Humans, Neanderthals, and Denisovans independently adapted to a wide range of geographic environments and their associated food odors, which reflects the evolutionary importance of dietary niches to our species. However, evolutionarily recent changes in human odorant receptors’ protein function have been linked to major dietary shifts.
We can only speculate how these two extinct human species perceived and chose to eat, but a recent study from Duke University researchers has shed some light on what they may have been able to smell.
They used a technique that allowed them to test smell sensitivity on odor receptors grown in a lab dish. They then compared the scents-abilities of three kinds of humans.
By examining the necessary genes, the researchers could characterize the receptors of each of the three human species. They did this by using published databases of genomes, including ancient DNA collections gathered by Svante Pääbo, winner of the 2022 Nobel Prize.
Claire de March of CNRS Paris Saclay University said, “It is very difficult to predict a behavior just from the genomic sequence. We had the odorant receptor genomes from Neanderthal and Denisovan individuals, and we could compare them with today’s humans and determine if they resulted in a different protein.”
Then, to determine how sensitive each type of receptor was to a certain fragrance, scientists evaluated the reactions of 30 lab-grown olfactory receptors from each hominin against a battery of smells.
The laboratory studies revealed that although the odors were fundamentally detected by modern and ancient human receptors, their sensitivity varied.
Hiroaki Matsunami of Duke University said, “The Denisovans, who lived 30,000 to 50,000 years ago, were shown to be less sensitive to the odors that present-day humans perceive as floral, but four times better at sensing sulfur and three times better at balsamic. And they were very attuned to honey.”
“We don’t know what Denisovans ate, but there are some reasons why this receptor has to be sensitive. Contemporary hunter-gatherers such as the Hadza of Tanzania are famous for their love of honey, an essential high-calorie fuel.”
“Neanderthals, who were still around up to 40,000 years ago and swapped a few genes with modern humans, were three times less responsive to green, floral, and spicy scents, using pretty much the same receptors we have today. They may exhibit different sensitivity, but the selectivity remains the same.”
de March said, “The Neanderthal odorant receptors are mostly the same as contemporary humans, and the few that were different were no more responsive.”
“The Neanderthal odorant receptors are mostly the same as contemporary humans, and the few that were different were no more responsive.”
Matsunami said, “Each species must evolve olfactory receptors to maximize their fitness for finding food. In humans, it’s more complicated because we eat a lot of things. We’re not specialized.”
The laboratory has also made use of its cell-based fragrance tester to observe genetic diversity among contemporary humans. Certain compounds can be smelled by some persons but not by others. Changes in functionality can explain that.
- Claire A. de March et al. Genetic and functional odorant receptor variation in the Homo lineage. iScience. DOI: 10.1016/j.isci.2022.105908