Sabertooth cats and early humans

It's been over two years (!) since I travelled down with my colleagues Manuel Domínguez-Rodrigo, Lucía Cobo-Sánchez, and Enrique Baquedano to the Florida Museum of Natural History to examine the fossils from a site called Haile 21A. What initially drew our interest was the co-occurrence of two partial skeletons of the sabertooth cat Xenosmilus hodsonae with over two thousand peccary bones within the sediments of an ancient sinkhole. I returned home from that trip just days before much of the country shut down because of the COVID-19 pandemic. What a two years it has been...but I am happy to report that we have completed our analysis, and the results appear in the journal Nature Scientific Reports. The study has enjoyed some modest media attention from both Rice University and my own institution.

Sabertooth cats—named for their imposing upper canines—roamed the landscapes of Asia, Europe, and the Americas for several million years before the last species went extinct ~10,000 years ago at the end of the last Ice Age. As apex predators, sabertooth cats played an important role in regulating ancient ecosystems. While they are fascinating in their own right, what draws me to these remarkable predators is the fact that they shared the landscape with, and often came into contact with, our early ancestors. The invention of sharp-edged stone tools ~2.6 million years ago allowed early humans to butcher the meat, organs, and other soft tissues from the carcasses of large animals. This change in diet no doubt would have increased the chances of running into a sabertooth. The question is: what were those interactions like? We know that some unlucky australopithecines fell victim to large cats like leopards, so it is likely that sabertooths too preyed upon our ancestors. Some researchers also argue that the abandoned kills of sabertooths would have provided scavengers, including early humans, with a ready meal. This is not an unreasonable idea. The enormous canines of sabertooths, while no doubt efficient killing weapons, were relatively narrow and thus prone to breakage. So, the idea goes, sabertooths intentionally avoided tooth-on-bone contact in order to protect their delicate teeth but, in so doing, left significant chunks of flesh and all the goodies inside of bones (marrow, grease, and the like) behind for others to eat.

Researchers have devised ingenious methods to reconstruct the killing and feeding behavior of sabertooths by analyzing the shape and chemical make-up of their teeth and bones. This information provides a wonderful window onto the adaptations of these animals. In order to directly infer what they ate and how they ate it, however, we really need to look at the bones of their prey. There are many sites around the world where sabertooth fossils are found in association with the bones of potential prey animals. The problem is that it's very difficult to be sure that sabertooths were the culprit. After all, lots of other animals and even geological processes can accumulate bones. So, it is only in very rare circumstances that we can be reasonably sure that sabertooths were responsible for the bones found at a site. It so happens that Haile 21A is just such a place: we can say with a good deal of confidence that the sabertooth cat Xenosmilus consumed about sixty peccaries there some million-and-a-half years ago.  

That's not to say this whole thing is straightforward. In fact, there are three carnivores in addition to Xenosmilus at Haile 21A, and one or more of them could reasonably be considered as suspects: a coyote-sized canid called Canis edwardii, a wolf-sized canid called Canis armbrusteri, and the sabertooth cat Smilodon gracilis. So why do we think the peccaries were eaten by Xenosmilus? The clues lie in the tooth marks left on the peccary bones. The marks are too big to have been created by Canis edwardii, so that's one suspect eliminated. We know, too, that modern wolves tend to gnaw on and break open bones, which results in lots and lots of individual tooth marks (try this at home with your dog). The peccary fossils, when they do preserve tooth marks, often only preserve a single, or perhaps a few, individual marks—quite unlike a large canid but very similar to what we see among modern big cats like lions and leopards. Another suspect down. That leaves us with the two sabertooth cats. To untangle this, we impressed the teeth from fossils of each species into clay in order to determine if the shape of their tooth marks could distinguish them. It turns out that yes, they can, and in most cases the tooth marks match up very well with Xenosmilus. In fact, the teeth of a Xenosmilus fossil from Haile 21A fit snuggly inside several tooth marks, which is about as close to a smoking gun as you can get.

Impressions of Haile 21A sabertooth teeth in clay (photo: Manuel Domínguez-Rodrigo)

Xenosmilus tooth placed inside a tooth mark
(photo: Manuel Domínguez-Rodrigo)

Now that we've identified our culprit, we can proceed with reconstructing how sabertooths consumed their prey. The peccary bones from Haile 21A show evidence for nibbling on or near muscle attachments, so much so that parts of the bone itself was chewed away completely. This is not what you would expect if Xenosmilus was afraid to graze the bone with its teeth. Nor would you see this if large hunks of meat were being left on the bones. The patterns of damage on the Haile 21A fossils in fact match well what we see on the bones of prey consumed by modern lions, who we know leave very little flesh behind. This means that little, if any, meat would be left on the peccary carcasses for a would-be scavenger. What Xenomsmilus did not do, or did not do very often, is break open the peccary bones. This, too, is consistent with observations of modern lions, who can gnaw off the softer parts of bones but typically do not crush or fragment them. So, a scavenger might have been able to scrounge some marrow and grease from the abandoned peccaries at Haile 21A. Our findings from Haile 21A do not appear to be a one-off, either. The 20,000-year-old fossils of juvenile mammoths at Friesenhahn Cave in Texas show that another species of sabertooth cat, Homotherium serum, also stripped clean the carcasses of their prey.   

That's all well and good, but it's important to point out that the fossils from Haile 21A and Friesenhahn Cave were deposited before humans ever set foot in the Americas. How, then, can we use these findings to test the idea that early humans scavenged from the remains of sabertooth kills? Importantly, the teeth and skeleton of Xenosmilus and Homotherium are very similar to those of other species of sabertooth cats that shared the landscape with humans in Africa, Eurasia, and the Americas between 2.5 million years ago and 10,000 years ago. We therefore think it is plausible that most of these cats consumed their prey in a similar fashion. If that is the case, an abandoned sabertooth kill would probably have been an insignificant and irregular source of meat. A scavenger hoping for a more substantial meal would need to be willing and able to drive these big cats from a kill, a strategy referred to as "confrontational scavenging." Cut marks left by sharp-edged stone knives indicate that early humans were indeed fully capable of gaining quick access to carcasses, either as confrontational scavengers or hunters in their own right. In fact, it has been suggested that early humans not only were major competitors but may in fact have contributed to the extinction of some species of sabertooths. I look forward to seeing more research on these iconic predators...there certainly are many more questions to answer.

References:

Domínguez-Rodrigo, M, Egeland, CP, Cobo-Sánchez, L, Baquedano, E, Hulbert, RC (2022). Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds. Nature Scientific Reports. doi.org/10.1038/s41598-022-09480-7

Cut marks, saw marks, and forensic anthropology

Human skeletal remains are not a common occurrence at forensic scenes but, when present, they can preserve a great deal of information about the events surrounding the deposition of a corpse. Forensic anthropology, the field that specializes in the analysis of human skeletal remains in medico-legal contexts, has garnered a good deal of attention from the popular media in recent years. Most of that attention comes from Fox's drama series Bones, which ran from 2005 to 2017 and followed the exploits of forensic anthropologist Temperence Brennan (a character from the novels of forensic anthropologist Kathy Reichs). Suffice it to say, forensic anthropology is now among the most popular courses offered in anthropology departments (including at UNCG where I teach), and undergraduate concentrations and graduate programs in forensic anthropology have popped up across the country. 

Forensic anthropology encompasses a wide variety of methods and techniques, one of which is forensic taphonomy. Taphonomy, broadly defined, is the study of how organic remains (like skeletons) transition from living to static entities. In a forensic context, we ask the question "what happens to a person between death and discovery"? A class of taphonomic data, known as bone surface modifications, or BSMs, is particularly useful for answering this question. Marks on bone surfaces, like carnivore tooth marks, saw marks, insect damage, and the like, can provide critical evidence concerning an individual's death and their body's journey after death. Some insects, for example, are only active on the surface, so if we find damage from that particular insect on human bones, we can be sure that the bones were exposed on the surface, at least for some period of time. A few years ago, in a high-profile murder case in North Carolina, where I live, marks on the bones of a human skeleton were used to help identify the saw used to dismember a body. 

Last fall, my friend and colleague, Travis Pickering, who has spent the better part of 25 years studying taphonomy, was solicited to write a review on the use of BSMs in forensic anthropology for the journal WIREs Forensic Science. He graciously invited me to collaborate on the undertaking, and he and I spent the last year researching how BSMs were integrated into the forensic sciences and how they've been used in crime scene reconstruction. The result of those efforts is an article titled "Cruel traces: bone surface modifications and their relevance to forensic science." (I wish I could take credit for the clever title, but that was all Travis.) As much work as they are, I enjoy writing review articles that cover such a wide swath of a particular field of inquiry because they force me to explore literature that I otherwise might not even have come into contact with. 

Several key themes emerge in our review, namely that: (1) the study of BSMs developed first in the paleontology and archaeology of the mid- to late-1800s and was later adopted by forensic investigators; (2) ultimately, a BSM's utility for forensics (or any other field) is only as good as our ability to link that BSM with a particular process, and that link can only be established through systematic observations of a process actually producing a specific BSM; (3) the features of the BSM itself are not always enough to provide a positive identification, and contextual information must always be used (e.g., serrated knives and shark teeth create very similar striations on bones surfaces, but if the bones were recovered far inland, a shark origin is much less likely); (4) the admissibility of expert scientific testimony in federal courts (the so-called "Daubert" standards) privilege the validity of a scientific methodology over the expertise and experience of any one scientific expert.

As an example, consider a linear striation on the surface of a bone recovered from a crime scene. Now, we might logically interpret that mark to have been produced by a knife. That's all well and good, but lots of things can create a linear mark on a bone: a small, sharp sand grain on the ground, the tooth of a scavenging dog, and so on. How might we know that the knife is, in fact, the source of the mark? Well, for one, we need to conduct an experiment where a knife is observed to create a particular mark on a bone's surface (this can be done with donated human skeletal material or, more commonly, the bones of other mammals like deer or pigs). That way, we know for sure what a knife mark looks like. There are lots of different types of marks, though, and even the same knife can create slightly different marks depending on how it is wielded, so one experiment is typically not enough. However, what if a knife was found alongside the human skeletal material? This sort of contextual information, when considered along with the morphology of the mark itself, can provide additional clues and make our identification that much more probable. When this evidence is presented in court, its admissibility, at least according to federal standards, will have less to do with the experience of the expert witness than with the rigor of the methodology used to identify the BSM. 

Importantly, no methodology can definitively, with 100% confidence, identify the source of a particular BSM. Why not? Well, forensic investigators do not themselves witness a crime: the relevant details must be reconstructed. This is where we get the phrase "crime scene reconstruction" and its common association with archaeology, and for good reason. Forensic investigators are in many ways like archaeologists: whereas archaeologists use artifacts and architecture to reconstruct ancient cultures, forensic investigators use evidence to reconstruct a crime. This means, though, that we must work with probabilities, rather than absolute certainties. When we are able to match up a BSM from a crime scene to an experimentally produced BSM, it becomes highly probable, thought not absolutely certain, that the object that created the crime BSM is the same as the object that created the experimental BSM.

A major hurdle for forensic investigators is that some BSMs can be difficult to tell apart from each other. The marks produced by different types of saws, for instance, share many features. So, too, do the marks produced by different types of knives. With so much overlap, how similar do the little bumps, grooves, and edges of a crime BSM have to be to an experimental BSM to be considered "the same"? What features should we even be looking at, and how do we define them? One analyst's "deep groove" may be another's "V-shaped striation." This sort of inconsistency makes it difficult for BSM analysis to attain Daubert-level methodological rigor. Travis and I conclude with the suggestion that computerized image analysis of BSMs coupled with statistical classification might get us closer to reaching that level of rigor. Either way, it will be interesting to see how the field progresses from here.

Peccaries and sabertooths

I spent my spring break down in Florida--not at the beach, but at the Florida Museum of Natural History in Gainesville. The draw? Sabertooths. My colleagues and I have long been interested in the behavior of these large cats, largely because they shared the landscape with the early hominins that we study at places like Olduvai Gorge. With the exception of the La Brea Tarpits in California, there is no better place in the world than Florida to uncover evidence for sabertooths. The state's karstic landscape contains an almost unrivaled collection of well-preserved Pleistocene fossil assemblages, many of which include the skeletal remains of sabertooths. One of these cats, Xenosmilus hodsonae, lived in Florida between about 2.5 and 1.5 million years ago. A nearly complete skeleton, and the species' holotype, was found a few miles west of Gainesville at a site called Haile 21A. We visited the museum's Florida Fossil exhibit to see a cast of the skeleton.

Mounted skeletons in the main hall of the Florida Fossils exhibit. The
Xenosmilus skeleton is just right of center.

Found alongside this important fossil, inside an ancient sinkhole, was a large collection of extinct peccaries. We are interested in this assemblage because it may teach us a great deal about sabertooth feeding behavior. Our working hypothesis is that the peccaries were victims of predation and that Haile 21A itself represents a Xenosmilus den. The fossil assemblage was excavated in the early 1980s and is now housed and curated by the Vertebrate Paleontology section of the Department of Natural History in Dickinson Hall. The collection is expertly managed by Richard Hulbert, Jr., who is one of the leading authorities on the vertebrate paleontology of Florida and a genuinely nice person.

Collections room of the Department of Vertebrate Paleontology in Dickinson
Hall.

My colleagues Manuel Domínguez-Rodrigo, Lucía Cobo Sanchez, Enrique Baquedano, and I were given access not only to the fossil collection, but a fully functional lab, a photography rig, and comparative skeletal material.

Our assigned lab space in the Vertebrate Paleontology
Section. 

We spent about eight hours a day for the past week looking through ~1,600 peccary specimens. Now, its time to analyze the data, so stay tuned...

Research in Spain

I am very lucky to have received a Giner de los Rios fellowship from the Universidad de Alcalá for the 2018-2019 academic year.  During my stay in Spain, which will last from March to the end of April 2019, I will be working as a visiting researcher at the Instituto de Evolución Humana en África (IDEA), which is co-directed by my friend and colleague, Manuel Domínguez-Rodrigo. My main goals are to work with colleagues on the analysis of faunal material excavated from sites at Olduvai Gorge and to construct a comprehensive database of neotaphonomic studies.

My family and I have been here in Madrid for just over a week now and are enjoying what I am told is unseasonably warm weather. I will be posting now and again during our stay...

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!

Early hominin meat-eating and expensive tissues

I actually was not aware of its publication until I came across it on John Hawks's weblog, but Joseph Ferraro and his coworkers have come out with a detailed taphonomic analysis of the faunal remains from Kanjera South, an important Oldowan site from Kenya that dates to about 2 million years ago. Their abstract does a nice job of summarizing the significance of the site and the study's findings (I guess this is what abstracts are supposed to do, after all; Ferraro et al., 2013: 1):

The emergence of lithic technology by ~2.6 million years ago (Ma) is often interpreted as a correlate of increasingly recurrent hominin acquisition and consumption of animal remains. Associated faunal evidence, however, is poorly preserved prior to ~1.8 Ma, limiting our understanding of early archaeological (Oldowan) hominin carnivory. Here, we detail three large well-preserved zooarchaeological assemblages from Kanjera South, Kenya. The assemblages date to ~2.0 Ma, pre-dating all previously published archaeofaunas of appreciable size. At Kanjera, there is clear evidence that Oldowan hominins acquired and processed numerous, relatively complete, small ungulate carcasses. Moreover, they had at least occasional access to the fleshed remains of larger, wildebeest-sized animals. The overall record of hominin activities is consistent throughout the stratified sequence - spanning hundreds to thousands of years - and provides the earliest archaeological evidence of sustained hominin involvement with fleshed animal remains (i.e., persistent carnivory), a foraging adaptation central to many models of hominin evolution.

This research team has been working hard out a Kanjera for many years now, and its really nice to see a comprehensive analysis of the faunal material from the site (we'd been getting tantalizing hints in various publications and presentations for some time).

Before we proceed, let me summarize the state of affairs just prior to these latest data. The 1.8 Ma time marker that Ferraro et al. mentions refers to the burst of evidence for meat-eating that emerges almost exclusively from Olduvai Gorge in Tanzania. One site in particular, the very well-known Level 22 at the gorge's FLK locality (also known as the Zinjanthropus Floor), dates to about 1.84 Ma and preserves thousands of fossils, many of which bear clear indications of hominin butchery. Now, up until a few years ago, it was thought that the animal bones from many of the other sites from Beds I and II of the gorge (ca. 1.9-1.2 Ma) were also largely the result of hominin activity. However, my colleagues and I showed that there are really only two sites, the previously mentioned FLK 22 from Bed I, and the site of BK, in upper Bed II (about 1.3 Ma), that are largely the result of hominin butchery (Domínguez-Rodrigo et al., 2007, 2009; Egeland, 2008; Egeland and Domínguez-Rodrigo, 2008). Now, we're not saying that hominins weren't at the sites; they certainly made, used, and left stone tools at these locations, but they were not doing a lot of meat-eating. There are a couple of other Oldowan sites here and there with some evidence for butchery, but if we ignore FLK 22 for the moment, good evidence for lots of meat-eating (or, to use Ferraro et al.'s term, "persistent carnivory") really doesn't pick up until much later, perhaps about 1.5 Ma.

What does all of this have to do with expensive tissues? Well, researchers have come up with several well reasoned, and very popular, human evolutionary models based ultimately on the shift to meat-eating. To start, brains and guts are very expensive tissues: one does a lot of thinking and the other does a lot of digesting, both of which take up good amounts of energy. If you start eating more meat, which is nutrient dense and easy to digest, you can divert energy from the guts to develop bigger noggins. Other possible correlates of a diet based increasingly on meat would be increased range size (carnivores, and other animal that eat high quality, easy to digest foods, tend to have larger ranges) and unique life histories (extracting nutrients using technology, and hunting with technology in particular, are difficult things to learn, and you don't want to die before you learn how to do them well, so perhaps we've evolved extended life spans to fit this need). People have traditionally seen the evolution of Homo erectus, with its bigger brain, long, lanky legs, and ability to leave Africa to colonize parts of Eurasia, around 1.8 Ma as great evidence for these shifts. Ok, all well and good, but, to use an old phrase: where's the beef? In other words, where is the evidence for sustained meat-eating just before and as H. erectus was evolving? Other than a single site, FLK 22, there really wasn't much...until now.

This is what makes the Kanjera evidence so important. I'm not sure it completely quashes my reservations (after all, we still only have two sites with good evidence for regular meat-eating between 2.6 Ma, when stone tools were first invented and used to butcher carcasses, and 1.5 Ma), but it is a good start.

References:

Domínguez-Rodrigo, M, Barba, R, Egeland, CP (2007). Deconstructing Olduvai: A taphonomic study of the Bed I sites. Springer, New York.

Domínguez-Rodrigo, M, Mabulla, AZ, Bunn, HT, Barba, R, Diez-Martín, F, Egeland, CP, Egeland, AG, Yravedra, J, Sánchez, P (2009). Unraveling hominin behavior at another anthropogenic site from Olduvai Gorge (Tanzania): New archaeological and taphonomic research at BK, Upper Bed II. Journal of Human Evolution 57, 260-283.

Egeland, CP, Domínguez-Rodrigo, M (2008). Taphonomic perspectives on hominid site use and foraging strategies during Bed II times at Olduvai Gorge, Tanzania. Journal of Human Evolution 55, 1031-1052.

Ferraro, JV, Plummer, TW, Pobiner, BL, Oliver, JS, Bishop, LC, Braun, DR, Ditchfield, PW, Seaman III, JW, Binetti, KM, Seaman Jr, JW, Hertel, F, Potts, R (2013). Earliest archaeological evidence of persistent hominin carnivory. PLoS ONE 8, e62174.

Archaic humans versus giant hyenas in Pleistocene Europe

María Patrocinio-Espigares and her colleagues have published an interesting study claiming to have identified evidence for competition between archaic humans and giant hyenas for access to a mammoth carcass from a site in Spain dated to over one million years ago. The site, Fuente Nueva-3, is found near the southern Spanish village of Orce, which is an extremely rich area for early Pleistocene fossils, including those of hominins. In fact, Fuente Nueva-3 and a nearby site, Barranco León, dated to 1.3 and 1.4 million years ago, respectively, currently preserve the oldest well accepted evidence for hominin occupation in all of Europe.

The excavations at Fuente Nueva-3 have been ongoing for well over a decade, but this paper reports on a partial skeleton of Mammuthus meridionalis, a species of mammoth, found in association with a few stone tools and, intriguingly, some coprolites (that is, fossilized poop). The materials were deposited near the edge of an ancient lake, and the authors argue that the mammoth (an old female) probably died of natural causes. The skeleton is relatively complete; only the legs and the head are missing.

Photo (A) and map (B) showing the distribution of mammoth bones, stone tools, and coprolites from Fuenta Nueva-3 . From Espigares et al. (2013: Figure 4).

Butchery marks (cutmarks from stone knives and percussion marks and notches from breaking open bones for marrow; although, some of the so-called percussion notches look a lot like the carnivore-created notches I've seen from modern assemblages) and tooth marks are pretty common on many bones from levels above and below the mammoth skeleton, but none whatsoever have been discovered on the mammoth bones in question. Nevertheless, the authors contend that the carcass was butchered by hominins, who removed the legs for consumption elsewhere, and later partly consumed by giant short-faced hyenas (Pachycrocuta brevirostris; they do not, however, tell us how they know the coprolites are those of a hyena).

I suppose this is possible. The authors correctly note that proboscideans are so big, and are covered by so much tough soft tissue, that butchery and tooth marks are unlikely to be inflicted. Pachycrocuta, though, as a recent paper by many of the same authors tells us, was about one-and-a-half times bigger than modern spotted hyenas and probably better adapted to bone-cracking than any other mammal that ever existed (Palmqvist et al., 2011) so, if anything would have left tooth marks on a mammoth-sized carcass, you would think it would be Pachycrocuta. I'll let the authors summarize their thoughts (Patrocinio-Espigares et al., 2013: 122; see the drawing by the very talented Mauricio Antón below for a reconstruction):

The Upper Archaeological Level of Fuente Nueva-3, dated around 1.3 Ma, provides the oldest evidence of a probable competition between Homo and Pachycrocuta, the two major bone-modifying and accumulating agents during early Pleistocene times in Europe. The evidence lies in the finding of an incomplete skeleton of M. meridionalis surrounded by 34 coprolites and 17 lithic artifacts. The skewed spatial distribution of these elements, the physical characteristics of the coprolites and the absence of the elephant limbs and cranium suggest that both hominins and hyenas scavenged the carcass of this megaherbivore, following a sequence of consumption in which the hominins arrived first, dismembered and transported the limbs, and probably also the cranium, and later the hyenas consumed the rest of the elephant carcass.

Original caption: Reconstruction of the possible sequence of interaction between hominins (A) and hyenas (B) during the exploitation of the carcass of M. meridionalis. From Patrocinio-Espigares et al. (2013: Figure 7). 

These conclusions are all based on indirect evidence (stone tools that may or may not have been used to butcher the animal, coprolites that may belong to hyenas that may have fed on the carcass). Either way, this does bring up the interesting issue of how hominins and carnivores interacted: were they competitors on the landscape for carcasses? Was this competition direct (i.e., fighting over access to carcasses) or indirect (one removing edible carcasses from the environment that the other in turn could not exploit)? Researchers have in fact suggested that competition from large carnivores went a long way towards preventing hominin populations from permanently colonizing Eurasia until after 600,000 years ago or so.

References:

Palmqvist, P, Martínez-Navarro, B, Pérez-Claros, JA, Torregrosa, V, Figueirido, B, Jiménez-Arenas, JM, Patrocinio-Espigares, M, Ros-Montoya, S, De Renzi, M (2011). The giant hyena Pachycrocuta brevirostris: modelling the bone-cracking behavior of an extinct carnivore. Quaternary International 243, 61-79.

Patrocinio-Espigares, M, Martínez-Navarro, B, Palmqvist, P, Ros-Montoya, S, Toro, I, Agustí, J, Sala, R (2013). Homo vs. Pachycrocuta: earliest evidence of competition for an elephant carcass between scavengers at Fuente Nueva-3 (Orce, Spain). Quaternary International 295, 113-125.

Reconstructing subsistence during the Plio-Pleistocene

I just finished going through an interesting analysis by Michael Pante of the large mammal faunal assemblage from the site of JK2, which is in Bed III of Olduvai Gorge and dates to approximately 1.0 million years ago. The study in important for a number of reasons, not the least of which is the fact that we have so few decently preserved faunal assemblages that date to this time period. What is more, JK2 preserves butchery marks, another rarity among sites of this age, which show definitely that hominins (in this case, probably Homo erectus) were cutting flesh from carcasses and breaking open bones for marrow.

Ultimately, Pante uses the frequency and anatomical placement of the butchery marks and the carnivore tooth marks to argue that Homo erectus was gaining early access to carcasses (that is, before other carnivores had a chance to consume the carcass). This is potentially important, because there has been a lot of discussion about the importance of meat in the diets of early hominins. If meat was a staple of the diet, it is possible that it partly drove other evolutionary changes such as increased brain size (meat is easy to digest, so if you could free up energy that is usually channeled to the guts to process food, it can be diverted to other important organs, namely the brain). Pante compares the frequencies of butchery and tooth marks in the fossil assemblage to experimental assemblages of bones exposed to various processes:

• Hammerstone-only, in which humans cut the flesh from bones and then broke them open with stones to access the marrow
• Carnivore-only, in which carnivores (mainly hyenas) consumed carcasses
• Hammerstone-to-carnivore, in which humans cut the flesh from bones, broke them open for the marrow and, afterwards, carnivores scavenged the remains
• Whole bone-to-carnivore, in which humans cut the flesh from the bones but left everything else (flesh scraps and marrow) for carnivores to scavenge
• Vulture-to-hominin-to-carnivore, in which vultures ate some of the flesh, humans broke open the bones for marrow, and then carnivores scavenged the leftovers

The important observation here is that each of these experimental scenarios results in different frequencies and locations of butchery and tooth marks. For example, when humans remove the flesh and the marrow, there are very few tooth marks, since carnivores have little reason to gnaw on bones that are devoid of edible tissue.

While I agree that Homo erectus probably gained early access to carcasses, what struck me is the fact that the JK2 assemblage really does not match up very well with any of the experiments. I have run across this myself in analyses of other assemblages, and I can't help but wonder that the experimental scenarios that we've come up with so far, while extremely useful, simply are not comprehensive enough to model the complexities we're seeing at these Plio-Pleistocene sites, a point that Pante concedes in the paper. Regardless, this paper provides additional data on a critical, and currently poorly sampled, time period.

In my mind, two of the most important things that Plio-Pleistocene taphonomists need to work out are (1) reaching consensus on exactly how we identify marks on bones and (2) producing experimental bone assemblages that can test a wider variety of potential behavioral scenarios.

References:

Pante, MC (2013). The larger mammal fossil assemblage from JK2, Bed III, Olduvai Gorge, Tanzania: implications for the feeding behavior of Homo erectus. Journal of Human Evolution 64, 68-82.

Neandertals in Denmark? Maybe not...

There has been quite a bit of discussion about the range and, thus, the colonization abilities of Neandertals. Traditionally, the Neandertal world was thought to be limited to western, central, and eastern Europe, north Africa, and western Asia, with Uzbekistan representing the group's easternmost outpost. However, more recent mitochondrial DNA analyses of human fossils from Siberia effectively extended the known Neandertal range some 2,000 km to the northeast, and excavations at other sites now show that they inhabited a wide variety of habitats, including coastal areas and relatively rugged mid-altitude zones. Basically, Neandertals appear to have been much more adaptable that we've historically given them credit for.

My colleagues and I just published a study, which was funded by Aarhus University, on some ~120,000-year-old fallow deer skeletons from Denmark that were thought for many years to have been butchered. Butchered animals bones, of course, mean that humans were around and, given the age of the finds, Neandertals were considered the most likely culprit. If the remains were indeed butchered, this would have been the earliest and best evidence for a human presence in the region before the end of the last Ice Age (about 18,000 years ago).

After having looked the bones over, however, we were forced to conclude that there is no definitive evidence that Neandertals, or anyone else for that matter, butchered these animals. The bones are indeed broken, and one of them does show marks that could be interpreted as originating from a stone knife. The reason we're so cautious is that no compelling reason exists to attribute the breakage or the mark to anything other than natural processes.

Reconstruction of a rather sunburned Neandertal (courtesy of Berlingske Tidende)

Although this isn't huge, international news, it did make quite a splash in the Danish media. You can check out some of these stories (if you don't speak Danish, I suggest Google Translate, it does a fair job):

• Here's the Aarhus University press release
• Stories from the larger national newspapers Berlingske Tidende and Politiken, and the smaller, regional newspaper Jyske Vestkysten

One of the main problems here is that Danish archaeology has traditionally been dominated by later prehistoric and Medieval research. So, no one has really take the time to look for well-preserved Paleolithic sites. Luckily, Trine Kellberg Nielsen, a Ph.D. student at Aarhus and one of the co-authors on our fallow deer study, has recently received support to systematically examine the issue of a Neandertal occupation of Denmark. Hopefully her work will help turn up definitive evidence...

UPDATE 3.28.13

Here is a poster that Trine recently presented highlighting her plans for future work in Denmark. The most interesting aspect will involve paleoenvironmental reconstructions that will attempt to highlight areas most likely to have been occupied by Neandertal groups.