Matthew Cobb ponders the age old question about whether during human evolution our sense of smell has been traded in in favor of our vision. How this would work, at least theoretically, is as we became more dependent on our eye sight, our smell became less and less important to us and so the receptor sites in our noses became less sensitive. Another way of putting it is that we “devolved” our sense of smell, deactivated certain genes, in favor of better eye sight.
Imagine having Lasik eye surgery and the doctor telling you it will cost you your sense of smell.
Well … Not so fast:
A study by a group of Japanese researchers (Atsushi Matsui, Yasuhiro Ho and Yoshihito Niimura), about to appear in Molecular Biology and Evolution [subscription needed], looks at this widely-accepted suggestion and finds little evidence to support it.
They looked at the olfactory receptor (OR) genes in five primate species (human, chimpanzee, orangutan, marmoset and rhesus macaque) together with two “strepsirhines” – the bushbaby and the mouse lemur, with the tree shrew as a comparison (“outgroup”). Surprisingly, they found no significant differences in the number of functional OR genes between the marmoset (New World Monkey) and the macaque (Old World Monkey) and the hominoids. In fact, humans had the second largest number of intact ORs (396), just behind the chimpanzee (399), and as against only 296 in the orangutan. This suggests that – whatever you might think – you can probably detect a similar number of odours as any of the other primates.
Maybe our evolutionary Lasik eye surgery was free!