October 23, 2017 - 16:57 AMT
PanARMENIAN.Net - The faintest whiff of a molecule from mammal blood known as E2D sends some animals into a predatory frenzy but frightens others -- including people -- into retreat, scientists have discovered, according to AFP.
Never before has the same molecule been known to provoke diametrically opposite behaviours in creatures ranging from horse flies to humans, hinting at deep evolutionary roots, they reported in the journal Scientific Reports.
Animals, and especially mammals, use their sense of smell to find food, hook up with partners, and detect danger.
Many of these chemical triggers are specific to one species, or work in combination with other odours.
But E2D -- said to give blood a metallic aroma -- appears to be in a class of its own.
"The odour of blood is characterised by a rare universality," senior author Johan Lundstrom, a biologist at the Karolinska Institute in Sweden, told AFP.
In earlier research, authors participating in the study isolated E2D from pig's blood and showed that wild dogs and tigers were no less attracted to its scent than to blood itself.
The new team duplicated those experiments, this time with wolves, and got the same result: the pack licked, bit and protected a piece of wood smeared with a synthetic version of the molecule as if it were a fresh kill.
Blood-sucking horse flies were likewise drawn to it, showing equal enthusiasm for E2D and animal blood.
But what about the hunted rather than the hunter?
If the molecule has persisted across tens, or even hundreds of millions of years, the scientists reasoned, then perhaps they would react too, though not in the same way.
"We hypothesised that prey species would be under evolutionary pressure to become sensitive to E2D, to help them avoid an area where a bloodbath is going on," said Lundstrom.
Sure enough, rodents in a cage recoiled from the molecule, as much as they did from the red stuff.