Bonobos, Our Other Closest Relative After Chimpanzees

We may look different than bonobos and chimpanzees, but we're far more alike than physical appearance makes it seem

Hiya!

Ever since Charles Darwin introduced his Theory of Evolution, we’ve been obsessed with comparing ourselves to others in the animal kingdom, especially primates. When DNA entered our knowledge base, we learned we share a significant amount with many other animals, but none more than chimpanzees. Research into the similarities and differences between our species has thrived for decades.

Then, experts discovered we share almost as much DNA (within .1 percent) with Bonobos, a less studied primate species, as we do with chimpanzees. Research into these distinctions between bonobos and us has a long way before catching up with what we know about chimps. But some recent studies discovered interesting ways bonobos differ socially from either chimps or humans. Maybe, there’s something we can learn from them.

Chimps + Bonobos = Us

Okay, so maybe the headline is a bit of an exaggeration, but it’s also kinda true. Allow me to explain.

It’s thought that first, our Human line of ancestry split from the line of bonobos and chimpanzees around eight million years ago, but chimps and bonobos didn’t diverge until much later, around 1.8 million years ago, perhaps prompted by the chimpanzees’ need to adapt to relatively open, dry habitats.

Chimpanzees are our closest relatives in the animal kingdom, sharing 98.8 percent of our DNA, so understandably, the majority of research over the years has explored differences and similarities between our species.

In addition to our shared DNA, a big reason for robust studies into chimps, specifically, is thanks to the fantastic work of conservationist and ethologist Jane Goodall. Her six decades’ worth of detailed and immersive research into chimpanzees’ social lives and behaviors redefined how behavioral studies are conducted. In the process, she inspired all of us to reexamine what it means to be human.

But, it turns out, chimps aren’t our only closest relatives. Bonobos, who get far less attention, share 98.7 percent of our DNA. Chimps and bonobos look similar initially, but there are a few physical differences.

To start, bonobos are smaller than chimps, and they have narrower shoulders, longer legs, and smaller heads, while chimps have a more sturdy and robust appearance. Additionally, chimps have black or darker lips, and their face darkens as they age, but bonobos have darker faces at birth, and unlike chimps, bonobos have pink lips similar to us.

But things get really interesting, as they so often do, when we delve beyond physical appearances. Chimpanzees and bonobos may look similar, but they couldn’t be more different socially. In turn, we may look wildly different than chimps or bonobos, but socially, we’re practically a perfect mix of both.

In fact, a part of me wonders if this might explain our struggle to find balance as a species and why we swing like a pendulum between a desire for peace and a need for violence.

Social Organization

The most significant discrepancy is that like, us humans, males dominate chimpanzee societies using testosterone-fueled aggression to incite what can become a deadly conflict. Chimps and humans live in primarily patriarchal societies and are known to kill our own kind — but such violence or aggression is rarely seen within bonobo communities.

Instead, bonobo societies are egalitarian but female-centered. Female bonobos use alliances with other females to deter male aggression by making up for size with numbers. In addition to using numbers to squash social aggression, the Pan African Sanctuary Alliance (PASA), the largest coalition of wildlife centers and sanctuaries across Africa, explains another, more biological solution:

“Peace is almost universal across bonobo communities. They have never been known to kill their own kind, and they have evolved to avoid conflict. In response to conflict, bonobos release a stress hormone that encourages social bonding for reassurance.”

The mere fact that bonobos evolved a stress hormone to diffuse aggression and encourage bonding is, well, phenomenal, and I applaud Nature for its ingenious solution. Imagine how handy such a gift would be, perhaps it would make domestic violence stats plummet. It’s unfortunate this trait isn’t one we share, but knowing us, someday, we’ll probably be able to buy a synthesized version of it.

In the meantime, there’s yet another strategy female bonobos use to prevent aggression from taking over their communities. To put it simply, they substitute aggression for sex.

Bonobos’ Surprising Sexuality

It turns out that bonobos have more sex than any other primate. This is because while most species use sex strictly for procreation and some, like dolphins or us, do it for pleasure too, bonobos are next level.

For them, sex is a normal part of social relations, not much different than a handshake — and it’s not just between males and females. Outside of family members, bonobos appear to engage in sexual acts with anyone they want, regardless of anatomy. Every partner combination has been observed. Not only do bonobos have sex more often, but they also do so in various positions, including face-to-face, which chimpanzees avoid.

If you didn’t already know this, you may have two initial thoughts, or at least I did. First: holy smokes, the females must constantly be pregnant, and bonobo communities must overflow with youngsters. Secondly: wait, how do they know who the fathers are?

Well, according to Scientific American, the answer to the first question is that:

Despite the frequency of sex, the bonobos rate of reproduction in the wild is about the same as that of the chimpanzee. A female gives birth to a single infant at intervals of between five and six years.

And the answer to the second question is that female bonobos either don’t know or don’t seem to care who their offspring’s father is. The job of raising offspring belongs strictly to the mothers. Female bonobos are even known to adopt a stranger’s offspring as their own.

Females in both chimp and bonobo societies will leave home after puberty and join other groups where they find mates and live out their days. However, compared to chimps or other primates, female bonobos begin puberty years earlier — at around five years old rather than eight or nine.

This fact surprised researchers because female bonobos’ developmental processes already typically take longer than chimpanzees. And despite the earlier beginning, female bonobos still have their first child around the same age as female chimps.

Meanwhile, bonobo males stay with their moms for their entire lives. Males remain dependent on their moms for protection from aggressive encounters with other males, and their moms often have the final say in who their sons mate with. According to the SA article, “the highest-ranking males of a bonobo community tend to be sons of important females.”

Perspective Shift

Clearly, whatever changes occurred in the less-than-one percent DNA difference between us, chimps, and bonobos, resulted in some significant physical transformations. We, Homo sapiens, look vastly different compared to either of the other primates, but when we look beyond appearance, we’re not so different.

Researchers suggest bonobos may have diverged to adapt to a more wide open habitat, and while that may explain their physical differences, I can’t help but wonder at the split in behavior too.

It’s almost as if one group of chimps, seemingly the females, decided they’d had enough of the aggression-fueled social structures and chose instead to venture out on their own and live away from other chimp societies — which would, in turn, fuel any physical adaptation requirements.

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A bonobo youth Image Source: WikiCommons