I started writing this blog post whilst sat in a half-deserted village high up in the Gaoligong mountains in China. Occupied by only 10 remaining elders who refused to leave their traditional lives behind, I had the privilege of staying here and immersing myself into daily life.

I am seated by myself as the morning sun blinds me as it peeps out from over the moss-covered tiled roofs. Two chickens are currently sneaking past me into the kitchen to morbidly watch their duck cousin be prepared for breakfast. They scream as my host shoos them away flapping her arms wildly.

The houses date back 50+ years and are made from old wood and bamboo harvested from the forest in the days before the nearby reserve was established. Mules are found on the ground floor of these dwellings with humans roosting above. As a result, night-time can be a very noisy affair!

I also experienced a huge storm at 3 am. I’ve slept through many tropical storms when I lived and worked in Indonesian Borneo, but this was something else. The walls rattled as the rain beat against it and droplets started to seep through and trickle down. I thought the storm would snatch the flimsy roof right off, but I am glad to report that all houses — and mules — were still standing when I woke up.

My PhD is all about understanding local nature and wildlife values, comparing gibbon (small ape) knowledge, and investigating patterns of natural resource use. I have spent the past few months collecting social data in the form of structured interviews and small group discussions with local communities in both Hainan and Yunnan provinces. To get the most candid answers, it is important to immerse yourself into local life.

I have drunk countless cups of green tea and bottles of “bai jiu” (lethal Chinese wine) as a result, been dressed up as a local Hei Lisu person, braved eating the 100-year old egg, and scoffed so many sunflower seeds that I am ready to sprout!

Before embarking on my PhD journey, I was given an antique book by Robert Van Gulik, a Dutchman fascinated by gibbons and their significance in Chinese culture. Published in 1967, “The Gibbon in China” is a magical collection of poems, stories and paintings dating back to 200 BC. Rich in its content, I was overwhelmed with the stories about “lonely”, “sad-looking” yet “magical” apes who sing haunting and melancholy songs in the Chinese mountains.

Taoists (those that believe in ancient nature-worship regarding the flow of “ch’i” energy in all living things) talked about gibbons being superior to humans. Gibbons were often referred to as “gentlemen” as discussed in my previous blog. Everyone loves good manners — bring a gibbon to meet the parents and they won’t be disappointed due to their impeccable “table manners” (unlike their mischievous macaque monkey cousins), according to an 8th-Century poet, Liu Tsung-Yuan. Their intelligence, supposedly similar to humans, is also regularly mentioned, especially when needing to drink water from a nearby river. Forming a chain by holding hands, gibbons would lower themselves down to the river. One should therefore never “…place a gibbon (Yuan-yu) in a barred cage [as] how could he then show his clever skills?” (4th Century statesman, Ch’u-tz’u).

Having read this book from cover to cover, I was pumped to record rich gibbon stories during my field season. I was therefore incredibly shocked and disappointed to learn that many traditional stories have not been passed down through the generations.

China is made up of 56 different ethnic groups, all of which used to be rich in culture and history with traditional dress and sigils (both of which are now rarely seen). I interviewed participants from six of these ethnic groups and asked them questions regarding  the importance of gibbons and forests in their local culture. Participants either didn’t understand the question or they would say there is no connection.

I was relieved to hear that a few elders still have a tale or two to tell, especially when it comes to gibbons being able to predict the weather:

“When gibbons sing, I know it will rain tomorrow.” (Anonymous).

An elder in Hainan province told me about how gibbons came to be which involved a naughty, lazy boy who was scolded with an iron on his butt. He then sprouted hair and turned into a gibbon.

I also had a surprisingly funny interview with a 70-something year old man who used to work in Burma harvesting wood to sell back to the Chinese. He spoke about his love of gibbons…to eat! We spent most of our interview crying with laughter as his opinion was so far from my own. He kept insisting that gibbons were incredibly ugly and thought I was crazy because I felt they had aesthetic value.

“Look at their ugly faces!” He would yell. “Ah, they taste so good! Such a shame the government won’t let me hunt them anymore.”

It is important when I conduct these interviews that I remain impartial. At the end of the day, my PhD is all about finding sustainable solutions for both humans and gibbons alike.

My favourite moment was with an 87-year old woman who heard that a “laowai” (foreigner) was staying in the village. Having never left her village or seen a Caucasian woman before, we had a very special, informal moment bonding over gibbons and discussing what life was like during her youth — and what life was like now.

https://www.instagram.com/p/Bu6JKNjAWA8/

Although I am still at the start of my PhD journey, I have teamed up with a local non-governmental organisation called Cloud Mountain, who carry out conservation education activities. We hope to work together to reintroduce some of these traditional gibbon stories back into these villages. With only 28 Hainan gibbons, 150 Skywalker Hoolock gibbons and 110 Cao Vit gibbons remaining (my three study species), hopefully we can remind people of their magical, shared history and raise the profile of these forgotten apes before it is too late.

If you would like to follow my PhD journey, you can do so here: Personal blog, Twitter, Instagram. Or come and meet me in the UCL Grant or Petrie museums next month!

I am a primatologist; that is, a scientist who studies the behaviour, abundance and conservation status of monkeys, lemurs and apes. My specialty area and the focus of my PhD research here at University College London, is the plight of the gibbons, the smallest of the apes.

Gibbons are often forgotten in the shadow of their great cousins — the orangutans, chimpanzees, bonobos and gorillas — receiving less funding, as well as research and media attention. This is very unfortunate seeing as 19 of the 20 species are on the brink of extinction. The Hainan gibbon, for example, is the world’s rarest primate with a mere 26 individuals making up their entire global population.

I am always thrilled therefore to see media articles raising some much needed gibbon awareness, even if the news story doesn’t always paint us humans in the best light.

In 2004, one of my supervisors from the Zoological Society of London, stumbled across a gibbon skull inside a tomb in Xi’an, Shaanxi Province, China. The skull is believed to be ca. 2,200-2,300 years old and the potential property of Lady Xia, the grandmother of China’s first emperor, Qin Shihuang, who is famous for his striking terracotta army. Inside this ancient tomb was a whole menagerie of other animal skeletons including a crane, bear and a leopard — yet another example of human-animal relationships that have dated back millennia.

Although this exciting discovery could tell us a lot about our evolutionary shared ancestry with gibbon species, there are still many unanswered questions. We are unsure if the skull, now said to belong to Junzi imperalis (meaning the ‘imperial man of virtue’ due to the strong historical relationship between humans and gibbons in Chinese culture) is in fact a new species and where it came from. There are strong indicators, however, suggesting that this potentially new species of gibbon could be the first ape to have vanished off the face of the earth due to human pressures. Now extinct, we need to look at our current impact on the planet to ensure we don’t do the same with our other cousins.

Part of my PhD research examines the relationship between humans and animals, especially amongst local communities found in gibbon habitat regions. This intrigue, along with my love of mingling with the public, led me to my new role as a Student Engager in the UCL museums. For example, the Ancient Egyptians also had a strong connection with animals which I hope to explore over the coming months in the UCL Petrie Museum, and the Grant Museum of Zoology also has a couple of gibbon skeletons hanging around. Come and see for yourself!

In the meantime, keep your eyes peeled for my upcoming blogs on Twitter: @gibbonresearch and @ResearchEngager

As a biology PhD student, I’ll be the first to admit that there are some studies in science that, whilst interesting, can leave you questioning who comes up with these and why they (and we) should care so much.  If you, like me, are the kind of person who loves these kinds of things, the list of past Ig Nobel prize winners is a cornucopia of great examples.  Often, though, all it takes is delving a little deeper to find the importance in what seems like a pointless topic.  My PhD involves collecting primate poo samples to look at their gut bacteria, and so does occasionally elicit the classic and very valid question: “But what’s the point of it?” from people, so I thought for this week’s blog post I’d try and answer exactly that.

Primates are our closest relatives and, in fact, your closest relatives are also primates, as are you yourself.  We’ve known about the anatomical similarities between humans and other, non-human primates for hundreds of years.  The Grant Museum of Zoology plays host to what used to be a teaching collection for doctors studying at UCL, where the bones and structures of animals from non-human primates to fish would be studied to understand how our own bodies developed from the ancestors we shared with other organisms.  Then, in the 1980s, with the birth of molecular sequencing techniques, we gained the ability to study the DNA of animals.  From this we began to understand just how closely related to other primates we really are, leading us to the famous fact that we are 98% genetically identical to chimpanzees, our closest relative.

The next big step, in my (admittedly, probably biased) opinion, in our understanding of the human body and how it works has been our realisation that gut bacteria are hugely important to human health and disease.  We might tend to think of bacteria as harmful or infectious, but actually the bugs that live in your intestine are a normal part of a healthy human body.  They outnumber our own cells 10 to 1, making us 90% bacteria in terms of cell numbers alone (although our own cells are much larger, which is why by mass we’re still mostly human), break down parts of our food that we ourselves can’t digest and even provide us with many hormones (such as 90% of our serotonin, the “happiness” hormone).  In addition, gut bacteria has lately been linked to everything from keeping us lean or helping to make us obese, to maintaining normal bowel functions or exacerbating conditions such as irritable bowel syndrome.

So where do non-human primates come into this?  Well, as with the Grant Museum’s collection all those years ago, it’s nothing new to study our relatives in order to understand more about ourselves.  While understanding the gut bacteria of primates across the whole primate evolutionary tree lets us take a look at how gut bacteria have evolved alongside us to create a mutualistic relationship, primates in particular are a very interesting group of animals.  Within the Primate Order there is huge variation in the ways that these animals live their lives, and it is by considering these differences that we can begin to understand how the variations between different human lifestyles affect our gut bacteria and so our health.  For example, by comparing primates that eat mostly vegetation to species that eat fruit or meat or even gum like lorises, we can start to ask questions about how much our diet affects what bacteria can survive in the gut.  Looking at animals that are highly social, such as chimpanzees or baboons, vs. those that are mostly solitary creatures such as bushbabies can tell us how gut bacteria is spread and shared between individuals, communities and even between different species living in the same area (this is not as crazy as you think – humans have been found to share skin bacteria with their pet dogs).

But it’s not just ourselves that we can learn things about when we study non-human primates.  One large aspect of my PhD looks at how life in captivity affects the gut microbiomes of primates.  Whilst life in captivity is not ideal for any animal, raising them in zoos and centres can have benefits for endangered species.  Studying the gut bacteria has the potential to offer suggestions on how we might be able to enrich the diets of captive animals to ensure they maintain healthy gut bacteria whilst living in zoos.  Furthermore, by looking at what nutrients are necessary to keep a healthy set of bacteria, we might be able to start thinking about conservations issues such as which plants are highly important to conserve alongside these endangered animals.

So, I hope I’ve convinced you that gut bacteria are important, that my area of research has the potential to be of great help, and above all, that primate poo is a great thing to study.

  by Suzanne Harvey

 

 

 

 

 

What links the evolution of language to the collection of baboon figurines at the Petrie Museum of Egyptology? I have previously speculated on the reasons why Ancient Egyptians might create figures of baboons performing acrobatics, playing the harp and even drinking beer. After months of sporadic research and conversations with museum visitors on the subject, I have finally chosen a favourite theory (without a hint of bias) that just happens to link directly to my own research on baboon communication.

This post was inspired by an essay entitled Some Remarks on the Mysterious Language of the Baboons, [1] which mentions this quote from the Egyptian Book of the Dead, Chapter 100:

I have sung and praised the sun disc, I have joined the baboons.

The reason that Egyptians considered baboons to be sacred is actually quite straightforward. When baboons wake in the morning, like many primates (humans included), they tend to stretch and produce vocalisations. To some, the pose baboons adopt while stretching – sometimes raising their front legs in the air – resembles worship. As they stretch more often at sunrise, this action together with their ‘chattering’ noises when moving from sleeping sites, was interpreted as singing and dancing to praise the Sun-god, Ra. [2]

 

This only explains the role of language in making baboons sacred. Of several Gods to whom they are sacred, the deity who links baboons unequivocally with language is Thoth. Thoth is often depicted as a baboon scribe who not only spoke and wrote, but who actually gave the gift of language to the Egyptians, rather than simply understanding it. [3]

The voice of the baboon is the voice of God

This title might seem a somewhat unusual interpretation of the famous vox populi, vox Dei maxim, but it is in fact the Ancient Egyptian variation on this theme. Their belief was that whoever understood the language of the baboons had access to religious knowledge that was usually hidden. This is very good news indeed for modern primatologists – though I’ve yet to decipher any religious revelations while analysing baboon vocalisations! I can however dispute the Greek author Aelianus’s assertion that baboon language is “utterly incomprehensible to ordinary human beings”. [4]

Thoth’s significance in language and wisdom suggests that my earlier supposition – that baboons playing harps and drinking beer was not linked to religion due to the absence of sober, worshipful poses – was in fact erroneous. It seems that Egyptians were motivated to experiment with baboons, trying to train them to perform feats such as playing the harp, to reveal the link to Thoth hidden within them.

A range of baboon statuettes are currently on display as part of the Foreign Bodies exhibition in UCL’s North Cloisters. They represent a unique interpretation of other species that are nevertheless similar to our own, and a fascinating insight into how a distant culture defined themselves in relation to other primates – believing themselves to be inferior to baboons in terms of both holiness and wisdom. Ancient Egyptians recognised the human-like intelligence, ability to communicate and dexterity of baboons that we are equally fascinated by today, albeit from an evolutionary science perspective, rather than a religious sensibility. The quest to discover the inner Thoth continues…

  by Suzanne Harvey

 

 

 

 

 

Given the wealth of figurines, statues, engravings and even mummies of baboons found in Egypt, it may seem odd that a baboon skull features as an object in our current Foreign Bodies exhibition in UCL’s North Cloisters.

The key to this puzzle is that baboons are not, and never have been, indigenous to the areas of Egypt in which their remains have been found. They were imported from Nubia and the mysterious Land of Punt for use at temples and burial sites, where their habit of stretching and ‘chattering’ was viewed as worship of the Sun God, Ra. Since these animals were sacred to Gods of wisdom and the underworld, themselves deified in the form of Babi and The Great White One, and imported at great cost – surely their lives in Egypt would be ones of luxury?

Life and death in a foreign land

The largest number of mummified baboons have been found at the tombs of Saqqarah, an arid desert environment that contrasts starkly with the natural forest and savannah habitat of baboons. In their natural environment, baboons spend most of their waking hours foraging for food in the form of leaves, seeds, fruit and insects, none of which would be possible in the desert. In fact, the environment of the temples and burial sites where baboons were kept, was so foreign to these species that most died from malnutrition, vitamin deficiencies, and fractured bones. Of around 200 mummies analysed, few had lived beyond 6-10 years, despite the natural lifespan of the sacred Hamadryas baboon being around 30 years.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

From a primatological point of view, this highlights just how unsustainable desert colonies of baboons were. First breeding usually occurs between 5 and 7 years – with the majority of adults dying so young, it’s unlikely that much successful breeding took place at the temples. Recent studies at UCL’s Gashaka Primate Project have shown that diet has a strong effect on reproduction in baboons, with age of menarche, infant mortality and interbirth intervals all highly dependent upon nutrition.[1] In order to sustain a desert population of baboons, the Ancient Egyptians would have required constant imports of new animals, making baboons very rare and expensive offerings to the Gods.

The lost baboons of the Petrie Museum

In 2010, oxygen isotope analyses were carried out on hairs from one of the British Museum’s baboon mummies, and researchers were able to locate the Land of Punt, by comparing markers in the ancient baboon to modern samples. 3000 years after the baboon was mummified, his homeland was located as modern day Eritreia and Ethiopia, where baboons remain today.

The baboons at the Petrie Museum date from a later period than those at the British museum, and documentation indications that they were were mummified after voyages to Punt ceased. So for now, all we can really say for certain about the Petrie Museum baboons is that they were a long way from home when they died…

  by Suzanne Harvey

 

 

 

 

 

Excuse me, is that baboon playing a harp?

This is a question that I long to be asked when I’m working at the Petrie Museum of Egyptology. Whilst there are many examples of baboon figurines in the collection, my favourites have always been the selection from Amarna, in which the animals are shown performing acrobatics, drinking beer and playing the harp. Baboons appear throughout Egyptian mythology, and the majority of the figurines at the Petrie and elsewhere depict baboons sitting in a realistic manner, rather than performing any elaborate tricks. These figurines are often found at burial sites. Hapi, an Egyptian God of the underworld, is depicted with the head of a Hamadryas baboon and is said to protect the lungs of the deceased.[1] For this reason, it is common to find the baboon head of Hapi as a lid of canopic jars containing lungs. So, if baboons are typically viewed as sacred animals used in funerary reliquary, why is that baboon playing a harp?

Monkeys of several species were kept as pets in Ancient Egypt, so it is possible that they were trained to perform tricks. Having studied olive baboon infant tantrums, I know from experience that they are athletic animals who are often keen to throw themselves around – but acrobatics seems a stretch, and whilst I’m sure they could be trained to pluck harp strings, I doubt it would be easy listening. Since my own biological and behavioural approach does little but rule out possibilities, there must be another explanation for the existence of these unusual figurines. The Petrie Museum attracts a lot of visitors who are either professional Egyptologists or well-read enthusiasts of the subject. So, in my first ever research engager micro crowd-sourcing exercise, I’ve compiled some of their theories here:

 

1. The figurines were crafted at a time when the Pharaoh Akhenaten brought in monotheism, demanding that his subjects worship only one God, the Sun God. Therefore, worship of the baboon God was forbidden, and these less serious depictions of baboons may have become fashionable – Suggested by a retired German doctor who researches the beginnings of monotheism in ancient cultures as a hobby.

2. They are part of a culture of fantastical animal stories used for entertainment, and would have been high status decorations in a wealthy household – Suggested by an American Professor of art, interested in representations of animals in Egypt.

3. As baboons, particularly alpha males, could be seen as the reincarnation of dead ancestors in the form of the baboon deity Babi (not to be confused with the baboon-headed deity, Hapi…) the statues may show baboons engaged in activities that dead relatives enjoyed – Suggested by a UCL masters student studying ancient writing.

Any or all of these theories may be relevant, but overall, it seems that perspectives from art, theology and graphology lead to more interesting interpretations of this object than my own biological anthropology approach. For anyone interested in cross-disciplinary or multiple interpretations of museum objects, our upcoming exhibition Foreign Bodies will be on display in UCL’s North Cloisters, with additional featured objects in all 3 of the UCL Museums from March 18th – featuring (amongst others) my favourite baboon harpist.

 

References:

[1] Hans Kummer: In Quest of the Sacred Baboon. (1995), Chichester: Princeton University Press.

  by Suzanne Harvey

 

 

 

 

 

It’s Christmas time, so for many of us this means a time of celebration. And what better way to celebrate than bringing a tree indoors, eating turkey and brussel sprouts, and dressing up as a fat man in a red and white suit? Of course these behaviours can be traced back to various historical practices. Saint Nicholas gave gifts in the 4^th century, trees have been decorated from the 15^th century, and turkey dinners were first eaten in the Victorian era. While each tradition has its own symbolism, it is likely that few who celebrate such a traditional Christmas are aware of its origins. With fewer than 6 in 10 people describing themselves as Christian in the UK’s 2011 census, the explanation for many cannot be found in an underlying religious belief system. These traditions are just that – traditions. Such behaviours can be embedded in our cultural lives from infancy, and whilst they may seem bizarre to the uninitiated observer, seem completely natural within their culture of origin.

Chimpanzee Culture

Sadly, to date no evidence has been found to suggest that chimpanzees celebrate Christmas. However, there is evidence that they have their own form of tradition, i.e. behaviours with no apparent origin except social transmission. Just as seasonal turkeys are an example of the human diet varying by culture, the chimpanzee diet shows cultural variation too. For example, termites are a staple of chimpanzee diets, being rich in nutrients and relatively easy to access using tools such as a ‘termite fishing wand’.

However, Nigerian chimpanzees studied as part of UCL’s Gashaka Primate Project do not seem to eat termites at all (none of the 381 faecal samples collected throughout the year showed termite remains).[1]

Army ants are extremely aggressive, with large, sharp mandibles. In fact they are so keen to bite that they have been used as sutures in remote areas: simply apply ant to wound, wait for it to bite, and decapitate for handy organic steri-strips. Ant nests are also very difficult to locate, with no obvious signs of nests above ground.[2] However, 42.3% of Nigerian chimpanzee faecal samples showed army ant remains, the highest of any population.[3] Termites on the other hand are easy to locate via distinctive nest mounds. Similar tools are used to ‘fish’ for termites and army ants, so Nigerian chimps are not incapable of harvesting termites. The methods generally include dipping long thin sticks into nests and waiting for termites to bite or ants to crawl up the stick before eating. There also seem to be enough termites available in the Nigerian chimpanzees’ environment to make them a practical food source.

 

 

 

 

 

 

 

 

 

 

 

 

 

While it is difficult to determine which behaviours are cultural in origin, this seems the most likely explanation. Perhaps eating termites would seem as unusual to these chimps as eating army ants does to us (with the exception of some extreme self-experimentation carried out by UCL Professor Volker Sommer in order to bring you this research…). For our upcoming exhibition in the north cloisters, I will be using objects from UCL Museums and Collections to explore primates as ‘foreign bodies’. Does this evidence of a primitive culture blur the line between human and non-human? While chimps do not celebrate Christmas, chimpanzee culture can at least offer some insights into the evolution of human traditions: turkey, brussel sprouts and all the trimmings…

 

by Suzanne Harvey

 

 

 

 

 

Apes in Art

For anyone interested in images of primates in the visual arts, Solly Zuckerman’s seminal book The Ape in Myth and Art is a must-read. Hidden in the back pages amidst the postscript is Ohara Koson’s print, Trained Monkey Looking at an Insect, somewhat inaccurately described as a “Chinese water colour of a monkey sniffing a flower, unknown artist.”  It is in fact a woodblock print of a trained Japanese macaque (a species better known for its preference for bathing in hot springs) looking at a bee, and can be viewed at the UCL Art Museum.  Koson is one of the best known artists of the Japanese Shin Hanga or ‘new prints’ movement, and 257 of his prints are listed by the Hanga Gallery. But what of the ape subject who appears in this portrait?

Whilst the pink face is natural, the pink waistcoat certainly is not. As he is described as trained, it seems likely that Koson’s monkey is part of the tradition of Sarumawashi, or monkey dancing, which has been a Japanese tradition for over a thousand years. The concept is so ingrained in society that there exists a single noun, 猿回し, meaning ‘showman who trains performing monkeys’.

Apes in Museums

Whilst these performing monkeys were trained to mimic human behaviours on stage, Koson’s print depicts a tethered, costumed animal following its urge to be inquisitive – a natural, rather than trained, ‘human’ quality. Do we need to train monkeys to demonstrate human-like traits? As various primate species have been shown to use such complex behaviours as deceit and manipulation, as well as the ability to learn, play and communicate, I would say no. Yet, when exploring the representations of primates in UCL museums and collections, anthropomorphism arises as a clear theme. There are of course many examples of primate specimens, including baboons and macaques, mounted to reflect their natural behaviour in the Grant Museum of Zoology, but the presence of primates in UCL museums isn’t limited to the zoological collections. As well as the Art Museum’s trained macaque, at the Petrie Museum, there are figurines of baboons playing harps, drinking beer and even performing gymnastics.

From images of performing monkeys, to figurines depicting physical feats monkeys could never achieve, each museum contains objects invaluable to researchers interested in social attitudes towards primates. These objects provoke unexpected and interesting questions: for instance, why might Ancient Egyptians have decorated their homes with beer-drinking baboons? Look out for my next post to find out why…

 

by Suzanne Harvey

 

 

 

 

 

Anatomy is destiny … The genitals themselves have not taken part in the development of the human body in the direction of beauty: they have remained animal, and thus love, too, has remained in essence just as animal as it ever was.

When Sigmund Freud wrote this in 1912, he may have been surprised to hear that some hundred years later, evolutionary theory would come to the same conclusions. Despite the frequently discussed individual variation in human penis size, the shaft of an average human penis is around twice the length and width of the shaft of an average chimpanzee penis. It is also useful to mention some more unusual facts: firstly, while chimpanzees have penises half the size of humans, they have testicles three times as large. Moreover, while silverbacks are formidable looking creatures, gorillas in fact have the smallest penis to body size ratio of any mammal. So, what causes these seemingly contradictory differences among the great apes, and how can evolutionary theory make sense of all creatures great and small?

Sperm Competition

As Freud’s quote suggests, the clue to the evolution of the penis is not just in their physical appearance but also in the social aspects of sex. In fact, generally speaking, the mating system of a species can be used to predict penis size. Chimpanzees live in large multi-male, multi-female groups, where females are able to mate with many males. Sperm can live for up to 4 days after ejaculation, and consequently when females mate with two males in close succession, sperm from two males can be in direct competition. The male who produces more sperm will have the best chance of fertilizing an egg. This evolutionary advantage of producing large amounts of sperm can explain the relatively large testicle size of chimpanzees. Correspondingly, the male gorilla’s huge stature is in fact the reason why he has such a small penis: when competition between males occurs through physical aggression, an alpha male may fight off rivals and control his own mating success without the need for sperm competition. Other physically smaller males have little access to females in the group.

Understanding the Human Penis

The mystery of the human penis is that ancestral hominids lived in similarly large and promiscuous social groups, but did not evolve the large testicles seemingly necessary to compete via sperm competition. One might be forgiven for thinking that larger penises evolved as a result of sexual selection; the theory that a preference for larger penises in females has led to greater reproductive success for males with larger penises, with these males passing on the trait to their offspring. However, the latest research shows that penis size may also be the result of sperm competition and natural selection.

The Semen Displacement Theory (Gallup and Burch, 2004) essentially explains the advantages of the size and shape of the human penis in terms of a device evolved to remove another male’s semen before fertilization.

As well as being larger and wider than other primate penises, the human penis has the unique shape of a shaft with a ridge leading to a wider tip, known as the coronal ridge. This is more pronounced than in other species. All of these elements are important in terms of semen displacement: the coronal ridge removes semen by ‘scooping it out’ as it passes over the tip, is trapped behind the ridge and pulled out during intercourse. Recent research shows that (using artificial genitalia) a penis with a coronal ridge will displace 91% of semen, while one without will displace only 35% (Gallup et al. 2003). Thrusting during sex creates a vacuum that aids this process, as the width of the shaft provides a plug in the vagina. In Gallup’s experiment, the same penis removed 90% of semen when fully inserted and only 39% when inserted three quarters of the way. Therefore, the length of the shaft simply improves reach and maximizes the amount of semen that can be removed.

So yes, when it comes to penises, size – and shape – matters when it comes to natural selection!

 

Suzanne Harvey is a PhD student in Biological Anthropology, working on social interactions and communication in wild olive baboons. She is also a teaching assistant on the UCL Arts and Sciences BASc, a new interdisciplinary degree, and can be found on twitter @suzemonkey.

 

 

References:

Freud, S. (1912). On the Universal Tendency to Debasement in the Sphere of Love. Oxford Literary Review 30: 109-146 DOI 10.3366/E0305149808000199, ISSN 0305-1498

Gallup, G. G. & Burch, R. L. (2004). Semen Displacement as a Sperm Competition Strategy in Humans. Evolutionary Psychology 2: 12-23

Gallup, G. G., Burch, R. L., Zappieri, M. L., Parvez, R. A., Stockwell, M. L. & Davis, J. A. (2003). The human penis as a semen displacement device. Evolution and Human Behavior 24: 277–289