Anthropology.net

In 2010 the draft genome for Neandertals was released by Svante Pääbo and colleagues. It was reported that European and Asian populations are between 1-4% Neandertal—but what percentage Neandertal are you?

Researcher extracts DNA from a Neandertal specimen

The company known as 23andMe recently released an analysis that claims to answer precisely this question. While personal genome sequencing has not yet hit the mainstream market, 23andMe looks at SNPs, or variations in single nucleotide pairs. Through a comparison between your SNPs and those found in the Neandertal genome draft, for a couple hundred dollars you will be given a percentage. The service has been given the name “Neanderthal Ancestry Estimator.”

Computational biologist Eric Durand developed the project, and has previously worked on both the Neandertal genome draft and Denisova genetics.

I encourage you to take a look at an outline of the methodology, online in a white paper. Are we really at the point where a private company can tell us a likely percentage of our Neandertal ancestry for $207? I’ll let you be the judge.

By Matthew Magnani

Last week at the Royal Society in London, research was presented suggesting that Neandertals not only interbred with H. sapiens sapiens, but that their genes were helpful to modern people moving out of Africa.

This pioneering study was led by Peter Parham of Stanford University, and was only possible after the draft genome of H. neanderthalensis was published. The researchers looked at human leukocyte antigens (HLAs), genes important to the functioning of the immune system.

Different regions of the world are known to have unique HLAs, because different variations create specific disease resistances. It would have been advantageous for the earliest modern humans to breed with a species (or subspecies) already adapted to living in a different climate. Moderns could have picked up helpful genes that were already in existence from Neandertal populations, which would have possibly allowed their populations to expand more rapidly. Why wait for random mutation when you can interbreed with a people already successfully adapted to an area?

Neandertal Child Reconstruction

While only approximately 6% of the modern European genome was contributed from earlier hominins, around half of specific HLAs can be attributed to these earlier forms of people. As a form of further substantiation, Europeans have HLA variations present within the Neandertal genome not found in Africans. Interestingly, Asian populations today also have a variation not present anywhere else, which could indicate Denisovan (mystery Siberian hominin) admixture.

As if the draft sequence showing interbreeding was not enough last year– this study has raised the bar on the type of information we can hope to glean from looking at ancient DNA. There was a time when archaeology and anatomy were the only windows we had into our ancestral relatives. It will be exciting to see what is uncovered next.

By Matthew Magnani

Very rarely is an entire family group of hominins buried and fossilized at the same time. It is even rarer for paleoanthropologists to discover such an assemblage. Fortunately for science but unfortunately for the hominins, caves occasionally collapsed on entire social groups.

Map of El Sidrón

At a site known as El Sidrón in Spain, excavations have been ongoing since 2000. To date, 12 Neandertals have been discovered in a context that points to a single geological event, circa 49,000 years ago. A group of 12 Neandertals is consistent with previous estimates of around 10 individuals per group.  At least six adults, three adolescents and four younger individuals were buried at once, most likely during a storm. The cold conditions of the cave system and immediate burial of the remains not only preserved the bones well, but were also ideal for DNA.

The remains were sexed based on both morphology and DNA analysis. After sex was determined, anthropologists identified the different Neandertal lineages based on mitochondrial DNA. Several of the adults were found to be male, and the other three female. It was discovered that all three males belong to the same matrilineal group, while each respective female has a different haplotype. When compared to modern Europeans, the authors noted that there is significantly less genetic diversity within the mitochondrial genome.

These results strongly imply that Neandertals exhibited patrilocal mating behavior. Females were the ones who would have changed family groups, not males. This type of insight into an extinct species is unique, thanks to the quality of DNA preservation available at El Sidrón.

Another interesting point of discussion in the study relates to Neandertal interbirth interval. One of the females was linked by DNA to two of the younger individuals, approximately several years apart in age. If the anthropologists are correct about the relationship, this puts the interbirth interval for Homo neanderthalensis at a value similar to hunter-gatherer groups today. This data, if replicated with other Neandertal individuals, could eventually dispel differential reproduction as a potential cause for Neandertal disappearance.

Knowing about Neandertal group dynamics could provide crucial clues as to why they went extinct. Future analysis of the remains recovered at El Sidrón will no doubt give more insights into our closest extinct relatives, and perhaps even why Homo sapiens flourished and Neandertals declined.

By Matthew Magnani

Lalueza-Fox, C., et al. (2011). “Genetic evidence for patrilocal mating behavior among Neandertal groups.” PNAS . January 4, vol. 108 no. 1 250-253.

Neandertals have long been touted as a species with “hyperarctic” adaptations. Their stout proportions and shortened distal limb segments are often explained to conserve heat. Similarly, the Neandertal cranium is traditionally said to be cold adapted. An article released on December 22^nd in the Journal of Human Evolution challenges these traditional notions, specifically those about Neandertal nasal adaptations.

The Neandertal nasal apparatus has conventionally been cited as cold adapted mainly because of the enlarged sinuses. The authors of this article, among them Chris Stringer, cite evidence that larger sinuses are not in fact typical of cold weather mammalian species.

Through observation of human populations and studies on other mammals, cold weather is more highly correlated with smaller sinuses. That is, animals from more northerly locations typically have smaller sinus cavities. As an example taken from lab studies, rats raised in colder conditions also show smaller sinus cavities.

But are Neandertal sinuses even large, as is typically maintained? The authors of this paper argue that there is nothing large about them. Through examination of Neandertal remains, the sizes of the frontal and maxillary sinuses actually fell within the range of Homo sapiens from temperate climates.

The Forbes’ Quarry Neandertal (left) and H. sapiens skulls. Frontal sinus in purple, maxillary sinus in red. Photo from Rae et al., 2010.

This study is very suggestive that Neandertal nasal anatomy is not due to cold weather adaptation. To be cold weather adapted, the sinuses would be smaller and not larger, as many anthropologists have maintained since the first remains were discovered. Not only are the sinuses not small, they are not large- which speaks to a larger problem. How many other basic assumptions do we take as fact just because they have been around for so long?

If not cold weather, what could have caused the differences in facial anatomy between H. neanderthalensis and H. sapiens? The authors of this paper do not offer many answers, but offer a couple of possibilities. Differences in masticatory stress (utilizing teeth as a tool, for example), or genetic drift are two potential reasons discussed.

This paper may be taking another step in overturning traditional understanding of Neandertals as a cold weather species. Generations of anthropologists have passed knowing that Neandertals differed in facial anatomy due to cold weather adaptation, unsubstantiated by data.

Rae, T.C., Koppe, T., Stringer, C.B. (2010).  The Neanderthal face is not cold adapted.  The Journal of Human Evolution. Article in Press.

Several views of a human jawbone and molars found in a Chinese cave.

National Geographic is running news that Erik Trinkhaus and others have published the findings of the oldest modern human outside of Africa, specifically in China. Not much is given on the locality and specifics of the fossil, but the article does state that the fossil mandible fragment and teeth are 60,000 years older than any other modern human fossil. That leads to some curious questions of interbreeding with other Homo species and curiosities about the presence of modern humans that did not ‘act’ modern… In other words, the archaeological record isn’t quite on the same page.

Hawks hasn’t posted on the paper and find yet, but he is quoted in the National Geographic article saying the mandible dimensions are within range of both Neandertals and modern human. Unsurprisingly, the Out of Africa theory is challenged. I still don’t know what to think of it all, the chin does look very robust.

The PNAS article is not yet published at the time of the National Geographic writing and me blogging this post. Seems like people are still jumping publication embargoes. I shouldn’t have to call out what a cheap shot it is to have sensationalist news getting out before the first hand reports do. I guess things will never change. So until I get my hands on the real paper, I’m just calling it as others are reporting it.

Every time big anthropology news has come out in the last year or so, I’m too busy and drowned under the sea of books and notes for my upcoming exams to immerse myself in it. This happened with Ardipithecus last fall, and now with the draft of the Neandertal genome coming out tomorrow, I can’t help but feel a bit left out. The complete mitochondrial Neandertal genome was released a little under 2 years ago… and now because of high throughput sequencing technology, the draft genome is now complete.

Currently, Science has put up a special section of their website dedicated to this. The news agencies are having issues with embargoes and what not, they put up articles and then take them down. But the word is out, Green and Pääbo’s project to sequence the Neandertal genome is out and there are some interesting findings:

• The comparison of 3 Neandertal samples to 5 modern human genomes showed that Neandertal genome is closer to some populations of modern humans than others
• About 10 loci had distinctly non-African hallmarks
• There’s an attributable 1-4% Neandertal ancestry to non-African modern human populations

There’s a lot more behind this all than I really have time for, unfortunately. So be sure to check out Razib, John Hawks, etc. for all the goodies.

Bergmann’s rule is an observation that body mass of endotherms increases with altitude and colder climate. Neandertals fit this rule, their barrel chests and wide hips, indicate they had large bodies, and thus smaller surface area relative to their body mass. This feature made them comparatively inefficient at radiating their body heat off into the surrounding environment than smaller bodied hominins…. which is an advantageous trait to have in cold environments.

Another similar theorem, Allen’s rule, summarizes the observation that endotherms from colder climates usually have shorter limbs compared to counterparts from warmer climates. Similar to Bergmann’s rule, shorter limbs keep blood and heat closer to the core of the body, reducing heat loss.

All this may sound like adaptionist mumbo-jumbo, but researchers have observed these adaptations to cold climate in other animals. Compare the profiles of polar bears, walruses, and mammoths to cheetahs, antelopes, and giraffes, and you’ll see how some of this makes sense.

Homo neanderthalensis from la Chapelle aux saints

Anyways, I digress. There are two different camps currently hashing out whether the Neandertal facial morphology is due to random genetic drift or a mix of archaic traits and climate influenced adaptations. One of the more hotly debated facial traits, the Neandertal nose, doesn’t quite fit what we expect to see in cold climate adapted species. The Neandertal nose is broad and wide, a feature seen in tropical climates. Physiologists have shown that narrow noses better warm the air being inhaled and prevent evaporation of water in such dry environments by recapturing moisture during exhalation. Wide noses dissipate heat very efficiently.

Some researchers, like Milford Wolpoff, have suggested that there’s a growth and development reason to why we don’t see narrow Neandertal noses. For example, the effects of large teeth and broad palates could have affected the reduction of the nasal aperture, and were most likely inherited traits from Pleistocene ancestors. In a new Journal of Human Evolution paper that Dienekes pointed out this week, researchers from the University of Iowa have investigated the relationships between nasal breadth, intercanine breadth, and facial prognathism. The paper is titled, “The paradox of a wide nasal aperture in cold-adapted Neandertals: a causal assessment.” They tested variants of the following hypothesis: Does the distance between the two upper canines correlated with nasal breadth in modern and archaic Homo?

Intercanine Breadth Measurement

Their sample set of modern humans included 119 crania of Bantu people and 112 crania of Western Europeans. The sample of human ancestors included 11 from the early Upper Paleolithic, 9 from the late Upper Paleolithic all coming from Eurasia. They also included 15 samples from the late Stone Age in Africa, and 14 Pleistocene Homo. Like I mentioned earlier, they measured the distance between the two canines, known as the ICB. In anatomical terms that’s the distance between the lingual tubercles of the maxillary canines, or the pointy parts of your vampire teeth. The lower facial prognathism (BPL) is a measurement of basion to prosthion. Upper facial prognathism (BNL) is a measurement of basion to nasion. Of course some fossils didn’t have all the measurements so predictions were made by least squares regression.

The authors conclude that intercanine breadth cannot fully explain nasal breadth from their sample set, which goes against what anatomist Gustav Schwalbe said in the later 1800′s and what E.V. Glanville reconfirmed in the late ’60s. They also note that the development of the anterior palatine bone does not affect the growth trajectory of the breadth of the nose. While, they do suggest that nasal breadth is affected by the ICB, the lower facial prognathism impacts nasal breadth more than any other trait.

They finally suggest that the plesiomorphic retention of a prognathic lower face is due to the extended time the premaxillary sutures remain open during development. This is lower face prognathism is not a derived trait, but rather a retention of archaic traits, seen in early humans. But that’s not to say the Neadertal nose never adapted to cold climates while the rest of their body did. Neandertals from colder climate have been characterized with a more narrow superior nasal dimensions, which have ultimately been linked to aspects of airflow dynamics.

N HOLTON, R FRANCISCUS (2008). The paradox of a wide nasal aperture in cold-adapted Neandertals: a causal assessment Journal of Human Evolution DOI: 10.1016/j.jhevol.2008.07.001

Dienekes pointed out another interesting paper that I want to share with you, this time on Neandertals and evidence of the Uluzzian Industry as seen from the Fumane Cave in Italy. The paper was published by Marco Peresani in the journal Current Anthropology, under the title, “A New Cultural Frontier for the Last Neanderthals: The Uluzzian in Northern Italy.” Persani describes the archaeological assemblage of the 11 layers of Fumane Cave, of which the oldest layers, 11 through 5 are Mousterian typology and the latest, 2-1 are Aurignacian. Layers 4-3 are Uluzzian, and date right at a critical transition period during human evolution — the time at which Neandertals are thought to have gone extinct in Europe (around 30,000 years ago).

The term Uluzzian was coined by Palma di Cesnola in 1988 after the observed assemblages from sites around the Bay of Uluzzo, found on the Ionian Coast. Julien Riel-Salvatore, the blogger behind A Very Remote Period Indeed, studied the Uluzzian technology and has in fact published or presented several pieces on the emergence of the Uluzzian during the transitional period of the Middle to Upper Paleolithic.

The Uluzzian is characterized from the Mousterian by larger stone tools, some bone items others splintered cores (perhaps bidirectional cores), lots of unidirectional or bidirectional cores, few burins, end scrapers, side scrapers, etc. In general, a modest modernization of the Mousterian. Some of the most famous Uluzzian sites are La Fabbrica, Castelcivita, La Cala, Grotta Brenardini, Grotta di Uluzzo (the namesake site), Grotta del Cavallo all of which are found in Italy. The Vindija cave in Croatia and the Klisoura cave in Greeze are also considered Uluzzian sites. Fumane Cave is the northernmost, now-understood-to-be Uluzzian site.

Figure 3 from the paper. Uluzzian implements found in units 3 and 4: splintered piece (1), backed knives (2, 3, 6), implement with curved back (5), bladelet core (4) (drawings by S. Muratori and G. Almerigogna).

The animal remains found in the older, deeper Mousterian levels, such as ungulates and macromammals suggest that the inhabitants regularly hunted animals found in moist/cool ecosystems… perhaps an alpine environment. Like I mentioned, layers 4-3 represent a different tool set, as if the inhabitants were (desperately?) experimenting with different technology which was replaced with the distinctly different Aurignacian formal blades and retouched tools soon after. The authors also suggest that Fumane wasn’t persistently occupied during the layer 4-3 period. All of which suggests that these last Neandertals were trying very different cultural items. Why? They had perfectly find tools… or did they?

Marco Peresani (2008). A New Cultural Frontier for the Last Neanderthals: The Uluzzian in Northern Italy Current Anthropology, 49 (4), 725-731 DOI: 10.1086/588540

Zooarchaeology is an anthropological sub-discipline which focuses on studying animal remains from archaeological sites. Animal remains can tell us a lot of about prehistoric peoples’ diets and behavioral tendencies as well as the ecological makeup of the area. A new PNAS paper investigates the zooarchaeological record of two Neandertal sites in Gibraltar, Vanguard and Gorham‘s Caves.

The paper, “Neanderthal exploitation of marine mammals in Gibraltar,” is authored by some familiar names such as Chris Stinger and J.C. Finalyson and Nick Barton, and the major conclusion is that the presence of mollusks, seal, dolphin, and fish from such sites suggests that Neandertals exploited a wide variety of foods — hammering yet another nail in the coffin of the Neandertals were dumb cavemen train of thought. John Hawks and Dienekes have both written that this research is yet another line of evidence in the modernization of Neandertal behavior.

The cave sites are part of the Gibraltar Caves Project, which began in 1994. Annual excavations followed the year after. The sites are located on the southeast side of the Rock, on Governor’s Beach. As far as I can tell, GPS coordinates were not provided. I’ve tried to track down the exact location of the sites but have found conflicting information. But the BBC has provided an image of the sites, by way of the Gibraltar Museum. The two sites are adjacent to each other and the Gibraltar Museum has dutifully also provided a prehistoric view of the sites when sea levels were much lower:

Gorham's & Vanguard Caves on Governor's Beach, Gibraltar.

Gorham’s Cave site indicates three distinct occupations. There’s an Upper Palaeolithic occupation with dates spanning 26-30,000 years before the present (BP). There’s another distinct layer containing the youngest Middle Palaeolithic and dated at around 31-32,000 BP, and a third, older Middle Palaeolithic layer which is underneath. This older layer is dated to 45,300 ± 1,700 years BP. Vanguard Cave shows similar patterns with radiocarbon dates of 45,000 years BP and similar lithic assemblages.

Cut marks from a Mediterranean Monk Seal finger bone found in Vanguard Cave

Vangaurd Cave has yielded evidence of Mediterranean monk seal (Monachus monachus) phalanxes with cut marks and lots of mollusk shells. The minimum number of mollusks found isn’t provided but the authors do say that a particular layer was dominated by mollusk shells. Additionally the concentration of knapping debris and Mousterian stone tools, along with a hearth, from this layer suggest that Neandertals were having a prehistoric cioppino feast.

Additional remains of ibex, red deer, boar, bear, along with dolphins birds, tortoises indicate that these prehistoric people were exploiting a wide variety of food sources. Roughly 50% of the animal remains were cut or burned, and a lot of the rest show percussion marks and fractures. Compared to Neandertals from Northern Europe, who sustained a diet of big game meat such as mammoth, deer and horse, these guys from Governor’s Beach had a different diet. Stringer told the BBC that these caves tell us that we can’t generalize Neandertals.

C. B. Stringer, J. C. Finlayson, R. N. E. Barton, Y. Fernandez-Jalvo, I. Caceres, R. C. Sabin, E. J. Rhodes, A. P. Currant, J. Rodriguez-Vidal, F. Giles-Pacheco, J. A. Riquelme-Cantal (2008). From the Cover: Neanderthal exploitation of marine mammals in Gibraltar Proceedings of the National Academy of Sciences, 105 (38), 14319-14324 DOI: 10.1073/pnas.0805474105

I’m back to internet land a bit earlier than expected and even though I’ve got several thousand unread items in my RSS reader, hundreds of emails and photos to sort through, I’ve stumbled upon some really interesting news first shared by Dienekes that I just had to pass on: A reconstruction of a Neandertal’s face using DNA and morphometrics.

Physical anthropologists often argue that the bones tell us how an organism looked like. Based off the morphology of the bones, we can estimate the structure of faces and bodies. Forensic anthropologists use this to help put a face to the remains of a decomposed murder victims. Paleoanthropologists have also used this technology to illustrate how human ancestors may have looked like. But we haven’t been able to strictly rely on morphometrics to illuminate the color of a person’s skin or hair. There’s just too much variation in skeletal morphology to make such correlations.

Advances in ancient DNA analysis like last year’s identification of a Neandertal carrying the allele for red hair, have helped us pinpoint more finer details in the phenotype of prehistoric human ancestors that can’t be resolved by measurements of bones alone. In a hodepodge synthesis of morphometerics and genetics, the National Geographic has analyzed the remains of 43,000 year old cannibalized Neandertals and created an image of what a Neandertal may have looked like.

Dubbed as Wilma, the NGS has created a documentary about the reconstruction process called the Neandertal Code, which airs Sunday, September 21st, 2008 at 9 p.m.

From what I can make of the anouncement, the reconstruction seems like more of an artistic endeavor than a scientific one. The skeleton was reconstructed based off of the bones of several female individuals, and when they didn’t have certain elements, male versions were scaled down. Also, it is uncertain what 43,000 year old specimens from this assembly of bones was used to figure out that this individual had red hair, fair skin and green-ish eyes. It is certainly possible that some elements came from darker Neandertals. Nevertheless, it is interesting to see how ancient DNA is being used to complement the reconstruction phenotypes of human ancestors.

Related to this, is an open access analysis of Neandertal brain size and development that has popped up in yesterday’s issue of PNAS. Using the remains of 3 Neandertal toddlers from Mezmaiskaya Cave in Russia and  Dederiyeh Cave in Syria, the authors of the paper conclude that the Neandertals shared similar brain sizes at birth to Homo sapiens, but brain growth rates during early infancy were higher which resulted in larger adult brain sizes but not necessarily earlier completion of brain development. I’ll try to give this paper a more thorough treatment once I take care of the mound of backlog. But you should check it out since it is free, “Neanderthal brain size at birth provides insights into the evolution of human life history.”