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Archive for the 'Suzanne Harvey' Category

Sexual Conflict in Nature and Museums: Specimen Ratios and Duck Genitalia

By Suzanne M Harvey, on 18 November 2013

Suzanne Harvey #2by Suzanne Harvey









The Duck Penis Controversy of 2013 is well known amongst science bloggers, evolutionary anthropologists and Fox News viewers alike [1]. Now, the time has come for the worlds of museum collections and duck genitalia to collide.

There are some interesting facts about duck penises. For example, they measure a third of the length of the duck’s body, and they cannot become erect outside of the female duck’s vagina (or, as we will find out later, a man made substitute created in the name of science)[2]. Probably most surprising of all, duck penises are corkscrew shaped. However, in March 2013, Fox News conducted a poll in which 89.14% of respondents agreed that the research that brought us these fascinating facts was a waste of public money. At a time when funding for basic science research is becoming more and more difficult to obtain, I disagree with 89.14% of Fox News respondents. And as is so often the case, by clicking on links that come up in a search for ‘penis’, we miss the fact that the most interesting findings of this research come from the vagina. The duck penis controversy not only gives us the opportunity to talk about research, but also the curious bias towards male specimens in museums.

Specimen Ratios and Sexual Dimorphism


Duckling preserved in fluid.
Research sugests 97% are of
ducklings are voluntarily
conceived despite
forced copulations.
Photograph: Grant Museum
of Zoology. 


On first arrival at the Grant Museum of Zoology, or indeed most natural history museums, it’s not obvious that the vast majority of specimens on display are male. But why is this the case? One possible explanation is the sexual dimorphism present in many species – the fact that males and females often look different, either in colouring or size [3]. Specifically, males are often larger than females due to competition for mates and sexual selection, and thus make more impressive specimens for display. Perhaps the most obvious example of sexual dimorphism at the Grant is the giant deer at the entrance to the museum, with his imposing 3.6m wide antlers.

It’s also been suggested that male animals were seen as a greater challenge and a more impressive trophy for the Victorian hunters who collected zoological specimens [4] – an acquisition policy that would not be used by the modern day Grant Museum! As well as this unavoidable bias in the specimens on display, some of the most popular blogs on this site have focused on the penis. With the onset of the duck penis controversy, we now have an opportunity to redress this balance, and assess the value of duck genitalia research from a more feminine perspective…

Corkscrews, Angles and Dead Ends: Welcome to the Duck Vagina

That ducks have corkscrew shaped penises is obviously a fact worth knowing, but surely the more interesting question is why do ducks have corkscrew shaped penises? The answer comes from sexual conflict. Forced copulations are common in ducks, presenting an evolutionary problem for females who only want to mate with high quality males of their choice. Females are rarely able to physically resist forced copulations, so in order to control the father of their offspring, their genitalia have evolved an elaborate structure that effectively prevents unwanted suitors from fathering offspring.

Here’s where the research comes in. By creating four substitute duck vaginas from glass tubes (one straight, one twisting in the same direction as a penis, one twisting in the opposite direction from the penis, and one with a sharp bend) researchers were able to assess which shape effectively prevents ducks from depositing semen at the site of fertilisation. The actual duck vagina is a combination of a sharp angle, and a anti clockwise spiral that twists in the opposite direction to the penis. As confirmed by the experiment, this makes it very difficult for males to inseminate females. The female must solicit males with a particular posture in order to make fertilisation likely, therefore gaining control over which males they breed with. In fact, while forced copulations are common, only 3% result in fertilisation.

Duck Vaginas

Glass substitute duck vaginas. A combination of
the two examples on the right most closely represents
an actual duck vagina. Photograph: adapted from
Brennan et al. 2009.

Ducks then are an example of the males and females of a species evolving equally elaborate genital anatomy under the pressures of sexual conflict and sexual selection. There are certainly some impressive male specimens in the Grant Museum, but those giant antlers and corkscrew penises did not evolve without the female of the species.







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.



[1] Yong, Ed. (2009). Ballistic penises and corkscrew vaginas – the sexual battles of ducks. Not Exactly Rocket Science. http://scienceblogs.com/notrocketscience/2009/12/22/ballistic-penises-and-corkscrew-vaginas-the-sexual-battles/

[2] Brennan, P., Clark, C., & Prum, R. (2009). Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.2139

[3] Machin, R. (2008). Gender Representation in the Natural History Galleries at the Manchester Museum. Museum and Society 6(1) 54-67. ISSN 1479-8360.

[4] Shamloul, R., El-Sakka, A., & Bella, A. J. (2010). Sexual selection and genital evolution: an overview. Journal of Sexual Medicine (7): 1734–1740.


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

By Gemma Angel, on 15 April 2013

Suzanne Harvey #2  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.

Monkey with beer potThis 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]


Caption for baboon chatterThis 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]

ThothThoth’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…


[1] H. Te Velde: ‘Some Remarks on the Mysterious Language of the Baboons,‘ in Kamstra, J. H., Milde, H. & Wagtendonk, K. (eds). Funerary Symbols and Religion. (1988), J.H. Kok: Kampen.

[2] G. Pinch: Egyptian Mythology: A Guide to the Gods, Goddesses, and Traditions of Ancient Egypt. (2004), Oxford: Oxford University Press.

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

[4] H. Te Velde, (1988), p.134.

From the Forests of Punt to the Deserts of Saqqara: Life and Death as a Sacred Monkey

By Gemma Angel, on 18 March 2013

Suzanne Harvey #2  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.

Baboon SkullThe 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.

Baboon environment























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

Baboon mummy

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…


[1] J.P. Higham, Y. Warren, J. Adanu, B.N. Umaru, A.M. MacLarnon, V. Sommer, & C. Ross: (2009). ‘Living on the edge: Life-history of olive baboons at Gashaka-Gumti National Park, Nigeria’, in American Journal of Primatology, Vol. 71 (2009), pp.293-304.



Musical Apes: Can Baboons Play the Harp?

By Gemma Angel, on 11 February 2013

Suzanne Harvey #2  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.



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

Do Chimpanzees Celebrate Christmas?

By Gemma Angel, on 24 December 2012

Suzanne Harvey #2  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 4th century, trees have been decorated from the 15th 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…



[1] Fowler, A. & Sommer, V. (2007). Subsistence Technology of Nigerian Chimpanzees. International Journal of Primatology.

[2] Schöning, C., Ellis, D., Fowler, A. & Sommer, V. (2006). Army ant prey availability and consumption by chimpanzees (Pan troglodytes vellerosus) at Gashaka (Nigeria), Journal of Zoology.

[3] Pascual Garrido, A. (2011). Insectivory of Nigerian Chimpanzees: Habitat Ecology and Harvesting Strategies. PhD thesis, Facultad de Psicología, Universidad Complutense de Madrid, España


How Did Man Lose His Penis Bone?

By Suzanne M Harvey, on 26 November 2012

The walrus penis bone, also known as an os penis or baculum, is one of the most popular objects at the Grant Museum. The human penis is haemodynamic, meaning an erection is achieved by blood pressure alone. In animals with an os penis, blood pressure still plays an important role, but the pressure functions to push a bone structure into the penis in order to achieve an erection. This has many benefits over an erection sustained by blood pressure alone, not least in keeping the glans open for sperm to pass through.

While the importance of shaft size and sperm competition has been discussed in my previous blog post, even the largest penis will offer no evolutionary advantage if sperm cannot escape: these much desired qualities will never be passed to offspring. This is not the only benefit. The os penis increases the potential duration of intercourse and also the frequency with which intercourse can take place. For example, a lioness can copulate 100 times per day, sometimes with only four minute intervals, but has only a 38% conception rate1 – males need to keep up if they’re to achieve the best chance of paternity. It comes as a surprise to many people that the os penis exists at all, but in fact humans, woolley monkeys and spider monkeys are the only primates to lack this handy piece of anatomy.

With such benefits to structure, strength, endurance and recovery time, the next question must be: where is man’s penis bone? This is where the story becomes more intriguing…

Was it sacrificed for the sake of woman?

While the lack of a human penis bone may have interested evolutionary scientists for many years, it has recently attracted attention from professors of Theology as well. The debate was reignited in 2001 with the publication of a letter entitled Congenital human baculum deficiency: the generative bone of Genesis 2:21-23. Without wishing to delve into a religion vs. science debate, perhaps the most surprising aspect of this article is that it was published in the American Journal of Medical Genetics, with its central theory that God took Adam’s os penis to create Eve in the Garden of Eden, rather than his rib:

Ribs lack any intrinsic generative capacity. We think it is far more probable that it was Adam’s baculum that was removed in order to make Eve. That would explain why human males, of all the primates and most other mammals, did not have one.2

The authors then go on to cite possible mistranslations of the Hebrew word ‘tzela’, which can be translated as ‘rib’ or more generally as a supporting structure such as a baculum. More recently however, a study using the dissection and microscopic analysis of human, dog and rat penises revealed something rather unexpected…

Perhaps it was there all along!

With the comprehensive list of benefits discussed above, the root of this problem seems to be in discovering how on earth humans manage to function without an os penis. As a rule, larger penises in humans can give an evolutionary advantage, but without the toughness of structure provided by a bone, how do they avoid buckling under the pressure? Well, through both microscopic analyses and collagen tissue staining, the elusive evidence has finally been discovered. In the core of the human penis, there is a tunica (or lining) with many elastic fibres acting to keep the penis rigid in much the same way as an os penis. This has been referred to as the distal ligament, and is a structure so robust that even after some venous removal, erection can still be achieved without the need for a fully formed bone structure.4 In somewhat less good news for men, the authors of this study further hypothesise that if damaged, the distal ligament may take as long as a broken bone to heal.

So we are left with the final puzzle of why man lost his penis bone but retained a structure that serves a similar purpose. For the answer to this, we may need to look to women. Sexual selection works on the premise of ‘honest signals’. Put simply, females need to select high quality males to ensure the best genes for their offspring, and a penis that works predominantly through haemodynamics takes a lot of energy to produce. Therefore this is an honest signal of the most healthy males in the same way that the healthiest stags grow the largest antlers. In the end, for all the dissection, microscopic analyses and experiments with cadavers, Adam may have given up his penis bone for Eve after all.


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.



1. Rudnai, J. A. (1973). Reproductive biology of lions (Panthera leo massaica Neumann) in Nairobi National Park. East African Wildlife Journal II: 241 – 53.

2. Gilbert, S. F. & Zevit, Z. (2001). Congenital human baculum deficiency: the generative bone of Genesis 2:21-23. American Journal of Medical Genetics 101(3): 284-5.

3. Hsu, G. L., Lin, C. W., Hsieh, C. H., Hsieh, J. T., Chen, S. C., Kuo, T. F., Ling, P. Y., Huang, H. M., Wang, C. J., & Tseng, G. F. (2005). Distal ligament in human glans: a comparative study of penile architecture.Journal of Andrology 26(5): 624-8.

4. Hsieh, C. H., Liu, S. P., Hsu, G. L., Chen, H. S., Molodysky, E., Chen, Y. H., Yu, H. J. (2012). Advances in understanding of mammalian penile evolution, human penile anatomy and human erection physiology: clinical implications for physicians and surgeons. Medical Science Monitor 18(7): 118-25.

Japanese Performing Monkeys: Apes in Art & Culture

By Gemma Angel, on 8 October 2012

Suzanne Harvey #2by 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…


Does Size Matter? Evolution and the Primate Penis

By Gemma Angel, on 17 September 2012

Suzanne Harvey #2by 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.




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

Where The Wild Things Are: 15th Century Christian Art…?

By Alicia C Thornton, on 3 September 2012

Suzanne Harvey #2by Suzanne Harvey






As a Biological Anthropologist, I study the social behaviour of baboons in Nigeria, treating these animals as a model for the evolution of early hominids. But while primatology is now an established discipline, and approaching primate behaviour from a scientific perspective is common, this was not always the case. Working across all three UCL Museums has provided an unusual opportunity to study the changing attitudes to primates throughout time and across cultures. In this quest to discover all things primate among the UCL collections, the most unexpected finding so far has been Albrecht Dürer’s The Virgin with a Monkey which can be viewed at the UCL Art Museum.

This is one of the most popular of Dürer’s engravings, with 14 copies made. It is interesting not only because it features a monkey, and not only because such images were rare in the 15thcentury, but because of the symbolism of its image in a piece of Christian iconography.  In researching such a piece, and as resident primatologist at the Art Museum, my first task was to identify the species. A simple task with a simple answer: none. It is similar to a green monkey, but both the colouring extravagant facial hair suggest that this is not a perfect fit.  This type of hair does exist in other primate species, but none of this size or overall appearance.




As the artist was known for the accuracy of his engravings, and here it is not possible to determine the species, it seems unlikely that he had a live model. It may be that Dürer’s monkey is in fact a generic old world monkey that could originate from anywhere in Africa; a combination of species Dürer may have seen on his travels around Europe with its many menageries. So, if this engraving was not intended to be scientifically accurate, then what was its purpose? It is possible that the use of an exotic animal functioned to demonstrate the artist’s talent; the contrast between traditional Bavarian scenery, religious images and an exotic animal showing a wide range of Durer’s abilities within this one engraving. But is there any significance to the artist’s decision to depict a monkey to showcase his talent?

Monkeys and Christianity

In Christian iconography, monkeys represent base instincts such as lust, greed and malice, and can even represent the devil. So, if we approach this from a theological angle, why is this monkey at the feet of the Virgin? One theory is that he is subdued by her purity and can no longer display his usual ignoble behaviour.  It is certainly true that much of his natural behavioural repertoire, though similar to that of most humans, would not befit an image of holiness and purity as portrayed here. An alternative explanation is that the monkey’s position represents the dominion of the Madonna over all other creatures, and the fact that he is tied up could support this theory.

In a time before zoos existed, private menageries were seen as an attempt to bring together God’s creations, and to recreate the Garden of Eden. Pope Leo X had one of the largest menageries of Dürer’s time, and later asked the artist to create an engraving of his rhinoceros one of the most famous of all Dürer’s works. While now firmly in the realm of speculation since Dürer’s visits to Italy were not entirely documented, it is possible that he might have seen some of the Pope’s exotic creatures on his first visit, before creating The Virgin and the Monkey. In 1515, after a second visit to Rome, Dürer produced The Triumphal Arch which, (along with Rhinoceros) is currently on display at the British Museum and includes one of the earliest representations of a South American primate, a marmoset. Incidentally, marmosets are known for their extravagant facial hair, which is similar to that of Dürer’s monkey.

Discussing the role of this monkey with museum visitors has been fascinating, and has shown that while many had heard of Dürer, and some of The Virgin with a Monkey, none had previously considered the potential significance of this exotic animal. So, whether Dürer’s monkey is a real or composite species, an embodiment of human sin, an example of God’s dominion, or a demonstration of artistic talent, so far he has proven to be a welcome surprise to museum visitors and staff alike.