Mother bonobos, too, pressure their sons to have grandchildren

If you thought your mother was pushy in her pursuit of grandchildren, wait until you learn about bonobo mothers.

  • Mother bonobos have been observed to help their sons find and copulate with mates.
  • The mothers accomplish this by leading sons to mates, interfering with other males trying to copulate with females, and helping sons rise in the social hierarchy of the group.
  • Why do mother bonobos do this? The "grandmother hypothesis" might hold part of the answer.

Like mother, like monkey.

Bonobo mothers, it turns out, can also be quite pushy in their quest to become grandmothers, according to a new study published in the journal Current Biology. The study describes how male bonobos are more likely to mate if their mothers are living in the group (so living near mom turns out to be a pretty good mating strategy for male bonobos).

The discovery originated among researchers observing bonobos in Africa. They noticed that older females in the group would involve themselves in relationships between male and female bonobos, particularly when it came to mating.

"I just wondered, 'What is it of their business?'" study author Martin Surbeck, Ph.D. told Inverse. "This all made more sense once we found out via genetic analysis that they were mothers of some of the adult males involved."

These would-be bonobo grandmothers push things along by leading their sons toward females in heat, protecting their sons from competing males during copulation, and they "form coalitions with their sons to help them acquire and maintain high dominance rank," the researchers wrote.

The same, however, is not true for chimpanzees. Researchers who observed chimps in Côte d'Ivoire, Tanzania and Uganda found that male chimpanzees whose mothers were present during mating attempts were actually less likely to succeed in having offspring. One possible reason: bonobos live in matriarchal societies while chimpanzees live in groups where all females are subordinate to all males.

"Such maternal behavior is more likely to be effective in bonobos, where the sexes are co-dominant and the highest ranks are consistently occupied by females, than in chimpanzees, where all adult males are dominant over all females," the researchers wrote. "We found that bonobo males with a mother living in the group at the time of the conception were about 3 times (odds ratio: 3.14) more likely to sire offspring than males that did not."

​The grandmother hypothesis

One explanation for why female primates experience menopause is called the "grandmother hypothesis". Instead of using precious energy to continually have children of their own, especially given long periods of gestation and child-rearing, aging females may be ahead to encourage their offspring to have children of their own. The researchers aren't exactly sure the grandmother hypothesis explains the pushy-mother behavior within bonobo societies, but it might be part of the story.

"The interesting twist is that in humans, [the hypothesis] was originally thought to happen through support of their daughters, while in bonobos it is through the sons," Surbeck told The Washington Post.

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  • Scientists say this can lead to drugs for first responders and soldiers, preventing PTSD and other mental issues.
  • The finding builds on the hygiene hypothesis, first proposed in 1989.

Are modern societies trying too hard to be clean, at the detriment to public health? Scientists discovered that a microorganism living in dirt can actually be good for us, potentially helping the body to fight off stress. Harnessing its powers can lead to a "stress vaccine".

Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.