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Yesterday morning, I woke up at 5am to winds at a high speed. About thirty seconds later, there was a torrential downpour. A minute after that, tornado sirens rang. In the course of three minutes after the alarms, my significant other and I had gotten up, put on suitable clothes and shoes, corralled the cats into their carrier, and booked it downstairs to the first floor of our apartment.  Fortunately, not much came of it and both of us came up within fifteen minutes. While nothing happened, my general instinct was to go to the area in which we would be the safest.

This is an instinct we share with multiple animals, but particularly so with our evolutionary ancestors.

A few weeks back, a chemical explosion occurred in a chemical plant near the New Iberia Research Center, a primate research institute which contains 360 chimpanzees and 6,500 new and old world monkeys.  While the wind blew the smoke north, rather than west closer to the primate research center, individuals outside the facility could feel the strong heat.

The researchers also noticed an interesting reaction from the primates as the incident occurred; the rhesus macaques housed outside were quick to drop from their perches for enrichment and get as close to the ground as possible to avoid overheating.   According to the director of the facility, Thomas Rowell, “The animals nearest the incident were down at the bottom of the cages, eating and milling about. The intensity of the heat, if you were standing … was overwhelming. At ground level, there was little, if any heat. They were smart enough to squat on the ground and not expose themselves to the intense heat.”

While there have been no signs of stress or illness, staff will be monitoring the primates to ensure individuals weren’t exposed to chemicals from the plant.

So, the truth is–I have nothing right now that I’ve been working on to post. I’ve been writing a guest blog post elsewhere, but my days are spent studying for the GRE, working with a collaborator on our project, and looking for a job so I can have some extra money before I go to Florida/have a cushion for student loan payments when I get back.

Fortunately, a reader e-mailed me about something and I thought it might be helpful for others. I’ve already addressed hir (I’ve removed the name and made it gender neutral for security reasons), but I wanted to post it in case others were curious and/or others had experiences they might want to share to help hir out:

I recently stumbled across your blog, thank you Google, and I had a few, brief questions regarding your schooling and field work in Anthropology/Primatology.

I’m going to start my Junior year in high school soon and much to my counselor’s gentle urging, I need to start thinking about majors and whatnot for when I go on college visits.

I have yet to find a school with an undergrad program in Primatology, so I figured Anthropology might be the best route.
If you could provide any insight to the college selection process and what seemed to work well for you, I’d be very appreciative.

Thank you so much and keep up with the blog, I’m an avid reader!

Sincerely,
[Reader]
Thank you, reader!

The truth is–Anthropology isn’t always the best or even a possible route. The first school I attended–while it sort-of-kind-of had an Anthropology department (which, essentially amounts to one cultural-based professor in the Sociology department), there was no Biological Anthropology component. Your better bet is to take a lot of Biology (specifically, Zoology if the school offers it) courses; this is important because a great deal of Primatology is also Ecology and Conservation (and often, its sister studies: Genetics, Plant Biology, Psychology, etc.) This was my biggest regret in college was that I never took a formal Biology course (I took electives to meet my requirements–which were incredibly helpful, but not the same as having an actual lab or strong course) and were I not financially crunched, I would have spent an extra year getting my Biology background.

During this time, you’re also going to want to take a Statistics course–maybe even two. I’ve been told this by a few people, the nature of Primatology is becoming increasingly quantitative in nature. Get ahead of the game by being adept at numbers, this will prove to be invaluable and give you an advantage over quantitatively challenged people like myself.

Now, back to your questions about schools: like I said, not every one will have a formal Anthropology department nor a professor experienced in Biological Anthropology. The main thing about choosing a college is that you need to be somewhere where you’re most comfortable. After that, explore the Biology (and if available, Anthropology) departments. From there, you should be nurtured for a year or two, get close to a faculty member that intrigues you (which means going into their office hours and talking with them!), and work together to find a field school, zoo, or other way you can gain research experience depending on your preferences.

If you’re like me, you’ll want to try anything and everything you can get involved with. I came into Primatology with a love of all the primates and no specific preference for field, captive, semi-free-ranging or other types, which made finding research trial-and-error (which isn’t to say I disliked the captive or field studies I did–on the contrary! They were fantastic and helped me figure out what both would be like and I wouldn’t be as experienced without either, so I’m immensely grateful for both at this point).

Another thing to consider about choosing a school, aside from the comfortableness of the environment and people, is the resources it can offer you. The one thing I learned about Primatology very, very early on is this: Sometimes, it’s not what you know, but who you know. So you’ll want to be able to pick a school where you’ll have a good advisor/professor–it’s the little things that can put you ahead of the pack and put you in line for grad school (but you shouldn’t think that’s all there is–your grades and test scores are equally as important and you should treat them as more important to be safe; the better those are, the better the scholarships you can potentially get as an undergraduate).

Other resources you should consider potentially seeking out are the following:
  • Does this school offer good programs for undergraduate research? (You are going to want to have research experience by the time you graduate)
  • What are nearby resources? (i.e. Zoos, Research Centers, etc.)
  • What classes are available? (Again, you’ll want a basic background in Biology, you’ll want at least one Statistics course, and probably some in Anthropology, Psychology, and others if available)

Essentially, it’s up to you. There are some schools that have specific programs, however, it’s really up to you and what you make of your undergraduate experience.

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.
References

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.

The yellow baboon orphan with the orphaned bush baby (Photo by: AP Photo)

At first, it sounds like the start of a terrible joke. (“An orphaned baboon and orphaned bush baby are together and …”) But surprisingly–not the case. At an animal orphanage in Nairobi, Kenya, a pairing of an orphaned female yellow baboon and orphaned bush baby have been found in each other’s company.

When you consider the characteristics of the two primates, the pairing is even more bizarre: bush babies (also known as galagos) are nocturnal and arboreal, whereas, baboons are diurnal and terrestrial. Additionally, yellow baboons live in much larger social systems compared to the bush baby, which stays in a small group of its mother and other siblings. For both, however, socializing is critical at young ages (as tends to be the case in all primate species) as that is how infants learn important social characteristics in groups. Given that the bush baby has a yellow baboon as a “parent,” it will be interesting to see what kind of social characteristics it manages to display in the future.

Even more surprising is that bush babies have, at times, been prey for yellow baboons (Hausfater 1976).  This suggests that later on, the twosome will have to be divided at some point. But, until then, we have the option of seeing a unique case of an animal odd couple.

More on this story can be found here.

References

Hausfater, G. (1976). Predatory behavior of yellow baboons. Behaviour, 56(1/2): 44-68.

So, I graduated about two weeks ago. It’s a bittersweet thing: graduating and having nothing to fall back on, but in the meantime, I’ve moved out of state, started studying for the GRE (which I’ll be taking in late July), and trying to find a job before August so I can make some money and have something to fall back on before I leave.

Why before August? Because I’ll be working with lemurs for a few months as a Research Assistant at a lemur reserve! On the side, I’ll hopefully be collecting some data for an original research project, but that’s up in the air. I’ll be there for three months for sure, but if I can get a job, this may become five months (with luck!) I’m looking very much so forward to this and I’ll hopefully be able to update everyone as things progress.

My goal is to keep updating this blog every two weeks up until I leave to work with the lemurs. After that point, I’ll do my best to update with other things, but this will largely be determined by how much access I get to internet, how busy I’ll be, and other things. I’ll more likely be collecting data whenever I can, if only so I can maybe–hopefully!–eke out a publication for submission before I get into the swing of applying to grad schools.

I’m starting to get an idea for the schools I’d like to apply to and some of the more specialized aspects thereof; I’m beginning to lean towards ethnoprimatology. Ideally, I’d like to study Formosan rock macaques in Taiwan or Japanese macaques in Japan with primate-human interactions, but truthfully–I’m open to studying any sort of project so long as I get to work with primates. And who knows? Maybe after this, I’ll be more likely to study lemurs.

I’m keeping my mind open, staying hopeful, keeping my nose to the grindstone for the GRE, and preparing to play with lemurs.

This post was chosen as an Editor's Selection for ResearchBlogging.org In light of Endangered Species Day, I found an interesting study involving one of my favorite endangered species, the Bornean orangutan (Pongo pygmaeus) that resonated with me.  When I was younger, I was a picky child; new foods were scrutinized and judged by smell, appearance, and if I was bold enough—taste and texture.  One day, after eating some new type of cereal, my mouth had an inky taste and upon looking in a mirror, my mouth was filled with blue ink.   I had unintentionally consumed the toy, but from then on, exceptionally crunchy foods became linked in my head with ink and a blue mouth.  It was a little jarring and I thought I was going to die at the time (in typical melodramatic fashion), but nothing really happened.  Eventually, I got over this as I became more social and attempted new foods recommended to me by friends and sharing.

Nenette, one of the most famous orangutans and star of self-titled documentary.

Unlike my younger self, it turns out orangutans are not hesitant to attempt to try new foods too.  In a study performed by Gustafsson, Krief, and Saint Jalme (2011), four captive orangutans (including the famous, Nénette–who was removed halfway through the study for surgery) were given 11 fresh plants and 4 infused plants in a beverage (containing marjoram, thyme, savory, and pellitory-of-the-wall) to determine the individual and group learning methods of trying new foods.  The four orangutans were kept in solitary conditions and then group conditions to measure rates of attempting new foods.

There were four behaviors investigated in conjunction with the consumption of the plant: holding, sniffing, tasting, and ingestion. To the researchers, tasting was defined as “licked, nibbled, or at least held to mouth” (or, in the 4 infused plants case, <100 ml of liquid) whereas ingestion was “a significant amount of the plant eaten” (or >100 ml of liquid) (Gustafsson, Krief, and Saint Jalme 2011). Interestingly, while holding was a common behavior for the first sessions in both group and individual settings, tasting and ingestion were especially high in the infused plants in the first session with the marjoram infusion, the first of the experiments. It is also curious that thyme was also consumed in large amounts when it was strongly infused in the first experiments. In the second experiments, the marjoram remained the same, but increased in thyme. Whereas, savory and pellitory-of-the-wall were low for tasting and ingestion in both sessions, suggesting orangutans might have a preference for certain tastes.

Orangutans consumed 9 out of the 11 fresh plants presented between the first individual and group sessions, indicating low neophobia.  Given that food availability fluctuates in areas where orangutans are endemic due to seasonality and potential climate change, being flexible in food consumption may be necessary to survive times when fruits and other preferred foods are unavailable (Knott 1998; Felton et al. 2003).  Assuming this trait is found in non-captive orangutans as well, dietary plasticity can increase survivability by falling back on newer foods.

Furthermore, as orangutans experience habitat loss and get removed from the pet trade and placed into rehabilitation centers, the potential for disease transmission increases as more individuals come into closer contact with one another.  In these situations, malaria parasites are measured to increase as individuals have more contact than they normally would in non-captive/semi-captive settings (Wolfe et al. 2003). As this occurs, it is possible that the flexibility in trying new foods will lead to more consumption of medicinal plants that would reduce morbidity effects.

Although testing orangutans’ flexibility in trying new foods seems superficial on first glance, it has great significance for conservation purposes for both potential food availability and zoopharmacognosy. Given that orangutans are an endangered species, it is warranted to study the willingness to attempt new foods for captive/semi-captive conditions and also fallback foods when preferred fruiting trees are removed due to logging.

Edit: Because it’s so good and really worth sharing, Barbara J. King also wrote about this study too. I really enjoy her take on it and if you’re reading this, it’s well worth your time to read hers. This study is just too good to not read about and get different perspectives on.

References

Felton, A.M., Engstrom, L.M., Felton, A., & Knott, C.D. (2003). Orangutan population density, forest structure, and fruit availability in hand-logged and unlogged peat swamp forests in West Kalimantan, Indonesia. Biol Conserv, 114(1): 91-101.

Gustafsson E, Krief S, & Saint Jalme M (2011). Neophobia and Learning Mechanisms: How Captive Orangutans Discover Medicinal Plants. Folia primatologica; international journal of primatology, 82 (1), 45-55 PMID: 21525772

Knott, C.D. (1998). Changes in orangutan caloric intake, energy balance, and ketones in response to fluctuating fruit availability. Int J Primatol, 19(6): 1061-1079.

Wolfe, N.D., Karesh, W.B., Kilbourn, A.M., Cox-Singh, J., Bosi, E.J., Rahman, H.A., Tassy Prosser, A., Singh, B., Andau, M., & Spielman, A. (2002). The impact of ecological conditions on the prevalence of malaria among orangutans. Vector Borne Zoo Dis, 2(2): 97-103.

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.

References

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.