In fact, according to a new study led by Harvard primatologists Liran Samuni and Martin Surbeck, bonobos, one of our closest living relatives, could be the latest addition to the list.

The research, published today in eLife, is the result of a five-year examination of the hunting and feeding habits of two neighboring groups of bonobos at the Kokolopori Bonobo Reserve in the Democratic Republic of Congo. They looked at whether ecological and social factors influence those habits. Four of those years were spent tracking the neighboring groups of great apes using GPS and some old-fashioned leg work to record each time they hunted.

Analyzing the data, the scientists saw many similarities in the lives of the two bonobo groups, given the names the Ekalakala and the Kokoalongo. Both roam the same territory, roughly 22 square miles of forest. Both wake up and fall asleep in the bird-like nests they build after traveling all day. And, most importantly, both have the access and opportunity to hunt the same kind of prey. This, however, is precisely where researchers noticed a striking difference.

The groups consistently preferred to hunt and feast on two different types of prey. The Ekalakala group almost always went after a type of squirrel-like rodent called an anomalure that is capable of gliding through the air from tree to tree. The Kokoalongo group, on the other hand, favored a small to medium-sized antelope called a duiker that lives on the forest floor.

“The idea is that if our closest living relatives, chimpanzees and bonobos, both have some cultural traits, then [it’s likely] our ancestors already had some capacity for culture.” — Liran Samuni

Out of 59 hunts between August 2016 and January 2020, the Ekalakala captured and ate 31 anomalure, going after duikers only once. Kokoalongo ate 11 duikers in that time and only three gliding rodents.

“It’s basically like two cultures exploiting a common resource in different ways,” said Samuni, a postdoctoral fellow in Harvard’s Pan Lab and the paper’s lead author. “Think about two human cultures living very close to each other but having different preferences: one preferring chicken more while the other culture is more of a beef-eating culture. … That’s kind of what we see.”

Using statistical modeling, the scientists found this behavior happens independent of factors like the location of the hunts, their timing, or the season. They also found the preference wasn’t influenced by hunting party size or group cohesion. In fact, the researchers’ model found that the only variable that could reliably predict prey preference was whether the hunters were team Ekalakala or team Kokoalongo.

The researchers make clear in the paper that they didn’t investigate how the bonobo groups learned this hunting preference, but through their analysis they were able to rule out ecological factors or genetic differences between the two groups. Basically, it means all evidence points toward this being a learned social behavior.

“It’s the same population, and it’s neighboring communities,” said Surbeck, an assistant professor in the Department of Human Evolutionary Biology and the paper’s senior author. He founded and directs the Kokolopori Bonobo Research Project. “These two communities basically live in the same exact forest. They use the exact same places, but, nevertheless, they show these differences.”

The paper amounts to what’s believed to be the strongest evidence of cultural behavior in this primate species.

The researchers believe this paper is only the tip of the iceberg and are already planning the next part of the work: looking at how the bonobo groups learned these behaviors.

One of the main goals driving this work is helping characterize the cultural capabilities of the last common ancestor between humans and our two closely related great ape cousins.

“The idea is that if our closest living relatives, chimpanzees and bonobos, both have some cultural traits, then [it’s likely] our ancestors already had some capacity for culture,” Samuni said.

Bonobos can play a special role in this mystery. Like chimpanzees, which they are often mistaken for, bonobos share 99 percent of their DNA with humans. Bonobos are often seen as less aggressive and territorial, however, favoring sex in various partner combinations over fighting. Chimp groups, on the other hand, sometimes battle when they meet in the wild, occasionally to the death.

Different Bonobo population groups are known to interact and even share meals, which along with their socio-sexual behavior has earn them the moniker “hippie apes.” It’s those free love and peace traits that make them prime for this type of study since scientists can observe two neighboring bonobo groups to distinguish whether a behavior that differs between two groups that interact regularly comes about because of some sort of a learning mechanism (or social preference) or because the environment dictates it, the researchers said.

The authors of the paper were not much surprised by their findings.

They had noticed this hunting preference anecdotally, and it’s already believed that bonobos have subtle cultural traits. After all, a number of social animals display cultural behavior, especially when it comes to feeding habits. Chimps teach their young to use sticks to fish for termites. Dolphin mothers teach offspring to fit marine sponges to their noses to protect them as they forage on the seafloor.

What excites the researchers about this discovery, however, is that it shows the value of studying this often-overlooked endangered species and diving into its culture.

“They’re like the missing puzzle piece,” Surbeck said.

The study, “Dietary Sphinganine Is Selectively Assimilated by Members of the Mammalian Gut Microbiome,” was published in July in the Journal of Lipid Research.

Sphinganine from milk Johnson Lab/Provided A new technique allows researchers to track specific nutrients as they are taken up by gut microbes in a mouse’s digestive tract. The image shows certain microbes (red) taking in a nutrient common in human milk called sphinganine; blue microbes have not taken it in.

The paper describes an innovative technique developed at Cornell to track the fate of metabolites — nutrients formed in or necessary for metabolism — through a mouse’s digestive tract and identify how they interact with specific gut microbes.

“We think the methods are expandable to many different microbiome systems,” said senior author Elizabeth Johnson, assistant professor of nutritional sciences in the College of Agriculture and Life Sciences. She noted that researchers investigating effects of a high-fat vs. low-fat diet, or a keto diet, might use the technique to track metabolites.

The methodology could reveal how specific metabolites promote specific bacteria. This could allow nutritionists to prescribe that patients eat foods containing specific metabolites to intentionally change the composition of their microbiomes, Johnson said.

Human milk and many other foods contain a class of lipid metabolites called sphingolipids. Previous research suggested that these metabolites help shape an infant’s microbiome, but it was not known if they actually interact with the microbiome.

The study identified two types of gut microbes, Bacteroides and Bifidobacterium, that use sphingolipids for their own metabolism.

While very little is known about the specific roles of gut microbes in human health, Bacteroides have been implicated in both beneficial and not-so-beneficial effects, depending on context. They are generally associated with microbiomes of healthy breastfed infants. Bifidobacterium, shown for the first time in this study to process dietary sphingolipids, are considered the quintessential beneficial bacteria, comprising up to 95% of breastfed infants microbiome.

They’re also a highly popular over-the-counter probiotic.

“Our lab is very interested in how the diet interacts with the microbiome in order to really understand how you can best modulate it to have positive effects on health,” Johnson said. “In this study, we were able to see that yes, these dietary lipids that are a big part of [breastfed] infants diets, are interacting quite robustly with the gut microbiome.”

Sphingolipids originate from three main sources: diet; bacteria that can produce them; and most host tissues.

Johnson, along with first author Min-Ting Lee, a doctoral student, and Henry Le, a postdoctoral researcher, both in Johnson’s lab, created a technique to specifically track dietary sphingolipids as they passed through the mouse gut.

“We custom synthesized the sphingolipid we added to the diet,” Johnson said. “It is almost identical to ones derived from breast milk but with a small chemical tag so we could trace the location of the sphingolipid once it was ingested by the mice.”

Lee then used a fluorescent label that attached to cells or microbes that absorbed the tagged lipid, such that any bacteria that had taken up sphingolipids lit up red. Microbes from the mice’s microbiomes were then isolated and analyzed. Populations with red microbes were separated from the others, and these were then genetically sequenced to identify the species of bacteria.

With further investigation, Le was able to identify the metabolites that Bacteroides and Bifidobacterium produce when exposed to dietary sphingolipids. Further investigations are underway to determine whether these microbially-produced metabolites are beneficial for infant health.

Johnson recently received a five-year, $1.9 million Maximizing Investigators’ Research Award from the National Institutes of Health (NIH) to expand on this work, to better understand how lipid-dependent host-microbe interactions affect human health..

The study was supported by seed funds from the Genomics Facility of the Biotechnology Resource Center at Cornell’s Institute of Biotechnology.

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Materials provided by Cornell University. Original written by Krishna Ramanujan. Note: Content may be edited for style and length.

The study, published today in eLife, reveals why killifish accumulate harmful mutations that cause age-related conditions such as cancer or neurodegenerative diseases that shorten lifespan. This may help scientists better understand how lifespan evolves among populations and may lead to new insights on human aging.

The very short lives of turquoise killifish — between three and nine months — make them an ideal model for studying aging. Killifish live in temporary ponds in Africa that dry up for part of the year, meaning they must hatch, mature and reproduce before this happens. Their eggs survive the dry periods in a hibernation-like state and hatch when rains fill the pond again, starting a new generation.

“Different wild turquoise killifish populations have varying lifespans, and we wanted to explore the reasons behind this,” explains lead author David Willemsen, Postdoctoral Research Fellow at the Max Planck Institute for Biology of Ageing, Cologne, Germany.

For their study, Willemsen and senior author Dario Riccardo Valenzano carried out field work in savanna pools in Zimbabwe to catch and collect genome samples from the killifish for sequencing and analysing in the lab. The team then compared the genomes of killifish living in the driest environments, which have the shortest lives, with the genomes of killifish from wetter environments, which live for months longer.

The short-lived killifish have very small, often isolated populations, leading to so-called population bottlenecks which, the team found, result in harmful mutations accumulating in their populations. By contrast, the longer-lived killifish have larger populations and new fish with new genetic material frequently join their populations. Over time, these larger populations make it more efficient for natural selection to remove harmful mutations.

“Limited population sizes caused by habitat fragmentation and repeated population bottlenecks increase the chance for harmful mutations to accumulate in the population,” Willemsen says. “Our work may help answer a key question about aging by suggesting that population dynamics, rather than evolutionary selection for or against specific genes, contribute to this accumulation of harmful mutations that result in aging and shorter life.”

The results support a model where, given the brief rainy seasons, killifish are under strong selective constraints to survive in the absence of water as dormant embryos and to rapidly reach sexual maturation and reproduce before the water completely evaporates. However, the team believes that killifish are not selected to be short-lived. Instead, harmful mutations that affect late-life survival and reproduction (together causing aging in the killifish) accumulate over generations without being constrained by selection.

“Harmful mutations passively accumulate in killifish populations, and this is even more prominent in smaller populations which happen to live in drier environments,” says senior author Dario Riccardo Valenzano, Group Leader at the Max Planck Institute for Biology and Ageing, and Principle Investigator at CECAD, the Cluster of Excellence for Ageing Research at the University of Cologne, Germany. “Our findings highlight the role of demographic constraints in shaping lifespan within species and could potentially be expanded to provide new insights on aging within other animal and human populations.”

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