Chemistry of Love: Owl Monkeys Shed Light on Evolution of Love - [Article]

(National Geographic, 13, Feb 2013) - It may not seem like monkey business, but emotional bonds in animals such as primates may have evolved into love as we know it.

Journal article: Till Death (Or an Intruder) Do Us Part:Intrasexual-Competition in a Monogamous Primate

Take owl monkeys, tiny tropical tree-dwellers that treat every day like it's Valentine's Day. A male and a female stick together as long as possible, never cheat, and never "divorce" their mates—extremely unusual behavior, even among people. (Also see "Male Monkeys Wash With Urine to Attract Females?")

Sometimes, though, young adult owl monkeys that can't find mates—monkeys that scientists call floaters—pick vicious fights with established pairs, eventually kicking one of them out.

Now, new research shows that the monkeys forced to take on new partners have fewer babies than owl monkeys that haven't been broken up, said Eduardo Fernandez-Duque, a biological anthropologist at the University of Pennsylvania in Philadelphia who led a new study on owl monkey relationships.

The results show how monogamy helps owl monkeys—and may even shed light on how human relationships evolved, said Fernandez-Duque, who has received funding for his work from National Geographic's Committee for Research and Exploration. (National Geographic News is part of the National Geographic Society.)

"Call it love, call it friendship, call it marriage—there is something in our biology that leads to this enduring, emotional bond between two individuals that is widespread among human societies," Fernandez-Duque said in a statement.

Only about 5 percent of mammals are monogamous, and the phenomenon most often arises when both parents are needed to raise offspring, as in the case of people.

With owl monkeys, fathers take on most of the childcare after a baby is born, relying on the mother only for milk. (See video: "Owl Monkey Fathers Know Best?")

But floaters—which Fernandez-Duque and colleagues first noticed in 2003 in Argentina's Chaco region (map)—can spell trouble in paradise.

Drawing on nearly two decades of observations of 18 owl monkey groups, the team discovered that pairs that stay intact produce 25 percent more babies than monkeys in severed pairs.

The exiled animal from those broken relationships, meanwhile, is usually injured and often dies.

Since the team studied more than 150 animals, "I felt very confident that what he was telling us is a real phenomenon—it's not a flash in the pan," noted Patricia Wright, who was one of the first people to study owl monkeys in the 1980s.

"He had the goods on the animals. I was really excited about that," said Wright, an anthropologist at Stony Brook University in New York.

Wright said she was personally pleased that the study reinforced findings that owl monkeys stay true to one another unless forced to separate.

"I knew that these little monkeys didn't fool around," she said.

Why monkeys that are broken up have fewer babies is unknown, though Fernandez-Duque suspects there's an emotional component. (See more pictures of all-star animal dads.)

Just as a man and a woman need time to get to know each other and form a deep connection, so do owl monkeys. So when a marauding monkey enters into a new relationship, there's a delay in mating—usually about a year, Fernandez-Duque  said.

In fact, pair bonding in monogamous animals, such as owl monkeys, may be "sort of evolutionary antecedent to love in humans," said Larry Young, a behavioral neuroscientist at Emory University in Atlanta and author of the new book The Chemistry Between Us: Love, Sex, and the Science of Attraction.

Young, who studies the brain chemistry of love and emotion, does most of his research on monogamous prairie voles.

Though human love is a rich emotion reflective of our advanced brains, he said, "the foundation of that emotion is very similar to the neuromechanisms that are causing the bond between these two prairie voles."

For instance, experiments have shown that if a vole loses its partner, the "widowed" animal shows depressive symptoms—measured by a lack of willingness to escape a dangerous situation.

According to Young, our brains are in the love seat, so to speak: The organs "have evolved the mechanism to produce an emotional attachment," he said.

That attachment is spurred by oxytocin—produced during intimate contact in both people and animals—and dopamine, which is responsible for feelings of exhilaration and happiness.

So, many splendored as it is, love, he said, "is really the result of a cocktail of chemicals."

Do Animals Get Depressed?

:'(|)

(National Geographic.com, 4, Oct 2012) - Primates, rodents may show signs of sadness, study suggests.

Learning more about depression in animals could one day benefit humans, say scientists who believe that mammals share the same basic wiring in their brain for emotions as humans do. (Although not every scientist agrees with that premise.)

In the October 5 issue of Science, Assistant Professor of Neuroscience Olivier Berton and his colleagues at the University of Pennsylvania reviewed recent studies of rodents, primates, and fish who lacked interest in their environment and their fellow animals.

We spoke with Berton about what we do—and don't—know about animal depression.

Do animals get depressed?

Depression is diagnosed in humans based on a list of symptoms that are all very subjective. Common core symptoms include feelings of guilt, thoughts of death, and loss of pleasure. Because animals can't communicate even if they have these kinds of experiences, strictly the answer is: We can't say.

What signs may indicate if an animal is depressed?

There are certain aspects of the disease that may be measured in animals. One of the core symptoms of depression is anhedonia, the decrease and loss of interest in pleasurable activities. We measure interest in food that animals like a lot or in motivation for sexual activity. We also measure how they are interacting socially with other animals in the group, and changes in sleep patterns and daytime activities. Another behavior that has been used frequently to measure animal depression is whether they readily give up when exposed to a stressful situation.

What animals seem to exhibit signs of depression?

Definitely the most convincing observations derive from nonhuman primates. Based on behavioral observation, trained observers can say a monkey looks depressed. Because their emotional behaviors are similar to that of humans, just by looking at their facial expressions or the way their gaze is directed, we can get an indication of whether an animal may be experiencing sadness.

Can you really study animals in this environment?

One problem is that many lab studies in primates and rodents are conducted in captive animals that are raised in relatively impoverished conditions compared to their natural habitat. This can cause depression-like changes. Currently there is not a lot of data available that compares animal emotional behaviors in the wild versus in laboratory setting.

How would animals deal with depression in nature?

I don't know. There are very few systematic studies of this kind. It is possible that behavioral disorders in animals in the wild may impair their chances of survival. Maybe there is a point where they cannot deal and are more easily preyed upon.

Could domestic animals be depressed?

Veterinarians frequently give antidepressants to dogs to treat their behavioral disorders. For example, if an owner leaves the house and the dogs experience stress related to being separated, they may develop abnormal behaviors such as scratching themselves until they bleed or eating the door. These are thought to represent canine versions of psychiatric disorders. Although human treatments seem to work in dogs, large-scale studies are lacking.