Not guilty, or not proven?

Fifteen years ago last month (October), Michael Peterson was convicted of murdering his wife, Kathleen Peterson, at their home in Durham, North Carolina. The case and the trial, which dragged off and on from 2003 to 2017, was summarized in the Netflix documentary "The Staircase." My wife Noell and I watched the first episode a few months back and were instantly hooked.

The defense attorney during the original trial, David Rudolf, and the producer of the documentary, Allyson Luchak, visited the Carolina Theatre on October 3rd, and Noell was able to procure tickets for us. David Crabtree, a reporter and anchor for WRAL down in Raleigh, moderated. The purpose of the production was to discuss the trial, the documentary, and the state of the judicial system in the United States.

One critical matter revolves around the original purpose of the documentary. After all, it was Peterson himself that asked for it to be filmed, and Crabtree's first question focused on this very point. Rudolf and Luchak responded that Peterson, who wrote several newspaper pieces in the early 1990s that were very critical of Durham's police force specifically and its criminal justice system in general, felt a documentary was the only way to ensure that he received a fair trial. Essentially, he hoped the district attorney, the judge, and the police would be less biased with a film crew on hand.

Another matter concerns the stairway itself. As viewers, it was impossible to ignore the amount of blood--it was absolutely covered. Head wounds like that suffered by Kathleen tend to bleed profusely, and one of the more shocking parts of the documentary was the common, even gratuitous, appearance of that bloody stairway. In fact, Noell and I repeatedly turned to each other and asked, "How can the family continue to walk by that bloody staircase every day?" Rudolf explained that the blood was not washed off the stairs or the wall because the defense's forensic experts needed to continue to analyze the spatter. However, the portion of the stairway that was covered in blood--the area that opened right onto the kitchen--was usually covered up with a panel of wood so that the family did not, in fact, have to constantly look at it.

One questioner asked about Duane Deaver, the State Bureau of Investigation blood spatter analyst whose questionable methods and misleading testimony for the prosecution played a significant role in convincing the jury that Kathleen Peterson was bludgeoned to death. Deaver was eventually fired by the SBI in 2011 (his appeal of the firing lasted until 2014, when it was finally upheld in a North Carolina court). Could charges be leveled against Deaver? Rudolf responded that only the District Attorney could bring charges against a prosecution witness--something that is very unlikely to happen.

What was particularly striking was how quickly some of Michael Peterson's family turned on him during the trial. The turning point, as we later learned from Rudolf, seems to have been the autopsy photos showing the bloody wounds on Kathleen's scalp. Once these were revealed, many family members, including Kathleen's sisters and Caitlin Atwater, Kathleen Peterson's daughter from a previous relationship, felt strongly that she (Kathleen) had been assaulted and killed by Michael Peterson. While the photos are indeed horrifying, Rudolf speculated that this was an intentional ploy on the part of law enforcement to split the Peterson family. One of the documentary's last episodes records a moving scene in the courtroom when, after Michael had accepted an Alford plea, one of Kathleen's sisters made a statement in front of the court that expressed her anger and sorrow.

Perhaps the most bizarre story to emerge from the trial and its aftermath is the so-called "Owl Theory." I'll admit that I thought the whole thing was ridiculous--after all, how could an owl kill someone? After learning more about it, however, I've come to think that it is at least plausible. The origin of the idea can be traced to the Peterson's neighbor, who suggested that a barred owl attacked Kathleen as she walked back into the house that night. According to this scenario, the attacking owl's talons caused Kathleen's scalp wounds and, reeling and bleeding from the attack, Kathleen then fell down the staircase and eventually bled to death. There are a couple pieces of evidence that lend some support to this idea. First, barred owls are apparently pretty ornery and are known to attack people. Second, there was a small feather found in Kathleen's hair and a twig found on the staircase. Third, her wounds were not consistent with a blunt force object. Finally, blood was found just outside the house, which suggests that Kathleen was bleeding before she fell down the stairs.

The defense, of course, argued that Kathleen's injuries were caused by a fall down the stairs--let's call this the "Fall Theory." (Rudolf was not aware of the "Owl Theory" until it was too late to include in the defense.) Someone asked a very interesting question: Was the Fall Theory created by the defense to protect Michael Peterson, or did they actually believe it? Rudolf responded that this is what Michael claimed to have thought happened, so that is what his team set out to demonstrate.

Rudolf was continuing on to Scotland, and he mentioned that in Scottish law, one of three verdicts can actually be rendered: guilty, not guilty, or "not proven." While this last one is, of course, unfamiliar to Americans, Rudolf argued that it can, in some cases, be a more accurate reflection of a trial's outcome, including perhaps the Michael Peterson case. An interesting point, although there is some pressure to remove this verdict from Scottish law.

Building a taphonomy database

The use of databases is deeply embedded in scientific research. Any table of information you put together is, in fact, a type of database. However, advances in computing power now allow us to accumulate and analyze huge digital datasets in a variety of formats. Before these datasets can be analyzed, though, they must be compiled and digitally transformed. Archaeology and paleobiology now have several large online databases, including Neotoma (paleoecology) and the Canadian Archaeological Radiocarbon Database, among many, many others.

Josh Miller and Russ Graham, who invited myself and a group of other researchers to the University of Cincinnati for a workshop on August 23rd and 24th, thought it was high time that taphonomists thought seriously about the creation of an online database. Over the course of those two days we discussed a variety of issues, including the data that might be included in a database, how those data should be coded, the degree to which they should be standardized, and where one might store a taphonomy database.

Welcome poster for the taphonomy workshop in the
University of Cincinnati library.

We are still in the process of putting our ideas into practice, so I can't reveal much as this point, but I do hope that something emerges from what was a very stimulating workshop. I am very thankful to have been invited and to have learned so much.

Oh, and if you ever fly into Concourse B of the Cincinnati/Northern Kentucky Airport, be sure to check out the beautiful replicas of North American Ice Age mammals:

Replica of a Megalonyx jeffersonii skeleton.

Replica of a Mammut americanum skeleton.

This was a pleasant surprise for a zooarchaeologist and taphonomist!

Paleoanthropology Society meetings 2018

The Paleoanthropology Society meetings were held in Austin, TX on April 10th and 11th. I'd never been to Austin and, for some reason, I envisioned a sleepy-ish college town, but boy was I wrong...it's big! There were, as always, several really interesting talks, but I was only able to stay for the first day. Also, this post is tardy by several months, so I'll keep it short.

The most important talk, in my opinion, came from Robyn Pickering, who presented an integrated view of U-Pb dates from flowstones in South Africa. Essentially, these things form during wet phases, when water is entering the caves and minerals are precipitating out of it. The fossil-bearing deposits occur between these flowstones, which means that sediment deposition occurred only during dry phases. The fact that hominin fossils are associated with drier habitats, then, appears to be largely an artifact the patterns of deposition within the caves, rather than a true reflection of habitat preferences. The other really fascinating talk involved the 3.6-million-year-old Laetoli footprints. The most famous, of course, is the "G" trackway that preserves the footprints of at least three bipedal individuals. Much less well-known (heck, I had forgotten all about it myself), however, is the "A" trackway originally identified as hominin but later hypothesized to have been formed by an ursid. Ellison McNutt and her colleagues reexamined the ursid hypothesis by convincing several American black bears to walk bipedally through mud. The Laetoli A prints, interestingly, are similar in some regards to bipedally walking bears and chimpanzees. However, the stride width of the Laetoli A prints is much narrower than that seen among bears or chimps, which McNutt et al. interpret as evidence for a pelvic stabilizing mechanism and/or a valgus knee--both of which are only seen in human bipedalism. So, they conclude that while the Laetoli A prints are not modern human in form, they most likely belong to a hominin, perhaps a species that did not utilize a modern human form of bipedalism.   

Our team, with Faith Wilfong as lead author, presented a poster about our ongoing work with modern bone scatters on the eastern edge of the Serengeti. Of particular relevance, too, was a poster from Charné Nel, Jason Heaton, and Colin Menter that provided a taphonomic analysis of baboon carcasses from Misgrot Cave, which is one of the comparative samples my colleagues and I used in our recent PNAS paper.

To wrap up the trip, I had a quintessential taxi experience on the way to the airport. The driver, a really nice dude named Chris, told me all about how he had moved to Austin from New England in the 1970s for college, tried to slip into the music scene, and eventually found himself working for a music shop that built guitars for members of the Rolling Stones. Ah, Austin... 

Transforming online pedagogy

I am, as usual, behind on my posts, so here is one from an event I attended way back in May...

UNCG's University Teaching and Learning Commons sponsored and hosted the Transforming Online Pedagogy and Practices Symposium, or TOPPS, this past May 7th through 11th. This wonderful event ran the entire week, although I was only able to attend Tuesday and Wednesday. I'm very happy I did so, too, because UTLC brought in Dr. Michelle Miller, a cognitive psychologist who specializes in memory and attention, as the keynote speaker. Her presentation, which revolved around the theme "Leveraging Psychology to Create Compelling Learning Experiences," was spread across two morning sessions.

The first session focused on memory and attention. Dr. Miller began by asking us to recall movie lines. It turns out that people are surprisingly good at recalling, verbatim, extended pieces of dialog from our favorite movies. Wouldn't it be nice if students could retain information like this in our classes? What is it about movie lines that encourages long-term retention? As we went around the room, folks identified several factors that explains this, including the fact that the lines appear as part of a dramatic scene in which we were (at the time of viewing) deeply engaged. In other words, we were fully attentive, and attention, as Dr. Miller pointed out, drives memory. The problem, though, is that many things can interrupt the link between attention and memory: excessive cognitive load (there is simply too much strain being put on attention), poor mastery of low-level processes (they have not yet been automatized and, thus, take up some attention), and "dysfunctional multi-tasking" (the myth that attention can be effectively split among several tasks).

So, how do we capture students' attention in order to exploit the link between attention and memory? Dr. Miller had several suggestions:

• Ask for responses, and do it often. Asking someone to retrieve information immediately focuses their attention on the task at hand. Student Response Systems in face-to-face courses and interweaving questions into online text can keep students involved and attentive.
• Work to automate lower-level tasks so that they require less attention. Assignments that require and reward repeated practice and even speed help students achieve mastery of tasks that teachers, as experts, take for granted. We thus need to ask ourselves: what skills can we reasonably automate in our courses? 
• Address attention myths. Most students (and most people, for that matter), for example, are under the impression that they can multi-task without negatively affecting their attention on any one task (reading and watching YouTube, anyone??). Another common misconception is that certain people are exempt from the attentional limitations of the human mind (well, most people can't multi-task, but I can...). Dr. Miller developed an online module called Attention Matters! that demonstrates to users how limited attention really is. She and her colleagues have shown that the module does help students realize how difficult it is to learn something without fully attending to it. Memory is, after all, not a fixed thing. It is constantly constructed and reconstructed.   

Ultimately, it is important to realize that memory is an adaptation; we are, in fact, evolved to remember things! However, our brains must use relevancy to decide how to parse out the limited amount of attention it has at its disposal. Items are also more likely to be recalled when learned within a context that creates cues.

Dr. Miller also stressed the visual nature of most learning--while people may prefer particular modes of content delivery (audio, verbal, etc.), the idea of "learning styles," as I found out, has been largely debunked. Okay, so what does the field of applied memory tell us? In other words, how do we make our material memorable? Well...

• Harness the "testing effect." Reading quizzes, repeatable quizzing, self-quizzing: forcing one to recall information helps build memory.
• Space it out. Break information into smaller temporal chunks and include exercises that involve information retrieval between chunks of information. When material involves categorization or problem types, interleaving can be particularly effective.
• Push powerful processing. Ask students to synthesize information and relate material to themselves. Visual diagrams, especially those that have audio and an interactive interface, can be especially powerful.

Dr. Miller demonstrated these principles with a simple request: draw a penny. Try it yourself. Suffice it to say, I was not able to recreate a U.S. penny on my pad of paper (I was able to produce a circle with a face and some of the correct words, though). Why? Do I need to know what a penny looks like? Nope. This knowledge is not relevant, so I've no reason to continuously look at a penny and remember what it looks like. So, I have never quizzed myself about it. There is also no context here--why does a penny look the way that it does? I've never been forced to synthesize the information about a penny. All that historical and political information would provide critical context.

An infographic entitled "How to remember (almost) anything" very nicely summarized the morning's session (see more details here):

• Quiz, don't reread. Actively recall information rather than passively rereading it.
• Visualize it. Associating information with sensations is memorable, and vision is a strong sensory cue for most people.
• Structure it. Break information into parts and put related pieces into meaningful order or structure.
• Give it meaning. Brains remember things that mean something to their owners. Before trying to remember something, make sure you understand it.
• Relate it to yourself. Personal relevance makes things stick and allows you to draw on what is already known.
• Create a cue. Find parts that are difficult to recall and link that piece of information to something that's more vivid.    

The second session revolved around thinking, motivation, and self-regulated learning. Having students "think" is, of course, what we as instructors want, but it is a skill that needs to be cultivated. What is more, we have to define what we mean by "thinking." This can be difficult, since it can manifest in a wide variety of ways, from problem solving and formal reasoning to critical thinking and analogical reasoning. Thinking can be difficult to develop, too, because it is often crowded out by content. The question, as Dr. Miller presented it, is: how do we balance thinking skills and content knowledge so that the complement each other?

This is what the literature tells us about thinking skills:

• Thinking skills are context specific, so they do not transfer as well as we think they do. Better transfer of skills can be attained through repeated practice across--and this is key--varying examples. This taps into the deeper structure of a problem, which is something that novices have real difficulty with because, for them, everything matters. In other words, students are unable to distinguish between the unimportant details and the more meaningful framework of a problem. (Raise your hand if you've ever said "Don't worry about the details here. Pay more attention to the general principles." Well, there you go.)
• Critical thinking is difficult to define and, thus, particularly tough to address. The barriers are myriad, and include a resistance to independent thinking and the fact that just because you can thinking critically doesn't mean that you will. Why? Well, it's hard! You have to be motivated to do hard things, so the problem requiring critical thinking must matter (back to relevance).     

Dr. Miller offered the following suggestions for producing thinkers:

• When designing a specific activity or an entire course, think first about the specific skills you, as the instructor, want to cultivate. Align the course and its activities to those skills, which counters the tendency to focus exclusively on content.
• Ensure that activities encourage transferability by creating lots of examples with different surface details.
• Use scenarios like case studies, problem-based learning, role-playing, and faux "clients" to work with.

We were then asked to consider our own educational experience in college. What classes were we both interested in and motivated for? What about not interested but still highly motivated? Or perhaps interested but not motivated? There are typically four types of students:

The interest/motivation dynamic requires different approaches for different learners, and there are several approaches to the problem of motivation.

• Classic incentive approaches. These incentives can come from the learner (intrinsic) or from the instructor/course/environment (extrinsic)
• Self-determination theory. This approach revolves around the ideas of competence ("I'm good at this, so I can do it," or "I'm no good at this, so I just can't succeed"), relatedness (we're all in this together), and agency (there is some choice on the part of the learner).
• Academic self-efficacy. This is the "You think you can do it, so you do it" approach. Imagine you offer someone $50,000 to prepare a presentation, in a single evening, on a topic that is completely alien to them. Most of us would say that this is quite simply not possible. No incentive, not even $50,000, can change one's motivation if they don't think the goal is possible.
• Mindset. This is based on the now well-known work of Carol Dweck, who distinguishes between a "growth" mindset (intelligence is mutable, so one can become smarter through hard work) and a "fixed" mindset (intelligence is fixed and unchanging, so no amount of work will make one successful).

One interesting suggestion that Dr. Miller made was to borrow from game design. There is, in fact, an entire movement within pedagogy to "gamify" assignments and classes. Games are highly motivating, so I think there is something to be said about this approach. What is it about games that makes them so motivating that they are actually addictive? Well, for one thing, people often get "in the groove" while playing games (this is referred to more formally as flow in the psychology literature), which involves effortless control of one's creative abilities. Games also involve failure, which is also a key aspect of learning. With games, though, the stakes are lower because one can quickly restart, learn from mistakes, and use multiple attempts. Games also have a sense of mission and a narrative, which creates user investment in the outcome. Perhaps our assignments can be designed with these tenets in mind. In particular, assignments and courses should tell learners why they are completing tasks and involve frequent low-stakes assignments (this provides lots of feedback, makes it easier to accept, and learn from, failure, and permits the slow advance toward a larger goal).

The UTLC also provided several sessions for online course design and implementation, including difficult-to-implement tasks like group work. Overall, this was a wonderful symposium.

Field dispatch: Olduvai Gorge 2018

I recently (two days ago, to be exact) returned from Olduvai Gorge, and we had another productive field season. For the fifth year in a row, I directed the UNCG Olduvai Gorge Paleoanthropology Field School in conjunction with our research project, The Olduvai Paleoanthropology and Paleoecology Project, or TOPPP. The 2018 field school was fantastic, with participants from across the United States in addition to Turkey and the UK.

Excavations at BK East, Bed II, Olduvai Gorge. From left to right: Vicky Wen (University of Wisconsin), Mathilde Ribordy (Harvard University), Alaz Peker (field school TA, Istanbul University), and Alicia Costa-Terryll (University of North Carolina at Greensboro).

Our research team continued work in Beds I and II, including the site of DS (contemporaneous with the famed FLK 22, or Zinjanthropus, site) and BK East (where I direct excavations). Be on the look-out for news on these sites within the next year or so.

I should also mention here the new Oldupai Gorge Museum. There has, of course, been a museum on-site at the gorge for many, many years. However, and thanks to a collaboration between the government of Spain, the Ngorongoro Conservation Area Authority, and the National Museum of Tanzania, a new state-of-the art facility opened in the fall of 2017. I saw the building during construction last summer, and it was fantastic to see it fully complete this summer. The highlight is most certainly the beautiful murals painted by renowned paleo-artist Mauricio Anton.

View of the interior of the Oldupai Gorge museum. The exhibits occur in a circular pattern surrounding the central space pictured here.

One of the murals by Mauricio Anton at the new Oldupai Gorge museum.

Undergraduate research at UNCG

Each year, the Undergraduate Research, Scholarship, and Creativity Office here at UNCG hosts the Thomas Undergraduate Research and Creativity Expo, which provides a venue for undergraduates engaged in faculty-mentored projects to present their scholarly and creative work to the university community. This, the 11th such event at UNCG, included over 200 students, four of whom worked with me on various topics:

• I participated in an Ashby Dialogue last year that focused on the use of Social Network Analysis (SNA) in archaeology. As part of that dialogue, I was asked to lead a discussion in my area of expertise, the Paleolithic. I soon discovered that there was, in fact, no example to discuss. So, I downloaded some data and threw it into Cytoscape to see if a SNA approach could provide some insight on social landscapes during the Magdalenian. This time period is justifiably well-known for its beautiful portable art, which provides a rich database of social information. I have since become really intrigued by SNA, and it just so happens that a colleague in the Department of Computer Science, Jing Deng, specializes in social networks. After a couple of informal meetings, Jing and I decided to recruit two undergraduates, one from anthropology and one from computer science, to work with us on a collaborative project. We secured some funding from the Undergraduate Research, Scholarship, and Creativity Office to support Amanda Chase (anthropology) and Nathan Arnold (computer science). While Amanda collected data on Magdalenian artwork, Nathan programmed, from scratch, an application that (1) allows users to upload archaeological data; (2) visualize the location of archaeological sites in true geographic space; (3) calculate the similarity of archaeological artifacts based on artistic motifs; (4) visualize the archaeological sites in "network" space to identify social relationships. Amanda (oral presentation) and Nathan (poster presentation) both did a great job, and Jing and I are currently putting together a grant proposal to secure long-term funding for this project.

• As part of my research at Olduvai Gorge and as director UNCG's Olduvai Gorge Paleoanthropology Field School, I am engaged in a long-term project to document the distribution of bones on modern landscapes. Olduvai lies on the eastern edge of the Serengeti, and I am particularly interested in the factors that influence where bones are distributed in this dynamic area. Ultimately, I hope to apply this information to the fossil assemblages that we are excavating within the gorge itself. In 2015 and 2017, we collected over a thousand bones from two microhabitats: an open, treeless grassland and a wooded area surrounding a seasonal watering hole. Faith Wilfong, who was recently accepted to the graduate program in anthropology at the University of Iowa, attended the 2017 field school and, with funding from the Undergraduate Research, Scholarship, and Creativity Office, helped me analyze these two bone assemblages. Faith found that the open grassland assemblage likely accumulated over decades, which, given how dispersed the bones are, implies that even diffuse scatters of bones require a long time to form through "natural" (i.e., non-human) processes. She also found striking differences in the density and pattern of distribution of bones within the two microhabitats. Bones were much, much more common in the wooded habitat and tended to be distributed most densely under trees. Faith presented these data as an oral presentation at the expo and as a poster at the Paleoanthropology Meetings in Austin.

• Finally, I worked with Ashley Nelson (who participated in the 2016 Olduvai Field School) on an open-access, online paleoanthropology database. The University Libraries here at UNCG offer Digital Partners Grants, which provide library expertise to a faculty member interested in working on a digital project. I was lucky enough to be awarded one of these grants, and I recruited Ashley to help put together a database that cataloged the location and artifact and fossil inventories of paleoanthropological sites. We are working with the extremely capable Danny Nanez, a web applications developer with the University Libraries, to get this database online and available for researchers to not only map paleoanthropological sites but query them based on age, artifact type(s), and the presence/absence of fossils. I hope that this will be a useful tool for researchers, students, and instructors alike. 

I should also point out that another one of our undergraduates, Curran Fitzgerald, working under the direction of our own Donna Nash, won first place for his poster presentation "Archaeoastronomical analysis of Wari ritual spaces in the Osmore Valley, Peru."

Building the National Museum of African American History and Culture

The Harriet Elliott Lecture Series is one of UNCG's marquee events. The College of Arts and Sciences has a large endowment to bring dynamic speakers to campus to address important and timely issues within the social sciences. The event cycles among the departments within the College here at UNCG, and this year's host department was History, who organized everything around the theme "The Power of History: Memory and Representation."

The keynote speaker was Dr. Lonnie Bunch, the founding director of the Smithsonian National Museum of African American History and Culture. As the Chair of the Harriet Elliott Steering Committee, I had the pleasure of meeting him in person before the keynote address on the evening of March 27th. An extremely pleasant person, Dr. Bunch was at ease discussing everything from history to baseball. (He did relate a disturbing story about White supremacists who would periodically visit the museum to laugh at the slavery exhibits.)

The keynote address, which was attended by about 190 people, was entitled "Building the National Museum of African American History and Culture." Dr. Bunch is a wonderful storyteller. He was so engaging, in fact, that I was hardly aware of the passage of time: I couldn't believe that an entire hour had elapsed. Some of the highlights:

• I was surprised to learn that serious schemes to create a museum dedicated to African American history and culture first appeared before World War I, and President Calvin Coolidge signed legislation in 1929 that created a commission to design and construct such a museum. Unfortunately, pressure from Southern politicians ensured that no funding was attached to the resolution, and the onset of the Great Depression sidetracked the enterprise. It was not until 2003, when President George W. Bush signed another authorization, that momentum for a museum again gained traction.
• The story about the museum's collection was particularly fascinating. With what was essentially the Smithsonian's version of Antique Roadshow, Dr. Bunch and his staff scoured the country for items. Ultimately, of the ~40,000 pieces in the museum's collection, about 70%, including a bible owned by Nat Turner, were pulled from peoples' attics, basements, and garages.    
• The final price tag for the museum came to $540,000,000, and the average visit lasts about 4-6 hours. (The average visit for the other Smithsonian museums is about 1.5 hours.)
• While assembling the collection was a gargantuan challenge, the most difficult task was deciding what sort of museum to build. The ultimate goal, Dr. Bunch said, was to confront what it means to be an American. So, the museum needed to create not only a Black experience, but an American experience. Dr. Bunch also wanted the museum to humanize history and, in so doing, help people embrace ambiguity and nuance. What, then, should the museum be about? Pain? Slavery? Famous firsts? Should the exhibits and the museum be for African-Americans alone? The answer was to find the right tension between all of them. My sense is that the purpose of the museum is to invite people to take ownership of our past, to confront memory, and to invite reconciliation. 

History organized a follow-up panel discussion, attended by ~85 people, entitled "History Matters: Searching for LGBT History" featuring John D'Emilio and Mandy Carter. Hats off to the Organizing Committee from History, especially Anne Parsons and Asa Egar, who put together an absolutely fantastic event.

I think the impact that the museum could have on Americans was expressed best by Princey Jenkins, a 93-year-old African-American who, when interviewed by Dr. Bunch during the planning phase of the museum project, said "People used to remember. Now they forget."

When did humans start deliberately disposing of their dead?

Research continues to reveal that non-human animals recognize death and express what we would call grief for the loss of a group member. There is no doubt that this narrows the perceived gap between humans and other animals and reinforces the continuity of life. As far as we know, however, we humans are the only species that is fully aware of our own mortality. With this realization comes the ability (or curse?) to anticipate and contemplate our death and the deaths of others. We express this "mortality salience" (to use the term of social psychologist Jeff Greenberg and his colleagues) in part through elaborate mortuary rituals. When did humans develop this mortality salience, and how might we tell?

While much of the symbolic meaning associated with these rituals does not fossilize, some behaviors, such as the creation and interment of grave goods, the intentional modification of human remains and, most pertinent to this post, the deliberate disposal of the dead, can potentially survive in the archaeological record. There is a growing consensus that by ~120,000 years ago Neandertals and other Middle Paleolithic humans intentionally buried their dead and, in some cases, perhaps even collected the bones of the dead for secondary burial (the evidence for grave offerings remains equivocal). The case for deliberate disposal before the Middle Paleolithic is more contentious, and the present debate revolves around the Sima de los Huesos in the Sierra de Atapuerca in Spain and the Dinaledi Chamber in the Rising Star Cave System of South Africa. Dated to between 300,000 and 600,000 years ago, these remarkable fossil assemblages are composed nearly exclusively of human bones. What is more, the skeletons are found in difficult-to-access chambers deep within the cave systems. These are extraordinary finds, and it is reasonable to ask: (1) if they represent the remains of corpses that were deliberately disposed of and, if so, (2) whether the process of corpse disposal was infused with some deeper cultural meaning, as it is among modern humans.

My colleagues and I recently put in our two cents worth on this topic in the Proceedings of the National Academy of Sciences (the study has garnered some modest publicity in Spain and the United States). Thankfully, both the Atapuerca and Rising Star research teams have published extensively so that their data are available to other paleoanthropologists. After my friend, colleague, and former PhD adviser Travis Pickering pored over the frequencies of skeletal elements from the Dinaledi Chamber, he told me the pattern was not what one would expect if complete bodies were being deposited in the cave. We therefore decided to put together a small database of skeletal element data from other sites with primate remains. I eventually found over 30 datasets that ranged from modern forensic cases and leopard-consumed baboons to 3.2-million-year-old autralopiths. Another good friend and colleague, Manuel Domínguez-Rodrigo, argued that a machine-learning approach would be appropriate here, since these sorts of algorithms might be able to distinguish among the different types of assemblages based on patterns of skeletal element preservation.

Essentially, we found that the pattern of bone preservation in the Sima de los Huesos and the Dinaledi Chamber is different from that seen in complete skeletons. Now, this in and of itself does not refute the hypothesis that the Sima and Dinaledi remains were deliberately disposed of--even intentionally buried bodies can be scavenged or moved around after their original deposition. (In fact, we think it is likely that carnivores consumed some of the softer bones at both sites.) What was most intriguing to us, though, was the fact that both the Sima and Dinaledi consistently clustered with an assemblage of baboon bones from an active cave system in South Africa called Misgrot. This cave, which was investigated by two other colleagues, Jason Heaton and Colin Menter, preserved over a thousand baboon bones, some of which were found as partial skeletons. Since the baboons aren't being intentionally dropped into the cave by conspecifics (the cave is used mainly as a sleeping site), it stands to reason that you don't need to invoke deliberate disposal to explain the skeletal part frequencies of either the Sima or Dinaledi. It is, in other words, possible to get a collection of partially complete, large-bodied primates into a cave through natural processes.

We are careful to note that these findings don't disprove the deliberate disposal hypothesis at these sites. Is it possible that some time before 300,000 years ago early humans were intentionally dumping bodies into caves? Sure. Is it even possible that this behavior had some sort of symbolic meaning behind it? Absolutely. But, as the aphorism made famous by Carl Sagan goes, "extraordinary claims require extraordinary evidence." So, to quote our paper, neither the Sima or Dinaledi "currently qualifies as unequivocal evidence for emergent mortality salience in the human lineage."

References:

Egeland, CP, Domínguez-Rodrigo, M, Pickering, TR, Menter, CG, Heaton, JL (2018). Hominin skeletal part abundances and claims of deliberate corpse disposal in the Middle Pleistocene. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1718678115