Humans, Neanderthals and Denisovans have independently adapted to a wide range of geographic environments and their associated food odors, reflecting the evolutionary importance of dietary niches to our species. However, evolutionarily recent changes in protein function of human odorant receptors have been associated with major dietary changes.
We can only speculate how these two extinct human species perceived and chose to eat, but a recent study by 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 odor sensitivity on odor receptors grown in a laboratory dish. They then compared the scent abilities of three types of people.
By examining the necessary genes, the researchers were able to characterize the receptors of each of the three human species. They did this by using published databases of genomes, including ancient DNA collections collected by Svante Pääbo, winner of the 2022 Nobel Prize.
Claire de March of CNRS Paris Saclay University said: “It is very difficult to predict behavior based on genomic sequence alone. We had the odorant receptor genomes of Neanderthal and Denisovan individuals, and we were able to compare them to today’s humans and determine whether they resulted in a different protein.
Then, to determine how sensitive each type of receptor was to a particular odor, scientists evaluated the responses of 30 lab-grown olfactory receptors from each hominin against a range of odors.
The lab studies revealed that while 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 found to be less sensitive to the scents that modern humans perceive as flowers, but four times better at perceiving 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 must be sensitive. Modern-day hunter-gatherers like the Hadza of Tanzania are known for their love of honey, an essential high-calorie fuel.”
“Neanderthals, who survived until 40,000 years ago and exchanged a few genes with modern humans, were three times less responsive to green, floral and spicy scents, and used pretty much the same receptors we have today. They may show different sensitivity, but the selectivity remains the same.”
the march said, “Neanderthal smell receptors are largely the same as modern-day humans, and the few that were different stopped responding.”
“Neanderthal smell receptors are largely the same as modern-day humans, and the few that were different stopped responding.”
Matsunami said: “Each species has to develop olfactory receptors to maximize their ability to find food. In humans, it’s more complicated because we eat a lot of things. We’re not specialized.”
The lab has also used its cell-based odor tester to observe genetic diversity among modern-day humans. Certain compounds can be smelled by some individuals, but not by others. Changes in functionality may explain this.
- Claire A. de March et al. Genetic and functional odorant receptor variation in the Homo lineage. iScience. DOI: 10.1016/j.isci.2022.105908