The Jealousy Brain Circuit Has Been Discovered in Monkeys. Here’s What It Means for Us.
The results of this study could have implications for autism, addiction, and domestic violence.
Jealousy. The green-eyed monster. We’ve all felt it at one time or another. In relationships, it's often motivated by more powerful, underlying emotions such as envy, insecurity, anger, or the fear of abandonment or rejection. Psychologists say jealousy, like all emotions, isn’t good or bad, it just is. It’s how you react or behave that counts. Certainly, it can cause a disaster in your life, left uncontrolled. But it can also put you in touch with your deeper feelings and lead to self-realization.
What scientists have been wondering is where emotions emanate from inside the brain and their purpose in terms of our evolution and survival. It’s difficult to study jealousy ethically in humans, however. But we can learn a lot from studying our primate cousins. After all, a chimpanzee and a human are 96% identical, genetically speaking. That means certain genes and brain circuits are likely to carry across species.
In this study, University of California, Davis researchers identified the jealousy circuit in the brains of male titi monkeys. The coppery titi monkey (Callicebus cupreus) is native to the Amazon River basin of Brazil. It’s one of the few primates who practice lifelong monogamy. Only 3-5% of mammals do. Prairie voles, a rodent, has been the subject of most previous monogamy studies. But since they aren’t primates, such findings may not cross over to our species.
These monkey’s exhibit certain human-like traits in their relationships. They form close bonds, become upset when apart, and the male will guard his partner from danger. Investigators at the California National Primate Research Center (CNPRC), at UC Davis, conducted the study. Its senior author was Dr. Karen Bales, a core scientist there. She said of titi monkeys in a press release, “They have behavior and emotions that we recognize as close to how we feel.” While both sexes of this species exhibit mate-guarding, male titi monkeys are known to display a particular jealousy response. They lash their tales back and forth and arch their backs when they become jealous.
Coppery titi monkeys pair-bond in order to share resources and childcare. Credit: Getty Images
To induce the “jealousy condition,” Dr. Bales and colleagues placed each female partner in with a strange male monkey, in full view of her mate. Scientists left each female in there for a half hour at a clip. They also had a control group, where they put a strange female in with a strange male. The viewing monkey’s behaviors was filmed and its brain scanned to see which areas were active with each condition.
When a jealousy condition was introduced, the circuitry in a region known as the cingulate cortex saw a dramatic spike in activity. This region is known to facilitate pair-bonding in primates. In our species, it’s associated with social exclusion or social pain.
"Increased activity in the cingulate cortex fits with the view of jealousy as social rejection," Bales said. Heightened activity was also detected in the lateral septum, an area associated with aggressive behavior. "Previous studies identified the lateral septum as being involved in the formation of pair bonds in primates," Dr. Bales said.
“The idea behind all of this is we have to first understand the way that the neurobiology of social bonding works normally before we can understand what happens in situations where social bonding, social behavior or social communication is impaired,” Bales said. “For instance, in disorders like autism or schizophrenia.”
CNPRC researchers are out to find the neurobiological underpinnings to jealousy. Credit: Geoff B. Hall, Wikimedia Commons.
Researchers tested the male monkey’s hormone levels, too. In the jealousy condition, they saw increases in testosterone and cortisol levels. Cortisol is the stress hormone. While testosterone is associated with competition and aggression between males. “Trying to keep your mate away from your opponent is evolutionarily geared toward preserving the relationship,” Bales said.
She went on,
The neurobiology of pair-bonding is critical for understanding how monogamy evolved and how it is maintained as a social system. Monogamy probably evolved multiple times so it is not surprising that its neurobiology differs between different species. However it seems as though there has been convergent evolution when it comes to the neurochemistry of pair-bonding and jealousy.
The next step, to find out if female titi monkeys, who also get jealous, have the same neurobiological response. “Sex differences in the neurobiology of social behavior may ultimately explain questions like why more boys than girls have autism, and why men and women act differently in romantic relationships,” Dr. Bale said. "A better understanding of this neurobiology may also provide important clues on how to approach health and welfare problems such as addiction and partner violence, as well as autism." The results of this study were published in the open-access journal, Frontiers in Ecology and Evolution.
To learn more about the science of jealousy, click here:
What do we see from watching birds move across the country?
- A total of eight billion birds migrate across the U.S. in the fall.
- The birds who migrate to the tropics fair better than the birds who winter in the U.S.
- Conservationists can arguably use these numbers to encourage the development of better habitats in the U.S., especially if temperatures begin to vary in the south.
The migration of birds — and we didn't even used to know that birds migrated; we assumed they hibernated; the modern understanding of bird migration was established when a white stork landed in a German village with an arrow from Central Africa through its neck in 1822 — draws us in the direction of having an understanding of the world. A bird is here and then travels somewhere else. Where does it go? It's a variation on the poetic refrain from The Catcher in the Rye. Where do the ducks go? How many are out there? What might it encounter along the way?
While there is a yearly bird count conducted every Christmas by amateur bird watchers across the country done in conjunction with The Audubon Society, the Cornell Lab of Ornithology recently released the results of a study that actually go some way towards answering heretofore abstract questions: every fall, as per cloud computing and 143 weather radar stations, four billion birds migrate into the United States from Canada and four billion more head south to the tropics.
"In the spring," the lead author Adriaan Dokter noted, "3.5 billion birds cross back into the U.S. from points south, and 2.6 billion birds return to Canada across the northern U.S. border."
In other words: the birds who went three to four times further than the birds staying in the U.S. faired better than the birds who stayed in the U.S. Why?
Part of the answer could be very well be what you might hear from a conservationist — only with numbers to back it up: the U.S. isn't built for birds. As Ken Rosenberg, the other co-author of the study, notes: "Birds wintering in the U.S. may have more habitat disturbances and more buildings to crash into, and they might not be adapted for that."
The other option is that birds lay more offspring in the U.S. than those who fly south for the winter.
What does observing eight billion birds mean in practice? To give myself a counterpoint to those numbers, I drove out to the Joppa Flats Education Center in Northern Massachusetts. The Center is a building that sits at the entrance to the Parker River National Wildlife Refuge and overlooks the Merrimack River, which is what I climbed the stairs up to the observation deck to see.
Once there, I paused. I took a breath. I listened. I looked out into the distance. Tiny flecks Of Bonaparte's Gulls drew small white lines across the length of the river and the wave of the grass toward a nearby city. What appeared to be flecks of double-crested cormorants made their way to the sea. A telescope downstairs enabled me to watch small gull-like birds make their way along the edges of the river, quietly pecking away at food just beneath the surface of the water. This was the experience of watching maybe half a dozen birds over fifteen-to-twenty minutes, which only served to drive home the scale of birds studied.
Explore how alcohol affects your brain, from the first sip at the bar to life-long drinking habits.
- Alcohol is the world's most popular drug and has been a part of human culture for at least 9,000 years.
- Alcohol's effects on the brain range from temporarily limiting mental activity to sustained brain damage, depending on levels consumed and frequency of use.
- Understanding how alcohol affects your brain can help you determine what drinking habits are best for you.
If you want to know what makes a Canadian lynx a Canadian lynx a team of DNA sequencers has figured that out.
- A team at UMass Amherst recently sequenced the genome of the Canadian lynx.
- It's part of a project intending to sequence the genome of every vertebrate in the world.
- Conservationists interested in the Canadian lynx have a new tool to work with.
If you want to know what makes a Canadian lynx a Canadian lynx, I can now—as of this month—point you directly to the DNA of a Canadian lynx, and say, "That's what makes a lynx a lynx." The genome was sequenced by a team at UMass Amherst, and it's one of 15 animals whose genomes have been sequenced by the Vertebrate Genomes Project, whose stated goal is to sequence the genome of all 66,000 vertebrate species in the world.
Sequencing the genome of a particular species of an animal is important in terms of preserving genetic diversity. Future generations don't necessarily have to worry about our memory of the Canadian Lynx warping the way hearsay warped perception a long time ago.
Artwork: Guillaume le Clerc / Wikimedia Commons
13th-century fantastical depiction of an elephant.
It is easy to see how one can look at 66,000 genomic sequences stored away as being the analogous equivalent of the Svalbard Global Seed Vault. It is a potential tool for future conservationists.
But what are the practicalities of sequencing the genome of a lynx beyond engaging with broad bioethical questions? As the animal's habitat shrinks and Earth warms, the Canadian lynx is demonstrating less genetic diversity. Cross-breeding with bobcats in some portions of the lynx's habitat also represents a challenge to the lynx's genetic makeup. The two themselves are also linked: warming climates could drive Canadian lynxes to cross-breed with bobcats.
John Organ, chief of the U.S. Geological Survey's Cooperative Fish and Wildlife units, said to MassLive that the results of the sequencing "can help us look at land conservation strategies to help maintain lynx on the landscape."
What does DNA have to do with land conservation strategies? Consider the fact that the food found in a landscape, the toxins found in a landscape, or the exposure to drugs can have an impact on genetic activity. That potential change can be transmitted down the generative line. If you know exactly how a lynx's DNA is impacted by something, then the environment they occupy can be fine-tuned to meet the needs of the lynx and any other creature that happens to inhabit that particular portion of the earth.
Given that the Trump administration is considering withdrawing protection for the Canadian lynx, a move that caught scientists by surprise, it is worth having as much information on hand as possible for those who have an interest in preserving the health of this creature—all the way down to the building blocks of a lynx's life.
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