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Carb-eating ancestors and off-gassing ears

by Cheryl Hogue
June 26, 2021 | A version of this story appeared in Volume 99, Issue 24


Snarfing down carbs is ancient

A stack of potato chips next to a Neanderthal skull.
Credit: C&EN/Yang H. Ku/Shutterstock
Pass the chips: Neanderthals crunched starchy carbs, as did ancient humans.

Modern humans gobble up doughnuts, potato chips, yuca fries, rice, and other starchy victuals with great gusto. Despite what advocates of certain low-carb diets may say about our ancestors eating more meat and less grain, noshing on foods dense in carbohydrates is a behavior we share with our long-ago relatives, according to an international team of researchers.

Neanderthals and ancient humans weren’t just meat eaters. They also chowed down on starchy grub like roots and tubers as far back as 600,000 years ago, the researchers found. This is much earlier than previously thought and long before humans developed agriculture and domesticated grains like rice.

The researchers made the conclusions after analyzing the multispecies bacterial communities called biofilms that formed tartar on the teeth of ancient humans and Neanderthals. The team extracted DNA from the biofilms and determined the types of bacteria that constituted the films. The scientists then compared the results with those taken from contemporary primates.

They found that the species of bacteria that Neanderthal and modern human teeth harbored were highly similar. But they differed from those on the teeth of modern chimpanzees, humans’ closest living relative.

Humans and Neanderthals shared types of Streptococcus bacteria that can bind to amylase, helping form biofilms. Amylase, an enzyme found in human saliva, begins the digestion process of breaking down complex carbohydrates into simple sugars. Chimpanzees have different species of oral Streptococcus.

The shared bacteria suggest that microbes adapted as Neanderthals’ and ancient humans’ diets changed to include starches, the researchers say. (Proc. Natl. Acad. Sci. U.S.A. 2021, DOI: 10.1073/pnas.2021655118).

Our ancestors grazed on starchy comestibles before the Neanderthal and modern human lineages split, the researchers conclude. This diet change could have allowed the development of the larger, more complex cortices of today’s humans’ brains.

Consuming energy-dense, starchy foods gives the brain rapid access to energy, explains lead author James A. Fellows Yates, a PhD student in archaeogenetics at the Max Planck Institute for the Science of Human History. In contrast, the body takes longer to break down fat and protein, meaning those foods don’t fuel the brain as quickly.

So the next time cookies show up in the break room, your brain can rationalize nibbling a couple because carb snacking is a longtime human behavior.


Headset sniffs blood alcohol level

A headset around a glass full of beer.
Credit: C&EN/Yang H. Ku/Shutterstock
Beer ears: Researchers converted a headset to capture ethanol off-gassed from a person's ears.

Headsets aren’t just for listening to music anymore. Researchers in Japan have modified a headset so that it can determine the wearer’s blood alcohol levels.

Our external ears turn out to be a decent spot to measure ethanol—and possibly other volatile organic compounds (VOCs)—off-gassed through the skin, researchers in Japan report (Sci. Rep. 2021, DOI: 10.1038/s41598-021-90146-1).

Other scientists have investigated other parts of the body, such as the palm of the hand, as possible sites for transcutaneous blood alcohol measurements. But they found that perspiration interferes with the measurements.

Sweaty ears, unlike damp palms, aren’t common. That’s because the skin on the ears has a relatively low density of sweat glands. So researchers from Tokyo Medical and Dental University and Kansai University decided to try ears for their measurements.

The researchers faced a challenge because skin off-gasses ethanol at a lower concentration than found in the breath, which is the target of widely available Breathalyzers. So they converted commercial headphones into an “over-ear gas collection cell” and attached a biosniffer—a fluorescence-based biochemical gas sensor that detects the presence of an ethanol metabolite. The researchers then .

compared blood alcohol measurements from the breath and ears of research subjects and found them to be similar.

The device might eventually prove useful for noninvasive metabolism assessments and for disease screenings that measure VOCs, the researchers say.

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