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paleoanthropology, genetics and evolution

Photo Credit: Rainy day at Amud Cave, Israel. John Hawks CC-BY-NC-ND

Looking at Luzon hominins, from the perspective of 1985

In light of this week’s paper by Ingicco and colleagues showing evidence of 700,000-year-old human activity from Kalinga, on Luzon, I’ve been doing a little reading.

I found an interesting article by Lawrence Heaney, published in the 1985 volume of Modern Quaternary Research in Southeast Asia. The title is: “Zoogeographic evidence for Middle and Late Pleistocene landbridges to the Philippine Islands”. In case you wonder about the title, the article shows that there were no land bridges to the Philippines, although there were several ancient land bridges connecting various islands within the Philippines.

The part worth quoting at length has to do with speculations that Homo erectus may have reached the Philippines.

Comments on Homo erectus and land bridges
Given the strong evidence against land bridges from Asia to the Philippines, what does this tell us about the probability of finding Homo erectus in the Philippines?
First, it must be recognized that this analysis has been general; it has not dealt with any specific species, and does not prove that a single species cannot behave in a different fashion from most or all others. The fact that a single species of monkey, Macaca fascicularis, is now recognized to occur in much of Southeast Asia including nearly all of the Philippines, could be taken as evidence that it is possible, however unlikely, that Homo erectus had a similar distribution.
However, it must also be recognized that if Homo erectus did occur on Luzon, for example, they arrived there by crossing over several sea channels that were over 10 km wide, and could have been over 25 km wide. It is possible to imagine a small population of monkeys floating accidentally out to sea on a mass of trees and branches and being rafted to an island 25 km away; it is far, far more difficult to imagine a similar thing happening to a group of proto-humans. Thus, I suggest that if Homo erectus did occur on Luzon, they arrived by deliberate construction of rafts and dispersal across sea channels.

The chapter goes on to consider whether any evidence about Homo erectus on Java suggested that they might have crossed water to islands. This discussion is a bit outmoded from today’s perspective: Although it has long been known that Java was connected to the Asian mainland during the Late Pleistocene, it was not always so evident that all of Java had such connections during the Early Pleistocene, since the island has coalesced as a result of Pliocene and Early Pleistocene uplift and volcanism. So some authors had suggested that the earliest evidence of Homo erectus on Java might have occurred before Trinil was part of the Asian landmass, for example.

More relevant today is that we now know that hominins occupied Flores, Sulawesi, and now Luzon, all prior to 100,000 years ago. Flores and Luzon were peopled during the early Middle Pleistocene.

What’s more, the Flores hominins may represent a hominin group that diverged earlier than the last common ancestor of Homo erectus and archaic and modern humans. This is not a question of Homo erectus dispersing to islands, it may be a question of a branch of hominins that–except for H. floresiensis–is presently unknown.

Link: Are physicists barking up the wrong tree?

Sabine Hossenfelder has a book coming out next month, Lost in Math: How Beauty Leads Physics Astray. She pursues the question of why physicists today follow research paths toward “beautiful” or “natural” theories, and critically examines past theories, noting that successful ones were rarely viewed as “beautiful” at the time they were proposed.

The implication is that today’s efforts to develop new theories may be barking up the wrong tree.

She has done an interview with Edge.org on her work: “Looking in the Wrong Places”, which is both thoughtful and provocative:

The problems that I see in my own community worry me a lot. Not so much because I’m so terribly worried about quantum gravity. On a certain level, even though it’s my personal interest, I realize that for most of the people on the planet making progress in quantum gravity is not that terribly important. It worries me because I have to question how well science itself is working.
The problems that I was speaking about in my own community—that people work on certain topics just because the money is there, because it’s something that is popular and that their colleagues appreciate—are problems that almost certainly exist in most scientific communities. My extrapolation from my own field would tell me that I should be very skeptical about whatever comes out of the scientific community. And that’s not good. Clearly that’s not good.

I’m looking forward to this book.

Link: Following fieldwork in Malawi

Emory University has done a nice story about Jessica Thompson’s archaeological fieldwork in Malawi: “Bonding over bones, stones and beads”.

Thompson's fieldwork in Malawi has uncovered hunter-gatherer remains that yielded DNA ranging in age from about 2,500 to 6,100 years old. And her work is ongoing at a site where a skeleton recovered in 1950 was recently dated to 8,100 years ago and also yielded DNA.
The samples are by far the oldest-known human DNA from Africa, preserved by the cool, arid ecosystem of the highlands of northern Malawi.

University press sites often do a really nice job telling stories that give the day-to-day context of fieldwork. This is a great example, seeing the joy of students making discoveries and hearing the way that Thompson is planning her upcoming field season.

A new perspective on Homo floresiensis from one of the discoverers

In the South China Morning Post, a great story featuring Indonesian archaeologist Emanuel “Wahyu” Saptomo: “Indonesian archaeologist recalls Flores ‘hobbit’ fossil find 15 years on, and what it meant for him and Indonesian archaeology”.

Saptomo’s comments provide a good account of how the American and European media have marginalized scientists from developing countries.

According to Wahyu, although Indonesia has led the research into Homo floresiensis, it has not been easy for the nation to gain global recognition for these efforts. Credit for the discovery often goes to Australia-based scientists, which Wahyu believes stems from how it has been reported.
Most of the journalists following the hobbit story work for “big companies”, he says, and cater to audiences that expect such significant discoveries to be made by Westerners.

I think the media environment has actually become much worse in the last 14 years since the Homo floresiensis story broke. Today most stories are written by freelancers and not staff journalists at big companies. Many freelancers are incredibly talented reporters, but few of them have the breadth of international contacts that help them to report a story like this in depth. Few will penetrate into research teams to find diverse voices beyond the first or corresponding authors of a study.

As a result, we see lots and lots of stories about the same new paper, all quoting the same few experts.

Scientists and teams of scientists can do much to make reporting more accurate and representative. They can make sure that any press release includes quotes from diverse scientists with different roles in the research. They can make sure that contact information is available for a breadth of researchers, especially those representing institutions in the country where research is undertaken.

It’s not just about providing information passively; teams can reach out. Scientists can do “inreach” with other experts in advance of a news release, so that external voices are armed with information leading to more team members, not just the “lead” scientist on a project. And scientists and institutions can do targeted outreach with trusted journalists to make sure they know the full story and can represent team members from countries where the research is done.

In today’s environment, scientists can do much to recognize key collaborators and broaden the narrative behind their science.

Chimpanzees don't necessarily live where biologists thought they did

Distribution maps of wild species are inaccurate for lots of reasons. When it comes to distribution maps of wild primates in tropical Africa, one of the biggest reasons why they’re inaccurate is that many of the areas have not been surveyed for wild primate populations by biologists in modern times.

This point helps to explain a paper from last year by Thierry Aebischer and coworkers (2017) describing evidence for chimpanzee geographic distribution in the Central African Republic.

Here we report the presence of a viable population of Eastern chimpanzees (Pan troglodytes schweinfurthii) in the eastern part of the Central African Republic (CAR). Their location at the northern limit of the chimpanzee distribution and their heterogeneous habitat in the forest-savanna ecotone make them an ecologically relevant population for the long term survival of the species (Plumptre et al., 2010). Surprisingly, the population appears confined to habitats east of the Chinko River as no evidence for chimpanzees was found west of that river despite considerable survey effort. This geographic distribution is in contrast to recent distribution models that predicted much more favorable environmental conditions west of the Chinko River and classified most parts of Eastern CAR and the entire eastern part of CNR as unsuitable (Junker et al., 2012; Plumptre et al., 2010). At least 25000 km2 (27%) (IUCN SSC A.P.E.S. database, Drexel University and Jane Goodall Institute, 2016), or 57290 km2 (62%) (Plumptre et al., 2010) of the supposed chimpanzee distribution in Eastern CAR as estimated by the International Union for the Conservation of Nature (IUCN) and the Wildlife Conservation Society (WCS), respectively, is most likely not or no longer occupied by chimpanzees. Our study thus showcases some limitations of relying solely on remote sensing data to predict distributions of endangered species in regions for which limited or no training data is available, and therefore illustrates the necessity of extensive field surveys to accurately assess population density in remote and scientifically underrepresented areas. This is especially relevant for species like chimpanzees that may adapt their lifestyle to diverse environmental conditions but are heavily affected by anthropogenic disturbances.

Over the years, there have been a number of scientists who have tried to work out the ancient geographic ranges of Neandertals and other hominins, based upon predictions about their ecological habitat preferences.

How do scientists determine which habitats the Neandertals preferred? First, they map known Neandertal sites. They consider what we know about those sites and their local ecologies. Of course, there is a huge bias in that hominin-bearing sites have been subject to much greater intensity of excavation and investigation. From each site comes some ideas about local ecology at the time Neandertals (or other hominins) lived there—mostly based on the faunal list.

Across many sites, this gives a picture of the habitat preferences or tolerances of Neandertals (or any other hominin population). Apply this to a climate model, and you can predict where you should have been able to find Neandertals at any point in the past.

The problem with this approach is epitomized by the chimpanzee survey. Chimps are absent many of the areas in the eastern Central African Republic that were predicted to be good chimpanzee habitat. Meanwhile, chimpanzees are living densely in some areas that were predicted not to have large chimpanzee populations.

It’s doubtful that we can do much better than this for any ancient hominin population. The quantity of data on ancient sites is highest for Neandertals, and lower for every other hominin.

Where they actually lived was likely episodic and fluctuated over time. The places where we find them are a footprint of thousands of years of low-intensity activity, not necessarily a guide to what they preferred or could tolerate.

Link: Sharing research highlights using video

Adrian Smith is a biologist and researcher on ants, who has written an account of his newfound skills for sharing his research highlights on video: “YouTube your science”.

He tells the story of sitting with his mom in a video studio, an experience which helped him realize how much his science was removed from the language that ordinary non-scientists can understand.

First-person accounts of science were not a part of my life when I was younger. I am a first-generation university graduate with no immediate or extended family members who are involved in scientific careers. As a child, I’d never known a working scientist. When I was filming that video with my mum, I realized that I was presenting myself as a professional scientist to a family member who also had never had a personal connection to science before me. Making videos and using press releases to distribute them has helped me to introduce myself and my colleagues to the world as scientists. I now view the impact of my research not just in relation to the metrics around my journal articles, but also in terms of how well I can make my work available to those outside my profession.

This is such an important moment in the history of science, and we need many more scientists to heighten the engagement of the public in our work.

Link: What about the coauthor?

Anna Reser writes about a troubling instance of “Hiding in Plain Sight”.

I saw a woman being erased from the history of science in real time.

The origin of the Africa-into-Neandertal mtDNA introgression hypothesis

I was reading through some papers for a post on neutral evolution versus selection in human diversification. That’s a topic I’ve written about several times, and one of my papers (written with Jim Ahern and Sang-Hee Lee) in particular focused on the relatively great morphological differences between human populations compared to some other primates.

The following passage, near the end of the paper, comes directly after a discussion of morphological distances (which is why genetics are “on the other hand” here).

On the other hand, the genetic similarities across the geographic range of hominoid species can indicate a history of gene flow (Gagneux et al., 2001). Genetic evidence for recent gene flow includes great similarities among some genes, amid a background of strong genetic differentiation among subspecies. From ancient DNA evidence, it would appear that the Neandertal-human difference is smaller than that among subspecies of either chimpanzees or gorillas (Krings et al., 1999; Hawks and Wolpoff, 2001), despite the relatively greater morphological difference. It is currently premature to claim that the known pattern of ancient mtDNA diversity is evidence of gene flow between the ancestors of Neandertals and the ancestors of living people, and indeed such a finding does not preclude the hypothesis that Neandertals speciated after this shared ancestor. But certainly the critical morphological evidence to address whether Neandertals were a distinct species is the pattern of change in both populations over time (Hawks and Wolpoff, 2001). The hypothesis that Neandertals and modern humans were conspecific predicts that they shared a common evolutionary trajectory, regardless of the degree of morphological difference between them. Future multivariate work may pursue the extent to which different characters may provide comple- mentary evidence of such shared trajectories among ancient human populations.

I’ve bolded the part that struck me as I was re-reading the paper today. Look at that, we predicted that the mtDNA of Neanderthals came from modern humans as an introgression!

What drove us to this provocative (and in our words, “premature”) hypothesis?

We were writing in this paper about how to interpret what seemed like large morphological differences between modern humans and Neanderthals. Modern humans and Neanderthals are morphologically more different from each other than different subspecies of chimpanzees, for example. We pointed out that it is puzzling that two “species” that look morphologically different still have mtDNA sequence divergence that (at the time) was estimated to be less than 500,000 years. That was a lot less than the estimated mtDNA divergence of chimpanzee subspecies.

At that time, what we knew about Neanderthal DNA came exclusively from Svante Pääbo’s research group. They had found that the mtDNA sequences of Neanderthals share sequence motifs that they never found in any mtDNA sequences of living humans. In particular, a paper by David Serre and coworkers from Pääbo’s lab had shown that 24 Neanderthal and 40 early modern humans in Europe had complete lack of haplotype sharing. This reinforced the finding that a Neanderthal mtDNA clade had once existed, an outgroup to all the mtDNA clades found in living people, and that no surviving descendants of the Neanderthal mtDNA clade had yet been found. Laurent Excoffier and Mathias Currat (2004) had also emphasized the lack of modern humans who share the Neanderthal mtDNA haplotype, especially unexpected in a growing population of modern humans.

That view carried a lot of weight before the initial sequencing of a part of the Vindija 33.16 genome in 2006, which for the first time raised the substantial likelihood of introgression from Neanderthals. And of course the last eight years have completely transformed matters. We now know that (1) modern people have Neanderthal ancestors, (2) the Neanderthal component of ancestry is higher in East Asia than elsewhere, (3), modern populations almost everywhere in the world experienced massive genetic turnovers during the last 30,000 years, meaning that the immediate post-Neanderthal populations of Europe have little to do with today’s Europeans.

At any rate, Krings and coworkers (1997) first recovered Neandertal mtDNA from the Feldhofer 1 skeleton, finding that it had a type never yet found in any living people. They estimated that this mtDNA haplotype had diverged from the mtDNA clade leading to modern humans around 465,000 years ago. That time of divergence appeared to put an upper limit on the time that modern humans and Neandertals parted ways.

That limit was surprisingly young, much shorter than the divergence times at which other primate sister species have become intersterile. In particular, as we pointed out in 2005, the time was very young compared to the mtDNA divergence times of today’s chimpanzee subspecies.

One possibility to consider for Neandertals and modern humans is that mtDNA had introgressed from one to the other, despite the fact that Neandertals and modern humans were more morphologically different than chimpanzee subspecies.

This has turned out to be almost certainly true. Yet the morphological difference between Neandertals and modern humans is still anomalously large compared to that between chimpanzee subspecies—or, more probably, the chimpanzee morphological differences are anomalously small compared to their great genetic diversification. The good evidence for recurrent introgression among Neandertals, modern humans, and Denisovans (and among chimpanzee subspecies) makes none of this much of a surprise today.

But the reason for the mtDNA introgression from ancestral African to Neandertal populations is unknown. Was there some adaptive value to the African mtDNA that caused it to succeed in later Neandertals? Did the original Neandertal mtDNA variation suffer from the high genetic load that other Neandertal genes later did? Was this all just chance?

At the moment, we have no easy way to tell.

References

Ahern, J. C., Hawks, J. D., & Lee, S. H. (2005). Neandertal taxonomy reconsidered… again: a response to Harvati et al. (2004). Journal of human evolution, 48(6), 647-652.

Currat, M., & Excoffier, L. (2004). Modern humans did not admix with Neanderthals during their range expansion into Europe. PLoS biology, 2(12), e421.

Serre, D., Langaney, A., Chech, M., Teschler-Nicola, M., Paunovic, M., Mennecier, P., ... & Pääbo, S. (2004). No evidence of Neandertal mtDNA contribution to early modern humans. PLoS biology, 2(3), e57.

Link: A plea to think about the ethics of sampling ancient bodies

Chip Colwell writes in The Conversation about the questionable ethics involved in some ancient DNA sampling: “Rights of the dead and the living clash when scientists extract DNA from human remains”.

As an archaeologist, I share in the excitement around how technology and techniques to study DNA are leaping ahead. As never before, the mysteries of our bodies and histories are finding exciting answers – from the revelation that humans interbred with Neanderthals, to how Britain was populated, to the enigma of a decapitated Egyptian mummy.
But, I have also closely studied the history of collecting human remains for science. I am gravely concerned that the current “bone rush” to make new genetic discoveries has set off an ethical crisis.

The link on the term “bone rush” points to “a short piece in Technology Review that attributes the phrase “bone rush” to me. I didn’t take the phrase from anybody else, and I think we’ve entered a scary atmosphere from the point of view of ethics of ancient DNA.

I haven’t written here yet about the case of the “Ata” body. The body was allegedly removed illegally from Chile and made the subject of a documentary film production. Tissue samples were removed and the body’s genome was sampled by geneticists from Stanford and the University of California–San Francisco. Colwell mentions the case in this essay, and there is more to say on this case.

In just the last few weeks, the egregious “Ata” case has been reported, NPR has carried out a DNA-free chemical sampling of a classroom skeleton, the FBI helped identify an Egyptian mummy using ancient DNA methods, ancient DNA was applied to an early Medieval case of head-binding, and the New York Times has reported that David Reich is sampling thousands of ancient bones, systematically removing the inner ears of ancient skulls. And those stories are just a small sampling of ancient DNA science news in the last few weeks.

My profession is the study of dead skeletons. Even for me, the current landscape of ancient DNA is bewildering. I think we should do as much as possible to bring the stories of ancient people to light. But every piece of evidence we have from past populations is precious, and every one can benefit from the engagement of a broader community, including possible descendant communities, local and national governments, and other stakeholders.

My concern is that scientists are rushing to bring out results, using today’s limited technology, without broadening the base of support for the science. Scientists may individually be working within the ethical framework they understand, but I believe we could do much better work.

Quote: Looking back at Clovis-first

This is a nice paragraph from Waters and Stafford (2013) on the Clovis-first paradigm for initial habitation of the Americas:

At least three major anomalies cannot be explained or no longer ignored by the Clovis-First paradigm. First, at 13,000 cal yr BP both North and South America were occupied by humans. In North America there is the Clovis complex, with its distinctive technologies and tools. In South America the sites of this age are characterized by generalized toolkits with many ake tools and some bifaces, but no diagnostic artifact type. Thus, at the time of Clovis in North America, you have sites of the same age and with different stone-tool technologies and assemblages in South America. Second, there are several credible sites dating before the time of Clovis. These sites have biface, blade, bladelet, and osseous technologies that date at least to 15,000 cal yr BP. These sites are found in both North and South America in well-dated and secure geologic contexts. Third, the current genetic evidence suggests an older-than-Clovis colonization of the Americas between 16,000 and 15,000 cal yr BP. It is now time to create a new model for the peopling of the Americas and explore new questions about the first inhabitants of the Americas.

I’m noting this, not because it’s news, but I ran across it in the course of lecture preparation. The book chapter (in Paleoamerican Odyssey) is mostly a review of the radiocarbon chronology for Clovis and pre-Clovis sites in the Americas.

After this book chapter was published, the flood of paleogenomic studies on early American skeletal remains began. Among those studies were results that suggested an initial habitation of the Americas in a single major wave preceding 15,000 years ago, as well as the results pointing to the contribution of a “ghost population” to some South American native peoples. Also after this book chapter have been several new archaeological discoveries, including evidence of human activity at Monte Verde as early as the Last Glacial Maximum.

When I lectured about this subject in my MOOC in 2014, the wave of archaeological information that clearly rejects a Clovis-first hypothesis was still fairly fresh, and some archaeologists were still hold-outs. Now there may be hold-outs, but the picture has been thoroughly transformed. Clovis culture now seems a mere afterthought to the main events in the initial habitation of the Americas.

This chapter provides a nice summary and has some good thinking in it about archaeological paradigms as applied to the Clovis phenomenon. What I also notice is that among its 33 citations in Google Scholar, not a single one is from any of the paleogenomic studies on early American specimens that came after this paper was published.

Archaeologists and paleogenomics specialists are embedded within different modes of publication and recognition of scholarship, as I noted earlier this week. “Should archaeologists really fear and loathe geneticists?”

It’s not that the two fields don’t cite each other; it’s that the citations are shallow, targeting just a few kinds of academic outputs. Some people have reacted to my earlier post by saying that the field of ancient DNA will eventually merge with archaeology, as their subjects of study become more and more entwined. I doubt it.

What I think is more likely is that the specialized studies of genetics will have their day and then fade, and a broader, more holistic kind of scientist—probably trained in archaeology or anthropology—will synthesize the genetic results.

Reference

Waters, M. R., & Stafford, T. W. (2013). The first Americans: A review of the evidence for the Late Pleistocene peopling of the Americas. Paleoamerican Odyssey, 541-560.

Is Facebook killing science news?

I’ve observed that the coverage of genetics and evolution in mainstream media has become worse over the last several years. It seems that social media, especially Facebook, may be contributing very negatively to that trend. In The Daily Beast, a report by Tanya Basu looking at patterns of social media sharing of science news: “Study: We F**king Love Lousy Science on Facebook”.

The headline is a bit unfair, I think, because the popular page “I F**king Love Science” actually carries a lot of science news stories. Its reporting and selection of stories to promote may not be ideal, but it would be hard to categorically say it is different from mainstream sources like The Daily Beast, Newsweek, or LiveScience for accuracy and scope.

The real problem is our Facebook friends. Now that Facebook promotes friends and family posts, whatever science you see is pretty much what they like and share. And it’s crap.

The problem is, it’s crap even when it comes from “top scientific thinkers and pop-culture icons”…

Second, you might think that getting access from top scientific thinkers and pop-culture icons might help drive serious science coverage and conversation. Indeed, astrophysicists like Tyson, Michio Kaku, and the late Stephen Hawking are the leading pages followed by Facebook users. But little of their content is original, and in fact, much of it is either generated from other sources or might not have anything to do with specific scientific discoveries at all.
That trend is made worse by groups like Smart Is the New Sexy, whose links were found to be “far afield from science topics.” That, in fact, illustrates a huge problem with Facebook “science” posts: For many of them with health or nutrition bents, advertising and promotions can sometimes form a dominant majority of content.

Ugh.

Look, few of us who write about science on blogs and social media are getting paid for this kind of work. That means that a lot of people who are writing about on blogs and social media are using their writing as a hustle to get paid for other things.

For some of us, we get paid for the occasional article, or even a whole blog, written for a mainstream outlet. That kind of work is frustrating to me, because not everybody can read what I write for many mainstream outlets, so I don’t do as much of that kind of writing as I could. But it’s respectable and often worthwhile, because mainstream outlets continue to have substantial readership that benefits from accurate science writing.

So where are the social media sources of science news getting their funding? Big personalities make it through simply being famous – lectures, tours, paid TV appearances, book sales. A good social media strategy for this kind of celebrity is just to spread things that their followers will share and spread.

Science media disseminating their work via your friend and family network have very low-paid writers or aggregators. They rely on clickbait, click-through lists, and using (or stealing) science images and video content without their context. Non-media groups that are “science-adjacent” on social media are selling things or supporting a sales network: supplements, treatments, etc. Meanwhile, there are the “true believers” who share contrarian science theories, or stories about mainstream scientists being wrong.

What can anyone do about this?

Help to bring attention to science writing that is accurate and not sensationalist. Stop and think for a moment before you share science news, to make sure that it actually is science and not a sales pitch or clickbait. Help to create high-quality science resources such as photos and videos, that are curated by real scientists and not click farms. Build something.

If you’re a scientist, stop allowing your institution or funder to issue press releases that you haven’t personally vetted. Let your voice be heard when a science media outlet gets your field of research wrong.

If you do nothing else, if you are a scientist, you need to develop some self-awareness of when you are acting like a crank. You have professional colleagues who have devoted years of effort and training to engage the public effectively in their work. Try talking with them.

Should archaeologists really fear and loathe geneticists?

Ancient DNA is following its Moore’s Law-like progression toward greater and greater sample sizes from past populations. Until this year, it may not have seemed apparent that every archaeological site will have ancient DNA techniques applied to it before long.

Ewen Callaway in Nature has a long feature article focusing on the tension between archaeologists and ancient DNA specialists as they try to understand the past with their different approaches: “Divided by DNA: The uneasy relationship between archaeology and ancient genomics”.

The article has a number of recent examples, mainly big studies of ancient DNA that were published in Nature with results pointing to major population replacements or migrations that had been unexpected by archaeologists. It is well worth reading in its entirety if you haven’t been following the field of ancient DNA super-closely.

Genetic information from ancient populations has settled some 100-year-old (or even 150-year-old) debates in archaeology. For example, we now know that the Indo-European languages did not spread into Europe and India along with the Neolithic revolution and introduction of farming from Anatolia. Instead those languages spread later, from an early Bronze Age origin on the steppe. We now know that the introduction of Bell Beaker pottery across much of Europe was in some places a result of people changing their material culture to adopt the new pottery style, and in other places (including England) the result of new people invading and almost completely replacing the resident farmers. We know now that the Inuit peoples of the Arctic are the latest wave of migration, largely replacing earlier Dorset culture peoples which contributed little to later populations. Those insights would not be possible without DNA evidence, and they demand that archaeologists and anthropologists rethink some of the ways they conceive of ancient population contacts and culture changes.

This is wonderful. Knowing who made past artifacts and how they are related to other people is transformative. All manner of woolly-headed archaeological ideas can now be thrown straight out the window. What’s not to like?

Some geneticists (and this article) compare the new ancient DNA approaches to the advent of radiocarbon dating. Knowing accurately when ancient people made sites and artifacts did indeed transform archaeology. Not always for the better, of course. The patina of white coat science sometimes enables scientists to push wrong ideas beyond the data’s real power.

But some archaeologists are dissatisfied with the course of these events.

I found a section near the middle of the article to express some of the main conflicts from the point of view of archaeologists.

“While I have no doubt they are basically right, it is the complexity of the past that is not reflected,” Heyd wrote, before issuing a call to arms. “Instead of letting geneticists determine the agenda and set the message, we should teach them about complexity in past human actions.”
Ann Horsburgh, a molecular anthropologist and prehistorian at Southern Methodist University in Dallas, Texas, attributes such tensions to communication problems. Archaeology and genetics say distinct things about the past, but often use similar terms, such as the name of a material culture. “It’s C. P. Snow all over again,” she says, referring to the influential ‘Two Cultures’ lectures by the British scientist lamenting the deep intellectual divide between the sciences and the humanities. Horsburgh complains that genetic results are too often given precedence over inferences about the past from archaeology and anthropology, and that such “molecular chauvinism” prevents meaningful engagement. “It’s as though genetic data, because they’re generated by people in lab coats, have some sort of unalloyed truth about the Universe.”
Horsburgh, who is seeing her own field of African prehistory start to feel the tremors of ancient genomics, says that archaeologists frustrated at having their work misinterpreted should wield their power over archaeological remains to demand more equitable partnerships with geneticists. “Collaboration doesn’t mean I send you an e-mail saying ‘hey, you’ve got some really cool bones. I’ll get you a Nature paper.’ That’s not a collaboration,” she says.

What’s going on here?

The two disciplines have different modes of work, publication, and citation. Much of the great archaeology on periods within the past 10,000 years is published in book form. The Horse, the Wheel, and Language by David Anthony has probably been the most influential presentation of the anti-Colin Renfrew view that Indo-European languages spread from the Pontic Steppe during the early Bronze Age. It runs 568 pages in paperback form, took years to write and publish, and brings together evidence from archaeology, linguistics, and genetics from much of Europe and West Asia. While the book is scholarly, it should also be recognized that it is a semi-popular presentation, much more accessible than the book-length archaeological reports that contain much of the primary literature. It is also the work of a single author who has synthesized results from three very different fields of study.

Meanwhile, the 2015 paper by Wolfgang Haak and colleagues that described ancient DNA evidence for this idea runs seven text pages in Nature and had 44 references. This may seem short or insubstantial, but this one paper took collectively years of effort from 39 authors, it reported 69 new ancient genomes, and included 141 pages of supplementary text.

These two works illustrate a massive change in the mode of scientific work in prehistory. Where archaeological research 30 years ago required the efforts of dozens or hundreds of people, most of these were not even recognized as authors of the research. Instead, nearly all the credit went to the scientist “at the top”. What other archaeologists most valued were theories that attempted to synthesize years of data.

The standard in genetics is different. What other geneticists value is the ability to lead and mobilize effective empirical research programmes that generate highly-cited peer-reviewed research papers. They often recognize trainees, postdocs, or tenure-track scientists as first authors of research papers, and this does nothing to detract from the role of team leaders.

The “two cultures” comment in the passage above is pretty appropriate to this situation. And as has been the case in the 1950s, the side perceived as “science” is winning and the more “humanities” side losing a struggle for hearts, minds, and funding.

Some cool bone tools from an ancient Chinese site

Today’s reminder that stone tools are not all that matter in human behavior: “Discovery of circa 115,000-year-old bone retouchers at Lingjing, Henan, China”.

Luc Doyon and colleagues document several pieces of bone that were used in the process of removing fine, small flakes from the edges of stone artifacts, called “retouchers”:

In this paper, we describe bone retouchers recovered at the Lingjing site (Xuchang, Henan, China) in a level dated to circa 125–105 ka BP. These artefacts represent the first evidence from Eastern Asia for the use of bone as raw material to modify stone tools. This discovery has implications for the ongoing debate on the nature of Late Pleistocene cultural adaptations in China. The lithic technology that characterizes most Chinese assemblages attributed to this period is interpreted either as reflecting a peculiar facies of the Middle Palaeolithic [34,35] or the persistence of essentially Lower Palaeolithic cultural traditions [36–39]. The Lingjing bone retouchers and the behavioural consistencies their analysis highlights show that in spite of the apparent simplicity of lithic reduction sequences identified at the site [40], Lingjing hominins integrated in their behavioural repertoire the use of bone fragments to shape stone tools. These results corroborate the view that early Late Pleistocene cultural adaptations from China must be understood as reflecting original cultural trajectories whose degree of complexity cannot be evaluated solely through the study of lithic assemblages.

Here’s a photo of one of the retouchers, made on an antler of an extinct deer:

Antler retoucher from Lingjing
Figure 8 from Doyon and coworkers (2018). Original caption: Retoucher 9L0151 from Lingjing. White bracket indicates the area where impact scars are present. Scale = 1 cm.

So-called “soft hammer” percussion uses bone or other non-stone materials to remove flakes from stone cores in a more controlled way. The use of bone and antler retouchers is widely known for Mousterian sites in Europe and western Eurasia. They are also known for MSA sites in Africa. It’s fair to describe these kinds of artifacts as a regular part of “Middle Paleolithic-MSA” technical modes of making sharp edges.

There has been some debate in the past about whether an equivalent mode of stone tool manufacture is present in China or other parts of East Asia. I think it’s fair to say that some archaeologists have had a very crystallized view of what technical abilities should be found together within assemblages, so that if you see one type of artifact, you should be able to predict the presence of many others. The Chinese archaeological record tends to disappoint such strict expectations.

There was once an idea that hominins had to be especially clever and sophisticated to use bone in their toolkits. Like most early assumptions based on limited evidence from European sites, this one didn’t stand the test of time. We have bone artifacts from some very early toolkits, and a range of different specialized uses of bone in Neandertal and other archaic human-associated sites.

But it is still interesting to see close study of bone artifacts from new parts of the world and different times. This particular case helps us to see the logical connections between the process of making stone tools and the infrastructure needed to keep those tools useful. They also remind us that some of the most important elements of ancient technology were not stone, and are not things that we see very often in the archaeological record.

Link: National Geographic looks at its history on race

NPR reports on National Geographic’s new issue devoted to the topic of race, and the way that the organization has examined its own history: “‘National Geographic’ Reckons With Its Past: ‘For Decades, Our Coverage Was Racist’”

I found it interesting to hear about one reporter’s look through the photo archives—the story is not only what was chosen to represent in the magazine over the years, but all the photos that were not chosen because they didn’t fit the editorial mold. As someone who has spent a lot of time working in South Africa, this passage stands out to me, looking back at a 1962 article on the country:

"There are no voices of black South Africans," Mason told Goldberg. "That absence is as important as what is in there. The only black people are doing exotic dances ... servants or workers. It's bizarre, actually, to consider what the editors, writers, and photographers had to consciously not see."

Of course the magazine grew to be enormously successful by knowing and catering to its subscriber base. Anthropologists also catered to their audience, an academic audience who reveled in strange practices and imagined exotic places.

Link: Archaeomagnetism in Iron Age contexts in southern Africa

Michael Greshko in National Geographic has written a neat story about the hunt for southern hemisphere records of Earth’s magnetic field: “What Ancient African Huts Reveal About Earth’s Magnetic Flips”.

To study the last few millennia—younger than ancient rocks, but older than direct scientific monitoring—scientists can measure magnetic orientations in certain archaeological artifacts. But this record is heavily biased toward the north. More than 90 percent of the data about the last 2,000 years of Earth’s magnetic field come from above the Equator.
To track the South Atlantic Anomaly, researchers are searching for more sites in the Southern Hemisphere. In 2015, scientists announced a fascinating new data source: burned huts in the Limpopo River Valley, an area that falls within modern-day Botswana, South Africa, and Zimbabwe.

Iron Age peoples of southern Africa burned their structures periodically, with fires hot enough to preserve the floors as durable clay. It’s remarkable that literally the floors beneath the feet of ancient people are connected to the dynamics deep within the Earth, and our protection from the stars.