Monday, March 29, 2010

Check out these two interesting hominin posts

John Hawks on John Hawks Weblog wrote about the undiscovered hominin from Denisova, Siberia. He cautions the usage of "species" when describing this individual as it is too soon to say whether the individual is indeed a distinct species.

On SEAArchNoel Hidalgo Tan wrote about stone tools found in Flores, Indonesia that dates back to about a million years ago. It is still inconclusive whether these tools belong to the "hobbits" or Homo erectus. 

A range of stone flakes were found (scale-bar: 10mm). Photo from BBC News.

Wednesday, March 24, 2010

Unearthed finger bone points to the possible discovery of an unknown hominin

DNA analysis from a finger bone unearthed from Denisova Cave, Siberia might lead to the discovery of an unknown hominin. Dubbed "X-Woman", information from her mitochondrial DNA suggests that she shared a last common ancestor with modern human and Neanderthals about one million years ago.

Since Neanderthals and modern humans split at about 500,000 year ago, it suggests that she did not originate from that divergent. Instead, she represents an unknown hominin lineage, presumably an unknown migration out of Africa. "X-Woman" is too young to be a descendant of Homo erectus (which migrated out of Africa to Asia about two million years ago) yet too old to be a descendant of Homo heidelbergensis.
"Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," said co-author Professor Svante Paabo, also from the Max Planck Institute for Evolutionary Anthropology.

Read more about this discovery on BBC News, DNA identifies new ancient human.

Said article can be found on Nature, The complete mitochondrial DNA genome of an unknown hominin from southern Siberia (Krause et al., 2010). Unfortunately I do not have access to said journal so if you have a copy I'd appreciate it A LOT if you can send it to me. Thanks Mark, for the pdf.

*Edit* Here's a pdf from Nature, Fossil finger points to new human species.

Saturday, March 20, 2010

Sexual And Natural Selection: Why Humans Are Still Evolving

Comparative photo between a masculine-looking (left) and feminine-looking (right) male. Photo from Dienekes' Anthropology Blog.

On Dienekes' Anthropology Blog, he shares with us a study on the correlation between female mate choice (sexual selection) and national health index (DeBruine et al., 2010). Female tend to prefer more masculine-looking males in countries where the national health index is low. Consequently, females tend to prefer more feminine-looking males in countries where the national health index is high. Head over to Dienekes's blog to read about his blog post, "Preference for masculine/feminine-looking men and national health".

With natural selection at work, females are predicted to be much shorter and stouter in the future. Photograph by Hans Neleman/ Getty on

Also read about "Evolution favours shorter and heavier women—like it or not", an article that foresees the evolution of females to be that of much shorter and stouter. Stephen Stearn, professor of evolutionary biology at Yale University thinks that humans continue to evolve even when we're in a post-industrial society. While there are no large-scale genetic changes, Stearn believes that natural selection is still at work.
“One [could express] the result as: women are going to get shorter and fatter,” he explains. But he prefers a different bent: “There is natural selection against women being slender.” Stearns’s work shows that plumper, shorter women tend to bear more children—who carry on those same traits. His analysis drew on data from the Framingham Heart Study: a survey, begun in 1948, that collected medical information from 5,209 subjects, and monitored them and their offspring for 60 years. 
The weight part of the equation, says Stearns, is straightforward: “A woman has to have about 20 per cent body fat to ovulate and conceive.” But he admits that he “can’t give a good explanation of why they are getting shorter.” A separate study by Open University’s Daniel Nettle found that shorter women are more likely to be in long-term, offspring-producing relationships—perhaps, he hypo thesized, because men evolved to disfavour tall women, who tend to reach puberty later. 

Thursday, March 18, 2010

Four Stone Hearth #88

I've been meaning to start blogging about Four Stone Hearth but I kept forgetting! Four Stone Hearth is published biweekly on Wednesdays. Interested blogger should write to Martin Rundkvist. Here's what Four Stone Hearth (The Fourth Stone Hearth) is according to its website:

The Fourth Stone Hearth is a blog carnival that specializes in anthropology in the widest (American) sense of that word. Here, anthropology is the study of humankind, throughout all times and places, focussing primarily on four lines of research:
  • archaeology
  • socio-cultural anthropology
  • bio-physical anthropology
  • linguistic anthropology
Each one of these subfields is a stone in our hearth.

Four Stone Hearth #88, St. Patrick's Day special edition, was just published yesterday on Ad Hominin. Blog owner Ciarán was nice enough to include my article on the shift of mating system of Sichuan snub-nosed monkeys from polygyny to polygamy. Thanks Ciarán! So readers, go on to Ad Hominin and check out the new issue of Four Stone Hearth.

Wednesday, March 17, 2010

A Shift From Polygyny to Polygamous Mating System In Sichuan Snub-Nosed Monkeys

The saying "You can't judge a book by its cover" can sometimes be applied to primate mating system and social system. Primate social systems sometimes differ from mating systems, as evidenced by reports of field observation (although sometimes first-hand field observations mistakenly report and link primate social systems to mating systems). For example, geladas (Theropithecus gelada) can be observed forming multimale-multifemale social groups (herd) as they graze nonchalantly up in the highlands of Ethiopia but when it comes to mating system, geladas mate in a OMU (one-male unit) where one male mates with multiple females of the unit (Gron, 2008). Primate mating systems can be approached in two different point of views: male coercion or female choice. The latter has been the focus of most primatologists in recent years. The Mating System of the Sichuan Snub-Nosed Monkey (Rhinopithecus roxellana), by Guo et al. (2010) on the current issue (Vol 72:1) of American Journal of Primatology is a paper that examines female choice (female mating strategy) in the mating system of Sichuan snub-nosed monkey (specifically the Qinling subspecies) population in the Qinling Mountains, China. I have the pdf. for the paper if anyone wants to read it.

A Golden snub-nosed monkey feeding on leaves. Photo from Arts on Earth.

R. roxellana basic unit consist of a OMU, which consist of one male and about eight females. They are arboreal herbivores; living in temperate, mountainous forests in China (Gron, 2007). Males and females exhibit sexual dimorphism, where males are heavier and bigger than females (Gron, 2007). Qinling Golden snub-nosed monkeys (Rhinopithecus roxellana qinlingensis) are considered a subspecies of Sichuan snub-nosed monkeys or Golden snub-nosed monkeys (Rhinopithecus roxellana) by Wilson and Reeder's Mammal Species of the World. R. r. qinlingensis can be differentiated from the other subspecies by its brilliant golden pelage.

The Golden snub-nosed monkey lives in temperate, mountainous forest of China. Photo from the Smithsonian.

Golden snub-nosed monkeys grooming. Photo from Wikipedia.

Thought to be of polygynous mating system (one male-multifemale), most of the Sichuan snub-nosed monkeys from Qinling Mountains population were observed in a polygamous mating system (multimale-multifemale) instead. About 18% of the females from this population were observed copulating with males outside of the unit (extra-unit males), in which the researchers call the "extra-unit mating behavior". This behavior was observed from field site by the researchers. Paternal DNA done on the population shows that more than 50% of the offspring were sired by extra-unit males. 94.5% of copulation with extra unit males were initiated by females.

Golden snub-nosed monkeys. Photo from Arts on Earth.

Three theories were proposed to explain the evolutionary purpose of extra-unit mating behavior: infanticide avoidance, inbreeding avoidance and gaining access to resources. However, Guo et al. (2010) posit that mating with extra-unit males in R. roxellana qinlingensis is adaptive and were probably due to infanticide avoidance. In five years of continuous study, there were no observation of infanticide or aggressive behavior of resident males towards immature individuals which includes those not sired by the resident males. Inbreeding avoidance is most probably not the reason why females copulate with extra-unit males although the researchers lack data to posit that females gain access to resources if they copulate with extra-unit males.

Finally, a gratuitous photo of a baby Golden snub-nosed monkey to start your day with an "Awwwww". Photo from Yorkblog.

I wonder if this mating behavior is specific to the focal population of R. r. qinlingensis, all R. r. qinlingensis or all Golden snub-nosed monkeys in general (R. roxellana). If the evolution of this mating behavior is purely to avoid infanticide and is adaptive, then we can posit that the female choice is merely to increase the fitness of her offspring.


Gron, K. 2007. Primate Factsheets: Rhinopithecus roxellana. Primate Info Net Retrieved March 17, 2010, from

Gron, K. 2008. Primate Factsheets: Theropithecus gelada. Primate Info Net Retrieved March 17, 2010, from

Guo, S. Ji, W. Li, M. Chang, H. Li, B. 2010. The Mating System of the Sichuan Snub-Nosed Monkey (Rhinopithecus roxellana). American Journal of Primatology Retrieved March 17, 2010 DOI:10.1002/ajp.20747.

Monday, March 8, 2010

Friday, March 5, 2010

Ethnoprimatology: Human-Macaque Interaction In Sulawesi

Ethnoprimatology is defined as the approach that draws from primate socioecology, ethnoecology/environmental anthropology, and conservation biology. This approach enable us to see the multifaceted interaction between humans and nonhuman primates in a dynamic ecosystem. It seems to be something I would like to do and learn more. What's a better way to incorporate the fundamentals of cultural anthropology and biological anthropology.

An ethnoprimatology paper by Riley and Priston (2010) on the American Journal of Primatology, Macaques in farms and folklore: exploring the human-nonhuman primate interface in Sulawesi, Indonesia (free abstract) explores the complex interaction between macaques and humans through overlapping resource use and cultural perceptions of macaques. If you do not have access to the paper, I can send you a copy of the pdf.

Macaca tonkeana, one of the endemic macaque species of Sulawesi. Photo from Wikipedia.

There are six species of macaques endemic to the island of Sulawesi. Macaca nigra, Macaca nigrescens, Macaca maura, Macaca tonkeana, Macaca hecki and Macaca ochreata. Despite constant crop raiding by macaques, farmers in Sulawesi show considerable tolerance to this behavior. This tolerance can be explained by a positive reinforcement in the farmer's local culture, folklore and religion. Two types of farming subsistence exists in Sulawesi: dryland crops and wet-rice agriculture.

Macaca nigra, one of the endemic macaque species of Sulawesi. Photo from Wikipedia.

Most dryland crops farmers are Muslim. They abstain from killing and/or eating these macaques (which Balinese Hindus would have no problem doing) as it is considered haram. In the Lindu highlands, the macaques are considered kin by the To Lindu people. In Buton, certain places in the forest are considered sacred, thus these places are protected by the locals. Macaques and other animals benefits from this protection, making these pockets of forest their refuge.

Wednesday, March 3, 2010

The IUCN Red List: Species Of The Day

The IUCN Red List has a Species of the Day feature that highlights species that are threatened of different taxa. Everyday, a species is showcased along with information about the threats they are facing.

Species of the Day for March 3, 2010 is a primate name Kipunji (Rungwecebus kipunji). Kipunji are endemic to Tanzania and was first discovered in 2003. For more about Kipunji, also read The Kipunji Might Have Interbred Baboons.

If you have a Twitter account, follow them at @SpeciesOfTheDay. For more information, go to the IUCN Red List website,