Anthropology.net

A brand new study in the open access journal PLoS One reports on the results of an analysis of the microwear on the teeth of Paranthropus boisei (also known as Australopithecus boisei). The results contest what we’ve all along assumed was going on with the form and the function of these robust australopithecine teeth. I even repeated this assumption in a recent post, discussing the dietary implications of a Neandertal.

The results indicate that marks on the teeth of Paranthropus boisei do not correspond with the size and shape of its teeth. This observation suggests that structure of the skull, mandible, and teeth are not enough to infer dietary preferences. Furthermore, evolutionary adaptation for eating may have been based on scarcity rather than on an animal’s regular diet.

The paper, “Dental Microwear and Diet of the Plio-Pleistocene Hominin Paranthropus boisei,” is authored by Peter Ungar, Frederick Grine, and Mark Teaford. Brian, from Laelaps, has written up a very excellent and thorough review of the research. You should check that out.

Why did the authors look at dental microwear on the surface of the teeth? They explain that dental microwear offers direct evidence of the mechanical properties of food item, and that makes a lot of sense. During mastication, the food an organism eats abrades with the surface of the teeth. The texture of the food may scratch and dent teeth, especially if really hard foods like nuts, roots, and tubers are chewed. Likewise, softer foods affect teeth less.

Based upon the size and morphology of Paranthropus boisei teeth, many previous researchers thought they ate tough foods. Hell, the type specimen for P. boisei has been nicknamed “Nutcracker Man.” They have saggital crests similar to gorillas They also have very large teeth with thick layers of enamel. Coupled with the massive jaws, many people thought that P. boisei consumed really dense, fibrous plants.

As I’ve said, the results of the microwear analysis indicates that P. boisei did not eat the hard abrasive foods that we thought they did. Using a confocal microscope, engineering software and scale-sensitive fractal analysis the authors analyzed the around 54 molars from seven specimens of P. boisei. These seven specimens came from different areas, Ethiopia, Kenya, and Tanzania, respectively. Also, these specimens cover over 1 million year of P. boisei existence. Any similarities or differences in the microwear on P. boisei teeth from these temporally and spatially different locations woulda screened out variations in diet reflected to time or environment.

For your viewing pleasure, the authors provided this photograph of detailing the degree of microwear of the teeth of the seven different specimens.

Here’s the legend: (A) KNM-CH 1, (B) KNM-ER 729, (C) KNM-ER 3230, (D) KNM-ER 3952, (E) KNM-WT 17400, (F) OH 5, (G) Omo L7A-125. Clearly you see scratches…

… But what Ungar et al. were looking for was the degree, complexity and directionality of wear textures. Again, hard, brittle foods like nuts and seeds tend to lead to more complex tooth profiles, while tough foods like leaves lead to more parallel scratches, which corresponds with directionality. Comparisons of the the dental microwear profiles of P. boisei to the microwear profiles of extant primates indicates they didn’t eat the same type of foods. Grey-cheeked mangabeys and brown capuchins sometimes rely on hard nuts or palm fronds, as do the mantled howling monkey and silvered leaf monkey. Also included in the comparison was microwear analysis on teeth of Australopithecus africanus.

The P. boisei teeth show light wear, suggesting that none of the individuals ate extremely hard or tough foods in the days leading up to death. The microwear patterns are more consistent with modern-day fruit-eating animals than with most modern-day primates. This conclusion is a fundamental shift in the way we think about the diets of early hominins.

Before you write off the anatomical and evolutionary mantra “form = function,” please consider this: I did not read any discussion on other possible causes for the lack of deep pitting from hard foods.

This is unfortunate. I wonder if the depth of the pits coulda have been buffed out over the millions years these fossils persisted? We know the fossilization process is a time intensive process, and many different weathering affects affect how surfaces of bone are preserved. Furthermore, many fossils are formed by being deposited in or around water sources. Water moves things, like rocks, wood, and bones. The abrasive edges of rocks are buffed down to smooth river stones over time. Couldn’t this have happened on a microscopic scale?

Yeah, I think it is certainly possible, even if the entire specimen, like OH 5, don’t show signs of massive weathering, we are talking about teeth that are very old. Teeth that were exposed could have been buffed out by other elements like wind, too. Suffice to say, many different things coulda happened to them to affect the degree of the abrasions. Comparing them to modern primate teeth is somewhat flawed because modern primate teeth haven’t been affected by the forces of nature for millions of years.

Ungar, P.S., Grine, F.E., Teaford, M.F., Petraglia, M. (2008). Dental Microwear and Diet of the Plio-Pleistocene Hominin Paranthropus boisei. PLoS ONE, 3(4), e2044. DOI: 10.1371/journal.pone.0002044

About a week ago, Michael from Greater Blogazonia broke the news of the World Atlas of Language Structures Online (WALS) database release. Following suite was Mark from The Ideophone, and Simon from HENRY. All three are lingustic anthropology focused blogs that I follow and trust, and they all praised this database. I’ve been poking around the database for the last seven days or so, and I’m really impressed. It is an awesome resource, executed really well, and under a creative commons license.

As I understand, the elevator pitch for WALS, is it is adatabase on all human languages. Over 2,500 languages are categorized. The structure of the database was compiled by phonological, grammatical, lexical data from over 50 different authors, which is a truly monumental effort. One of the coolest features is the integration of each language’s geographic origin using Google Maps. For anyone who wants to see where a language is spoken and what its relations are to neighboring languages, this visualization technique is perfect. For example, if you’re curious to see the distribution of and diversity of Indo-European languages, you’ll be presented with this index page:

I won’t rehash the excellent reviews done by other anthropology bloggerss, but I will close with what Mark of The Ideophone said,

“WALS Online is a formidable linguistic resource done well. It bears all the hallmarks of a well-executed web application that is here to stay for years to come.”

I humbly tip my hat to the people at the Max Planck Digital Library, and the authors who worked together to create this resource. As you may know, I’ve been working by myself to develop a similar project, but one that databases all the known hominin fossils. I’ve been working with integrating the Google Maps API into the project to show where fossils have been found, kinda to give an impression on the spread different hominids had. Synthesizing all the data is a monumental effort, and I’m impressed to see what WALS has done. I’ve got a lot to learn. I hope other anthropologists can see how great of a resource this is, and how releasing it under a liberal license, helps people learn and use the data.

In 1999, hunters looking for sheep stumbled upon the remains of a man in Tatshenshini-Alsek Park, British Columbia, Canada. The man was found at the foot of a glacier. After reporting the discovery, a team of archaeologists and forensic anthropologists worked with the Champagne and Aishihik First Nations to recover the remains. His affiliation wasn’t really well known.

Several months later, carbon dating on the hat and robe found on the man was completed. The remains of the man, named Kwaday Dän Ts’inchi, was calculated to be at least 340 years old. The closer interval of Kwaday was calculated to be 160 years old. That puts his death somewhere between 1670 and 1850 AD. Because many of these indigenous people in modern day Yukon and Alaska practice an oral tradition, this date didn’t help figure out which tribe Kwaday Dän Ts’inchi belongs too.

Since 1999, not much was heard from Kwaday. But, a symposium dedicated to Kwaday Dän Ts’inchi just wrapped up this weekend in Victoria. All sorts of research has been done on Kwaday, such as analysis of the clothing, tools associated, migratory patterns, even the contents of his stomach. People shared their studies at this symposium. The most interesting research shared was an analysis of the genealogy of Kwaday Dän Ts’inchi.

The genealogy was constructed by sampling some DNA from Kwaday’s remains. The results linked Kwaday Dän Ts’inchi to 17 living people. 15 of these people self-identify with the Wolf Clan, meaning the young man was may have been a member of the Wolf Clam as well. I don’t know which genetic loci was screened, I’m guessing a basic STR marker screen, the ones used in criminology, was done. I’d like to know what was done, because the thoroughness and robusticity of the test greatly effect the results. So does the comparison pool. Who were the outgroups? And how many people was the DNA compared too?

The news article reporting this doesn’t drop names about who did this study. A shame really, the author, Murray Langdon, discusses the ethics of working on and with Native Americans, but no mention was made to who did the genetic study. If you’re out there, mystery researcher, please comment and let us know how you analyzed and compared Kwaday Dän Ts’inchi ancestry.

Last month’s annual meeting of the Paleoanthropology Society hosted a talk by Amanda Henry, a graduate student at George Washington University. She analyzed the microfossils of plant material found in the dental plaque on Neandertal teeth from Shanidar, Iraq.

What is dental plaque? Much to the chargin of dentists out there, the composition and origin of dental plaque isn’t known to most. We may know it simply as something we work so diligently every morning and evening to brush away. Plaques are a type of biofilm. Bioflims are an amalgamation of microorganisms, who excrete a goo to protect themselves and allow them to stick together. Inside this gooey microecosystem, these crafty microorganisms also trap food particles to use as energy sources for themselves. If left untreated on teeth, these plagues of microorganisms grow and the amount of anaerobic respiration increases reciprocally. One of the byproducts of anaerobic respiration are acids which consequently demineralize adjacent tooth surface, and form cavities. That’s why you should brush and floss twice a day.

In September of last year, I shared news of how Neandertals may have also been aware of their dental hygiene. We saw how they may have used toothpicks. But, they didn’t have Sonicare toothbrushes and dental hygenists scraping away plaques every six months. Inevitably, some plaques persisted and in the teeth of a 35,000 year old Neandertal (Shanidar III). Amanda Henry was able to recover plant material. Henry gets into a discussion on how this showed evidence that Neandertals ate plants.

Not too novel, but definitely important to finally confirm. Much like the conclusion that Neandertals were mobile, plant consumption among them is one of those things we knew was most likely the case. How? Based upon the dental anatomy and morphology of the teeth, we knew they had very robust molars to grind down plant materials. Comparison to extant apes, like chimpanzees and humans, confers that Neandertals may have also been omnivorous. Furthermore, the results of a 2006 Science paper, an isotopic analysis of hominid teeth revealed that hominids ate a variety of foods.

I was gonna get into a discussion on how this one finding doesn’t mean all Neandertals died without brushing after a nice yummy salad meal. Nor does it elucidate how many times this Shanny-3 ate his greens. But, Henry acknowledges that and cautions that Shanidar III is only one fossil and does not provide enough evidence to make conclusive statements about the entirety of the Neandertal diet. I commend her on that. Even with this disclaimer, Matt Sponheimer, lead author of the 2006 isotopic analysis still wanted to have the last word, rehashing that,

“…[this study] does not indicate whether an individual Neandertal ate plants once or a thousand times.

It also doesn’t show the relative proportions of a food type in the individual’s diet.

“Thus it is but one flawed technique of paleodietary reconstruction among many,” he said.”

While we consider Matt’s critiques, let’s also consider one I thought of — The most simple explanation of the presence of plant material in plaques on the teeth means that this Neandertal chewed plants. Without an isotopic comparison of the recovered plant material to Shanidar 3′s teeth, we don’t know if this guy was really digesting the plant. Maybe Amanda Henry is looking into that…

One last thing, if Shanidar 3 really was eating plants, did his foot injury have anything to do with this? See, Shanidar III has a degenerative joint disorder in his foot. That woulda caused a lot of pain and limited his mobility. Would that have anything to do with why he was chewing on sedentary food sources?

Trinkaus, E. (1982). The Shanidar 3 Neandertal. American Journal of Physical Anthropology, 57(1), 37-60. DOI: 10.1002/ajpa.1330570107

Sponheimer, M., Passey, B.H., de Ruiter, D.J., Guatelli-Steinberg, D., Cerling, T.E., Lee-Thorp, J.A. (2006). Isotopic Evidence for Dietary Variability in the Early Hominin Paranthropus robustus. Science, 314(5801), 980-982. DOI: 10.1126/science.1133827

(GIS) are a critical aspect of modern day archaeological and paleoanthropological research. GIS systems expedite analyzing and managing large amounts of spatial data, and can really improve mapping locations where artifacts or fossils are found. Unfortunately, the price point and learning curve involved in using GIS applications, like ArchGIS make it an unapproachable technology.

An article in advance in the Journal of Human Evolution introduces how the most basic version of Google Earth can be easily used in lieu of other GIS software to display and share paleontological data. This is definitely not the first time we’ve seen news on how Google Earth has aided anthropological research, but it is one of the first times I’ve seen it be embraced in an academic, peer reviewed journal. So if you’re interested in how Google Earth can help you with managing your data, without having to invest a lot of time, effort, and money in complex GIS software, check this paper out: “Google Earth, GIS, and the Great Divide: A new and simple method for sharing paleontological data.”

The authors of the paper walk people thru how Google Earth can be used to map localities. They also ramp up the intensity, and introduce how Google Earth maps can have other maps overlaid, and how the KML files can be shared amongst people. Ultimately, they make the claim that Google Earth is the tool to disseminate paleontological information but they miss talking about some critical points.

First, Google Earth works best when connected to the internet. Unless you’ve downloaded all their maps to your computer and stored it in cache, you’re out of luck in using it in the field with no internet connection. That kills its utility for many field researchers. Also, the free version of Google Earth comes with lower resolution imagery that may not be good enough for many researchers. That’s why it hasn’t been fully adopted by the anthropological community… The gold standard seems to buy high resolution satellite or aerial imagery and map it using a higher end GIS software package.

Lastly comes concerns on how Google deals with your data. Google is known for being wanting to be the hub of entire internet, some people are cool with that. Some people aren’t. Paleontological and archaeological data is often sensitive data for a multitude of reasons and using Google’s product may not match well with how public you want your data.

Dienekes, Blaine, Razib, and Simon have all chimed in introducing us to a new paper from the American Journal of Human Genetics. It seems like a really interesting one, one that takes mtDNA to construct a phylogeny used to investigate what was happening to early Homo sapiens genetic diversity and populations within Africa. This study focuses on what was going on before the migrations out of Africa. The paper is titled, “The Dawn of Human Matrilineal Diversity,” and is open access. The research has already made it all the way onto some of my favorite news sources, such as Digg and Slashdot, but the big timers like CNN, BBC, the Economist, and the AFP are also carrying word.

The researchers constructed a mitochondrial phylogeny of 624 sub-Saharan individuals. They paid close attention to what’s going on with the phylogeny of the Khoisan, because previous research like Knight et al.‘s study on another loci, the Y-chromosome has shown that the Khoisan are carriers of oldest-diverging Y haplogroup, the Y-haplogroup A, indicating they may represent the deepest clade of modern humans. Recent research identified that the pygmy Khoisan populations share an ancestral and indigenous lineage of mtDNA with a neighboring population, the Bantu and this new study confirmed this.

The phylogenetic tree in this newer study is really informative. I’ve included it to the right. The researchers honed in on the mitochondrial haplogroup L, which is one of the oldest mtDNA haplogroups out there. The tree shows that early humans split into two small groups, demarcated by the L0 branch splitting from the L1’5 branch around 140,000 years ago. Based upon these two branches, the researchers were able to identify that one group was concentrated around eastern Africa (the L1’5 branch), while the other, the Khoisan’s L0 branch, in southern Africa. The sub-branches within the L1’5 clade represent all of the other L haplotypes in the entire remainder of humanity, including haplogroups of those that left Africa… further suggesting east Africa peoples were the main migrators out of Africa.

How could this happen? As populations of early humans migrated within Africa and reached southern Africa, they were cut off from the eastern African populations for a significant period of isolation to diverge into two separate clades. From ScienceDaily,

“Recent paleoclimatological data suggests that Eastern Africa went through a series of massive droughts between 135,000-90,000 years ago. It is possible that this climatological shift contributed to the population splits.”

The press is suggesting that this phenomenon indicated humans “started down the path of evolving into two separate species.” But that’s not true, they missed the part of the paper where populations came back together as a single, pan-African population about 40,000 years ago.

But, something is a little fishy, because as I already indicated, the coalescence calculations in this new paper indicate the Khoisan matrilineal ancestry diverged from the rest of the human mtDNA pool about 140,000 years ago. At that time, the five additional, currently extant maternal lineages (Haplogroups L1’5) existed in Eastern Africa, before the emergence of L0 branch. Looking at the phylogenetic tree, these haplogroups are more ancestral to the haplogroup L0 branch by at around 40,000 years, implying that the Khoisan may not be the deepest clade of living humans alive. This doesn’t match the Y-chromosome data, but we know already that mtDNA and Y-chromosome coalescent times aren’t the same… but this doesn’t match scores of other studies that indicate the Khoisan are a basal group of humans based off of their linguistic and cultural traits.

What this ultimately indicates is that eastern Africa may have truly been the cradle of humanity, at least the maternal cradle of modern humans. Which matches the fossil record, since some of the oldest remains of early human remains are also found in Eastern Africa, such as BOU-VP-16/1 and Omo 1 from Ethiopia.

BEHAR, D., VILLEMS, R., SOODYALL, H., BLUESMITH, J., PEREIRA, L., METSPALU, E., SCOZZARI, R., MAKKAN, H., TZUR, S., COMAS, D. (2008). The Dawn of Human Matrilineal Diversity. The American Journal of Human Genetics DOI: 10.1016/j.ajhg.2008.04.002

KNIGHT, A. (2003). African Y Chromosome and mtDNA Divergence Provides Insight into the History of Click Languages. Current Biology, 13(6), 464-473. DOI: 10.1016/S0960-9822(03)00130-1

Quintana-Murci, L., Quach, H., Harmant, C., Luca, F., Massonnet, B., Patin, E., Sica, L., Mouguiama-Daouda, P., Comas, D., Tzur, S., Balanovsky, O., Kidd, K.K., Kidd, J.R., van der Veen, L., Hombert, J., Gessain, A., Verdu, P., Froment, A., Bahuchet, S., Heyer, E., Dausset, J., Salas, A., Behar, D.M. (2008). Maternal traces of deep common ancestry and asymmetric gene flow between Pygmy hunter-gatherers and Bantu-speaking farmers. Proceedings of the National Academy of Sciences, 105(5), 1596-1601. DOI: 10.1073/pnas.0711467105

A week ago, I shared with you news of Bill Jungers’ conclusions on how the morphology of the Homo floresiensis foot affected its locomotion. Science has dedicated a short two page ditty on this topic and you may wanna check it out for a more authoritative take on it.

In other related Homo floresiensis news, John Hawks was contacted by Peter Brown who wanted to share his response to the claims that the LB1 specimen showed signs of recent dental work. I didn’t share this news, which first really emerged in Kate Wong’s Scientific American blog post, because I felt it was as absurd as the analysis done by Obendorf et al. last month.

The news really emerged from Maciej Henneberg proposition that the mandible of LB1 appears to have a filling, possibly a root canal, in its lower left first molar. This was all based off of a photograph and that would indicate it is a modern human. We all know from Obendorf et al.‘s research how flawed it is to analyze a photograph or screen capture.

Peter Brown supplied a relatively high resolution of the LB1 mandible and I can’t see any indication for a filling on the occlusal surface of any of the teeth, let alone the first molar on the left side.

Furthermore, CT scans of the jaw show no modification either. So, its a dead end line of inquiry. Simple as that.

Culotta, E. (2008). PALEOANTHROPOLOGY: When Hobbits (Slowly) Walked the Earth. Science, 320(5875), 433-435. DOI: 10.1126/science.320.5875.433

Pardis Sabeti, one of my favorite Iranians and anthropologists out there, has a news focus dedicated to her in the latest issue of Science. You should check it out if you wanna get to know a little bit more about her and her current research focus.

For those that don’t know who she is, she holds a M.D/Ph.D dual degree from Harvard where she graduated with highest honors. Pardis Sabeti did her undergraduate work in MIT. In between, she also was a Rhodes Scholar at Oxford. She’s spent a significant amount of time studying human evolution and has over 20 publications to her name and is currently a professor at Harvard.

Her most impactful papers have been “Genome-wide detection and characterization of positive selection in human populations,” “Linkage disequilibrium in the human genome,” and “Detecting recent positive selection in the human genome from haplotype structure.” Combined, all three papers have been cited a total of over 1,300 times.

She’s best known for work in developing the LRH and XP-EHH tests which detect genetic variants under positive selection. They help us with estimating the ages of alleles to reconstruct the mode and tempo of evolutionary change. Because of this, she’s been called by CNN as one of the “Geniuses who will change your life,” and I hope that in my lifetime she will be recognized with a Nobel prize. We’ll see about that.

But if you’re into human evolutionary biology and want to understand the rate of human evolution, you should definitely track Sabeti’s work. You may also wanna check out this interview of her.

Balter, M. (2008). PARDIS SABETI PROFILE: Picking Up Evolution’s Beat. Science, 320(5875), 442-443. DOI: 10.1126/science.320.5875.442

Almost all primates live in groups with an observable and definable social hierarchy, and humans aren’t an exception. We may overlook it in our day to day lives, but every so often it becomes evident that we interact best when we understand the pecking order. The social brain hpyothesis argues that the cognitive demands of living in complexly bonded social groups selected for increases in executive brain. Two new papers in the current issue of the journal Neuron investigate this phenomenon by looking at the activity in specific regions of the brain, like the striatum, which reflects a common signal of reward in both the economic and social domains.

The research was conducted by researchers at the National Institute of Mental Health. fMRI was used to monitor the activity of the brain of 72 participants who were playing an interactive computer game for money. From this press release,

“They were assigned a status that they were told was based on their playing skill. In fact, the game outcomes were predetermined and the other “players” simulated by computer… Participants intermittently saw pictures and scores of an inferior and a superior “player” they thought were simultaneously playing in other rooms.

Although they knew the perceived players’ scores would not affect their own outcomes or reward –and were instructed to ignore them – participants’ brain activity and behavior were highly influenced by their position in the implied hierarchy.”

Several interesting observations where made when the researchers compiled all the fMRI data. For example, the striatum showed activity in a situation where a rise or fall in rank was a possibility as much as it did to the monetary reward. The stratium is a critical part of the brain where dopamine is regulated, and a previous study investigated the genetics of dopamine and the linkage it had to agressive social behaviors. Overall, this observation implies that social status is highly valued in our subconscious minds, even as much as money. The press is gorging itself on this sound bite, they just love it when something as complex as social hierarchy and brain functions are reduced to something as simple as gaining money.

Another interesting observation involved subjects that were presented a ‘superior competitor’ in the game. When that happened, it triggered activity in,

“an area near the front of the brain that appears to size people up – making interpersonal judgments and assessing social status. A circuit involving the mid-front part of the brain that processes the intentions and motives of others and emotion processing areas deep in the brain activated when the hierarchy became unstable, allowing for upward and downward mobility.”

Also when the player preformed better than any superior competitors, another area towards the front of the brain which controls planning was activated. In contrast, when the player did worse than an inferior competitor different activity was shown in centers of the brain associated with emotional pain, frustration, and stress. Pretty cool.

One last cool results was associated with players who were at the top of the hierarchy, not only did they say they had a more positive experience but more activity was associated in the emotional pain circuitry when they perceived an outcome that could drop them down in rank.

These results kinda thwart any Utopian anarchists out there. This data shows that our brain’s hierarchical consciousness seems to be ingrained in the human brain, so much so that there are distinct circuits activated by concerns over social rank.

Coinciding with these two studies is this short little paper in the latest Nature investigating the genetics and expression of Neuropeptide Y (NPY). Neuropeptide Y is just that a peptide that functions as a neurotransmitter, it is involved in regulation of energy balance, memory and learning. In mice and monkeys, it has been observed that stress stimulates the expression of this gene product. That’s not very surprising because Neuropeptide Y alters adrenergic receptors, the ones that bind adrenaline and noradrenaline, two stress hormones. As seen in the above results, stress is an important behavioral response in social hierarchy.

Anyways the new Nature study finds that,

“haplotype-driven NPY expression predicts brain responses to emotional and stress challenges and also inversely correlates with trait anxiety… Lower haplotype-driven NPY expression predicted higher emotion-induced activation of the amygdala, as well as diminished resiliency as assessed by pain/stress-induced activations of endogenous opioid neurotransmission in various brain regions. A single nucleotide polymorphism (SNP rs16147) located in the promoter region alters NPY expression in vitro and seems to account for more than half of the variation in expression in vivo. These convergent findings are consistent with the function of NPY as an anxiolytic peptide and help to explain inter-individual variation in resiliency to stress…”

Like I said above, I’m pretty sure we’ve all had experiences where we felt threatened by inferior individuals and we’ve all had the glee when we thought we were at the top of our game. The fMRI study has shown what areas of the brain are active in these situations, and the genetics of NPY indicate how the allelic differences of NPY affect stress responses. All in all, I’m impressed with these trio of papers. They illuminate a lot about how we subconsciously process social hierarchy, which is a very human thing.

Zhou, Z., Zhu, G., Hariri, A.R., Enoch, M., Scott, D., Sinha, R., Virkkunen, M., Mash, D.C., Lipsky, R.H., Hu, X., Hodgkinson, C.A., Xu, K., Buzas, B., Yuan, Q., Shen, P., Ferrell, R.E., Manuck, S.B., Brown, S.M., Hauger, R.L., Stohler, C.S., Zubieta, J., Goldman, D. (2008). Genetic variation in human NPY expression affects stress response and emotion. Nature, 452(7190), 997-1001. DOI: 10.1038/nature06858

The latest edition of the anthropology blog carnival Four Stone Hearth is now up and ready to be read – as ever we are offered a very nice mix of writing from around the anthropological zone of the blogosphere.

The next edition will be at remote central on May 9th – so for now, many thanks to Jason for putting this one together.