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How many odours can humans smell?

Mar 25, 2014

Humans are capable of detecting at least one trillion different smells, scientists say.

If researchers at Rockefeller University are correct, the human nose can pick up many more different smells than the 10,000 previously thought. This would make it much more precise than the eye – which can pick out 10 million different colours – and the ear, which can identify almost half a million different tones.

The scientists made mixtures containing 128 odour molecules of common scents such as grass, oranges and mint. Volunteers were then given three samples in which two were the same, and managed to identify the ‘odd one out’ when over half the molecules were different. The scientist then calculated all the possible combinations of 128 molecules to reach a figure of one trillion.

This is still two to three times less than animals like dogs can smell, but does not necessarily mean that humans have evolved to have a less effective sense of smell. Thanks to technology like showers and fridges, humans come in to contact with fewer smells than they used to, and rely less on their sense of smell to survive – so it may simply be that we pay less attention to smell than our other senses.

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