For many, there is no mistaking the order of fresh cilantro or the smell following an early summer morning rain. However, new research now shows that the human nose is able to distinguish amongst many more odors that had once been thought.
People have often said that humans are able to distinguish amongst 10,000 individual odors. However, new research suggests that total is one hundred million times more or 1 trillion.
A researcher from Rockefeller University of New York Leslie Vosshall, who was co-author of the recently published study, says they debunk the 10,000-odor limit.
Vosshall said that animals use sense of smell to avoid dangers, find food and even mates, but humans are far better smellers than previously thought.
The 10,000 number has appeared in popular magazines as well as scientific literature, but few researchers ever tested it.
For the new study, said researchers, they thought humans would be able to smell well over 10,000 scents, due to the fact a typical nose contains more than 400 olfactory receptors.
The human eye contains just three color receptors, but can see more than 10 million different colors.
Testing if people were able to smell more than 10,000 individual scents would be impossible. Therefore, Vosshall with her colleagues tested a smaller subset of odors and changed the combinations, then extrapolated results to make an estimate of the total scents that could be distinguished by the human nose.
Researchers created different mixtures of 128 scent molecules. Individually those molecules resembled odors like citrus and grass, but when combined the smell was unfamiliar.
The volunteers were given three vials with the scents and they were told to identify the odor, which was done by the volunteers for over 260 groups of vials.
The correct identification of the different odors were counted and then extrapolated to give an estimate to the number of scents the average human could distinguish from the mixtures containing the 128 molecules.
The results were that humans are able to smell 1 trillion individual scents. Researchers said that number might very well be even higher.