Comment on "A parsimonious neutral model suggests Neanderthal replacement was determined by migration and random species drift"

Note: This comment was originally posted on the article's Nature Communications site on Nov. 10, 2017.  

As strong supporters of open, reproducible science, we are happy to see that Kolodny and Feldman replicated our research, published six years ago, and obtained results very similar to ours—results that they, like us, referred to as a “neutral model” for apparent Neanderthal extinction.

To obtain their results, Kolodny and Feldman use a protocol that parallels our 2011 paper, using both an analytical panmixia model and a spatially explicit model as we did. However, our modeling experiments also showed that given demographic imbalances between semi-isolated Neanderthal populations and more widespread 'modern' human populations, migration (very difficult to demonstrate empirically in the paleoanthropological record) is not necessary to eliminate Neanderthals as a morphologically recognizable group. It can be accomplished by gene flow and demic expansion alone, probably triggered by ecological responses to the onset of glacial conditions that can be identified empirically.

A subsequent paper in 2012 further explored the impact of fitness differences and also demonstrated that culturally mediated mating taboos have minimal to no biocultural impacts on these processes in the long-term. Both our papers predicted low-level introgression of Neanderthal genes into the modern human genome on the basis of the modeling work.

Although our 2011 paper was published in the well-known journal Human Ecology, Kolodny and Feldman seem to have missed it, so we provide the citation here.

Barton, C. M., Riel-Salvatore, J., Anderies, J. M. & Popescu, G. Modeling human ecodynamics and biocultural interactions in the Late Pleistocene of western Eurasia. Human Ecology 39, 705–725 (2011).

The authors did cite our 2012 paper but not in reference to our methods, results, or conclusions. We provide the citation here for those who are interested in this work.

Barton, C. M. & Riel-Salvatore, J. Agents of change: modeling biocultural evolution in Upper Pleistocene western Eurasia. Advances in Complex Systems 15, 1150003-1-1150003–24 (2012).

A subsequent paper, also in Human Ecology, discusses additional dimensions of the modeling environment.

Barton, C. M. & Riel-Salvatore, J. Perception, Interaction, and Extinction: a Reply to Premo. Human Ecology 40, 797–801 (2012).

We have published the code of the models used in all three papers in the NSF supported Model Library of the Network for Computational Modeling in Social and Ecological Sciences (CoMSES Net). This code is freely accessible for downloading and use.

Barton, C Michael (2011). Hominin Ecodynamics v.1. CoMSES Computational Model Library.

Barton, C Michael (2012). Hominin Ecodynamics v.2. CoMSES Computational Model Library.

Barton, C. Michael (2012). Hominin Ecodynamics v.1.1 (update for perception and interaction). CoMSES Computational Model Library.

C. Michael Barton, Arizona State University
Julien Riel-Salvatore, Université de Montréal
J Marty Anderies, Arizona State University
Gabriel M Popescu, University of Bucharest

Trigger on teaching archaeology in Canada

This quote stood out, as part of the thinking and reading I've been doing since my last post on Canadian trends in the hiring of PhD to staff archaeology faculty positions:

"By December, however, I had accepted an appointment at McGill for the following academic year. [Raoul] Naroll urged me not to accept this appointment, arguing that in Canada I would find myself in an academic backwater from which all the best students would gravitate to the United States to do graduate work. I thought to myself that if Canadian academics did not return home, such a brain drain would certainly continue. If I and others did return home, the situation might change. My mind was made up." B. Trigger (2006: 241)

Reference:

Trigger, B.G. 2006. Retrospection. In The Archaeology of Bruce Trigger: Theoretical Empiricism (R.F. Williamson & M.S. Bisson, eds.), pp. 225-258. McGill-Queen's University Press, Montréal.

A 'Canadian connection' in North American faculty jobs in Archaeology?

In a paper in press in American Antiquity, Speakman and colleagues (2017) present some data about which archaeology programs in the US and Canada have been most successful at placing their graduates over the past 40 years or so. They conclude that “success in obtaining a faculty position upon graduation is predicated in large part on where one attends graduate school” and that “success in landing a faculty position begins the moment one applies for graduate school” because “being accepted into a top program, as well as the reputation of scholars in that program… really does make a difference.” To me (and for them), these overall conclusions are unsurprising, though it is nice to see impressions and rules of thumb being backed up with some hard numbers. In a nutshell, if you’re interested in being an archaeology prof in North America, you better graduate from Michigan, Arizona, Berkeley, UPenn, ASU, Harvard, TAMU, UCSB, Chicago or UNM, in that order, since these are the ten North American programs in their “tier I”. The second tier also does pretty well in placing grads, and it comprises UCLA, Florida, Pitt, UT Austin, Wisconsin, Tennessee, OSU, UNC Chapel Hill and Virginia.

The authors indicate some readers might be uncomfortable with their approach which divided the 110 North American universities in their sample into six tiers (I, II, III, IV, V, and 0), based on the number of their grads who have secured a faculty position. I’m personally not too bothered by it, as I think this is a rather apt reading of the data they present, rather than a direct judgement of the quality of the faculty in these different programs.

What did strike me, from my position as an archaeology professor at a Canadian university, is how these trends don’t quite seem to jive with the reality of the Canadian market. Based on the data presented, Canadian program are not particuarly great at placing their graduates into faculty positions. The Canadian institutions they list are, in decreasing order of success, McMaster (Tier III – 8 grads placed in 20 years), Calgary (Tier III – 6 grads), followed by Alberta, McGill and Toronto (all three in Tier IV, tied with four grads each), Simon Fraser University (Tier V, 2 grads), and finally UBC, Manitoba and Montréal in Tier 0, meaning programs that haven’t placed a single grad between 1994 and 2014.

Looking at this from a Canadian perspective, I was struck that this list excluded two Canadian universities with dedicated Archaeology programs leading to the PhD, namely Memorial University and Université Laval, though this is likely a result of the bias the authors themselves bring up about the completeness of the AAA AnthroGuide from which they gathered most of their data. Also excluded is the new PhD program at the University of Victoria, which didn’t exist for the period the authors consider.

Additionally, my admittedly subjective impression is that there are a proportionally a lot more archaeology faculty trained at Canadian institutions hired into Canadian program. In the database provided as part of the article’s supplementary material, only 59 of the 1084 (or 5.4%) archaeology faculty listed obtained their PhDs from Canadian programs; this drops to 4.6% (or 28/608) if you consider only those PhDs awarded between 1994 and 2014. This is much lower than my gut feeling of the proportion of Canadian-trained archaeologists is in actuality in most Canadian programs. For instance, at UdeM, out of our seven archaeology and bioarchaeology faculty, two (so 28.4%) received their PhD from Canadian institutions (actually, Québec, in this case); these figures will have to be adjusted next year, following the hire of a public archaeologist we're currently advertising for. Looking more broadly, at SFU, out of 16 tenured/tenure-track faculty listed on their website, fully 8 (50%) come from Canadian institutions, while neighboring UBC has 2/6 (33%) graduates from Canadian programs. At the other end of the country, at MUN’s archaeology department 7/11 (63.6%) tenured/tenure-track faculty listed received their doctorate from a Canadian program. The disparity between these numbers and the overall representation of Canadian PhDs in archaeology programs in North America as a whole is pretty staggering.

There are a couple of ways to think about this trend. On the one hand, it is probably not terribly surprising, considering that, by law, priority is given to Canadian citizens for positions in Canada; insofar as having a Canadian PhD is loosely correlated with being a Canadian citizen, this probably reflects that fact up to a degree. Likewise, scholars working on topics in Canadian archaeology are more likely to be trained in Canada and, in turn, to be appealing to Canadian programs wanting specialists in these issues. The flipside of both these considerations, of course, is that correspondingly fewer Canadian-trained archaeologists must serve as faculty in US archaeology programs, which would have the effect of depressing the already low representation of Canadian programs south of the border. Whether it also has the effect of creating a distinctive Canadian archaeological tradition is an open question; I would surmise that it doesn’t, considering the level of methodological and theoretical integration that currently characterizes the field, but this is just an impression. That said, these (admittedly partial) data suggest one thing rather clearly: if you want to teach archaeology in Canada, receiving a PhD in archaeology from a Canadian program would appear to give your chances a serious boost.

References: 

Speakman, R.J., C.S. Hadden, M.H. Colvin, J. Cramb, K.C. Jones, T.W. Jones, C.L. Kling, I. Lulewicz, K.G. Napora, K.L. Reinberger, B.T. Ritchison, M.J. Rivera-Araya, A.K. Smith and V.D. Thompson. 2017. Choosing a path to the ancient world in a modern market: The reality of faculty jobs in archaeology. American Antiquity: https://doi.org/10.1017/aaq.2017.36.

Reconstruction Prehistoric Hunter-Gatherer Mobility

This past Friday morning, with my colleagues Becky Wragg Sykes and Suzie Pilaar Birch, we held a first webinar as part of our project "Reconstructing Prehistoric Hunter-Gatherer Mobility". This is a project sponsored by INQUA (the International Union for Quaternary Science), and it aims to "[e]stablish the current state of knowledge and unite diverse research practices regarding prehistoric hunter-gatherer mobility, as an essential step to building coherent and robust frameworks for future interdisciplinary inquiry". Basically, in spite of the importance of mobility to our understanding of what it means to be a forage, we felt there has been comparatively little critical reflection of how to define the concept and measure it across multiple scales and classes of material evidence. Our project hopes to bring together researchers interested in tackling the theoretical and empirical dimensions of hunter-gatherer mobility in a multidisciplinary light to develop robust frameworks to its archaeological study across diverse contexts. The project now has a web page (Reconstructing Prehistoric Hunter-Gatherer Mobility) which serves as a nexus for the different people involved and a repository of information about our activities. It's still getting of the ground, but it will be considerably more fleshed out in the very near future.

Turning to last week's activity, the first webinar's goal was to get project members together to introduce the overall scope of the project as well as to outline the goals we hope to achieve. Aside from a problem with one of the hosts' mic filtering through AdobeConnect as though she was a modern-day incarnation of Zuul, I have to say, I was extremely pleased with how the webinar worked. We were able to combine both live voice and camera interventions and include a spirited discussion on a live chat in addition to running a slideshow. It was my first time participating in a webinar, and color me impressed! I was happy to see that the participants included a range of archaeologists specialized in various methods (lithics, zooarchaeology, stable isotopes) as well as people with specialties in anthropological genetics, among others - it made for a very productive discussion, indeed we had to cut off discussion after about two hours, which I'll take as a sign of the interest the project is generating!

The project grew out of a seminar Becky and I organized at the 2014 UISPP meetings in Burgos that went very well and was quite well attended; that enthusiasm is in part what prompted us to develop it into INQUA Project 1502P. As part of this structure, we were awarded some seed funding to hold a first workshop, which we were able to considerably supplement by a Connection Grant from the Social Sciences and Humanities Research Council of Canada which we were awarded this past October. The next phase of the project will be that first workshop that will be hosted by the Anthropology Department at Université de Montréal on February 12-13 2016. More details will follow in the coming weeks, both on the blog and on the RPHGM website, so be sure to check back again soon!

Back from the dead!

Hey there, le blog est mort, vive le blog! I’m back. Quite a few things have happened since I last posted here… bought a house, had another kid, graduated a couple of solid MA students, sold the house, got a new job with a fancy new title (Associate Professor – boom!), moved back to my hometown of Montréal for said new job. I’ve now been at the Université de Montréal for over a year, have some fantastic new grad (and undergrad) students, am involved in a bunch of new projects, so I figured blog content could get a shot in the arm as a result… there’s also a host of new debates going on about in paleo circles and academia in general to which I think I have something to contribute, so here I go again…

On the variability of Upper Paleolithic burials: Hype, facts and fiction (and Neanderthals?)

A new study of mine (written with Claudine Gravel-Miguel of ASU) is getting a bit of press, and I really want to write a post on AVRPI to serve as a proper companion piece to it, since the narrative in the press is already slipping away from what the paper actually says. In short, our paper does not say that Upper Paleolithic burials were not more sophisticated than those of Neanderthals. Rather, it emphasizes how heterogeneous Upper Paleolithic burials are (a point I recently also mentioned in relation to 'Venus' figurines), and that many of them were fairly simple. As a result, we need to be very careful about using exceptionally lavish as representative of Upper Paleolithic burials as a whole, as emphasized in the official CU Denver press release "Early human burials varied widely," which is a bit meta, being illustrated as it is by... one of the Sungir burials, arguably some of the fanciest Upper Paleolithic burials known!

 

Not a typical Upper Paleoilthic burial!

In short, the study is about the variability in Upper Paleolithic burials and its main goal is to move us away from facile and unwarranted generalizations about them. It will be published in a couple of months in The Oxford Handbook of the Archaeology of Death and Burial, which is edited by Sarah Tarlow and Liv Nilsson Stuz (pre-order your copy today!). In the meantime, if you're interested, you can access a pdf of the paper's uncorrected proofs on my Academia.edu profile at Upper Paleolithic mortuary practices in Eurasia: A critical look at the burial record. The paper presents a review of the known corpus of Upper Paleolithic burials, with some cautionary notes that emerge from trends in the data we now have. Our review includes all Upper Paleolithic inhumations known to date, with the exception of the Climente II burial in Romania, which was just recently redated to the late Upper Paleolithic (Bonsall et al. 2012), a study that came out well after our manuscript had been sent to the editors. Still, it provides the most up-to-date compendium of Upper Paleolithic burials currently available, along with key references and all available dates for each, and as much information about the context of the burial and associated artifacts and features as an be gleaned from the literature. Overall, our review confirms many of the conclusions that some earlier studies based on smaller samples had reached: there are fewer women than men buried, and fewer juveniles (especially infants) than adults buried. Also, there are more burials in the Late Upper Paleolithic than in the earlier part of that period, and the more recent burials tend to be more sober than the earlier ones.

That said, we make a series of key observations that break with the conclusions of previous reviews. First, there are really not a lot of Upper Paleolithic burials (just over three per thousand years for all of Eurasia!). Second, most burials are very tightly clustered in space and time, with Liguria (Italy), Moravia (Czech Republic), and parts of Russia showing an unusually high concentration of these things. Furthermore, the geographic range over which you find burials seems to contract as opposed to expand over time, and the earliest burials postdate the arrival of modern humans into Eurasia by up to 10,000 years. There also isn't any correlation between the presence of ornaments and climatic variability, which is in contrast to, say, Paleolithic art, which increases in abundance in moments of climatic downturn. Additionally - and this is one of our most important points - Upper Paleolithic burials differ widely in terms of how elaborate they are, and this even within single regions and sometimes even within single sites! This means that it is absolutely unwarranted to read Upper Paleolithic burials as a single class of evidence. And, it is especially unwarranted to take the most elaborate burials (e.g., those from Sungir) to characterize the practice of Upper Paleolithic burial as a whole. If anything, these extremely lavish burials occur kind of early on, and are clear outliers in terms of how representative they are of Upper Paleolithic interments as a class of evidence.

But wait, you might be tempted to say, don't all these burials include grave goods and things like ochre. Well, this is another point we make in the paper: most of the things that have been called grave goods are personal ornaments, and most of them are fairly simple. For instance, in the Gravettian (ca. 30-21,000BP in uncalibrated radiocarbon years), of 35 buried individuals, 8 have no ornaments at all and 11 have ornaments comprising fewer than 10 beads on their entire body. To give you a sense of how few that is, a Catholic rosary comprises 59 beads. So, 11 of these burials have fewer than 1/6 of the length of a rosary by way of ornaments, hardly a cumbersome investment in time, resources and effort like that implied by the notion of including 'offerings' in a grave. In fact, if you look at the distribution of these beads on the body of these buried individuals, they are located where you would expect most people to have worn them in life, if the purpose of these artifacts was to convey information about their wearer at a distance. In other words, they are found on the upper body, usually (70% of the time) on the head, but also on the neck/torso area (17% of the time). To us, this and the fact that the remaining 13% of all ornaments is found distributed all other (lower) parts of the body, suggests that the majority of ornaments were probably worn by the deceased in life and buried with them when they died. An additional idea to emerge form this pattern is that most prehistoric beads from other period (like the Middle Stone Age of Africa) may have been worn on the head as part of caps, headbands, headdresses, bonnets and whatnot, rather than on the torso as necklaces, as is often assumed.

Now, obviously, there are exceptions to this rule, and a few burials do show extremely elaborate ornaments that leave little doubt as to their nature as grave offerings(e.g., Sungir). But these are in the minority (in fact the Sungir burials are excluded from our Table 17.3 because they are so far from the norm of contemporary interment). Additionally, these burials also tend to be the ones that have the most decorated body parts overall anyway, reinforcing that the fairly sober ornaments found with most burials were probably personal possessions of the deceased.

What about ochre? To be fair, ochre in some form is found with most Upper Paleolithic burials. That said, however, the Upper Paleolithic as a whole tends to be associated with ochre and other coloring materials, so it's not unexpected that it would be found in the fill of many graves dug into Upper Paleolithic sediments. In fact, because many of these interments were discovered a long time ago, the definition of what exactly is meant by 'ochre' in most cases is pretty vague. Suffice it to say that if you're looking for a grave completely covered in ochre, again, you're looking at a fairly small subset of the entire sample.

So, to sum up, most of the ornaments traditionally considered as grave goods are likely personal ornaments worn n life by the deceased and if the inclusion of ochre in many graves is a byproduct of their having been dug into Upper Paleolithic deposits. This means that the two features usually invoked to describe most Upper Paleolithic burials as symbolic really don't support that view for the vast majority of cases. Basically, what you see is a few Upper Paleolithic people being buried wearing things they would have worn when they died, and in pits or depression dug into contemporary sediments. That of course, doesn't mean that they weren't symbolic and/or highly meaningful to the people burying the dead - after all, after 20,000 years most present-day burials in the US would leave behind very little in the way of extravagant material culture, in spite of their being heavily symbolic. However, if we're going to assume that they are symbolic, then logic dictates that we must extend the same interpretation to similar cases in other periods, such as the Middle Paleolithic, where people were certainly interred in pits and depression along with items of daily life (which in that period generally didn't include ornaments or ochre). Really, this is not a paper about Neanderthal burials, but rather a paper that forces us to rethink some of the preconceptions we have about what differentiates Upper Paleolithic populations in Eurasia from other prehistoric populations (e.g., Neanderthals). So, the Past Horizons headline gets it wrong: some Upper Paleolithic burials clearly were more sophisticated than those of Neanderthals. It's just that there's no reason to think that the vast majority of them were. What requires explanation is why you have so few of these extremely elaborate burials - by itself, the fact that they exist tells us little about the human experience in the Upper Paleolithic as a whole.

Cavemen, quadrupeds and science, oh my!

So... there's a new paper in PLoS ONE about how 'cavemen' depicted four-legged animals better than 'modern' artists (Horvath et al. 2012). I usually try to refrain from paper bashing here, but there is such a high density of wrong (if not downright fail) in this one, that it's hard not to. Becky Farbstein agrees, and points out that:

1) anyone using the word 'cavemen' with a straight face in a scientific publication today cannot be taken to know anything about the time period in question;

2) the paper's conclusions are only surprising or noteworthy if you assume that cavemen (and by extension hunter-gatherers) are somehow less advanced at a fundamental level than 'modern' folks (again, whatever that is);

3) and - extremely importantly - that there is no reason to expect that an artist, archaic or modern, necessarily operates with the goal of depicting quadrupeds realistically; to assume that this is the case fundamentally misinterprets what art can be and usually is, i.e., not strictly about representing reality.

Basically, as a friend said on Facebook, "With their methodology, you could argue that gravity was invented in the Renaissance because figures in 15th-century paintings begin to be grounded, rather than seeming to float as in Medieval art!" The same friend also added that that's why everyone needs to study at least some art history, but that's another issue (and for those readers wondering, I have [way] more than one snarky friend on FB).

I agree with all of this. However, another extremely problematic aspect that I haven't yet seen discussed concerns the data the authors use to make their case. Even if you disregard the points above, issues with the composition of their 'caveman art' sample data alone should be enough to laugh these people out of town. I was immediately suspicious when I saw the elephant image that accompanies the press release on the paper - an elephant is not usually what one associates with 'cavemen'. So I dug into their data, in the off chance they simply had an extensive sample of prehistoric art. After all, they boast about their data base being 1000 images strong. As it turns out, only 35* of those are 'prehistoric'. That's less than 4% of their total sample (I wonder how often they could bootstrap a similar trend from their modern sample just by randomly selecting 35 representations at a time...). But surely, these images all come from the same site or a handful of sites that date to the same period, right? Sadly, no: we're looking at 11 Paleolithic drawings (9 from Lascaux, one from Niaux, and another from Altamira) that span several thousand years and two countries. At least with those, a tenuous link to the idea of cavemen paintings could be made. But the 24 other representations come from sites scattered across Libya (consistently misspelled as 'Libia' in the paper, for crying out loud!), Morocco, various parts of India, and South Africa, with little if any chronological control. The point is that these pictures don't actually form a coherent body of evidence by any stretch of the imagination. Oh, and these conflate paintings, incisions, and engravings, all of which impose their own specific constraints on how art is produced. Add to that there is no reason to think that many of these representations were necessarily meant to be seen only in two dimensions or outside of the panels on which they were created (and in relation to the other designs these panels comprise), and you've got some of the shoddiest sample selection I have ever seen in a scientific paper.

I can't really figure out what their 'modern' sample is, but the issues with the prehistoric sample alone are enough to damn the paper. I don't care if they think that they can simply disregard context to focus on how walking was represented - the fact is you can't dissociate art from its context. Furthermore, with such a tiny and far-flung (temporally and spatially) sample of 'caveman' art, we can basically have no confidence at all that we're actually looking at how 'prehistoric' people represented animals, let alone their gait.

*Edit (Dec. 6, 2012; 11:43PM: Table 1 in the paper states a prehistoric sample of 39 'prehistoric' representations, whereas the supplementary information only details 35. Given this, I went with 35 being the most reliable value, since it's impossible to figure out what the other four representations were (of and from). Ultimately, however, using one or the other figure does not affect my point here - it's still less than 4% of the total sample, and a very small number of representation given the staggering geographic and temporal scales over which they are spread.

Reference:

Horvath G, Farkas E, Boncz I, Blaho M, Kriska G (2012) Cavemen Were Better at Depicting Quadruped Walking than Modern Artists: Erroneous Walking Illustrations in the Fine Arts from Prehistory to Today. PLoS ONE 7(12): e49786. doi:10.1371/journal.pone.0049786 (Link)