Archive for the ‘Pan’ Category

I didn’t understand the value of hunting until I was 10 years old. I never had an opinion on it either way, but I could never understand why someone would just want to go out and kill an animal. It wasn’t until I was watching my dad, uncle, and cousins sit on their porch and spy a white-tailed deer in the backyard. Where we live, these deer are common. Not exactly habituated, but it’s common practice in more rural areas to provision them with salt licks and feed; if nothing else, to get a good look at them while you’re looking outside and basking in the northern Midwestern landscape.

On this particular night in late-autumn, celebrating my birthday with my cousin, they had spotted a deer eating from the salt-lick. It was a male and he had a gorgeous set of antlers–I can’t recall how many points, but enough to make my uncle and cousin jump from their seats and slowly creep towards where they had a small gun stowed. Carefully, my uncle opened the door and a loud pop! sound later, the deer ran off. He had missed, but afterwords, I looked at my dad and asked, “Why’d he shoot the deer? It wasn’t eating his garden or anything.”

“The deer population this year is high; if we don’t hunt, they’ll cause a lot of trouble for us and themselves.” He stated, matter-of-factually. I didn’t understand what it meant at the time, as I dropped the subject in lieu of birthday cake, but as I grew older–I understood. Without hunting, the populations would rise to unsustainable levels; more deer would mean less available food when resources were already scarce in the winter months and potentially lead to more dangerous accidents for drivers, as my aunt and grandmother both experienced first-hand years later. But, at the time, I understood more why it would be dangerous for us–which later gave me enough curiosity to understand why it would be bad for “them.”

Yesterday, Dr. John C. Mitani of the University of Michigan wrote an opinion article on the endangerment and potential extinction of both lesser and great apes. In it, he brings up a multitude of reasons for saving great apes from behavioral quirks, the primate heritage, and drawing connections between human primates and non-human primates. He even points out that politicians in Congress have put aside party differences in being able to provide conservation aide for apes. It was well-written and provided a bevy of reasons in which people should consider taking action to provide great apes with the aide they require in order to maintain populations and mitigating anthropogenic effects.

While there is nothing I would contest against what Dr. Mitani says, it’s what he doesn’t say that’s most interesting to me (which, could also have been removed due to editing or other reasons–I’ve had my share of time in journalism and I understand that not everything written goes to print). And this is something I’ve noticed before when people talk about conservation and taking action.

A critically endangered Sumatran orangutan (Pongo abelii) and a caretaker at Bukit Lawang (Photo from: WikiMedia Commons)

For me, before I had been given an education in conservation, to understand the importance of doing so was best expressed in a practical, utilitarian format–how conservation tactics (like hunting) provided benefits to both humans (in terms of safety) and wildlife populations (in terms of sustainability).

I believe it’s possible to foment interest in conservation by using the anthropogenic hook and then using primates as further bait to take action. Harcourt et al. (1986) discovered that knowledge about wildlife species was a critical factor in attitudes about wildlife. Furthermore, negative perceptions of conservation are driven through a lack of education in how it can affect both wildlife and humans (Fiallo and Jacobsen 1995). In knowing that we are also great apes and share a heritage, why are we apt to leave ourselves out of this equation? Particularly when helping ourselves is one of the best things we can do for our evolutionary lineage. Kofi Annon, Secretary General of the United Nations once wrote:

Saving great apes is about saving people. By conserving the great apes, we can protect the livelihoods of many people who rely on forests for food, clean water, and much else. Indeed, the fate of the great apes has both practical and symbolic implications for the ability of human beings to move towards a more sustainable future.

In addition to the effects helping humans can have on non-human primates, in turn, non-human primates have an effect on us. Recently, it was discovered seeds ingested and passed through orangutan (Pongo pygmaeus wurmbii) guts in addition to being spat out can remain viable and germinate (Nielsen et al. 2011). Given that orangutans can consume around 118 species of fruiting plant and a large day range, orangutans can disperse seeds throughout a great range in the Sumatran rain forest, potentially providing more future fruit trees for both human and wildlife consumption (Nielsen et al. 2011).

When written like that, the purpose for conservation changes: not only does conserving apes help the environment, but it helps others–including us. Humans nor great apes exist in a vacuum; we frequently co-exist and affect each other. But maybe that’s where the discomfort and hesitance in using a more utilitarian approach lies.

I understand the utilitarian format is not without potential problems: in approaching ape conservation from a “What can it do for us?” perspective, we can run the risk of focusing only on anthropogenic needs rather than the needs of both.

I also realize thinking about just ourselves is part of the issue. I’m not sure if I believe the trope that humans are inherently selfish and the like; and definitely, there is a sense of greed that needs to be addressed. But if we need to be taking action immediately, why aren’t we willing to combine the two more frequently when we talk about conservation if it means it will change perceptions and get people to act?

Regardless of thoughts on human influence, we are a part of ecosystems all over the world, for better or worse. I welcome any readers to share their thoughts on this subject.


Fiallo, E.A. & Jacobsen, S.K. (1995). Local communities and protected areas: attitudes of rural residents towards conservation and Machalilla National Park, Ecuador. Env Conserv, 22: 241-249.

Harcourt, A.H., Pennington, H., & Weber, A.W. (1986). Public attitudes to wildlife and conservation in the Third World. Oryx, 20: 152-154.

Nielsen, N.H., Jacobsen, M.W., Graham, L.L.L.B., Morrogh-Bernard, H.C., D’Arcy, L.J., & Harrison, M.E. (2011). Successful germination of seeds following through orangutan guts. J Trop Ecol, 27: 433-435.

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ResearchBlogging.org With great sadness, I write about the passing away of Japanese primatologist, Professor Toshisada Nishida. Nishida studied chimpanzees (Pan troglodytes schweinfurthii) and was considered the leading scholar on the Tanzanian chimpanzees in the Mahale mountains. While he was known for his work on chimpanzees, he was also known for his work on studying Japanese macaques, red colobus monkeys, and bonobos.

Nishida was one of the trailblazers of Japanese primatology. In addition to having the second longest running field site at Mahale, he was known for being the first Japanese primatologist to be published in a western journal (Nishida 1973), and authoring the first Japanese primatological research report in a non-Japanese primatology journal (Nishida 1976). Furthermore, he is credited with training an entire generation of Japanese primatologists (Mitani, McGrew, & Wrangham 2006).

In tribute to Nishida’s lifelong pioneering work, John Mitani, William McGrew, and Richard Wrangham (2006) wrote a beautiful article detailing Nishida’s contributions to primatology. In it, they mention the importance of his work for establishing quantitative analysis for primatology, clarifying social structures of chimpanzees, and during a period of time when it was believed that chimpanzees were largely nomadic with a lack of boundaries defined by communities, he provided data and support to constitute that chimpanzees lived in very specific social groups with variations in party size and composition, and with female members transferring between these groups. All of these findings have helped not only determine behavioral ecology of chimpanzees, but also provide a potential framework for early human ancestors.

Toshisada Nishida and the chimpanzees of Mahale (Photo by: International Primatological Society)

Through Nishida’s research, we have learned a significant amount of information about chimpanzee social behavior and characteristics which may explain some human behaviors. For example, in an anecdotal report, an adult male chimpanzee with morbidity symptoms similar to influenza was found using a stick to encourage sneezing and clear his blocked nasal passage (Nishida and Nakamura 1993). Even though anecdotal, Nishida & Nakamura were able to contribute to the addition of further evidence corroborating the advanced cognitive abilities of wild chimpanzees.

In another example, “leaf-clipping displays,” as Nishida wrote, were usually communication signals given by adult males to estrous females in a possessive manner, adolescent males to estrous females as a courtship behavior (or, conversely, estrous females might offer these leaf-clippings to adolescent males for copulations), or even to human observers for sharing food (Nishida 1980). To most, this probably means nothing–however, I would argue, don’t humans have behaviors like this? For example, it’s common on first dates for individuals to give flowers as a form of courtship, no? While I wouldn’t argue that example is an evolutionary behavioral characteristic, it is something shared between chimpanzees and humans and gives further reason to give empathy towards our evolutionary ancestors.

After all, a large part of Nishida’s ambition was dedicated to his desire to teach others about the value and wonders of nature. Given the nature of his work and the impact of his contributions to primatology, I believe his work and his proteges will continue to contribute to teaching others of the appreciation of nature and wildlife and the inherent value both possess. While I was never able to meet him in person, I find his work to be inspiring and him as one of the greatest figures of international primatology.

Mitani JC, McGrew WC, & Wrangham R (2006). Toshisada Nishida’s contributions to primatology. Primates; journal of primatology, 47 (1), 2-5 PMID: 16132169

NISHIDA, T. (1973). The ant-gathering behaviour by the use of tools among wild chimpanzees of the Mahali Mountains Journal of Human Evolution, 2 (5), 357-370 DOI: 10.1016/0047-2484(73)90016-X

Nishida, T. (1976). The Bark-Eating Habits in Primates, with Special Reference to Their Status in the Diet of Wild Chimpanzees Folia Primatologica, 25 (4), 277-287 DOI: 10.1159/000155720

Nishida, T. (1980). The leaf-clipping display: A newly-discovered expressive gesture in wild chimpanzees. Journal of Human Evolution, 9(2): 117-128.

Nishida, T. & Nakamura, M. (1993). Chimpanzee tool use to clear a blocked nasal passage. Folia primatologica, 61(4): 218-220.

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When I talk with friends about primates and disease, it always surprises me how many are unaware as to how SIV came to be associated with HIV. The long misguided associations of it being a “gay flu,” disease of immigrants and intravenous drug users is long gone, but many stigmatizations remain around the world. Though I suspect many readers are probably well aware of the fact that SIV is the precursor to HIV, this post is to explain how that came about.

Among the many emerging infectious diseases in the last fifty years, few are as intimidating to public health resources as the global Human Immunodeficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) epidemic.  Since the emergence of HIV/AIDS, the world’s economy, social practices, political relationships, and other aspects of human life have been altered dramatically.  Initially seen as the “gay flu,” it was once thought that homosexuals, intravenous drug users, immigrants, and other marginalized groups were the source of the virus.  However, recent genetic evidence show the origins of HIV are not linked to these groups.  Instead, the origin of HIV/AIDS comes from a very unlikely source, one of which we are all too familiar—our non-human primate ancestors.  In our primate kin, a similar virus to HIV evolved over time and allowed them to become the hosts for a disease known as Simian Immunodeficiency Virus (SIV).  The analysis of evidence leads scholars to believe HIV is a zoonotic disease transmitted from non-human primates to human primates based on similarities between SIV and HIV on the host identification and location, viral genetic levels, and plausible theories on routes of transmission.  Through non-human primates and human interference, SIV became transmissible to humans and developed into HIV.

In order to understand HIV within a proper context, we must first discuss SIV.  As it currently stands, thirty-three primate species are known to be the natural hosts of SIV.  SIV is a retrovirus, which is a virus that replicates in the host cell via an enzyme known as reverse transcriptase.  Through this process, the virus reproduces itself as a part of the host cell’s DNA strands within the cell; thus, making it difficult for the host’s immune system to recognize and ward off further infection.  In addition, the virus mutates at an exceptionally high rate to avoid an immune response (Althaus & De Boer 2008).  This mutation rate has also led to the shifting of types; types of SIV vary and are recognized depending on the species in which they inhabit.  For instance, an infected chimpanzee’s strain would be considered SIVcpz, whereas a sooty manabey’s would be SIVsmm.

A sooty mangabey (Cercocebus atys); the natural host of SIVsmm. (Image from: Primate Info Net)

This distinction is important to note as it is believed the two types of emergent HIV strains are descended from specific SIV strains; namely, SIVcpz and SIVsmm.  Evidence for this is supported in the locations where strains are found.  As it turns out, the sooty mangabey is endemic to western Africa; specifically, Sierra Leon to Gabon, which is the area thought to be near where HIV originated.  HIV-2, for instance, is believed to originate from SIVsmm and sooty mangabeys.  Coincidently, areas in which SIVsmm appears are the exact same as HIV-2 (Gao et al. 1999).

Further support comes from assessing the infectious quality of the SIVsmm strain in human cell cultures.  In a polymerase chain reaction study performed by Gao et al. (1992), researchers took mononuclear blood cells from two rural HIV- Liberian agricultural laborers and an HIV+ urban dweller.  Then, researchers proceeded to infect the blood cells with a strain of HIV-2.  When all three strains were assessed for major proteins in the retroviral genome and long terminal repeats, it was discovered one of the strains (from an uninfected individual) matched SIVsmm more closely than any HIV strain discovered previously.  Upon further examination, when the HIV-2 strains were compared with SIVsmm, it was indicated that the two strains formed a single phylogenetic group of lentivirus; thus, confirming the link between SIVsmm and HIV-2.

On a viral genetic level, HIV-2 and SIVsmm are considered a match due to the correlation between viral genetic material in the HIV-2 and SIVsmm strains.  HIV-1, on the other hand, is not quite as clear as far as viral genetic link.  HIV-1 is believed to be a mosaic of multiple SIV strains.  In one of the first SIVcpz strains to be characterized, SIVcpzANT, it was confirmed to have a vpu gene that was discovered in a divergent HIV-1 strain (Santiago et al. 2002).  SIVcpzANT resembles HIV-1 on a genetic level, however, it is impossible to determine the location where SIVcpzANT may have originated from as it was detected in a chimpanzee in the Antwerp Zoo whose geographic source was unclear.

As the links between HIV and SIV have become clearer, one hypothesis has provided an alternative origin for HIV.  It is thought that in the late 1950s, oral polio vaccines with materials extracted from primates were the cause of the HIV virus (Blancou et al. 2001).  These vaccines were believed to have caused a mutation which led to the development of the viral strain. The areas where the first tests of polio vaccines occurred were also the very same areas in which AIDS was first discovered.  However, it is widely thought the genetic origin of HIV-1 predates the same time as some of the earliest polio vaccines (Hahn et al. 2000).  Thus, the probability of the polio vaccines’ viral strain mutating into an entirely new virus is highly unlikely, given that it did not exist at that point.  Furthermore, no support has been provided to maintain chimpanzee tissues were used in the creation of the vaccine (Blancou et al. 2001).  The odds of the oral polio vaccine hypothesis being the source of HIV is unlikely, based on the incongruity in timeline and no evidence to support the claim of using chimpanzees.

While the link between HIV-2 and SIVsmm is clear through the polymerase chain reaction study performed by Gao et al. (1992), it does not exactly explain how the jump from sooty mangabey to human was made.  Among the many explanations, the most likely hypothesis is a zoonotic transfer from sooty mangabey to human.  It is posited by Hahn et al. that HIV subtypes arose from cross-species transmission events which may include human cutaneous or mucous membranous exposure to contaminated sooty mangabey blood (2000).  For instance, in more rural areas, individuals were likely to hunt bushmeat (including non-human primates) which may have been contaminated with the virus.  Then, when a hunter was cutting open the bushmeat, he may have accidentally cut himself and became infected.

A poacher in Kenya placing bushmeat in a bag to be sold later. (Photo by: Wildlife Direct)

Despite this being the most popular hypothesis of transmission route from primate to humans, many still have lingering questions as to why it would happen now as multiple viral strains have been around for centuries.  After all, bushmeat consumption has existed for centuries and SIVsmm is believed to have persisted for 100,000 years (Omenn 2010).  Yet, the earliest evidence for HIV dates back to 1959 in a vial of blood at Emory University for a study on malaria (Hahn et al. 2000).  If it is the case that bushmeat consumption and hunting were involved in transmission route, it seems much more likely that it would have happened at a much earlier time in history.

Part of the reason for the jump from primates to humans occurring when it did involves a basic understanding of biology.  Over time, mutations tend to occur within genetic material because of specific selection pressures enabling SIV and HIV to survive.  As the viral genome began to change, it eventually became able to transfer to humans and subsist within the human body as a result of mutations overcoming previous barriers (Platter 2009).  Eventually, the “right” mutation occurred at the “right” time to be able to infect humans.

In addition to this, other pressures on humans occurred, making it easier for the SIV virus to cross-over and mutate into HIV.  At the same time, for humans, working conditions in western Africa led to a decline in public health.  During the time of some of the first HIV infections in 1959, Africa was in the midst of colonialism.  Africans were forced into a cash economy system and hard labor practices to obtain necessary resources (Chitnis et al. 2000).  As part of these labor practices, individuals often migrated to where jobs were located, typically resulting in a mixture of people from all over Africa, and thus, any diseases.  Concurrently, infectious disease barriers were being broken down and individuals’ immune systems were weakened by simultaneous infections.  Furthermore, many of these practices (such as creating railways) often encroached into primate habitats, thus, increasing workers’ exposures to infected non-human primates (Chitnis et al. 2000).  Through the working conditions, many workers were given better access to infected primates—thus, increasing the chances of infection.  Without the workers realizing it, many of their immune systems weakened, making the viral transmission more likely to transpire.  Since these first infections, the disease has spread rapidly; currently, there are 33.3 million people worldwide living with HIV/AIDS (UNAIDS 2010).  While the disease transmission patterns have changed over time, it still has a large prevalence rate worldwide.

Since the onset of the initial HIV epidemic, evidence has continuously come to light supporting the hypothesis in which HIV is a zoonotic virus originally occurred in non-human primates.  These claims are supported through the similarities of the virus, locations of the virus, and genetic similarities between viral strains.  Historical implications further enhance the plausibility of this situation which has become widely accepted throughout the scientific community.  Because of this zoonotic disease, many researchers are beginning to give greater attention to emerging infectious diseases with zoonotic origins as human populations grow and affect climate change in wildlife.  Although it is possible for HIV/AIDS to continue to mutate and evade biomedical treatment, as we begin to acknowledge the origins of the disease we may be able to find out more about the virus and begin to treat it more effectively.


Althaus, C.L. & De Boer, R.J. (2008). Dynamics of Immune Escape during HIV/SIV Infection. PLoS Comput Biol, 4(7).

Blancou, P., Vartanian, J.P., Christopherson, C., Chenciner, N., Basilico, C., Kwok, S., & Wain-Hobson, S. (2001). Polio vaccine samples not linked to AIDS. Science, 410(6832): 1045.

Chitnis, A., Rawls, D., & Moore, J. (2000). Origin of HIV Type 1 in Colonial French Equatorial Africa? AIDS Res & Lentiviruses, 16(1): 5-8.

Gao, F., Yue, L., White, A.T., Pappas, P.G., Barchue, J., Hanson, A.P., Greene, B.M., Sharp, P.M., Shaw, G.M., & Hahn, B.H. (1992). Human infection by genetically diverse SIVsmm-related HIV-2 in West Africa. Nature, 358: 495-499.

Gao, F., Bailes, E., Robertson, D.L., Chen, Y., Rodenburg, C.M., Michael, S.F., Cummins, L.B., Arthur, L.O., Peeters, M., Shaw, G.M., Sharp, P.M., & Hahn, B.H. (1999). Origin of HIV-1 in the chimpanzee, Pan troglodytes troglodytes.  Nature, 397: 436-441.

Hahn, B.H., Shaw, G.M., De Cock, K.M., & Sharp, P.M. (2000). AIDS as a Zoonosis: Scientific and Public Health Implications.  Science, 287(5453): 607-614.

Omenn, G.S. (2010). Evolution and public health. PNAS, 107(S1): 1702-1709.

Platter, B.E. (2009). Evidence of contemporary modern human evolution contained within the human genome. Leth Undergrad Res J, 4(1): 1-16.

Santiago, M.L., Rodenburg, C.M., Kamenya, S., Bibollet-Ruche, F., Gao, F., Bailes, E., Fahey, B., Muller, M.N., McClure, H.M., Heeney, J., Pusey, A., Collins, D.A., Boesch, C., Wrangham, R.W., Goodall, J., Sharp, P.M., Shaw, G.M., & Hahn, B.H. (2002). SIVcpz in wild chimpanzees. Science, 295(5554): 465.

UNAIDS. (2010). UNAIDS report on the global AIDS epidemic.

Wertheim, J.O. & Worobey, M. (2009). Dating the Age of the SIV Lineages that gave rise to HIV-1 and HIV-2.  PLoS Comput Biol, 5(5): e1000377.

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This post was chosen as an Editor's Selection for ResearchBlogging.orgThis post was chosen as an Editor's Selection for ResearchBlogging.org Within human culture, the hymen has great significance for its perceived correlation to female sexual status.  For many cultures, the presence of an intact hymen before marriage suggests purity and cleanliness.  Outside of weddings and marriage, hymens have also had cultural relevance as the word “hysteria” is derived from womb-fury, which was associated with the hymen*.  Over time, the role of the hymen within culture has changed from being a cause of madness to, in more scientifically-minded societies, being seen as a biological part of the human female body.  And so, too, with these shifting perceptions, the human comprehension of the hymen has changed as well.  Even though cultural perspectives on the presence and function of the hymen have changed, little is understood in which circumstances the hymen may have been sexually selected.  Some scholars posit cultural practices as a method for selection, while others suggest a more morphologically related explanation based on evolutionary responses to the environment.  It is thought that because the hymen offers a barrier of protection in the external vaginal opening, through evolving human cultural practices, it enhances a woman’s individual fitness.  The sexual selection of the human hymen is related to hygienic purposes in order to reduce infertility and has been supported indirectly through cultural practices.

Hymen: the stigmatized tissue

Among the many tissues within the human body, few are more stigmatized than the hymen.  This is largely in part due to the human cultural perceptions of the hymen as a measure of sexual status.  And while the hymen is well known for the cultural perceptions, few are aware of the actual anatomical and physiological aspects.  Commonly misconceived as a part of the internal vaginal canal, in reality, the hymen is not inside of the vagina at all.  The hymen is a membrane-like tissue which is considered part of the external genitalia, whereas the internal vaginal orifice is partly covered by the labia majora.  Although hymens are only present in the female sex, there are variations of the types that may naturally occur.  Hymen morphological variation can range from crescent-shaped, ring-shaped, folded upon itself, banded across the opening, holed, or, without an opening within the hymen at all.  Such cases are considered “imperforated hymens” and only occur in 1 in 2,000 females (Kurman 2002).  Variation exists in the types present within females and in the evolutionary morphology of its presence.

Although debated by scholars, it is thought some human females are not the only ones to be lacking a hymen.  Throughout the Primate order, only two living species (other than humans) are known to have hymens: lemurs and chimpanzees (Cold & McGrath 1999).  It is unclear what circumstances may have lead to the evolutionary reversion for the hymen to reappear because tissues tend to not preserve in the fossil record.  In addition, we do not have clear physical evidence to distinguish whether the hymen is a retained ancestral trait, or it arose three times within lemurs, chimpanzees, and humans as a homoplasy.  However, there are multiple theories which support the idea of the hymen as a retained ancestral trait in response to ecological conditions where it would have been beneficial to retain a tissue on the external genitalia.

The Evolutionary Theories

An aquatic ape? (Photo by: Barry Bland via DailyMail)

One of the methods scholars posit as a reason for the hymen to be selected for is in relation to our evolutionary history.  In one of the more contested human evolutionary theories, the aquatic ape theory, it is thought the hymen was selected for as a response to the ecological conditions in which hominid ancestors were living.  In this theory, hominids spent a substantial amount of time in waters due to competition for food resources (Hardy 1960).  Over time, the hominid ancestors waded further into waters, as competition grew less fierce.  In order to support this claim, Hardy draws on the loss of hair from hominoid ancestors to present modern human as evidence by paralleling them to numerous other aquatic mammals that tend to lack hair.  In addition to the hair loss, the presence of the hymen was thought to be an adaptation to the new aquatic environment.

Within the new habitat, hominids were more at risk to microbes rarely encountered on land.  Morgan hypothesizes that the hymen evolved as an independent adaptation to avoid vaginal infections caused by microbes within the aquatic environment (Morgan 1972).  As hominids walked upright more frequently within the aquatic habitat, the likelihood of contracting vaginal infections increased.  These vaginal infections were considered to cause infertility and as a result, reduce reproductive success (Hobday et al. 1997).  Therefore, females that possessed these tissues to ward off infections were more likely to be reproductively successful and pass on the adaptation to offspring.  After enough time passed, the tissue remained in hominids as an apomorphy.

While this is possible, many scholars refute the possibility of the aquatic ape theory.  In direct reference to the hymen, the aquatic ape theory fails to take into account the fact the hymen only offers limited protection for the vagina due to the fact it does not cover the entirety of the genitals.  In defense of the aquatic ape theory, some scholars believe that even partial coverage is more beneficial than none at all (Morgan 1972).  However, this does not take into account the likelihood in which these infections would persist in female populations.  Furthermore, this theory also does not recognize the probability of the hymen tearing from sexual intercourse or other methods, thus, further reducing the chances in which the hymen would offer protection.  Therefore, evidence seems to deviate from the role of the aquatic ape theory’s ecological selection.

Another alternative suggests a different source for the hymen’s function.  In a more recent hypothesis, Hobday et al. postulate that the hymen is an embryological structure (leftover from the conjunction of the sino-vaginal bulb and muellerian ducts) retained into juvenility but also serving as a barrier against infectious microbes (1997; Raveenthiran 2009).  As humans tend to be more altricial and weaker at birth than other primate ancestors, the necessity for having further protection was naturally selected for into childhood and adolescence.  Although it has yet to be determined, given the change to an upright posture and a reduction into the size of the birth canal, it is not likely the function of the human hymen is necessarily the same as the one in lemurs and chimpanzees (Hobday et al. 1997).  Currently, it is unclear when this trait may have evolved, as it is unlikely to be a trait shared with chimpanzees given the morphological changes from chimpanzees to humans.  In this context, this suggests the idea that the hymen evolved three times.  The hymen in Hobday’s exaptation theory serves as a homoplasy, and it is postulated this evolutionary adaptation may have benefitted humans for more hygienic reasons, which may not have been necessary in primate ancestors.

A pair of ring-tailed lemurs (Lemur catta) grooming. (Photo by: Mike Powles via ARKive.org)

Particularly because human infants are altricial at birth and unable to groom themselves, hygiene is an important factor when considering the health of an infant.  Even though it is possible for the mother to groom, it is impossible for her to remove microscopic foreign infectious agents from the vaginal area.  Having a membrane-like tissue to prevent foreign materials, such as fecal matter and other such substances, would provide protection to infants during this vulnerable time (Hobday et al. 1997).  Furthermore, it is assumed that this would be naturally selected for, as variations of hymens exist.  Thus, hymens that offer more protection would be more likely to pass on their genes to offspring, as fewer infections would occur in the very young, leading to fewer cases of infertility.

The phenotypic variation expressed in hymens can provide scholars greater insight into the legitimacy of claims in that the hymen might reduce infertility.  One of the ways in which this hypothesis can be examined further is making the comparison between intact hymens and imperforated hymens.  While imperforated hymens are rarer in the general population, they have subsisted nonetheless.  Currently, scholars believe that the transmission of the imperforated hymen is a dominant trait (Sterling et al. 2000).  As such, the phenotypic trait would be more likely to occur in the general population over time.  The imperforated hymen can be reversed through surgical intervention, but without doing so, can lead to a significant delay in menarche and puberty, abdominal pain, urinary accumulations (which may lead to infections), smegma blockage, and prevent menstrual blood from escaping; all of which, over time, could lead to increased mortality risk (Posner & Spandorfer 2005).  Given that the chance of mortality increases if build up of smegma and other accumulations increase over time without intervention, as imperforated hymens are a health risk, this lends credibility to hymens being a naturally selected trait.  While having too thick of a hymen might lead to some infections, having a less thick and breakable hymen might function as a filter for infectious microbes.

This exaptation hypothesis, much like the aquatic ape theory, tends to receive criticism for its explanation of the hymen’s function.  For instance, following the breaking of the hymen through loss of virginity or other physical methods, females would be likely to lose the protection from microbial agents (Maul 2007).  While this may be the case, Maul fails to take into account that it is possible for a female to have offspring after the first sexual intercourse assuming she has reached menarche.  If she is able to have viable offspring from her first sexual encounter, it is not as critical for her body to ward off against infections.  Her female offspring would also be likely to carry the trait of having a hymen which would offer the same protections.  Furthermore, Maul also does not recognize the fact that adolescents would be old enough to begin to clean the vagina on their own, thus, offering another source of defense against microbial infections.

The other substantial criticism of Hobday et al.’s hymen exaptation hypothesis is that the hymen is not necessarily a beneficial trait when considering sexual selection pressures.  If the hymen is selected to be occlusive, it may cause difficulty for the first intercourse and subsequent coituses if the hymen is too obstructive to be penetrated (Cox 1995).  In the case intercourse provides to be a difficult and painful experience for both individuals, intercourse might occur less frequently.  Therefore, the chances of passing on the phenotype of an occlusive hymen are reduced in this situation.   This criticism is weak, at best, as it does not regard the fact it reduces reproductive fitness as females are less likely to have intercourse due to painful coitus; thus, limiting the number of offspring produced.  In addition, it also fails to take into account the significance of human cultural values on virginity and the status of the hymen.

The Cultural Experience

            Across multiple human cultures and societies, the presence of the hymen is an important trait within women.  For centuries, within various mythologies and religions, cultural practices, and human perceptions, the hymen has had a significant role in the female status.  In one of the more notorious examples, the Islamic ideology of men receiving 72 virgins in the wake of suicide-killings is compelling enough to shift the incentive from living to the desire for death (Franck et al. 2005).  As the 72 virgins symbolize indefinite personal gain, the loss of life becomes inconsequential as the future gain of these women with present hymens outweighs the current experience of life.  On the contrary, while these men gain incentive to take their lives for the women with virginal status, women who have been found to lose their virginal status prior to marriage are sometimes forced into these suicide-killing situations as a way of restoring honor to their families (Franck et al. 2005).  In this ideology, men, regardless of having virginal status or not, are rewarded with women who maintain virginity, whereas, females are punished with death for not retaining theirs.  Although this example is extreme, highly rare within the modern world, and exists within an oppressive, patriarchic paradigm, it highlights the significance of the presence of the intact hymen within a human society as a form of sexual selection pressure.

Throughout human history, the intact hymen has been regarded with reverence and general positivity.  Many scholars support the idea of the human hymen been sexually selected via cultural methods for its symbolic importance in patrilineal societies.  By having a partner who has an intact hymen, it is thought males can be certain of a female partner’s sexual history (Hobday et al. 1997).  Therefore, in the case of females becoming pregnant after first coitus, males can be more certain of their paternity in offspring.  Conversely, this may serve as an indirect form of mate guarding as tearing the hymen might serve as a method of making females less attractive to other males, due to the uncertainty of paternity in any potential offspring (Buss 2006).  In situations such as these where the intact hymen and virginal status are preferred traits, it is likely the hymen is a sexually selected attribute.

In some cultures, cherry pie is a very big deal. It's like a cool drink of water, or a sweet surprise.

Indirectly within multiple human cultures, the hymen may have been sexually selected as a trait which contributes to a female’s hygiene, but also as a valuable feature in attracting a mate.  Sexual selection is defined as differential mating success among individuals within a population (Panhuis et al. 2001).  As such, it is possible the hymen can serve as a sexually selected characteristic among females. Typically, sexual selection is expressed in males, but the presence of an intact hymen can serve as an unintentional form of intrasexual competition between females.  Given that it might be more likely for men to choose virgin women as mates due to potentially being able to ascertain paternity status in offspring, the intact hymen might make it more likely for a female to be chosen as a mate (Maul 2007).  Women who are chosen as mates are also thought to be more likely to have better access to resources that may increase individual fitness as she would have to spend less energy on procuring resources for herself.  It must be noted, however, these factors are dependent upon the male preference for the intact hymen and perceived associated virginal status.

Although it is commonly thought to be the case that the tearing of the hymen equates to a loss of virgin status, new evidence has come forth to suggest otherwise. In recent years, data has come forth to suggest the presence of an intact hymen is no longer an entirely accurate depiction of virginal status.  Among one of the many claims, a recent study linked 52% of a group of adolescent girls having an intact, non-disrupted hymen after first sexual intercourse (Adams et al. 2004).  This finding suggests not only is it necessarily true the intact hymen correlates with a lack of previous sexual history, but even possibly a beneficial aspect for an intact hymen to exist after sexual intercourse.  For instance, in the Yungar society of Australia, some women were brutally tortured, starved, and killed regularly if they lacked an intact hymen previous to marriage (Hobday et al. 1997).  Accordingly, in some social contexts, having a more elasticized hymen to withstand penetration and tearing might be beneficial.  The presence of an intact hymen to persist may serve as a signal to males that she retains her chastity; thus, being able to continue living without stigmatization or persecution.  As the hymen is still revered and important within some societies around the world as a signal of paternity certainty, other societies place less importance as evidence comes to light to suggest otherwise.

In addition to the fact in which having an intact hymen is no longer necessarily indicative of virginal status, recent technology has made it even more difficult to distinguish sexually active status.  Through technological advancements have been made in feminine hygiene products, the use of tampons may actually be likely to tear the hymen as well as speculum examinations by gynecologists (Rogers & Stark 1998).  Occurrences such as these are frequent in the westernized world, as many menstruating females can afford hygiene products.  However, in areas of the world where females have limited access to hygiene products and routine gynecological examinations, this phenomenon is rarer (Farage et al. 2011).  Recent surgical advances have also made it possible for some women to reconstruct the intact hymen, further adding to the complications of discerning sexually active females.

Surgeries which restore the intact hymen are often referred to as hymenorrhaphy or a hymenoplasty.  In a hymenoplasty, the remnants of a torn hymen are stretched and stitched to the vaginal orifice (Prakash 2009).  Within the surgery, the hymen is stretched out and essentially recreated from pre-existing tissue.  In many countries, women will go to great lengths to get their hymen repaired to former status for reasons from fear of being thought of as unchaste (which might result in any consequence ranging from divorce to death) to cosmetic reasons to maintain a sexual partner’s happiness (Prakash 2009).  But in the context of sexual selection, the hymenoplasty could be considered as a deceptive signal.  Much like the elasticized hymen which fails to tear even after sexual intercourse, the hymenoplasty can also serve as an indication to others that the female retains her virginal status.   The signal sent from this procedure can be used to deceive males into choosing a female as a mate, thus, serving as a strategy to outcompete other females without the presence of a hymen.

Though the function of the hymen is still widely debated among scholars, its presence can serve as a sexually selected trait that increases fitness in females.  Females that live in cultures where males give preference to females with an intact hymen and perceived virginal status often receive benefits of better access to resources.  In addition, it is hypothesized that these females are more likely to be reproductively successful for reasons related to an evolutionary function in which the hymen served as a barrier, preventing infectious microbes from entering the vaginal orifice.  Therefore, females with an intact hymen until first coitus were thought to avoid infections which may have lead to infertility. As such, it was beneficial to choose women as mates who retained an intact hymen.  Despite recent studies suggesting the hymen is less elastic than previously thought, the importance of the hymen still remains in certain cultures around the world and still continues to thrive as a sexually selected trait.

Note: * = Initially, I was under the impression the term hysteria was linked to the hymen as it was once believed the hymen was part of the uterus. Not entirely true, however, hymens are linked to hysteria through the perceived womb fury. (More information on this can be found here)


Adams, J.A., Botash, A.S., & Kellogg, N. (2004). Differences in hymenal morphology between adolescent girls with and without a history of consensual sexual intercourse. Arch Pediatr Adolesc Med, 158(3): 280-285.

Buss, D.M. (2006). Strategies of human mating. Psych Topics, 2: 239-260.

Cold, C.J. & McGrath, K.A. (1999). Anatomy and Histology of the Penile and Clitoral Prepuce in Primates.  In Denniston, G.C., Hodges, F.M., & Milos M.F. (Eds.), Male and Female Circumcision, (pp. 1-8), New York: Plenum Publishers.

Cox, G. (1995). De Virginibus Puerisque: the function of the human foreskin considered from an evolutionary perspective. Med Hypoth, 45: 617-621.

Farage, M.A., Miller, K.W., & Davis, A. (2011). Cultural aspects of menstruation and menstrual hygiene in adolescents. Exp Rev Obst Gyn, 6(2): 127-139.

Franck, R., Hillman, A.L., & Krausz, M. (2005). Public safety and the moral dilemma in the defense against terror. Def and Peace Econ, 16(5): 347-364.

Hardy, A. (17 March 1960). Was Man more aquatic in the past? New Scientist, 642-645.

Hobday, A.J., Haury, L., & Dayton, P.K. (1997). Function of the human hymen. Medical Hypotheses, 49, 171-173

Kurman, R.J. (2002). Blaustein’s Pathology of the Female Genital Tract (5th edition). New York: Springer-Verlag, 160.

Maul, A. (2007). An evolutionary interpretation of the significance of physical pain experienced by human females: defloration and childbirth pains. Med Hypoth, 69(2): 403-409.

Morgan, E. (1972). The Descent of Woman. New York: Stein and Day.

Panhuis, T.M., Butlin, R., Zuk, M., & Tregenza, T. (2001). Sexual selection and speciation. Trends Ecol Evol, 16(7): 364-371.

Posner, J.C. & Spandorfer, P.R. (2005). Early detection of imperforate hymen prevents morbidity from delays in diagnosis. Pediatrics, 115(4): 1008-1012.

Prakash, V. (2009). Hymenoplasty—how to do. Indian J Surg, 71: 221-223.

Raveenthiran, V. (2009). Surgery of the hymen: from myth to modernization.  Indian J Surg, 71: 224-226.

Rogers, D.J. & Stark, M. (1998). The hymen is not necessarily torn after sexual intercourse. Brit Med J, 317(7155): 414.

Sterling, J.R., Gray, M.R., Davis, A.J., Cowan, J.M., & Reindollar, R.H. (2000). Dominant transmission of imperforate hymen. Fert Steril, 74(6): 1241-1244.

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This post was chosen as an Editor's Selection for ResearchBlogging.org Over the past few weeks, I’ve made no secret about my growing love for medical anthropology. I’ve been dying to try and make a connection between primatology and medical anthropology, but for weeks, I haven’t been able to think of anything–that is, until now.

Peter Walsh, a primatologist affiliated with the Max Planck Institute for Evolutionary Anthropology, has set up an initiative to establish a working vaccine for ebola to protect populations of African great apes from the viral disease. Ebola is responsible for killing one-third of the gorilla population and a sizable amount of chimpanzees in the last twenty years (Walsh et al. 2007). With that in mind, creating a working vaccine seems like a worthwhile solution: prevent these (critically, in some cases) endangered primates from losing group members by creating a vaccine that is responsible for killing up to a third of the population.

Or does it? I have some reservations, but I’ll get into that a little while.

Ebola: Nightmares are made of this

An electron micrograph of the ebola virus. This is the thing nightmares are made of. (Photo from: WikiMedia Commons)

As stated previously, ebola is a virus; a zoonotic virus that not only infects our primate kin, but ourselves as well (which I’ll get into a little later.) Ebola was originally recognized in 1976 in the western equatorial province of Sudan and what is now the Democratic Republic of Congo (previously, Zaire.) Overall, there are five specific subtypes currently discovered that have been confirmed in Sudan, Gabon, Uganda, Republic of Congo, the Ivory Coast, and the Democratic Republic of Congo.

Currently, fruit bats (Epomops franqueti, Hypsignathus monstrosus, and Myonycteris torquata) are thought to be the natural host species, or reservoir of the Zaire virus (Pourrut et al. 2007). The Zaire virus strain is considered the most virulent and devastating to chimpanzee, gorilla, and human populations.

The ebola virus is believed to be transmitted from bat-to-bat by both vertical means (mother-to-offspring) and horizontal (infected bat biting non-infected bat or via mating); still, the link between transmission from bats to great apes and humans has yet to be found. However, there is a potential ecological hypothesis which posits during the end of the rainy season and beginning of dry season in Africa (November to February), fruit abundance is at its highest peak which is a primary food source for both great apes and fruit bats. It is possible that when bats consume and drop partially eaten fruits or pulp, the fluids from the bat would remain and contaminate great apes that consume the fruit (Gonzalez et al. 2007). Ebola can also be spread via aerosols in breathable droplets (Johnson et al. 1995). However, given that fruit bats and great apes do not typically share the same niche in the ecosystem, the contamination of partially eaten fruit is a more likely option.

Apes, Humans, and Vaccines: Naturally Selected for Each Other?

When I think of bushmeat, this is the image that always comes to mind. A gorilla's head used for cooking purposes. (Photo by: Karl Ammann)

While this seems likely for great apes, this does not explain how humans become initially infected with the ebola virus.  However, evidence is beginning to suggest that the zoonotic origin of the human infection comes from bushmeat hunting (Rouquet et al. 2005).  In a 1996 outbreak in Gabon, an epidemiological survey showed that index case-patients were infected by physical contact with an infected chimpanzee.

And now, the skepticism part: there has been a live attenuated vaccine developed by Integrated BioTherapeutics Inc. that has proven efficacy in establishing a challenge to the virus dose in rhesus macaques. Walsh intends to use this in experiments in chimpanzees with later use in gorillas, as well.

The practice of vaccinating wildlife is sometimes risky; live attenuated could always cause disease and/or revert to virulent pathogen because of selection pressures caused by vaccinations. (Think: MRSA and antibiotics in humans.) In a species such as gorilla, where it may be difficult to track populations down, this may prove to become a costly endeavor.

In terms of selection pressures, ebola viruses mutate at about the same rate (10-5 to 10-4 per site per year) as many other RNA viruses.  Although slower than influenza A and retroviruses, it does undergo a rapid evolution comparatively (Suzuki & Gojobori 1999). That said, while not as large of a risk, there is still a potential for mutation within the virus to occur.

Ebola and Bushmeat: Under Pressure

So what does this mean for humans? Well, for one: the vaccine is only produced for great apes so far. Yet, there are examples of other forms of bushmeat (i.e. duikers) that have been historically contaminated with the virus as well (Leroy et al. 2004). This means that while we may have protection in one form of bushmeat, many other forms can expose humans to ebola pathogens as well.

Second, it is true that ebola does kill a third of the gorilla population and also has a significant toll on chimpanzee populations—what about the other two-thirds? As Walsh et al. (2007) suggest, the other significant players in the role of gorilla deaths tend to be bushmeat hunting and habitat loss. Given the fact that bushmeat plays a role in both transmission of the virus and population declines for gorilla, perhaps it would be more effective to examine the bushmeat trade.

I’m not suggesting that we give up on this idea quite yet; it is absolutely worthwhile to pursue a vaccine which will protect chimpanzees and gorillas. However, I am saying that before we get too excited about eliminating one ultimate cause that we perhaps examine the “big picture” a little more—before there’s ultimately a bigger problem at hand.


Gonzalez JP, Pourrut X, & Leroy E (2007). Ebolavirus and other filoviruses. Current topics in microbiology and immunology, 315, 363-87 PMID: 17848072

Johnson, E., Jaax, N., White, J., & Jahrling, P. (1995). “Lethal experimental infections of rhesus monkeys by aerosolized Ebola virus.” International journal of experimental pathology 76(4): 227–36.

Leroy, E.M, Rouquet, P, Formenty, P., Souquière, S., Kilbourne, A., Froment, J.M., Bermejo, M., Smit, S., Karesh, W., Swanepoel, R., Zaki, S.R., & Rollin, P.E. (2004). Multiple Ebola virus transmission events and rapid decline of central African wildlife. Science (New York, N.Y.), 303 (5656), 387-90 PMID: 14726594

Pourrut X, Délicat A, Rollin PE, Ksiazek TG, Gonzalez JP, & Leroy EM (2007). Spatial and temporal patterns of Zaire ebolavirus antibody prevalence in the possible reservoir bat species. The Journal of Infectious Diseases, 196 Suppl 2 PMID: 17940947

Rouquet, P., Froment, J.M., Bermejo, M., Kilbourn, A., Karesh, W., Reed, P., Kumulungui, B., Yaba, P., Délicat, A., Rollin, P.E., & Leroy, E.M. (2005). Wild animal mortality monitoring and human Ebola outbreaks, Gabon and Republic of Congo, 2001-2003. Emerging Infectious Diseases, 11 (2), 283-90 PMID: 15752448

Suzuki, Y.  Gojobori, T. (1999). A method for detecting positive selection at single amino acid sites. Mol. Biol. Evol., 16: 1315-1328.

Walsh, P.D., Tutin, C.E.G., Oates, J.F., Baillie, J.E.M., Maisels, F., Stokes, E.J., Gatti, S., Bergl, R.A., Sunderland‐Groves, J., & Dunn. A. (2007). Gorilla gorilla. In: 2007 IUCN Red List of Threatened Species, IUCN.<www.iucnredlist.org>

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Meeting Jill Pruetz.

None of my friends will tell you I’m like the average college student. I don’t party. I don’t consume excessive amounts of alcohol (well, in fairness, it doesn’t take much–two glasses of wine and I’m done and falling asleep for the night.) I’ve never gone to a concert in my life and I don’t see movies all that often. Likewise, I love learning. I love reading a good textbook. I can pore over a textbook easily and be excited about what I learned and think of how I can make this apply in a “real life” setting. I love just sitting at home and looking at scientific journal articles, looking at videos of things like chimpanzees mourning the dead.

I’m not like the rest of my family, either. My family is a group of athletes by nature; many of my cousins grew up adoring animals (the only thing I think I’ve had in common with them), but eventually grew up and found more affection for sports and other things. Whereas, I was more interested in politics and things that immediately affected people. I identified as a social scientist first above all else.

So when I heard Jill Pruetz would be coming to give a talk at the university I’m currently attending for our Darwin Day ceremony as the keynote speaker–I was excited. I had been told about how kind she was before this when I discussed wanting to study with her to my teaching assistant at La Suerte last summer; but I didn’t know what to expect about her. And I’ve done some research on Pruetz’s work but I can’t believe how underrated it is by some of my peers. They can all recite Goodall, some can get Fossey’s work, and even rarer–Galdikas’ (though, never by her name), yet none of them know of Pruetz.

Jill Pruetz, Associate Professor of Anthropology at Iowa State University and National Geographic Explorer. (Photo by: National Geographic via Jim Heemstra/Iowa State University)

At the risk of being called a sycophant, her work is, well, to me–unbelievable in the best possible way. Not only does she study chimpanzees in a habitat more similar to some of the earliest human ancestors (savannahs); but–she finds unique things that are variations found within other chimpanzee species in other parts of Africa. And as weird as it might sound to some–I feel a little bit of a spark of “kinship” with those chimpanzees for being different.

The Fongoli chimpanzees have been noted to pass on elements of “culture”–learning and sharing by observation how to become effective hunters by using and sharpening wooden branch spears. They also have an understanding of fire, a sense of empathy, use caves and play in water as methods to adjust to hotter temperatures. These findings are astounding and show the breadth of behavioral variation in a species dependent upon the geographic climate.

Pruetz, herself, was an incredible speaker. As someone who’s had a lot of public speaking experience under her belt (and spoke to audiences with 400+ people on a few occasions), the way she spoke was fantastic. Her presentation was phenomenal with her words, the videos she presented, and the pertinent information in understandable ways. But that isn’t what made me feel privileged to be in her presence (although, I very much so was before this): the way she interacted with us was what did it. During her speech, a little girl would ask a few questions every now and then–intelligent ones, at that!–ranging from “What are the chimpanzee’s predators?” to “How can you tell them apart?” and her responses were gracious, patient, and clear.

I had asked her a question about the effects of climate change on the behavior of the Fongoli chimps in the decade she has researched there. As soon as it left my mouth, I felt stupid as hell; after 10 years, how can you really tell these things? Way to go, dumbass, I thought. But, much previously, she answered the question with grace and poise and was kind enough to not make me feel like a dumbass at all.

After taking our questions, I was able to go up and talk to her with two of my friends. She was kind and patient, willing to discuss with us and invite us to apply to her school for graduate work (which I was thinking about already, but now it’s a definite). I don’t care much for musical rockstars or celebrities, but I really get starstruck when it comes to scientists who do and find amazing work and discoveries in the field. The three of us left raving about the talk–dying to be just like that one day in terms of providing something of scientific worth to the world.

Meeting Jill Pruetz was like meeting your most admired rockstar. Except mine studies chimpanzees that spearhunt, play in water, rest in caves, and understand fire.

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“Marla tells me how in the wild you don’t see old animals because as soon as they age, animals die. If they get sick or slow down, something stronger kills them. Animals aren’t meant to get old. Marla lies down on her bed and undoes the tie on her bathrobe, and says our culture has made death something wrong. Old animals should be an unnatural exception. Freaks.” – Chuck Palahniuk, Fight Club

Death. Every philosopher has an opinion on it and very little do we know of it. I’m not talking about the situations where some young adult drinks themselves into alcohol poisoning and then gets revived—I’m talking about biting the dust, pushing up daisies, becoming a root inspector, kicking the bucket, taking a dirt nap, or whatever euphemism you fancy.

This post was chosen as an Editor's Selection for ResearchBlogging.org We all know primates die; no one argues that much. But there is also significant evidence showing primates experience an awareness and emotional response to death as well.

Koko and All Ball (Photo by: Koko.org)

Most famously, there is the example of Koko the western lowland gorilla (Gorilla gorilla gorilla) experiencing mourning symptoms after her pet kitten, All Ball, escaped from its cage and was hit by a car.  Francine Patterson, Koko’s caretaker, reported that she believed Koko had made sounds similar to human sobbing and communicating her distress through American Sign Language with signs such as “Bad-sad-bad” and “Frown-cry-frown-sad” (Patterson 1987).

In a recently published article for the American Journal of Primatology, James Anderson (2010) suggests context has a significant part in how primates respond to death as well. Evidence from deaths of individual group members suggest different reactions; mortality events from causes such as predation versus illness and even characteristics like age, sex, and social status may seem to play a role in these responses.

A female chimpanzee with mummified infant on her back. (Photo by: D. Biro)

Compared to the situation with Koko, a captive gorilla; wild primates have also been recently recorded to display some mourning symptoms as well. For mothers with young infants that die, reactions can tend to have longer mourning symptoms. For example, two chimpanzee (Pan troglodytes verus) mothers were found to transport their deceased infants for a prolonged period of time—68 and 19 days after death in the respective cases (Biro et al. 2010). In these situations, although the infants mummified, the mothers still treated them as living entities—swatting insects away and grooming them.

Morbidity events (which can become later mortality events) may draw emotional reactions from group members as well. Unlike chimpanzees, little evidence of compassion for group members is displayed in wild gelada baboons (Theropithecus gelada) (Fashing et al. 2010). In a situation where a mother (Tesla) was succumbing to a parasitic infection, conspecifics only peered back once at her and her infant (Tussock, who died a day later) before leaving the plateau to search for food. Days before her death, female group members allomothered Tussock as Tesla slowly trailed behind the group. It is unclear why these same females did not respond to the infant upon returning to the plateau; though, perhaps something to do with the costs of infants to females and can be burdensome to take on caring for an infant which is not biologically hers.

While it remains to be seen how much and in what specific circumstances the context and characteristics affect reaction, I know I’ll be looking forward to further research on this subject and the development of thanatological primatology, even if the deceased primates are “old, unnatural freaks.”


Anderson, J.R. (2010). A primatological perspective on death. American Journal of Primatology PMID: 21197638

Biro, D., Humle, T., Koops, K., Sousa, C., Hayashi, M., & Matsuzawa, T. (2010). Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants. Current Biology, 20(8), R351-R352. DOI: 10.1016/j.cub.2010.02.031

Fashing, P.J., Nguyen, N., Barry, T.S., Goodale, C.B., Burke, R.J., Jones, S.C., Kerby, J.T., Lee, L.M., Nurmi, N.O., Venkataraman V.V. (2010). Death among geladas (Theropithecus gelada): a broader perspective on mummified infants and primate thanatology. American Journal of Primatology PMID: 21136522

Patterson, F. (1987). Koko’s Kitten. Scholastic, Inc. ISBN 0-590-44425-5

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