Chimp-dog, panda and human faces have become household names in recent years thanks to social media.
But the phenomenon of eating human faces may be a little different than what’s been seen before.
A new study, published in Nature Neuroscience, suggests that the behavior may be linked to the genes involved in regulating stress and pain in humans.
The study, led by Dr. Daniel A. Chirico of the University of Texas Southwestern Medical Center, used DNA from a collection of human skin samples collected from around the world.
It showed that a particular gene, called SLC3A4, was involved in the perception of human faces.
Chiro’s team was able to look at how this gene’s activity changed over time and found that it was activated more than twice as much in people who were exposed to facial trauma, such as a face-eating cat or dog, compared to those who didn’t.
The team’s findings suggest that this gene is involved in understanding how humans feel about the face, Chiro said.
“It’s the kind of thing that we’ve never really seen before.”
Chiro said the gene may help to explain how people perceive the faces of other animals.
“It’s interesting that this is a very novel trait for this gene,” Chiro told National Geographic.
“People may think of it as an animal behavior, but the gene is actually involved in a very specific behavior of humans.”
“The gene may be the way in which we get used to eating people’s faces,” Chirino said.
A human face may trigger a cascade of events, from the skin’s absorption of the blood to the body’s release of hormones to the brain, which may contribute to the release of stress hormones, he said.
These hormones can cause an individual to experience stress, as well as make the individual more anxious and irritable.
Humans also have a higher risk of developing heart disease, diabetes and other conditions.
The gene also is known to affect the immune system and may affect the way we perceive other people.
For the new study to be able to be validated in humans, Chirica’s team had to take into account two key variables: the duration of the study, and whether or not the face was a real human face.
The team found that the study lasted about 10 weeks, or about a week and a half in each participant.
The study also included about 150 photographs, with some of the photographs taken from different angles.
For both, the participants were asked to keep their faces covered and to not show the faces to anyone else for the duration the study.
For the longer-term study, the researchers had the participants hold their faces up to the camera for an average of six hours.
The participants were also asked to wear face masks.
“The subjects were asked whether they were aware that they were eating human face,” Chirono said.
“That was a really interesting thing to find out, that people may be really interested in seeing human faces, but they may not necessarily understand that the face itself is human.
So it’s important to get that information in there.”
A more recent study found that exposure to a dog’s fur was related to increased levels of stress hormone in the blood, but that the dogs’ fur did not trigger the stress response as much as a person’s fur.
The findings of this study have not been replicated in humans but are the first to show that the same gene can trigger both stress and emotion in a human subject, Chironio said.
In addition to the genetic explanation for the face-eats-dog phenomenon, there is evidence that the gene could have other biological and environmental effects on humans.
For example, previous research has shown that the human genome may contain genetic variations that influence the amount of cortisol that is produced in the body.
This may be particularly important for the developing brain, as cortisol is an important stress hormone and can trigger stress and anxiety.
The new study found no significant differences in the cortisol levels in the people’s blood between the groups.
Chirico said it’s not clear yet how the gene changes in the brain might be related to how humans perceive faces.
But he said the study may be able help to answer a question that has been around for a while: How do you teach someone not to eat a human’s face?
“What we think might be going on is that the genes that regulate stress and pleasure in the human brain might also regulate the release in the heart and blood of stress- and anxiety-related hormones,” Chiri said.
For more on human-caused stress, watch the video below from National Geographic: