Anthropology.net

Monte Verde, Chile is a very interesting archaeological site. First discovered in 1976, the site is about 500 miles south of Santiago and has yielded artifacts of a small settlement of 20 to 30 people living in a dozen huts along a small creek. Aside from artifacts, a wide variety of midden has also been unearthed from the site indicating these people survived on extinct species of llama, gomphotheres, shellfish, vegetables and nuts.

In 1979, Tom Dillehay conducted radiocarbon dating of the bones and charcoal found at Monte Verde. The results were shocking at the time. The dating of the organic materials was at 14,000 years before the present. This conflicted with other archaeological evidence of the settlement of North America, such as the artifacts that supported Clovis theory… none of which had dates earlier than 13,000 years ago. To have people living in Chile 14,000 years ago would have meant that people arrived in the Americas earlier than 13,000 years ago. Lots of people rejected the radiocarbon dating because of it challenged the Clovis theory. It wasn’t until 1997 that archaeologists reviewed the evidence, visited the Monte Verde site, and approved of the date.

Since then, lots of other evidence, such as genetics and more artifacts have helped provide more understandings on the mode and tempo of the peopling of the Americas. I’ve covered some of the recent evidence. If you’re interested in reviewing them, check out this collection of blog posts related to the peopling of the Americas.

Today’s Science has published a new report from Monte Verde, authored by Tom Dillehay and others. The paper, “Monte Verde: Seaweed, Food, Medicine, and the Peopling of South America,” announces the discovery of the remains of nine species of seaweed and algae found from hearths in Monte Verde. Radiocarbon dating of the layer yielded a date of 14,220 and 13,980 years ago… which is right in line with the 1979 dates.

The finding of seaweed and algae in Monte Verde is a curious one, and what makes this paper unique. See, Monte Verde is about 10 miles away from the ocean. The authors interpret that the seaweed and algae was of some value for the people of Monte Verde for them to haul it inshore… Perhaps it was used for food or medicine?

Who knows, really? What we can interpret from this evidence is that prehistoric people stuck to the shore. Sticking to the shore woulda made traveling throughout the Americas much more efficient, according to some scholars who subscribe to the coastal migration hypothesis. The general view of this hypothesis is that the early immigrants would have spread down the coast much faster than they could move inland because they could exploit familiar coastal resources more readily and get much of their food from the sea. Not much evidence has been found to support this hypothesis, partially because sea levels are 200 feet or so lower 14,000 years ago than they are right now. Any seaside sites would have been covered up as the ice melted after the last ice age. Finding seaweed from site like Monte Verde indicates that 14,000 years ago people relied on some sea life, and kept relatively close to the shore even though they established a rather permanent settlement inland.

From my personal experience with hiking the Santa Cruz mountains as well as working at an archaeological site in the Monterey Bay, I too have seen evidence that prehistoric peoples were relying heavily on sea life for food. Often, I’ve found mussel shells deep within the forest. I have also seen how people were regularly hunting fur seals from a rookery.

Dillehay, T.D., Ramirez, C., Pino, M., Collins, M.B., Rossen, J., Pino-Navarro, J.D. (2008). Monte Verde: Seaweed, Food, Medicine, and the Peopling of South America. Science, 320(5877), 784-786. DOI: 10.1126/science.1156533

Perhaps the biggest anthropology news of this week has been the analysis of ancient DNA from fossilized human poop found in 14,000 year old cave in Oregon. The paper, “DNA from Pre-Clovis Human Coprolites in Oregon, North America,” was published in this recent issue of Science. Even though the study is literally based off of crap, it is a significant find for those interested in the peopling of the Americas.

The current consensus, that the Americas was originally populated by peoples from Siberia and north east Asia, has been based off of comparing and contrasting sequences of DNA from modern day people. While the evidence for this conclusion is overwhelming, it does have one flaw — if there were people from other origins, say from Europe, who died off and did not integrate into the original gene pool, their genetic impact may not be detectable by comparing and contrasting modern DNA sequences. This is where this brand new study really shines.

By studying ancient DNA, the authors potentially had the possibility of detecting any impact of non-Siberian DNA which may have not made it into modern day populations. But that wasn’t found. Instead, the null hypothesis was confirmed — the DNA extracted from coprolites links these people from prehistoric Oregon to two genetic groups of early Americans that moved from east Asia 18,000 years ago. mtDNA was only screened in this study, and not Y-chromosomal or other nuclear DNA loci for several reasons. First off, there’s many more mitochondria in a cell than a nuclei and since discarded red blood cells (who have no nuclei) are found in fecal material, that’s the primary reason it was the only genetic loci screened. mtDNA is also circular, and many think that physical confirmation make it more stable, and less prone, to degradation compared to linearized nuclear DNA which has ends exposed to the elements.

The study actually involved extracting mtDNA from 14 coprolites, which were found in the Paisley caves in 2002 and 2003. Dennis Jenkins led the excavations, he is also one of the co-authors of this current paper. I’m curious in looking deeper into how the researchers purified their ancient DNA. If you don’t remember, there was a recent paper that used ion-exchange columns to purify DNA and remove inhibitors that affect downstream amplification and sequence comparison. Anyways, I’m sure they did a good job.

The coprolites resembled human crap, but unfortunately, according to Thomas Dillehay, they may have not been excavated under sterile conditions and coulda definitely been contaminated by modern human DNA. This is a serious issue to consider when dealing with ancient DNA studies. The DNA of any persons who handled the fossilized crap coulda been inadvertently placed on the sample. I don’t know if any Native American’s were part of the dig, or handled the poop, but since no European DNA signatures were detected and six signatures were confirmed to be Native American only, I think it is safe to conclude that the excavators/curators probably did not contaminate the fossil poo. A similar concern was raised last August, when ancient DNA was analyzed from 2,000 year old chewing gum.

But what about people who occupied the site for the last 14,000 years? Gary Haynes also raises a criticism… Anyone who chose to urinate in the Paisely caves may have contaminated the samples too. Very vivid imagination, Dr. Hayes. Surely that’s a possibility. Over 14,000 year it coulda happened… anyone spitting in the saves and on these samples woulda also done the same. But I imagine there would have to have been a lot of peeing and spitting events that to contaminate 6 spatially separated samples (only 6 coprolites yielded DNA). If they caves were occupied, which I don’t know much about them, over time that possibility becomes more real.

John Noble Wilford, of the New York Times, writes that this find supports an earlier date of people in the Americas. I think that’s a bit misleading… like I mentioned very recent studies, such as this one and this one, have already estimated a temporal distribution of people across Beringia and into the Americas. They did so based upon coalescent theory, which is an indirect method. This study also relied on coalescent theory, but used much more ancient samples, therefore making it a bit more direct.

So, what about Clovis? How does this find affect the understandings of origins of the Clovis culture? The Clovis culture is thought to have emerged in the Americas around 13,000 years ago. If these fossilized crap piles aren’t contaminated, this shows that people where on the North American continent at least 1,000 years before the well-known Clovis people. During this time, it is possible these people could have been indirect or direct ancestors of the Clovis people and influenced the emergence of new archaeological technology associated with Clovis peoples. I suggested that recently.

Balter, M. (2008). ARCHAEOLOGY: DNA From Fossil Feces Breaks Clovis Barrier. Science, 320(5872), 37-37. DOI: 10.1126/science.320.5872.37

Gilbert, M.T., Jenkins, D.L., Gotherstrom, A., Naveran, N., Sanchez, J.J., Hofreiter, M., Thomsen, P.F., Binladen, J., Higham, T.F., Yohe, R.M., Parr, R., Cummings, L.S., Willerslev, E. (2008). DNA from Pre-Clovis Human Coprolites in Oregon, North America. Science DOI: 10.1126/science.1154116

National Geographic News has just published an article about the recent symposium in Alaska regarding a possible connection between Yeniseic languages in Siberia and Na-Dene languages in the Americas. John Roach’s article, Siberian, Native American Languages Linked — A First, highlights the recent work of Edward Vajda, who defended his connection during the February symposium. Vajda goes deeper than cognate lists in his parallels, providing several corresponding grammatical systems, particularly verb prefix structure. Ket, his primary Siberian source, is the only living Yeniseic language (which remains highly endangered) and bears some striking grammatical similarities to Navajo. Yeniseic languages have a unique verb prefix system: unique enough that Vajda could not find a corresponding system throughout Northern Asia. Na-Dene was the closest family geographically with a similar system. Johanna Nichols, a groundbreaking Historical Linguist and Linguistic Anthropologist, attended the symposium and made comment. Roach quotes:

With the exception of the Eskimo-Aleut family that straddles the Bering Strait and Aleutian Islands, this is “the first successful demonstration of any connection between a New World language and an Old World language,” Nichols said.

Vajda has not yet published his findings, so the extent of his linguistic claims is not yet clear. However, based on Roach’s summary of his discussion, there are two major points of controversy. First, Roach states that Vajda found “several dozen” cognates. Whether or not the comparative method for linguistic reconstruction was used remains to be seen. Regardless, a cognate list under 50 seems a bit thin to solidify a connection at all, let alone begin reconstruction. Furthermore, the public at this point has no access to the words to assess their status as true cognates. Without a doubt, a consistent and corresponding element of grammatical structure is a strong argument for a common ancestor, but we must consider the systems of linguistic change, particularly sound change (which requires cognates), as a central factor.

A second point of controversy is the matter of depth: how long ago does the proposed connection date back? Vajda makes no direct claims, but states that this would be the oldest known language link if it corresponds to the late Pleistocene migrations evident in the archaeological record. Unfortunately, the field of linguistics currently has no reliable absolute dating techniques, and relative dating such as glottochronology, has been widely discredited. In this case, it seems the lack of cognates would help secure this relationship as an old one. If that were indeed the case, a volume of cognates would become evident in the reconstructions of Proto-Yeniseic and Proto-Na-Dene. Whether or not Vajda has taken this into consideration remains to be seen. At any rate, Nichols is not convinced of a 10,000 year-old connection:

“I don’t think there is any reason to assume the connection is [10,000 years] old … this must surely be one late episode in a much longer and more complicated history of settlement,” she said.

At this point it is very difficult to make any generalizations. Vajda has not yet published his findings, but merely opened the door to discussion on the topic. Until he does, the foundation of our support or criticism is unknown.

According to this open access PLoS One paper, 95% of Native Americans share their heritage to six women. I don’t have much time to review this paper because I have to take a final exam in 30 minutes, but here’s the title and link to the paper, “The Phylogeny of the Four Pan-American MtDNA Haplogroups: Implications for Evolutionary and Disease Studies.” The title is pretty self explanatory, a cladistic analysis of Native American mtDNA haplogroups was undertaken. The authors were able to trace 6 distinct branches of the phylogenetic tree that arose from different women. Of course that doesn’t mean that only six women made it across Beringia, but a significant portion of Native Americans can trace their ancestry to six distinct mothers.

To compensate for a rather lackluster post, the abstract may give you a bit more information,

“Only a limited number of complete mitochondrial genome sequences belonging to Native American haplogroups were available until recently, which left America as the continent with the least amount of information about sequence variation of entire mitochondrial DNAs. In this study, a comprehensive overview of all available complete mitochondrial DNA (mtDNA) genomes of the four pan-American haplogroups A2, B2, C1, and D1 is provided by revising the information scattered throughout GenBank and the literature, and adding 14 novel mtDNA sequences. The phylogenies of haplogroups A2, B2, C1, and D1 reveal a large number of sub-haplogroups but suggest that the ancestral Beringian population(s) contributed only six (successful) founder haplotypes to these haplogroups. The derived clades are overall starlike with coalescence times ranging from 18,000 to 21,000 years (with one exception) using the conventional calibration. The average of about 19,000 years somewhat contrasts with the corresponding lower age of about 13,500 years that was recently proposed by employing a different calibration and estimation approach. Our estimate indicates a human entry and spread of the pan-American haplogroups into the Americas right after the peak of the Last Glacial Maximum and comfortably agrees with the undisputed ages of the earliest Paleoindians in South America. In addition, the phylogenetic approach also indicates that the pathogenic status proposed for various mtDNA mutations, which actually define branches of Native American haplogroups, was based on insufficient grounds.”

Achilli, A., Perego, U.A., Bravi, C.M., Coble, M.D., Kong, Q., Woodward, S.R., Salas, A., Torroni, A., Bandelt, H., Macaulay, V. (2008). The Phylogeny of the Four Pan-American MtDNA Haplogroups: Implications for Evolutionary and Disease Studies. PLoS ONE, 3(3), e1764. DOI: 10.1371/journal.pone.0001764

Last night I caught some of the new History Channel show, “Journey to 10,000 BC.” I really didn’t know about in advance to tell y’all. Had I known before hand I woulda surely made an announcement. But no worries, if there’s anything I know about channels like Discovery and History, is that they replay these sorts of episodes so much. Actually, if you’re interested in catching it, it will show again on Saturday, March 15 at 8 p.m.

Anyways about the show, I’m thinking History Channel put this out to coincide with the movie 10,000 B.C., which not surprisingly isn’t that accurate of a movie. Not like I expected it to be remotely realistic, but still I kinda hoped that it would be somewhat informative because it is about as much education most people will get about prehistory in their entire life. Anyways, “Journey to 10,000 BC” wasn’t much better. It had horrible cut scenes and exclusively focused on life in North America about 13,000 years ago. A lot of other very important things were happening elsewhere, such as the emergence of Neolithic revolution, i.e. the Natufian culture that shoulda been also included.

Even though I subscribe to the Siberian origin of native Americans, I did appreciate how Dennis Stanford made a cameo and explained his hypothesis that the Clovis archaeology could have originated from sea-faring Soluteran people from Europe. For those that don’t know what I’m talking about, some of the first archaeological evidence in the Americas are associated with a type of stone tools found in Clovis, New Mexico. The Clovis typology is significantly different from Siberian archaeology, see Siberian tools around that time were largely modified ivory points with a blade inset. Clovis tools were much different. Clovis tools are highly refined thin, fluted projectile points created using bifacial percussion flaking.

Dennis Stanford publicized his hypothesis in 2004, along with colleague Bruce Bradely, in this paper, “The North Atlantic ice-edge corridor: a possible Palaeolithic route to the New World.” Like I indicated earlier, Stanford suggests that 13,000 years ago or so Europeans made boats and crossed the Atlantic to the Americas. With lower sea levels then, this was more feasible than nowadays… and by then people were crossing large bodies of water all over the world, i.e. Polynesia and the Pacific. The problem with Stanford’s hypothesis is that there’s no evidence of boats in the America’s from that time period, nor is there a genetic European signature in Native American populations. Stanford says that the reason why boats haven’t been found is that sea levels have risen since then and obliterated any trace of boats… convenient. Anyways, his idea is a bit out there, and not substantiated much. It is really possible that the reason why Clovis typology is unique is that arose in the Americas independently.

I also appreciated the discussion the show gave to climate change and glaciation events in North America. This sorta information isn’t readily inserted into shows like these, and help viewers visualize large scale environmental changes. But, I really couldn’t get over the cheesy cut scenes where a prehistoric woman with remarkable Vogue-like complexion was taken down by a smilodon, and early people crossing massive waves in unconvincing boats canoes. So it is totally up to you to watch, I neither recommend it nor thoroughly think it is a waste of time. If you don’t know much about the peopling of the Americas, this show maybe a great introduction to some lines of evidence.

Bradley, B., Stanford, D. (2004). The North Atlantic ice-edge corridor: a possible Palaeolithic route to the New World. World Archaeology, 36(4), 459-478. DOI: 10.1080/0043824042000303656

To supplement last September’s conclusion that the peopling of the Americas was initiated by a pretty diverse group of people who camped out in Beringia for a long time, long enough to differentiate from their Asian sister-clades, comes this study published in this week’s PLoS One, “A Three-Stage Colonization Model for the Peopling of the Americas.”

The new study offers up perhaps the largest published alignments of Native American mtDNA, spanning all Native American haplogroups. Over 77 full mitochondrial coding genomes were constructed from 812 concatenated mtDNA hypervariable region (HVR) I and II sequences. They took these mitochondrial genomes, aligned them up, and applied the same algorithims, Bayesian skyline plotting, used in a recent paper to estimate prehistoric population sizes. Bayesian skyline plots are a unique approach to the coalescent modeling, that assume a single migration event, and thus test the generally agreed consensus that there was a single migration of people in the Americas.

The dominant model on the peopling of Americas started with the the ice sheets advancing and sea levels falling about 17,000 years ago. It is during this time that people are thought to first migrate across the Eurasian landmass and into the Americas. It was thought that a very small number of people, maybe even as small as 70 or so, who crossed over. Perhaps they were nomadic hunters, following game herds from Siberia across what is today the Bering Strait into Alaska, and then gradually spreading southward. Based upon the distribution of Amerind languages and language families, a movement of tribes along the Rocky Mountain foothills and eastward across the Great Plains to the Atlantic seaboard is assumed to have occurred some 10,000 years ago.

What this new study found doesn’t indicate that the peopling of the Americas happened in one fell swoop. Rather, it supplements the paper I mentioned above, “Beringian Standstill and Spread of Native American Founders,” and offers up an interesting time frame, a three stage colonization event that is effectively illustrated by the authors. I’ve cut out the figure the authors provided, it’s to your left. The first stage began about 40,000 years ago with a gradual ancestral population expansion of people from an East Central Asian gene pool into Beringia. The second stage of ‘proto-American Indians’ was marked by almost no population growth for about 20,000 years, which confirms the previous Beringian standstill conclusion. The last stage started about 16,000 years ago with a massive rush of people, about 5,000 strong, fleeing out of Beringia and into the “ice free, inland corridor between the eastern Laurentide and western Cordilleran Ice Sheets and/or along the Pacific coast.” This challenges the n=70 founding population estimation.

The authors offer up no discussion about a possibility of bidirectional gene flow, which was shown in the September 2007 Beringian Standstill study that I keep referring too. I’m thinking its cause the skyline plots test for single migration events and not backflows.

Either way, it is a very enlightening study especially because other models, such as the Clovis archaeological model, which says the peopling of the Americas happened in 11,000 years, estimate really rapid colonization events. That’s awfully fast. Pushing back first rush of people to 16,000 years ago can help us better explain how the Clovis culture radiated so fast.

Kitchen, A., Miyamoto, M.M., Mulligan, C.J., Harpending, H. (2008). A Three-Stage Colonization Model for the Peopling of the Americas. PLoS ONE, 3(2), e1596. DOI: 10.1371/journal.pone.0001596

John Hawks shared an interesting news bit the other day. The study basically sampled head lice off of 1,000 year old Peruvian mummies and with some sequence variation comparisons to other lice, the authors were able conclude that lice have been with humans ever since they migrated out of Africa. I’ve tracked down the original paper to investigate their claim.

The paper, “Molecular Identification of Lice from Pre‐Columbian Mummies” is published in an early release of the Journal of Infectious Diseases. The authors amplified the Cytb and Cox1 genes of lice found on three 1,000 year old Peruvian mummies. The mummies are associated with the Chiribaya culture, a post Moche movement, that originated in the Azapa Valley of Northern Chile. I’ve cut and pasted a photo of one of the mummies sampled from the article, in this photo the authors show the lice still present on the head.

They next sequenced these amplified genes, and constructed phylogenetic trees of the genetic similarities these lice have to sequences of lice from other areas of the world. What they found from their cladistic analysis was that the lice associated with the mummies clustered only with sequences in the type A clade. Since type A clade are almost exclusive to Asia and Africa, the authors could confidently claim that the lice were not of European origin, which sports the type B clade of lice.

New World mummies as old has 10,000 years ago have lice, and the genetic evidence from this study now confirms the lice that existed in New World for the last 1,000 years was not of European origin. This work also tells of migration patterns of humans, much like the study on rat genetics did early this week. We can see that founding populations of people from the Old World carried over the type A clade of lice, over the Bering straight and to the Americas.

I really appreciated this article. Had it not been for this one citation to the Bible, about the presence of lice in historical populations, I would say this article is a perfect example of simple, enlightening science. The authors didn’t obfuscate their research and provided a very graceful example of how a host-specific parasites of human brought in an additional line of evidence to understand human migrations. One last thing, I wonder what’s the genotype of the lice found on the mummies in Arizona?

Raoult, D., Reed, D., Dittmar, K., Kirchman, J., Rolain, J., Guillen, S., Light, J. (2008). Molecular Identification of Lice from Pre-Columbian Mummies. The Journal of Infectious Diseases DOI: 10.1086/526520

A new study of over 600 mtDNAs from 20 American and 26 Asian populations is shedding some unique insight on how the Americas were peopled. As you may have been taught, it was thought that the Americas were founded by a not so diverse founding population or two. Before this paper, only about 70 left their genetic print in modern descendants, a very small but effective founder population.

But, there are new results, which were published almost two months ago, that show that there was much more genetic diversity in the founder population than was previously thought. I didn’t catch it until I saw both Razib and Science Daily report on it a couple days ago.

The paper, “Beringian Standstill and Spread of Native American Founders,” was published in the freely accessible PLoS One. Beringia is a fancy way of naming the Bering Land Straight that once connected the north east Asia continent to north west America continent.

One of the more interesting lines of evidence they found from their sequence comparison and their revised phylogenetic map is that the ancestral population literally chilled out in Beringia for a long time. The authors estimate about 15,000 years. That’s long enough so that specific mutations accumulated which separated the New World founder lineages from the Asian sister-clades.

The other more interesting thing that was uncovered was that the founding haplotypes are uniformly distributed across North and South America. They do not show a nested structure from north to south. That means that after what the authors are terming the Beringian standstill and what I’m calling the Beringian chillout, the initial North to South migration was very swift. It was not a gradual diffusion.

And as Razib pointed out in his post, during the last 30,000 years, there was a lot more bouncing back and forth from Northeast Asia and North America. The analysis shows that there was a series of back migrations to Northeast Asia as well as forward migrations to the Americas from Beringia, “more recent bi-directional gene flow between Siberia and the North American Arctic.”

Overall, this study tells us a lot on how people were moving about in the northern hemisphere. But what about oceanic travel, and the recent chicken population genetic similarities? They seem to have made some cultural if not genetic contribution to populations here.

Related sidenote, I like how this study one ups an older PLoS paper, which I reffered to above (the 70 people one). If you want, check out that paper, “On the Number of New World Founders: A Population Genetic Portrait of the Peopling of the Americas.”