Shopping for rocks in the Olduvai Basin

The invention and proliferation of stone tool technology was one of the most significant events in human evolution--the ability to use stones as tools and, eventually, the wherewithal to modify them into sharp-edged knives and other implements enabled our early ancestors to access foods that would have been difficult or impossible to obtain and consume with their relatively small, unspecialized teeth. If you spend some time working with stones, it eventually becomes apparent that not all of them are created equal: some break easily, others are tough to fracture; some produce razor-sharp edges, others generate dull ones; some are close by and/or easy to get a hold of, others are far away and/or difficult to access; some are durable and last a long time, others are brittle and must be discarded after a single use.

Now, we know that a modern human can learn to recognize these attributes and, what is more, they can (not to say that they necessarily do) plan their days with them in mind ("well, let's see...there are two ways to get to the pond for fresh water, Path #1 and Path #2, but only Path #1 has an outcrop of durable rocks on the way, so I'll kill two birds with one stone and take Path #1"). The question, then, is this: to what degree did our early human ancestors appreciate the sometimes subtle differences among rocks, and what can this tell us about their cognitive capacities?

Before we can even answer this very interesting question, however, we need to figure out a way to (1) rank rocks in terms of their usefulness, and (2) determine where on the landscape early humans were getting their rocks in the first place. There is a long history of research on these topics in Paleolithic archaeology, and my colleagues and I added some data to the debate in a recently published paper in Quaternary International. My interest in the topic goes back to the late 2000s, when David Braun wrote a couple of really interesting papers on the stone tools from Kanjera South, a two-million-year-old site in Kenya. Most studies on rock "usefulness" are based on rather subjective and imprecise categories. These categories, and the studies that utilize them, have provided key insights, including the fact that rock selection by early humans was not random. Braun, however, explored the possibility that the material sciences might provide some useful tools to help archaeologists objectively describe the characteristics of rocks.

As I mentioned above, there are a host of features that one might consider when selecting a rock. We chose to concentrate on fracture predictability, largely because the creation of many types of stone tools involves breaking a rock into smaller (and hopefully useful) pieces. If a rock breaks differently every time you hit it, there is no way to predict what you're going to end up with. Sure, it might be useful, but, then again, it might not. With a rock that fractures predictably, though, you can be reasonably sure that the time and energy you've expended will pay off with the production of a useful tool. Flint knappers have known for a long time that homogenous rocks break more predictably than do heterogeneous rocks because they are stronger (they can resist strain) and more elastic (they can resist deformation) when impacted by an outside force. Thankfully, a rock's strength and elasticity are highly correlated with its hardness, something that can be quickly assessed with a rebound hammer. These nifty handheld devices, which were originally designed for use on concrete, fire a spring-loaded plunger onto the surface of a stone. The plunger then bounces back, or "rebounds," after impact. The distance of that rebound reflects the hardness of the stone. Braun and others have used this technique to estimate fracture predictability for the rocks available to early humans at several Pleistocene archaeological sites in Kenya.   

In 2014, we set out to produce comparable data in our neck of the woods, the Olduvai Basin of northern Tanzania. What is today a deep gorge surrounded by open grasslands was, about two million years ago, a stream-fed soda lake surrounded by lush vegetation. Largely unchanged, however, are the volcanic highlands that border the basin to the south and east and the numerous hills--remnants of Archean-aged metamorphosed bedrock--that rise above the plains. Importantly, both the volcanos and the hills are made up of rocks from which stone tools can (and, in the past, could) be made.

A view of Olduvai Gorge in the foreground and, in the background, Naibor Soit, a granulite outcrop from which quartz could be procured (photo: Amy Schnell).

With the help of students from the UNCG Olduvai Gorge Paleoanthropology Field School and Earlham College's Summer Collaborative Research Program, I and my good friends and colleagues Cynthia Fadem and Ryan Byerly have been traipsing around the Olduvai Basin hammering as many rocks as we can get a hold of. Since 2014, we've accumulated a database of 110 specimens, and some interesting patterns have emerged. It turns out that the volcanic rocks that occur as rounded cobbles within the seasonal streams that drain the volcanic highlands have high rebound values and, thus, high fracture predictability, while the metamorphic rocks from the hills show either intermediate or low rebound values. Now, if early humans were selecting their rocks based on fracture predictability, we might expect that most of the artifacts from the archaeological sites would be made from volcanic sources. It turns out, however, that among Olduvai's artifact assemblages, volcanic rocks tend to be very rare, while metamorphic rocks, especially those made largely of quartz, are very common, which implies that fracture predictability was not a major concern. But why not? We might interpret this pattern to mean that early humans in the Olduvai Basin were not clever enough to recognize the value of predictably fractured volcanic rocks. We're skeptical of this hypothesis, though, because experimental work indicates that there are good reasons not to select volcanic rocks, since they:

• usually occur as rounded cobbles, which are tough to flake because they don't have very many of the acute angles that make flake removal possible;
• require more raw muscle power to flake; and
• may not be as durable as other rock types.

What is more, the quartz-rich rocks in the Olduvai Basin:

• are readily available from conspicuous landscape features that are very close to most of the archaeological sites; and 
• are very friable, which, although reducing their fracture predictability, makes them relatively easy to smash into lots of small chunks, among which are typically a handful of useable tools.  

Finally, it's not like volcanic rocks were not utilized at all. In fact, early humans appear in some cases to have selected them over metamorphic rocks when they wanted to create handaxes rather than simple flakes. This makes sense given that the more complex production sequence of a handaxe probably requires a more predictably fractured rock. Unfortunately, you can't subject fragile artifacts to the impact of a rebound hammer. However, if you can tell where the artifact originally came from, we can correlate the hardness of our geological specimens with their archaeological counterparts without subjecting the latter to any damage. Well, in addition to hammering rocks, we also subjected them to X-ray fluorescence, which can help identify their chemical composition. The volcanic rocks are easily distinguished from the metamorphic rocks just by looking at them, but the metamorphic rocks themselves, even those from different hills, can look very similar to each other. Luckily, the chemical signatures of each metamorphic hill are distinct enough for statistical algorithms to correctly match chunks of rock to the correct hill with 75-80% accuracy.

In the future, we should be able to match Olduvai's metamorphic artifacts to the hills from which they were being collected, which in turn will give us an idea of how far early humans travelled when shopping for their rocks.

References:

Egeland, CP, Fadem, CM, Byerly, RM, Henderson, C, Fitzgerald, C, Mabulla, AZP, Baquedano, E, Gidna, A (2019). Geochemical and physical characterization of lithic raw materials in the Olduvai Basin, Tanzania. Quaternary International. doi.org/10.1016/j.quaint.2019.09.036

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...

Back from the Gorge...

I returned from Tanzania last Thursday. We had another successful field season and another great group of students for the field school. Updates to come...

Osteology in the Carolinas 2

Here's another post from my backlog. In February of 2014, I attended the first Osteology in the Carolinas meeting. This year's event was held on February 7, 2015, hosted by UNCG, and organized by our own Bob Anemone. Twelve papers were given, and there were around 20-30 attendees, some from as far away as Virginia and South Carolina. Another set of really interesting papers, one of which was given by a UNCG anthropology undergraduate, Alexa Uberseder (great job, Alexa!) on our work at Olduvai Gorge this past summer. Some snippets from my notes:

• Gwen Robbins Schug (Appalachian State) focused on re-imagining the idea of social collapse, a theme made very famous by Jared Diamond's 2005 book "Collapse: How Societies Choose to Fail or Succeed." In that book, he cites examples of past societies that apparently outstripped their resources and thus collapsed. Gwen made the point that "collapse" may not be the best word, as a detailed examination of the archaeological record indicates that when societies undergo dramatic changes, significant reorganization usually occurs, but the cultural framework remains intact. In fact, what often happens, as her work among South Asian prehistoric sites demonstrates, is that people decide to either remain in cities or move to more rural settings. The latter typically results in a signature that can be misunderstood as a total collapse of society.  
• Megan Perry (East Carolina), who spoke at least year's meeting, and one of her graduate students, Kathryn Parker, both gave talks on attempts to identify the origin of people living in Byzantine and early Islamic times in the Middle East. By assessing the isotopic signatures in food items or geological formations on the landscape, it is possible to determine where people did most of their eating and to track trade routes.
• David Hines (University of Florida and Regime Crimes Liaison Office Mass Graves Investigation Team) summarized some recent work on extracting DNA from skeletons in mass graves in associated with ethnic cleansing in Bosnia. Interestingly, they found that some bones are better for producing DNA profiles than others (as it turns out, the pelvis and femur work best).
• The last talk for which I took detailed notes was by Ashley Gosselin-Ildari (Duke University), who spoke about the use of clickers in large, introductory biological anthropology courses to encourage active learning. This was interesting, and timely, since I started using an on-line Student Response System (SRS) called Socrative to achieve the same goal. I am looking forward to hearing the student reaction at the end of the semester.

Overall, another enjoyable get-together...

Giving a talk at the Smithsonian

I am off for our nation's capital tomorrow morning to give a talk for the Smithsonian Paleoanthropology Seminar. I'm very happy to be reciprocating the visit of my friend and colleague, Dr. Briana Pobiner, who came down to North Carolina last fall to talk about her outreach work. I'll be discussing some of the recent goings on at Olduvai Gorge, and then on Thursday I'll be sitting down with some folks to talk about research we conducted some time ago on the possibility of a Neandertal occupation of southern Scandinavia. Looking forward to it! 

Field dispatch: Back from the gorge

We just got into Arusha this evening after breaking camp at Olduvai and having a great visit through Ngorongoro Crater. I am very happy to report that the 2014 University of North Carolina at Greensboro Olduvai Gorge Paleoanthropology Field School was a fantastic success, and so was this year's campaign. The students, pictured below, were absolutely fantastic. I'll provide more specifics later once I get settled back in North Carolina...

The 2014 UNCG Olduvai Gorge Paleoanthropology Field School. Top row (from left): Victoria Johnson (Teaching Assistant, NYU), Kathryn Dunn (Berea), Rachel Burroughs (Western Michigan), Meaghan Davey (Ohio State), Curran Fitzgerald (UNCG), Jim McClanahan (Miami-Ohio), Adam Darkow (Akron); Bottom row (from left): Andy Ritz (UConn), Cindy Teears (UNCG), Heather Easterbrook (South Florida), Alexa Uberseder (UNCG), Zach Pierce (Texas-San Antonio).

Field dispatch: Off to the gorge!

I am sitting in Amsterdam's Schiphol International Airport waiting for my connection into Kiliminjaro International Airport so we can begin the 2014 field season at Olduvai Gorge. This will also be the inaugural year of the Olduvai Gorge Paleoanthropology Field School, which I am directing through UNCG. We have 11 students from all over the U.S. participating, and we are looking forward to a productive work season over the next month.

Internet access is, of course, spotty at best out at the gorge, but I will try and post a couple updates over the course of the next month... 

Early hominin habitat preferences

I'm in the middle of working on a paper for a special issue of Quaternary International that will bring together recent work at Olduvai Gorge and Peninj, and my contribution focuses on how (or if) carnivore avoidance played a role in conditioning where hominins chose to concentrate their activities. The overarching question, in essence, is: what it is about the areas that preserve accumulations of stones and bones at Olduvai that made them so attractive to hominins (and carnivores)? I came across a new paper by Rhonda Quinn and her colleagues (2013) that uses isotopes to reconstruct the habitat preferences of early hominins in the Turkana Basin of northern Kenya, so I thought I'd take this opportunity to think out loud about the issue of early hominin habitat preferences.

After describing the paleogeography of the Turkana Basin between about 2.4-1.4 Ma, Quinn et al. discuss how they sampled and analyzed a number of nodular pedogenic (i.e., those formed in soils) carbonates for their carbon isotope composition, which can be indicative of vegetation cover. The key part of their analysis is that they split their samples into two different groups: those not associated with artifacts (which presumably represent the sorts of habitats that were available for hominins to select) and those in close proximity to archaeological sites with lithic material (which represent the habitats that hominins actually chose). In essence, they were testing whether or not hominins selected sites with significantly different vegetation regimes relative to what was present in the region as a whole. Interestingly, the answer seems to be yes: the archaeological sites show higher levels of woody vegetation relative to the environment at large.

These graphs show the number of carbonate samples from archaeological locales (dark gray) and non-archaeological locales (white) that fall within particular vegetation types between (a) 2.4-2.2 Ma, (b) 2.0-1.8 Ma, (c) 1.8-1.6 Ma, and (d) 1.6-1.4 Ma. Note how the distributions from the archaeological localities are shifted slightly to the left (i.e., towards more wooded habitats) relative to the general environment. From Quinn et al. (2013: Figure 5).    

I'll let the authors summarize their thoughts (Quinn et al. 2013: 72-73):

Our results demonstrate that lithic archaeological sites had significantly more wooded vegetation compared with what was present throughout the basin from 2.4 to 1.4 Ma. Even as environments became increasingly more grassy, lithic sites continued to be located in a more wooded landscape. Moreover, as the basin transformed from fluvial to lacustrine and back to fluvial hydrological regimes encompassing numerous microenvironments and highly variable geomorphic settings, hominin lithic sites maintained a constant pattern of f_wc [= fraction woody cover] circa 40%. We suggest that our results demonstrate that tool-making hominins utilized behavioral strategies to maintain a relatively more wooded habitat through time potentially to mitigate the effects of environmental perturbations in the basin.

We interpret our results to indicate that during tool-related activities, hominins demonstrated a preference for more wooded environments in the basin than what was generally available at the time. 

This is a pretty interesting finding, although their time bins are, as they acknowledge, pretty broad (about 200,000 years-a lot can happen in that amount of time). It also would have been very interesting if they had considered in their analysis sites that lack lithic material but preserve butchered bones. Perhaps there is something different about those areas that encouraged hominins to butcher carcasses but take all their tools with them.

The pattern they document in the Turkana Basin seems to compliment what is seen at Olduvai. Many of the archaeological occurrences in Bed I (ca. 1.9-1.8 Ma) are found in more wooded (certainly not grassland) habitats, and this appears to change once you hit upper middle Bed II times (after, say, 1.4 Ma), where sites might be located in more open habitats. This period is not covered by the Quinn et al. study, but the expectation would be that archaeological sites after 1.4 Ma in the Turkana Basin would, like those at Olduvai, start to appear in more open habitats.

We always have to be careful about sampling issues, though. I gave a talk a couple of years ago at the University of Arizona and, after mentioning that the Bed I sites all appeared to be within, or very close to, more closed, wooded habitats, while Bed II sites looked to be located in more open settings, Steve Kuhn asked a really great question: is this a real pattern or perhaps just an artifact of sampling? He was asking, in other words, whether the Bed I sites that have been analyzed to date just happen to be in these sorts of environments and the open habitat sites simply haven't yet been found (and vice verse for the Bed II sites). This is an excellent point since, it should be noted, that most of the Bed I sites cluster within a very small area of the gorge that probably does not offer an unbiased view of either Bed I landscapes or hominin behavior.

References:

Quinn, RL, Lepre, CJ, Feibel, CS, Wright, JD, Mortlock, RA, Harmand, S, Brugal, J-P, Roche, H (2013). Pedogenic carbonate stable isotopic evidence for wooded habitat preference of early Pleistocene tool makers in the Turkana Basin. Journal of Human Evolution 65, 65-78.

Field dispatch: back from the gorge

Just arrived at Washington Dulles from Tanzania this morning, and I'm waiting around for my flight back to North Carolina. By all accounts, the 2013 field season was a great success. At our excavations in the DK area, we piece-plotted several hundred bone specimens, not to mention the hundreds of fragments that were recovered from the screens. There are a handful of possible stone artifacts, although we can't say for sure as of yet. The real key will be to fully analyze the faunal material to identify butchery marks that will confirm that hominins were using stone tools to process animal carcasses. My research assistant, Victoria, and I have washed most of the faunal material from this year's and last year's excavations, and we will return to Tanzania at some future date to do the analysis (we leave all the materials in-country for analysis rather than shipping them back to the states). Best of all, our resident group of giraffes was around again. Goodbye for this year, Olduvai!

Jerry and Nicholas removing backfill at the beginning of the field season.

View of trench before 2013 excavation.

My research assistant, Victoria Johnson, happy to be at her first Paleolithic excavation.

Member of our resident giraffe group in the morning on the way to the site.

Concentration of faunal material in Unit K10.

Tori Johnson at the total station looking on as a Maasai goat herd passes by the site.

View of the trench at the end of the 2013 excavation season.

Field dispatch: update from Olduvai Gorge

University of Colorado-Denver fieldschool student Tracy Lancaster preparing to piece-plot materials in Unit L10.

I'm sitting here at the Sundown Restaurant in Karatu with my first real internet connection in about two weeks. The work at the gorge has been going very well; our excavations at DK have now exposed nearly four square meters of deposit, and faunal material is very common. Importantly, most of it appears to be very well preserved. Unfortunately, we have not come across any definitive stone tools as of yet, although a few pieces that were excavated yesterday may have been produced by hominins. I'll provide a more detailed summary of this year's field season next week when I get another stable internet connection...

View of our excavation trench in the DK area. The thick deposit at the top of the sequence is Tuff IB, which is dated to approximately 1.85 million years ago.

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.

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.