and only half of them work, she said. “We lost this function because we can see so well. You can’t have multiple super powers. You can only have one.”
Being able to study genes and what they produce gave Prof Teeling a means to study how evolution changed the gene mix that controls our sense of smell. You could sequence genes and look at them and see how they were different across species, she said.
She began thinking about the differences in olfactory genes in water and land animals. "Different odours were important for survival in the sea versus on the land," she said. "This evolutionary change separating sea and land animals happened hundreds of millions of years ago. We wanted to see what caused this change."
A specialist in bat genetics, she decided to study this in bats, looking at the smell receptors in two lineages of bat which separated 64 million years ago. They are distinct species, but they share characteristics. Both species for example developed ecolocaiton enabling them to fly and locate food in the twilight and dark. They both also prefer fruit as their main diet.
She worked with Dr Liliana Dávalos of Stony Brook University and Sara Hayden at the University of Washington and colleagues in Stirling and in Texas A&M universities, together publishing their findings in the current issue of Molecular Biology and Evolution.
These were two widely separated species, but both developed similar olfactory receptors. One was the new world leaf-nosed bat that mainly eat figs. The other was the old world fruit bat. The research suggests that the receptors in the two species developed through different and independent mechanism, but both were responding to the same challenge, finding fruit in low-light conditions, Prof Teeling said. “And both use the same receptors for smelling fruit.”