I recently returned from Atlanta, which hosted the 2016 meeting of the Paleoanthropology Society. As usual, there were some really interesting talks, one of which (I hope) was a presentation I gave on behalf of my colleagues with some data we collected on stone raw materials in the Olduvai Basin. Here are my favorite talks as recorded in my notes:
- The meeting's first presentation was by Catalina Villamil, a graduate student at NYU, who examined variability in the orientation of the foramen magnum across several groups of primates and marsupials. Basically, her analyses found that among primates a more anteriorly oriented foramen magnum tends to be associated with orthograde postures (that is, postures that involve a vertically oriented trunk) rather than bipedal locomotion. This is important since, as she and others point out, paleoanthropologists often look for an anteriorly oriented foramen magnum to identify bipedalism and, thus, a fossil's identification as a hominin. It appears, then, that this is not necessarily a very good indicator. This calls into question inferences for bipedal locomotion for fossils like Sahelanthropus, whose purported hominin status rests partly on foramen magnum location.
- Michael Pante and his colleagues presented data from high-resolution 3D scans of experimentally produced stone tool cutmarks, carnivore tooth marks, and crocodile tooth marks. This is really important, as there has been a good deal of disagreement over the identification of surface modifications on fossil bones, largely because of a lack of consistency and precision among analysts in the definition of features used to differentiate marks created by various agents. Intriguingly, they suggest that some ancient marks that are thought to have been created by stone knives show similarities with crocodile marks. Theoretically, one could scan an unknown mark, compare it to the 3D structure of marks of known origin, and determine the "fit" of the two in order to make a probabilistic assessment. The only drawback, as Pante stated, is the time it takes to adequately scan the marks (24 hours in some cases). So, this method cannot yet be applied to whole assemblages. Regardless, I am in total agreement that this is the direction bone surface modification studies should be going and, at the very least, we should subject questionable marks (or extremely important ones−Dikika anyone?) to this sort of analysis. In a similar vein, J.A. Harris et al. reported on a Bayesian approach to identifying surface marks, which also produces a probability that a mark belongs in a specific category.
- Several talks touched on stone tool production and/or use among modern humans and chimpanzees and their implications for understanding Paleolithic technologies. Susanna Carvalho summarized her team's work in Guinea on wild chimpanzee stone tool use. She reported, really interestingly, that young chimps start to learn nut-cracking by observing close kin (this makes sense as these are the individuals with whom they grow up), while older chimps slowly shift their observations to more skilled individuals. She also provided what I thought was a cool quote: [Chimpanzee] "tools are not modified prior to use, but by use." David Braun piggybacked nicely on this talk when he reported some fun experiments conducted with these same chimps. Some background: Dave has previously demonstrated that hominins at the ca. two-million-year-old site of Kanjera South (Kenya) were pretty "choosey" when it came to the types of rocks they used for stone tools. Specifically, it appears as if these hominins intentionally selected rocks for their durability (i.e., their ability to hold a sharp edge over time). Dietz Stout has documented a similar level of selectivity (in this case, for stone with little or no impurities) at the 2.6-million-year-old site of Gona (Ethiopia). While this implied some level of cognitive sophistication, Dave related to us that he was often asked how these hominins could have possibly known about such physical properties of stone; where they, in fact, the first engineers? To explore this further, he designed an elegant experiment in which he transported the same rock types being used by the Kanjera hominins a few thousand kilometers west for use by the chimps living at Carvalho et al.'s open-air laboratory in Guinea. They laid the stones on the ground and recorded the frequency with which they were chosen by the chimps for nut-cracking. They found that the chimps selected harder rocks for hammers (not too surprising) and a soft, chalk-like rock for anvils. This latter observation was mystifying at first−after all, wouldn't you want a hard rock on the bottom, too?−until it was realized that successive nut-cracking events with these more malleable stones eventually resulted in the production of a deep impression that prevented the nut from slipping out from under the hammer upon impact. Pretty cool. They also witnessed how juveniles tended to "recycle" tool sets from older, more experienced individuals (that is, they passively took control of hammers and anvils after they were abandoned by those who knew what they were doing), which essentially provided a mechanism for how knowledge of raw material characteristics could be transmitted within a group. The two major take-home messages here were: (1) the properties that we, as modern humans, think are relevant when selecting a rock for use as a potential tool are different than those identified by chimps (and presumably, ancient hominins), and (2) an awareness of raw material characteristics (hardness, durability, what have you) does not necessarily require extensive knowledge of stone engineering and/or geology, and this information can be transferred in an entirely passive manner. This runs counter to interpretations that consider selectivity and multi-stage reduction sequences among Oldowan hominins as evidence for sophisticated cognition and/or complex modes of learning (however, see here for an example of recent work indicating that active teaching was probably not necessary to transmit knapping skills). The last lithic paper I'll mention came from Nada Khreisheh, who reported that an individual's skill with handaxe production correlated best with psychometric tests that involve planning.
- David Patterson, a graduate student at George Washington University and the person largely responsible for manning the laptop to ensure that everyone's PowerPoints loaded properly, produced some fascinating data on stable isotopes across the ancient landscapes of Koobi Fora (Kenya) between 2 and 1.4 million years ago. Tons of data here, but what I found to be most interesting was the observation that one of the only taxa in the Turkana Basin with a pattern of C4 enrichment was fossils of the genus Homo, which suggests that something special was going on with this bipedal ape over this time span: more C4 plants, or the consumption of C4-eating animals? This theme also appeared in a paper from Kay Behrensmeyer et al. who, in their analysis of the paleoecology and paleogeography of a slice within Koobi Fora's Okote Member (ca. 1.51-1.53 million years ago), found that hominins were so-called "transient" species−that is, they appear and then disappear within the sedimentary sequence. This could indicate that they utilized a greater diversity of habitats than other animals.
- The last talk before lunch on the first day was given by Yohannes Haile-Selassie, who reported on a new species of australopithecine, Australopithecus deyiremeda and its implications for diversity within the hominin family tree during the Middle Pliocene. Full disclosure here: even though this species was announced over a year ago, I had never heard of it. This just goes to show how difficult it is to keep up with the literature with a heavy teaching load and (most importantly) a toddler. In fact, I have so little time to go through the newest primary literature that I depend on conferences like this and Texas A&M's fantastic Anthropology in the News feed for the latest in paleoanthropology. Anyway, Haile-Selassie suggests that the hominin phylogeny may be as diverse prior to three million years ago as it appears to have been after three million years ago.
- Behrensmeyer's presentation also criticized the use of the term "mosaic" in paleoecological reconstructions, mainly because it is so imprecise. Many of the reconstructions, including those from Amy Rector and colleagues for Cooper's D and Kay Reed et al. for the lower Awash valley, tend to converge on some sort of "mixed" habitat (usually between forest and bushland, or bushland and grassland). In these cases, though, the imprecision reflects the type of data (in this case, mammal fossil assemblages).
- Darryl de Ruiter presented on the new Homo naledi assemblage on behalf of the Rising Star team. As in their recent publications, de Ruiter maintains that the most likely explanation is that the bodies were deposited intentionally by members of the group using the cave system as a grave site of some sort. John Shea suggested that the assemblage could represent young, adventurous males that became stuck within the depths of the cave. An interesting hypothesis, although de Ruiter pointed out that it appears as if the assemblage includes individuals of both sexes and all ages. No news on the age of the assemblage...this is going to be very intriguing for some time.
- Because of my work in Armenia, my ears perked up during Simonyan et al.'s presentation (given by Miriam Belmaker) on test excavations in southern Armenia. They reported the recovery of a large assemblage of obsidian artifacts that show techno-typological affinities to the late Lower and Middle Paleolithic. Obsidan hydration dates (which, as Belmaker acknowledged, can be pretty temperamental) indicate at least two separate occupations, one at ~120,000 and the other >200,000 years ago. I look forward to hearing more about this as research progresses.
- My team, including my friends and colleagues Cynthia Fadem, Ryan Byerly, and Audax Mabulla and UNCG undergraduate researcher Curran Fitzgerald, presented on our recent work with lithic raw materials in the Olduvai Basin. Building on the work of folks like Dave Braun, we reported on data we collected with a Proceq Schmidt Rock Hammer, which, by measuring rock hardness, provides an objective and quantitative proxy for raw material "quality." These sorts of data are critical if we want to start understanding why hominins chose the rocks they did for tool manufacture. We also collected a ton of additional samples to determine if the handful of macroscopically similar, but spatially discrete, quartzite outcrops in the basin could be distinguished based on their elemental composition. Encouragingly, this does appear to be the case, which means that determining the source of the quartzite artifacts from the Olduvai archaeological sites is a real possibility.
- The most thought-provoking paper was given by Stanley Ambrose and his colleague Jibril Hibro. They argued that Neandertal-modern human admixture should not yet be viewed as a given. The weakest link in these studies is that African genetic diversity was woefully underrepresented, which means that genetic variants identified as deriving from Neandertals (or other archaic populations) could, in fact, have already been present (but unsampled) among African populations. So, the question that has not yet been adequately addressed is, as their paper's title suggests, Is Neandertal-human genetic admixture in Eurasians actually African ancestry? This paper certainly reminded me to be cautious in our interpretation of the genetic data.
- The last paper I'll comment on was the very last of the conference, given by Randolf Donahue and colleagues. They introduced Fossilfinder.org, which allows anyone to examine high resolution photos taken by drones around Lake Turkana for fossils and other items of paleoanthropological interest. This forms part of the "Citizen Science" movement, which attempts to harness the public to essentially crowd source the collection of data. I have looked at some of the photos myself and, even at relatively high resolution, it is not easy to pick out materials. Nevertheless, I am anxious to see how this project progresses...
