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

Suzanne MHarvey18 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

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.

 

References

[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.

 

Do Chimpanzees Celebrate Christmas?

GemmaAngel24 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…

 


References:

[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

 

Does Size Matter? Evolution and the Primate Penis

GemmaAngel17 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.

 

 

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

Constantly Changing, Ever Evolving. HIV: Adapting to Change

GemmaAngel30 July 2012

by Alicia Thornton

 

 

 

 

 

As someone whose background is in biological sciences, working in the Grant Museum of Zoology feels a little like coming home. Robert Edmond Grant collated the collection for the teaching of comparative anatomy and zoology, showing the differences and similarities between species. The collection is hugely diverse; from sponges and other marine invertebrates (in which Grant held a particular interest) to skeletons of primates, elephants, big cats and other mammals. The collection even has examples of some animals which are now extinct. Most notable are the quagga, a zebra-like creature from Southern Africa which was hunted to extinction in the wild around the time that Grant was teaching at UCL; and the thylacine or Tasmanian tiger. The thylacine was a marsupial native of Australia, also hunted to extinction, during the early 20th century. The museum also has bones from a Dodo, which died out  as the result of a combination of factors, including hunting and predation by imported species introduced by European settlers.

 

For me, what the collection shows so well, through its diversity, is how every organism is adapted to the environment in which they live. Each species or subspecies has evolved to have a unique way of living and their biology gives a complete illustration of this.  For example, the shape of a jaw indicating the type of diet an animal has, or the dimensions of the limbs showing how an animal may swing through trees or stalk prey in grassland.  As I near the end of the first year of my PhD, I find that it is sometimes easy to get too engrossed in the details of my research and lose sight of what interested me about the topic in the first place. The Grant museum serves as a perfect reminder. My own research is focused on infectious diseases, and specifically human immunodeficiency virus (HIV). The way in which the virus has evolved and continues to evolve has been one of the biggest challenges for scientists and medics working in HIV treatment, care and research.

Like all viruses, HIV requires a living cell to reproduce. During infection, the virus enters the human cells and uses the machinery of the host cell to replicate, producing further infectious particles and releasing them to continue the infection cycle. In order to be successful and survive, the virus must find mechanisms by which it can evade the response of the host immune system that is designed to eliminate it. In fact, HIV is perfected suited to this; having the ability to infect cells which constitute a key component of the immune system as well as those which are out of the reach of the immune system.

Due to the nature of its replication, HIV evolves particularly fast and thus has the ability to survive changing environments.[1]  A huge range of drugs to treat HIV have been developed  since the beginning of the epidemic. These drugs have been a huge success, allowing people to live much healthier lives. Where they are readily available they have dramatically reduced the numbers of people who develop AIDS[2] and increased life expectancy of HIV positive individuals to almost that of HIV negative individuals[3].  Yet they never eliminate the virus completely and as new drugs are introduced, the virus rapidly evolves, giving rise to drug resistant strains and making treatment even more challenging.[4]

The 19th International AIDS conference was held in Washington DC, USA in July 2012. This is the largest of the HIV conferences with over 20,000 delegates, taking place every two years, and is attended by a mix of medics, nurses, public health professionals, advocacy groups and policy makers. Finding a cure for HIV was a key theme of the conference and like all HIV conferences, a large volume of work presented was focused on the development of new drugs and drug combinations. Increasing the range of drugs available means that doctors are more able to combat the development of drug resistance and keep their patient’s viral replication supressed.

The extent of the HIV epidemic is the result of a complex combination of social and scientific factors. However, there is no doubt that the virus’ ability to continually change and adapt to the environment in which it survives is a one of the key reasons that the infection remains such a challenge to control.

 

[1] Rambault A, Posada D, Crandall KA & Holes EC.  The Causes and Consequences of HIV Evolution. Nature Reviews Genetics 2004; 5(1): 52-61.

[2] Mocroft A, Ledergerber B, Katlama C, Kirk O, Reiss P, d’Arminio Monforte A, Knysz B, Dietrich M, Phillips AN, Lundgren JD; EuroSIDA study group. Decline in the AIDS and death rates in the EuroSIDA study: an observational study. Lancet. 2003; 362(9377):22-9.

[3] Nakagawa F, Lodwick RK, Smith CJ, Smith R, Cambiano V, Lundgren JD, Delpech V, Phillips AN.  Projected life expectancy of people with HIV according to timing of diagnosis. AIDS. 2012; 26(3):335-43.

[4] UK Collaborative Group on HIV Drug Resistance; UK CHIC Study Group.  Long-term probability of detecting drug-resistant HIV in treatment-naive patients initiating combination antiretroviral therapy.  Clin Infect Dis. 2010; 50(9):1275-85.