Some Neanderthals couldn’t smell their own stink, suggests a new study reconstructing the nose of early humans

If you walk through the woods and pass a beehive, you can catch the sweet smell of honey in the wind and suddenly be flooded with memories: having tea with grandma, or eating hot biscuits on a Sunday morning.

If you were taking that walk 300,000 years ago with a Denisovan — a now extinct hominid closely related to Homo sapiens and first discovered in 2010 — by the time you smelled the honey you might have your companion is already climbing the tree for sugar food.

That’s because the Denisovans seem to have been very sensitive to sweet smells like honey or vanilla, suggests new research published in the journal iScience in January. That may have helped them find food. Meanwhile, one group of related species – Neanderthals – developed a mutation that could save them the smell of their own body odor.

A reconstructed image of the face of a Denisovan woman.

Portrait of a young female Denisovan based on a skeletal profile reconstructed from ancient DNA.Harel Mayan

Humans have a lot of genetic variation in our olfactory receptors, which control smell, allowing us to detect a wide range of smells. Researchers think it helped humans adapt to new environments as they spread across the globe, sniffing out new foods and new predators.

It’s a good idea that humans have a bad sense of smell, compared to dogs, for example. But dogs around the world live so differently that the comparison may not mean much. Understanding our earliest relatives – the other Homo species that migrated out of Africa alongside us – can provide a better context for our own smell, and give us a sniff of life at our origins.

The researchers Kara Hoover, a biological anthropologist from the University of Alaska at Fairbanks who is now working at the National Science Foundation, and Claire de March, a biochemist at the Université Paris-Saclay, reconstructed smell receptors from the genomes of three Neanderthals, one. Denisovan, an ancient human, and a database of modern human genomes. It was an attempt to recreate the nose of our closest ancient relatives.

A museum employee looking at a Neanderthal model.

An employee of the Natural History Museum in London looks at a Neanderthal model in his 20s on display at the museum’s “Britain: One Million Years of the Human Story” exhibition in 2014.Will Oliver/PA/Getty Images

“We really need to understand ourselves within our own context,” rather than comparing humans to dogs or monkeys, as previous research on smell receptors has done, Hoover said. “When people look at people, they see us as this weird outlier. But really, we weren’t.”

Bringing an ancient nose to life in the laboratory

A man in a white work coat in a white laboratory holding up a tray of scented grains.

An inspector smells samples of wheat grain at a warehouse in Ostermundigen, Switzerland.Arnold Wiegmann/Reuters

Hoover compared the Neanderthal and Denisovan genomes to those of humans, targeting 30 olfactory receptors – genes that allow us to detect smells. She identified 11 receptors that contained unique DNA variations in the extinct species, variations not seen in humans.

Then de March constructed these unique receptors in the laboratory, by mutating human receptors to match the amino acid sequence of the extinct Neanderthal or Denisovan.

She then exposed the faded receptors to hundreds of odors and measured their responses to how quickly and intensely they lit up with activity.

Computer illustration of an ancient Denisovan wearing fur.

Computer diagram of Denisovan.Claire of March

The sample size in this study was small, since only a few individual Neanderthals and Denisovans have been genetically mapped. Graham Hughes of University College Dublin, who studies sensory perception in mammalian genomes and is not affiliated with the study, also noted that DNA degrades over time, which could have an impact on the results of any assessment of ancient genomes.

Still, “The fact that we can now look at the genomes of ancient species and determine their possible sensory spaces and dietary specialties is very exciting for the field of sensory perception,” said Hughes Insider in an email.

Hoover was surprised that the Neanderthals, Denisovans, and humans seemed to have the same store of smell.

It was not that our deceased relatives could smell a smell that could not be detected by humans, or vice versa. Instead, the Denisovan turned out to have a more sensitive nose than humans, and Neanderthals seemed to have a weaker nose – especially, in one group, for intestinal body odors.

A lucky mutation for cave-bound Neanderthals

Model showing a Neanderthal family near a fire.

An exhibit showing Neanderthal family life in a cave at the Neanderthal Museum in Krapina, Croatia.Reuters/Nikola Solic

One of the Neanderthals had a genetic mutation that reduced his ability to smell androstadienone – a chemical associated with the smell of urine and sweat. That could be a big help to those living in close proximity to other Neanderthals in caves.

“It’s kind of funny that they would stop smelling, that’s what it would be,” Hoover said.

The Neanderthal used in the study represents an entire population of the species that lived at high altitude in Siberia. The other Neanderthal samples, from different parts of the world, did not have that mutation.

Only two genes related to smell from the Neanderthal genome differed from humans’.

Any other name would make Denisovan smell ‘sweet’

The Denisovan’s penchant for sweet scents may have helped them find high-calorie, sugary foods like honey. The receptors also responded with increased sensitivity to spicy smells, such as cloves or herbs.

Woman smelling a basil plant.

Rosilda Rodrigues smelling basil while working in an urban garden in Rio de Janeiro.Pilar Olivares/Reuters

Hoover described this as one of our first biological insights into Denisovans.

It is difficult to jump from genetic information, to the activity of odor receptors, and then to an individual’s subjective sensory experience – much less how they might behave in response.

“Everyone may perceive things a little differently, and we cannot say that what we consider to be a ‘sweet’ smell is the same as the smell of another species,” said Graham.

Still, the study opens a bridge from DNA to the real-world experience of our extinct relatives. More similar research, with more samples of ancient genomes, could reveal a clearer picture of Neanderthal and Denisovan life.

“Ultimately, what our work has shown us is that we are more alike than we are different” when it comes to smell, Hoover said.

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