Bonobo Mothers Meddle in Their Sons’ Sex Lives – Making Them Three Times More Likely to Father Children

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Sergey Uryadnikov/Shutterstock

Ben Garrod, University of East Anglia

Dating is never easy, for any of us. Scenarios play over in our heads, classic questions and worries bombard us. Will she like me? Does he share the same interests? Will my mum be watching us have sex? Thankfully, that last question isn’t actually one us humans have to deal with. But new research shows that for bonobos, sex really is often a family affair. What’s more, rather than being an embarrassing hindrance, motherly presence greatly benefits bonobo sons during the deed.

Along with chimpanzees (Pan troglodytes), bonobos (Pan paniscus) are our closest living relatives. Restricted to a 500,000 km² thickly-forested zone of the Congo Basin, these endangered great apes were only formally discovered in 1928, which until 2017 made them the most recently-described living great ape species.

Operating in female-led social systems, bonobos are capable of showing a wide range of what were long held as human-specific feelings and emotions, such as sensitivity, patience, compassion, kindness, empathy and altruism.

They’re also perhaps the most promiscuous non-human species on the planet. While chimpanzee sex is tied closely to reproduction, up to 75% of bonobo sexual behaviour is purely for pleasure. From saucy greetings and social bonding to conflict resolution and post-conflict make-up sex, sex serves hugely important functions in most aspects of bonobo social behaviour. Even the mere discovery of a new food source or feeding ground is enough to spark a wave of communal sexual activity.

Bonobo sex isn’t generally a private affair. Sergey Uryadnikov/Shutterstock

It seems that the number of reasons for a bonobo to have sex is surpassed only by the number of forms in which they do it. Indiscriminate of sex and age, the only combination strictly off limits in bonobo society is between a mother and her mature son. In addition to standard penetrative encounters, they frequently engage in manual genital massage and oral sex. These positionally creative apes are also the only animal (other than us) to practice tongue-on-tongue kissing or face-to-face penetrative sex. The prominence of bonobos’ sexual behaviour in social life has led researchers to brand bonobos as the “make-love-not-war apes”.

Meddling mothers

Bonobo mothers, however, seem to make a war out of seeing their sons successfully make love. They’ve frequently been observed to form coalitions with their sons to help them acquire and maintain high dominance rank, protect their sons’ mating attempts from interference by other males and even interfere in the mating attempts of other, unrelated males.

The new research, published in Current Biology, shows that these strategies pay off. Males who had a mother present in their social group engaging in these behaviours were about three times more likely to produce offspring than males whose mothers were no longer part of the group.

Mothers of successful bonobo fathers were present more than twice as frequently during conception than in chimpanzees, a species in which males are socially dominant, and in which maternal presence provided no benefit to sons. Thus, it appears that the dominance of females in bonobo social systems allows mothers to exert behavioural influence to boost the sexual fitness of their sons.

This elevated female social power doesn’t just let bonobo mums get involved in their families’ sex lives, but is likely responsible for a host of peaceful and progressive traits rarely seen in the mammal world. Females practice sex even when not ovulating, male-male competition is much reduced, and the species is remarkably tolerant to bonobos from outside of their social group. Perhaps us humans ought to take note of how positively society can change when females are in positions of influence. It’s probably better if we keep our sex lives parent-free, though.The Conversation


Ben Garrod, Professor of Evolutionary Biology and Science Engagement, University of East Anglia


This article is republished from The Conversation under a Creative Commons license. Read the original article.

Evolution and the Mammalian Spine

A two-toed sloth hangs from a tree branch. These sloths are adapted to moving upside-down through the forest canopy. Photo: kungverylucky/stock.adobe.com

Differences in numbers of vertebrae are most extreme in mammals which do not rely on running and leaping, such as those adapted to suspensory locomotion like apes and sloths, a team of anthropologists has concluded in a study appearing in the journal Nature Ecology & Evolution and funded in part by The Leakey Foundation.

Previous research had posited that running speed specifically determines variation in vertebral numbers–a conclusion not supported by the new work.

“The classic body plan of many mammals is built on a mobile back and this body plan is conserved regardless of running speed,” explains New York University anthropologist and Leakey Foundation grantee Scott Williams, the paper’s senior author. “More specifically, we find that a particular type of locomotor behavior–suspensory locomotion, which involves hanging below tree branches, rather than speed–is associated with increases in variation in numbers of vertebrae across mammals.”

The work centers on an effort to better understand why certain aspects of mammals remain consistent over time–a phenomenon known as evolutionary stasis.

Despite the diversity evolution has yielded, there remain consistencies across a wide range of distantly related organisms. Of particular note is the number of neck (cervical) and back (thoracic and lumbar) vertebrae of mammals.

Almost all mammals, from tiny rodents to long-necked giraffes, have exactly seven cervical vertebrae. Images: stock.adobe.com

“Nearly all mammals have the same number of cervical vertebrae, no matter how long or short their necks are–humans, giraffes, mice, whales, and platypuses all have exactly seven cervical vertebrae,” explains co-author Jeff Spear, an NYU doctoral student.

In fact, the majority of mammals possess 19 or 20 thoracic and lumbar vertebrae, for a total of 26 or 27 “CTL” vertebrae (for “cervical, thoracic, and lumbar” vertebrae). There is little variation in these numbers, either within species or across different species–or even different species separated by over 160 million years of evolution. Humans, with 24 CTL, are one of the exceptions.

Earlier work had hypothesized that fast running constrains the number of CTL vertebrae in mammals and that slower mammals are freer to vary their CTL numbers, suggesting an association between speed and vertebrae count. However, this conclusion was based on data from a limited sample of mammalian diversity.

In order to learn what causes evolutionary stasis, and why there are exceptions, such as in humans, the scientists aimed to create a clearer picture using a larger and more diverse sample of mammals and phylogenetic methods–those that account for evolutionary relatedness in analyses.

In their study, they counted the vertebrae of thousands of individuals for nearly 300 species of mammals. The researchers then compared variation in the number of CTL vertebrae to traits such as speed, habitat, locomotion, spine mobility, posture, and limb use.

Ancestral state reconstruction of presacral vertebral numbers. The left panel uses a heat map that reflects low (yellow) and high (purple) morphological heterogeneity indices. The right panel plots numbers of presacral vertebrae, with a heat map showing the presumed primitive number of presacral vertebrae (26–27, yellow), in contrast to marked decreases (blue) or increases in numbers of presacral vertebrae (red to black). 

The analyses did not seem to show an association between vertebrae count and running speed. Rather, this trend was primarily driven by animals adapted to suspensory and other “antipronograde” behaviors, where limbs are held in tension during slow climbing, clambering, and suspension.

This observation led the researchers to hypothesize that the classic body plan of certain mammals–therian mammals, which give birth to live young–is built on a mobile back and that this body plan is conserved regardless of running speed.

This was based on an existing understanding of genetic activity relevant to vertebrae.

“Changes in types of vertebrae are determined by Hox genes–the genes that organize animal bodies along the head-tail axis, ensuring that your eyes go on your face and your legs go at the base of your torso,” explains Spear. “But changes in Hox gene expression sometimes creates vertebrae that are intermediate in type, which can impinge the mobility of the spine.”

For animals following the ancestral body plan, from possums to tigers, departures from the ancestral types of vertebrae in the back creates a risk of inefficient locomotion and are weeded out by natural selection, he adds.

“Mammals that depart from this body plan, however, such as apes adapted for antipronograde behaviors, are more free to vary in their number of CTL vertebrae,” says Williams. “Our own atypical number of CTL vertebrae, then, may be the consequence of our evolutionary history as antipronograde climbers.”


Increased variation in numbers of presacral vertebrae in suspensory mammals

Authors: Scott A. Williams, Jeffrey K. Spear, Lauren Petrullo, Deanna M. Goldstein, Amanda B. Lee, Amy L. Peterson, Danielle A. Miano, Elska B. Kaczmarek and Milena R. Shattuck

This research was supported by grants from the National Science Foundation (BCS-0925734) and The Leakey Foundation.

This article was provided by New York University. Click here to read more about this research in Jeffrey Spear’s “Behind the Paper” article.

From the Field: Kevin Hatala, Nariokotome, Kenya

Kevin Hatala is an assistant professor of biology at Chatham University. He was awarded a Leakey Foundation Research Grant in our fall 2017 cycle for his project entitled “Paleoecological investigation of 1.5 Ma footprint sites near Nariokotome, Kenya.”

Research team members conducting a “bone walk” to survey for skeletal fossils in 1.5 million-year-old deposits. Photo credit: Kevin Hatala.

Our research team recently returned from fieldwork near Nariokotome, in northwestern Kenya. Our research was focused on surveys and preliminary excavations of sites in this region that preserve 1.5 million-year-old (Ma) fossil footprints. While fossil footprints have been historically rare sources of data in paleoanthropology, recent discoveries suggest that footprints are not as rare within the human fossil record as we may have assumed. Efforts to recover these data can offer fresh opportunities to test and refine hypotheses concerning hominin anatomy, behavior, ecology and/or land use patterns.

Research team members at the monument dedicated to the discovery of the Turkana Boy skeleton. From left to right: Stephen Longoria (National Museums of Kenya), Matthew Macherwas (National Museums of Kenya), Francis Ngasike (Nariokotome), and Sammy Lokorodit (Nariokotome). Photo credit: Kevin Hatala.

The skeletal fossil records from the east and west sides of the Turkana Basin at around 1.5 Ma are quite well-known to paleoanthropologists. On the east side of Lake Turkana, the Koobi Fora region is home to an abundance of hominin fossils from this time period, which have been attributed to species such as Homo erectus, Homo habilis, and Paranthropus boisei. On the west side, far fewer fossils are known but one of the most famous hominin fossils – KNM-WT 15000, also known as “Turkana Boy” – was discovered here. Fossils attributed to Paranthropus boisei are also known from West Turkana at this same time interval.

Our work is aimed at uncovering new fossil footprint and skeletal fossil data that we can use to better understand the ecological contexts of hominins living on the east and west sides of Lake Turkana around 1.5 Ma. We previously conducted similar work near Koobi Fora, but this was our first field season on the west side of the lake. Overall, it was a remarkable success!

An approximately 1.5 million-year-old hippo track found during preliminary excavations. Photo credit: Kevin Hatala.

We worked with a small field team, which included myself, Dr. Neil Roach (Harvard University), Stephen Longoria (National Museums of Kenya), Matthew Macherwas (National Museums of Kenya), Sammy Lokorodit (Nariokotome), and Francis Ngasike (Nariokotome). Our co-PI Dr. Kay Behrensmeyer (Smithsonian Institution) was prohibited from travel due to a government shutdown, which threw an unexpected wrench into our plans. But, thanks to cell phones, we were still able to coordinate with her remotely from the outcrops.

Fossilized bovid tracks found during preliminary excavations. Photo credit: Kevin Hatala.

Within just a short two-week field season, we located four fossil footprint surfaces, all at slightly different stratigraphic levels dating to around 1.5 million-years-ago. We started excavations and these surfaces have already revealed footprints from a variety of animals, in a variety of contexts. These data will help substantially to build upon the limited skeletal fossil record that is known from this region. We also conducted a series of fossil surveys, called “bone walks”, in which we recorded all skeletal fossils present on the ground surface within the same sedimentary deposits. This provides us with unbiased samples of skeletal fossils, distinct from those in which individuals might preferentially collect only the most exciting finds, such as primates and hominins.

With these new data (including a few particularly exciting fossils!), we’ll head back to the museum and labs for analysis. We hope that this evidence can help us begin to develop a more complete picture of hominins and their environments in the Turkana Basin around 1.5 million-years-ago and provide us with insights into how ecological contexts may have shaped some of the patterns and processes that occurred at this particular time and place in human evolution.

Homo naledi and the Chamber of Secrets

May 14 is the final day for discounted ‘early bird’ tickets for our upcoming lecture, “Homo naledi and the Chamber of Secrets” with Dr. Jeremy DeSilva. The lecture will be held at the Houston Museum of Natural Science on May 21 at 6:30 pm.

The largest collection of ancient human bones ever discovered in Africa was excavated from chambers deep within South Africa’s Rising Star cave. In 2013, six women scientists squeezed through the twisting passages of this cave to unearth more than 1,500 fossils representing at least 15 individuals of the newly discovered early human species Homo naledi.

In this lecture, paleoanthropologist and Homo naledi study team member Dr. Jeremy DeSilva will discuss what we know about these fossils and how these findings are changing not only science, but how we define “human.”

Early bird tickets are $16 (through May 14) or $10 for Leakey Foundation supporters and HMNS members. To receive the Leakey Foundation supporter discount, call the museum box office at (713) 639-4629 and use the promo code “LECLeakeyFnd.”

Starting May 15, tickets will be $14 for museum members and Leakey Foundation supporters, general admission tickets will be $20.

Student tickets will also be available at the box office. Show your valid student ID for $8.00 student admission.

Get your tickets now!

National Parks Could Save Endangered Species

The West African chimpanzee population has declined by nearly 80 percent in recent decades. Habitat loss is threatening their livelihoods across the continent, and especially in Senegal, where corporate mining has started eating up land in recent years.

Research led by Leakey Foundation grantee Stacy Lindshield shows protected areas like national parks are effectively preserving many mammal species in Senegal. Photo credit: Purdue University/Stacy Lindshield

The geographical distribution of West African chimps in Senegal overlaps almost perfectly with gold and iron ore deposits, and unfortunately for the chimps, mining is a key piece of the country’s development strategy.

A new study of animal populations from inside and outside a protected area in Senegal called Niokolo-Koba National Park, shows that protecting such an area from human interaction and development preserves not only chimps but many other mammal species. The findings were published in the journal Folia Primatologica.

“We saw the same number of chimpanzee species inside and outside the park, but more species of carnivores and ungulates in the protected area,” said Leakey Foundation grantee Stacy Lindshield, a biological anthropologist at Perdue University.

Although habitat loss is the biggest threat to West African chimps, they are sometimes killed for meat. This is uncommon in Senegal, where eating chimpanzee meat is a taboo. But this isn’t the case in other West African countries, where researchers might see a bigger difference in chimp populations inside and outside protected areas. The researchers say that National parks could be especially effective at protecting chimps in these nations.

The difference in the number of species of carnivores and hooved animals (known as ungulates), inside and outside the park was stark — their populations were 14 and 42 percent higher in the park, respectively. This is in sharp contrast with what Lindshield was hearing on the ground in Senegal: There’s nothing in the park; all the animals are gone.

“There were qualitative and quantitative differences between what people were telling me and what I was seeing in the park,” she said. “Niokolo-Koba National Park is huge, and the area we study is nestled deeply in the interior where it’s difficult for humans to access. As a consequence, we see a lot of animals there.”

Hunting practices and human-carnivore conflict are two big reasons for ungulates thriving inside the park. These animals are frequently targeted by hunters, and some carnivore species turn to livestock as a food source when their prey species are dwindling, creating the potential for conflict with humans. Because the two sites are relatively close geographically and have similar grassland, woodland and forest cover, the researchers think human activity is the root of differences between the two sites.

Lindshield’s team conducted basic field surveys by walking around the two sites and recording the animals they saw. They also installed camera traps at key water sources, gallery forests and caves to record more rare and nocturnal animals.

“We’re engaging in basic research, but it’s crucial in an area that’s rapidly developing and home to an endangered species,” Lindshield said. “This provides evidence that the protected area is effective, at least where we are working, counter to what I was hearing from the public. The management of protected areas is highly complex. Myriad challenges can make management goals nearly impossible, such as funding shortfalls or lack of buy-in from local communities, but I think it’s important for people to recognize that this park is not a lost cause; it’s working as it’s intended to at Assirik, especially for large ungulates and carnivores.”

Lindshield hopes her future studies will uncover not only which species exist in each site, but population sizes of each species. This metric, known as species evenness, is a key measure of biodiversity.

Data from the unprotected area in Senegal was collected by Jill Pruetz of Texas State University. Stephanie Bogart and Papa Ibnou Ndiaye of the University of Florida, and Mallé Gueye of Niokolo-Koba National Park, also contributed to this research. Funding was provided by the National Science Foundation, National Geographic Society, Leakey Foundation, Rufford Foundation, Primate Conservation Inc., Jane Goodall Research Center at the University of Southern California, Purdue and Iowa State University.


Journal Reference:

Stacy Lindshield, Stephanie L. Bogart, Mallé Gueye, Papa Ibnou Ndiaye, Jill D. Pruetz. Informing Protection Efforts for Critically Endangered Chimpanzees (Pan troglodytes verus) and Sympatric Mammals amidst Rapid Growth of Extractive Industries in Senegal. Folia Primatologica, 2019; 124 DOI: 10.1159/000496145


Materials provided by Purdue University. Originally written by Kayla Zacharias.