Ancient humans had the same sense of smell, but different sensitivities

If you had the cleaning habits of a Neanderthal, maybe it’s a good thing your nose wasn’t as sensitive to urine and sweat as a modern human’s.

And if you lived the hunter-gatherer lifestyle of a Denisovan on the Asian steppes, your keen nose for energy-rich honey was almost certainly an advantage.

Although we can’t really know what these two have become extinct human perceived or preferred species for food, a new study by Duke University scientists has discovered a little more about what they might have been able to smell.

Using a technique they developed that allows researchers to test sensitivity to smell odor receptors grown in a laboratory dish, researchers Claire de March of the Université CNRS Paris Saclay and Hiroaki Matsunami of Duke University were able to compare the smelling abilities of three types of humans. Their work appeared on December 28 in the open access journal iScience.

Using published databases of genomes, including ancient DNA collections amassed by 2022 Nobel Prize winner Svante Pääbo, the researchers were able to characterize the receptors for each of the three human species looking at relevant genes.

“It’s very difficult to predict behavior just from the genomic sequencesaid de March, who conducted this work as a postdoctoral research associate at Duke. resulting in a different protein.”

They then tested the responses of 30 lab-grown people olfactory receptors of each hominin against a battery of odors to measure the sensitivity of each type of receptor to a given fragrance.

The laboratory tests showed that modern and ancient human receptors were detecting essentially the same odors, but their sensitivities differed.

The Denisovans, who lived between 30,000 and 50,000 years ago, were shown to be less sensitive to odors that modern humans perceive as floral, but four times better at detecting sulfur and three times better at balsamic. And they were very in tune with honey.

“We don’t know what the Denisovans ate, but there are a few reasons why this receptor must be sensitive,” said Matsunami, who is a professor of molecular genetics and microbiology at the Duke School of Medicine. 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 40,000 years ago and apparently shared a few genes with modern humans, were three times less sensitive to green, floral and spicy smells, using virtually the same receptors we have today. “They may show different sensitivity, but the selectivity remains the same,” Matsunami said.

“Neanderthal odor receptors are mostly the same as contemporary humans, and the few that were different were not more sensitive,” added de March.

Odor receptors have been linked to the ecological and dietary needs of many species and presumably evolve as the species changes ranges and diets.

“Each species must evolve olfactory receivers to maximize their fitness to find food,” Matsunami said. “In humans, it’s more complicated because we eat a lot of things. We’re not really specialized.”

The lab has also used its cell-based smell tester to see genetic variation between modern humans. “Some people can smell certain chemicals, but others can’t,” Matsunami said. “This can be explained by functional changes.”