john hawks weblog

paleoanthropology, genetics and evolution

Oldowan

  • Oldowan hunting behaviors at Kanjera South

    Mon, 2013-04-29 16:28 -- John Hawks

    Joseph Ferraro and colleagues have done some neat analyses of the faunal remains from Kanjera South, Kenya [1]. Kanjera South is an archaeological assemblage of Oldowan artifacts and associated animal bones from around 2 million years ago. The site was once a plain next to a lake, and gradually built up clay and silt sediments over years and years of flooding and soil formation. Stone tools and bones stand out in the sediments, representing recurrent activities of ancient humans over a few hundreds or thousands of years. As a result, the site has a good statistical representation of fauna that were hunted by early humans, relatively early in the evolution of our genus.

    This is not the earliest site with evidence for meat acquisition by stone toolmakers. We know that people were butchering animals with stone tools around 2.6 million years ago. But the first really good evidence for hunting strategies is much more recent -- around 1.8 million years ago at Olduvai Gorge. There are actually very few Oldowan-era faunal assemblages large enough to study hunting behaviors. Kanjera South shows that the activities documented at Olduvai Gorge were happening a bit earlier, and the site helps to clarify the kind of context in which we might expect to find more evidence of hunting behavior.

    Hunting versus scavenging is the tiredest chestnut in anthropologists' Oldowan arsenal. Were early hunters really competent enough to bring down a duiker on their own? Or did they steal away pieces of half-eaten zebra carcases when the lions took a break?

    In reality, there is no contradiction here. Undefended meat doesn't last a day in the open, whether on the plains or near waterholes. So scavenging meat from other carnivores usually means facing them down -- not a job for an incompetent killer. Meanwhile, present-day peoples who hunt and gather rely quite a lot on "power scavenging", or taking advantage of other carnivores' successes. The present value of a dead carcass is higher than that of a live animal, as long as it may still escape you. Whether the hunter has to predict prey behavior, or the scavenger has to predict competitors' behavior, both strategies require a depth of planning. So, when it comes to Oldowan-era sites, we should expect to see a mixture of hunted and scavenged remains.

    In that context, we can make some inferences about hominin hunting practices by assessing which kinds of animals they hunted, and which they scavenged. Looking at tooth mark and cutmark evidence is not a perfect way of sorting hunting and scavenging -- because both kinds of marks are rare on faunal elements in archaeological contexts. But sometimes those comparisons lead to clear results. For example, here is the chart showing the number of tooth-marked midshaft fragments from long bones at Kanjera South, in comparison to experimental bone assemblages:

    Figure 3 from Ferraro et al 2013

    Figure 3 from Ferraro et al. 2013. Original caption: Tooth-marked mid-shaft fragments: results from experimental assemblages and excavations at KJS. Figure follows a published model [26]. Hominin-first assemblages refer to remains initially defleshed and demarrowed by hominins, then subsequently exposed to large-bodied carnivores (primarily hyenas). Carnivore-first assemblages refer to remains initially defleshed and/or demarrowed by large-bodied carnivores (primarily hyenas and/or lions). Data for body sizes 1–4 [21]. Modern data (with single standard deviations where available) derived from the literature [23]–[26], [56]–[58]. KJS frequencies are from Table 2 and Table S1. Multiple symbols for KJS indicate the results of multiple analysts. X’s indicate minimum and maximum estimates of damage (see Table S1). doi:10.1371/journal.pone.0062174.g003

    These are cool data. Carnivores who get to chew on bones for a while tend to leave the middle of them covered in tooth marks. If humans get access to the carcass early, they will strip off the meat from those midshafts, break them into bits, and otherwise prevent the taphonomic pathway to carnivore tooth marking. And in the graph we see that the Kanjera South faunal assemblage looks like cases where humans were the agents of defleshing and butchering.

    If humans had primary access to the carcasses, then the transport decisions of ancient hunters should have shaped the bone assemblage at Kanjera South. It is very common in analyses of the fauna from African Oldowan-era sites to divide the prey animals into three size classes -- small, medium and large. The majority of prey species were bovids, ranging from small antelopes to water buffalo, although most were in the small and medium size categories at Kanjera South. Ferraro and colleagues show that for medium-sized bovids, the hominins were taking two strategies. These bovids were too big to carry wholesale to a central place for sharing. So the hunters disarticulated the animals and carried back the legs, leaving the axial skeleton for the most part behind.

    Except for the heads:

    But why acquire, transport, and process an abundance of medium-sized heads? In living animals, these remains contain a wealth of fatty, calorie-packed, nutrient-rich tissues: a rare and valuable food resource in a grassland setting where alternate high-value foodstuffs (fruits, nuts, etc.) are often unavailable [2], [3], [29], [49], [52], [63], [76]–[78]. Medium-sized heads are also relatively dense and durable elements, and their internal contents are generally inaccessible to all but hyenas and tool-wielding hominins [63], [79], [80]. As a result, they are often seasonally-available as scavengable resources in East African grasslands [63], [76], [79]–[83]. Additionally, bone surface modification studies at KJS clearly demonstrate that hominins accessed internal head contents: several cranial vault and mandibular fragments bear evidence of percussion striae. Considered in sum, the presumed availability of these isolated remains across the landscape, the relative abundance of these remains in the KJS assemblages, and unambiguous material evidence that hominins exploited their contents on-site is most parsimoniously interpreted as reflecting very early archaeological evidence of a distinct hominin scavenging strategy – one that included a strong focus on acquiring and exploiting fatty, nutrient-rich, energy-dense within-head food resources (e.g., brain matter, mandibular nerve and marrow, etc.) [e.g., 24,63,76,82,84–86].

    This is John Speth's scenario for fat acquisition from lean animals. The brain is the last part of the body to become fat-depleted during times of stress. If hunters are energy-limited, further lean meat is not going to be valuable to them because protein takes energy to digest. What they need most is fat, and the most ready source of fat is the brain. Accumulation of head elements, whether from hunted or scavenged sources, is an effective behavioral strategy in those circumstances. It's one that we think Neandertals pursued at the end of winter in some parts of Europe, and a strategy followed by hunters in ethnographic and historic contexts as well.

    The paper's conclusion is well-framed as a summary of the overall value of evidence from Kanjera South.

    With regard to evolutionary ecology, the relative uniformity of hominin activities documented through the KJS sequence indicates an evolved foraging adaptation well-tuned to local ecological contexts. This point implies that hominin involvement with, and their presumed consumption of, animal remains had substantial fitness implications. In turn, sufficiently strong selective pressures are implicated as having favored the evolution of persistent hominin carnivory no later than 2.0 million years ago. This date is approximately 200,000–500,000 years earlier than previously documented [11], [20], [33], [45], and increases the known time depth of this adaptation within the hominin lineage (range of dates reflects varied interpretations of faunal materials from Olduvai [20]–[42]).

    This one was fun to read, because the data being built up at Kanjera South are really capable of testing hypotheses about hunting behavior in a way that some of the Oldovai Gorge assemblages have done up to now. Putting the faunal exploitation together with the stone tool evidence, we see a really interesting picture. As I reported a few years ago ("Plant processing with early Oldowan tools"), Kanjera South is one of the locations where we have good evidence of plant exploitation of some kind by Oldowan peoples. The site has also provided evidence about stone material transport decisions and the planning depth of stone flaking ("Technological sophistication of the earliest toolmakers". It is a good illustration of how deep knowledge of a single site, with teams returning to excavations over multiple seasons, can yield a richness of statistical information about hominin behavior.

    References

    1. Ferraro JV, Plummer TW, Pobiner BL, Oliver JS, Bishop LC, Braun DR, Ditchfield PW, Seaman JW, Binetti KM, Seaman JW, et al. Earliest Archaeological Evidence of Persistent Hominin Carnivory Petraglia MD. PLoS ONE [Internet]. 2013;8(4):e62174. Available from: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0062174
    Tags: 
    Oldowan
    Kanjera
    hunting
    diet
    Kenya
    Africa
    Early Pleistocene
    Lower Paleolithic
    Synopsis: 
    A faunal exploitation study finds clues about brain consumption and prey choices

  • Behavior of the first North African humans

    Thu, 2013-03-07 23:49 -- John Hawks

    Mohamed Sahnouni and colleagues describe the archaeology of El-Kherba, Algeria. [1]. This locality is a paleontological exposure associated with the nearby Ain Hanech site, and Sahnouni and colleagues have excavated an Oldowan archaeological assemblage with large mammals such as hippos, rhinos and horses.

    Dated to 1.78 Ma, the El-Kherba cut marks and usewear traces represent the earliest North African evidence showing a clear causal link between Oldowan stone technology and processing of large animal carcasses for meat, broadening the geographic range of Plio-Pleistocene hominin subsistence activities to include the Mediterranean fringe. As was shown in the East African Plio-Pleistocene archaeofaunas, early hominins were foraging for large mammals in northern Africa by circa 1.8 Ma. The evidence from the modified bones at these sites indicates that early hominins were involved in evisceration, disarticulating and removing meat, and breaking bones of large mammals to extract marrow.

    It's a great site because it is the first to document human activity in North Africa. Australopithecines were present in Chad by 3.4 million years ago, and given their mobility and range it seems likely they would have been present to the north of the Sahara also. But none have ever yet been found. As it stands, humans were at Dmanisi by 1.78 million years ago and also in Java by that time. The extent of human migration outside of Africa makes it clear that the Mediterranean coast of Africa itself should have been well within their range.

    And yet, stone tools are known from Ethiopia from 2.6 million years ago, and nearly as old in Kenya. Did the earliest stone toolmakers range beyond the Rift Valley? So far there's no equivalently early evidence of tool manufacture in South Africa. And in North Africa, the earliest tool assemblage is at El-Kherba.

    It would sure be useful to uncover evidence of A. boisei or related robust australopithecines in the Ain Hanech area. In East and South Africa, early Homo lived alongside late robust australopithecines, sharing the same landscape. No robust australopithecine has ever been found outside East or South Africa, while Homo erectus spread across the Old World tropics and into the temperate zone. What kept robust australopithecines, otherwise seemingly adaptable, out of Eurasia? If they truly never lived near the Mediterranean coast, we would probably conclude that they weren't as tolerant of different habitats as we might have expected.

    The cutmark evidence described in the paper is fairly clear and comparable to that known from East Africa well before this date. The cutmarks on animal bones, including hippopotamus, along with a "meat polish" on some of the stone flakes, indicate that ancient humans had access to animal carcasses very shortly after the animals' death and were using stone flakes to process them. Again, basically like Oldowan evidence that has long been known from Olduvai Gorge and other sites. I would like to see a better comparison of where this assemblage fits compared to both large and small archaeological assemblages from Olduvai.

    The question of whether and to what extent early humans hunted large mammals involves a long debate that wouldn't fit well in this paper. Still, the evidence here adds to that literature. The ancient people who left these remains were relying upon large mammal acquisition within a broader hunted diet including smaller prey species. Together with sites from across Africa and Eurasia, this one shows that early humans maintained this diet pattern across a range of ecologies and geographies.

    References

    1. Sahnouni M, Rosell J, van der Made J, Vergès JM, Ollé A, Kandi N, Harichane Z, Derradji A, Medig M. The first evidence of cut marks and usewear traces from the Plio-Pleistocene locality of El-Kherba (Ain Hanech), Algeria: implications for early hominin subsistence activities circa 1.8 Ma. Journal of Human Evolution. 2013;64(2):137 - 150.
    Tags: 
    Algeria
    Oldowan
    Africa
    North Africa
    technology
    stone tools
    hunting
    Synopsis: 
    Archaeological report from El-Kherba, Algeria, with implications for human occupation range

  • Stone tools on the moon

    Thu, 2012-11-29 21:46 -- John Hawks

    Moon rock is expensive here on Earth, but on the moon it's as cheap as dirt. So maybe future moon colonists could make stuff out of it using 3-d printing technology?

    Typically, lasers use 300 to 400 watts to melt conductive metals. But the moon material was more similar to ceramics — Bandyopadhyay’s area of expertise. He had used that material for 3-D printing through selective laser sintering, where a powder is fused with intensely focused pulses of light, layer by layer, to form a specific object. He knew that throwing metal-specific levels of power at an insulator like this would only cause most of the energy to be absorbed, and the molten material to lose viscosity.

    “If you go higher, then what will happen is you will go from honey to water, and then what happens?” says Bandyopadhyay. “It flows so much that you cannot make a part. So you need to have, you know, high enough to melt, but low enough not to overflow, basically. That’s the challenge.”

    Now imagining casts made from lunar regolith.

    I hate the idea of having to depend on tools made from an inferior material, when slightly greater expense and more time could transport metals from the asteroid belt. Oh, wait a minute - that's the basic tradeoff of Oldowan technology in Africa, isn't it?

    Tags: 
    Oldowan
    space
    3-d printing

  • Digging deeper into the earliest Acheulean

    Thu, 2011-09-01 01:00 -- John Hawks

    I've been ranting on Twitter all day about the new paper on the "earliest Acheulean" by Christopher Lepre and colleagues [1], published in Nature today. The first time I read through the paper, I really thought they'd miffed it. I mean, really, they published a paper on the earliest Acheulean artifacts without putting a picture of them in the paper.

    What actually bothered me more was the lack of any discussion at all about why the assemblage is Acheulean as opposed to, say, Developed Oldowan. The word Oldowan appears only in the context of saying that many localities within the same Kokiselei site complex have only Oldowan-typical assemblages. This started bothering me less as I ran through the citations to earlier work on the Kokilelei localities. But that raised another point of irritation: This Acheulean locality was briefly described already, a long time ago. Why is this news? And given that both descriptions are so superficial, where's the fuller account?

    I had to stop and think about why I was finding this all so irritating. I mean, it's a paper about dating an archaeological locality. It's a perfectly good paper about dating an archaeological locality, full of details about the local geology, methods of sampling and analysis. My reactions weren't a criticism of the paper, really -- although if you're going to write a high-profile paper about your site, maybe you should actually feature the archaeology of the site?

    I've been digging through references all afternoon, trying to get straight exactly why this paper doesn't mention the Developed Oldowan at all. I'm not saying I favor the Developed Oldowan -- just that we deserve some kind of thoughtful review of what constitutes an "earliest Acheulean" site. Is it a purely typological definition based on the presence of bifaces made on large flakes, or is there something more here? That's going to take me a bit longer to review, so I'll just report on some of what I found.

    This isn't news. Hélène Roche and colleagues reported on this locality in 2003, in Comptes Rendus [2], including a date range between 1.79 and 1.65 million years ago. They describe it as "without doubt, one of the oldest Acheulean assemblages in Africa." That's right, if you can read French, you're eight years ahead of Nature.

    This paper adds precision to the earlier estimate, and it's really important to do this well. But if you've been reading about the archaeology of Plio-Pleistocene Africa, finding a date of 1.76 million years for this locality with an Acheulean assemblage is totally expected.

    Roche and colleagues [2] provided only a short description of the KS4 assemblage. Even so, it's more than provided in the current paper by Lepre and colleagues [1]. Here is what the current paper includes about the assemblage:

    The KS4 assemblage (Supplementary Fig. 2) is characterized by the presence of pick-like tools with a trihedral or quadrangular section, unifacially or bifacially shaped crude hand-axes, and a few cores and flakes, all derived from the same mudstone bed. A single subsurface, in situ origin for KS4 is ensured by excavations at the main test trench that recovered several spectacular sets of refitted lithic artefacts (Supplementary Fig. 3). To the exception of a few cores made on basalt, the rest of the assemblage has been knapped from large cobbles or tabular clasts of locally available aphiric phonolite.

    The supplementary information does include photos of three bifacial artifacts and two refits. But there is no technical analysis of the artifacts beyond the paragraph above. There's not even a summary of the number of artifacts found at the site.

    Roche and colleagues added more details (my translation of the French):

    Kokiselei 4 is a highly eroded site in which a series of more or less extensive trenches (total 19 m2) were dug. Among these only one (KS4A) yielded in situ artifacts in sufficient numbers to form an archaeological horizon, with a vertical dispersion limited to only fifteen centimeters, and no faunal remains. Some objects, distributed in a more diffuse fashion, were found in two other test pits (KS4B and KS4C); these are lower in elevation than the main horizon. In parallel to the test pits, a systematic surface collection across 104 m2 (metric grid) was performed, which comprises the total sample of lithic material from KS4 (n = 167). It is characterized by robust, rough pieces of varying sizes, often very large, some scrapers and notches made on cobbles or flakes, by very large cores, by proto-bifaces or bifaces, and by picks with a trihedral section. Two thirds of the proto-bifaces or bifaces are manufactured on oblong pebbles, relatively flat, some quite large, whole or broken into two in the middle according to the major axis and very few retouched. Only a few are free of cortex and / or shaped enough to be called bifaces, the proto-bifaces in turn are made more coarsely, as if the concept of an elongated shape and sharp point was well integrated, but the operating scheme was inadequately implemented. All the tools characterizing a very early Acheulian are present, and it is to this cultural period that we attribute KS4.

    Roche and colleagues also described the other localities, all Oldowan, at a similar superficial level of detail. The conclusion that Acheulean and Oldowan were two industries overlapping at the same time in this area was suggested in that paper.

    That, obviously, leads to the real scientific story here. How could there be two different stone tool traditions overlapping across some fairly large area for more than 300,000 years? If we count Developed Oldowan, that makes three. Some people would count two Developed Oldowans A and B!

    I'm inclined to think that the scenario is false. These really aren't distinct cultural traditions. Archaeologists have created definitions of archaeological assemblages, and the definitions have changed over time. Initially the definitions were entirely typological -- you have a handaxe, you've got Acheulean. Over time, the definitions have become less typological and more inclusive of technical elements -- you make bifacial artifacts on very large flakes, you've got Acheulean. But these technical categories are not unique or necessarily difficult to invent, and may have been repeatedly invented in different groups, just in the way that different groups of chimpanzees have invented nutcracking and termite fishing methods. For these early assemblages, we don't have any way of telling who made what -- the only hominin fossils from Kokilelei, for example, are teeth of A. boisei. We don't know how many different kinds of hominins there were. Maybe there was only one.

    Early Homo is a bundle of mysteries, in other words, and the archaeology doesn't help. Can we make any sense of the development of early stone tool technology, from its initial beginnings to the handaxe-dominated assemblages? What does it mean that both Oldowan-like and Acheulean-like industries dispersed widely throughout the Old World? This is a really interesting scientific problem, involving information transfer, emergent sets of behaviors, invention and creativity, and their effects on survival.

    The paper by Lepre and colleagues discusses the problem of Oldowan and Acheulean coexistence briefly, reviewing the idea that Homo erectus may be tied to Acheulean, leaving open the question of whether more than one toolmaking species existed before 1.5 million years ago. The paper is noncommittal, but I would frame the question very differently. It's self-evident that Acheulean cannot have been a culture, because no human or animal culture exhibits its spatial and temporal properties -- appearing episodically across three continents over a span of 1.5 million years. The real question is whether we can make sense of the many different Acheuleans, and whether other Oldowans (possibly Developed Oldowans) might have similar heterogeneity. Asking whether an Oldowan-bearing population in Africa first dispersed to Dmanisi is begging the question.

    Finding these answers is surely a lot more interesting than what the press has done with this article.

    That's probably what irritates the the most about this: how boring the article and reporting seem to make this topic. When I did the Google News search this afternoon, there are no fewer than 165 news articles worldwide. Nature made its cover image this week a photo of one of the bifaces. You can't get much more of a press push than that for an archaeology story. None of the stories go beyond the very simple "oldest Acheulean" story. Now, I'm used to seeing the "oldest X" storyline a lot in paleoanthropology, it's a perennial favorite of journalists who can't think of anything more interesting to write. But in this case, it's the worst angle -- because it's the part that isn't actually news!

    References

    1. Lepre CJ, Roche H, Kent DV, Harmand S, Quinn RL, Brugal J-P, Texier P-J, Lenoble A, Feibel CS. An earlier origin for the Acheulian. Nature. 2011;477(7362):82 - 85.
    2. Roche H, Brugal J-P, Delagnes A, Feibel C, Harmand S, Kibunjia M, Prat S, Texier P-J. Les sites archéologiques plio-pléistocènes de la formation de Nachukui, Ouest-Turkana, Kenya : bilan synthétique 1997–2001. Comptes Rendus Palevol. 2003;2(8):663 - 673.
    Tags: 
    archaeology
    Early Pleistocene
    Lower Paleolithic
    Acheulean
    Oldowan
    Turkana
    West Turkana
    Kokiselei
    Kenya
    Africa
    Synopsis: 
    A paper reports on the earliest evidence of the Acheulean, but misses the key story.

  • Cutmarked bones from Dikika critiqued

    Wed, 2010-11-17 00:18 -- John Hawks

    Manuel Dominguez-Rodrigo, writing with my University of Wisconsin colleagues Travis Pickering and Henry Bunn, has challenged the interpretation that two bovid bones from Dikika bear cutmarks made by hominins [1]. I wrote about the Dikika cutmark claims earlier this year (Australopithecus afarensis used stone tools). The new paper is a strong critique of that earlier work.

    Our taphonomic configurational approach to assess the claims of A. afarensis butchery at Dikika suggests the claims of unexpectedly early butchering at the site are not warranted. The Dikika research group focused its analysis on the morphology of the marks in question but failed to demonstrate, through recovery of similarly marked in situ fossils, the exact provenience of the pub- lished fossils, and failed to note occurrences of random striae on the cortices of the published fossils (incurred through incidental move- ment of the defleshed specimens across and/or within their abrasive encasing sediments). The occurrence of such random striae (some- times called collectively “trampling” damage) on the two fossils provide the configurational context for rejection of the claimed butchery marks. The earliest best evidence for hominin butchery thus remains at 2.6 to 2.5 Ma, presumably associated with more derived species than A. afarensis.

    These authors are experts on cutmarks, both from their work on Oldowan faunal assemblages and from experimental work where they have controlled the actual circumstances of cutmarking, trampling and weathering. Their critique of the two Dikika bones takes two main paths:

    1. The surfaces of the bones themselves are relatively poorly preserved, with evidence of "trampling" modification and subadult status for one specimen and evidence of "moderate weathering" on the other. The matrix containing the bones was highly abrasive, making spurious marks more likely. This would make it difficult to get clear results even in an experimental context.

    2. The purported cutmarks themselves are similar to marks that occur in bones subject to trampling damage. Dominguez-Rodrigo and colleagues argue that some of these marks are more diagnostic of trampling than of cutting or hammerstone damage.

    The authors do not say they have disproven the hypothesis that A. afarensis cut on these bones with naturally-occurring stones, but they clearly question whether such a hypothesis is credible:

    The Dikika “butchery mark” evidence does not, however, withstand peer scrutiny undertaken from an actualistic perspective and with a configurational approach. Our approach in assessing the Dikika claims was intentionally conservative: the claims are extraordinary because of their singularity and because of the inferred age of the fossils. Thus, natural processes of bone modification need to be eliminated before precluding nonanthropogenic origin(s) for the surficial marks on DIK-55–2 and DIK-55–3. High probability trampling damage on both specimens does not allow for this elimination and, again, taking our contextualized, maximally conservative position, forces us to reject even marks A1 and A2, the two morphologically strongest claims of cutmarks on DIK-55–2.

    Their discussion emphasizes that, in their view, a hypothesis that an unusual tool type was responsible for cutmarks should be accompanied by experimental or actualistic evidence concerning the effects of that tool type. I think that for discoveries as potentially important as this, it is very reasonable for reviewers to expect such evidence will be provided. Also, a full statistical workup of other faunal bones from the site would be worthwhile. If the matrix really is abrasive and readily gives rise to trampling scratches, these should be evident in a wider distribution of bone from the site.

    But for the moment, it looks like we should continue to treat cautiously claims of very early stone tool use. Possibly further comparisons will back up the hypothesis of cutmarks with more evidence. Since it took only three months from the initial publication of the Dikika evidence to this response, maybe we won't have to wait long for more comparisons!

    References

    1. Dominguez-Rodrigo M, Pickering TR, Bunn HT. Configurational approach to identifying the earliest hominin butchers. Proceedings of the National Academy of Sciences [Internet]. 2010;107:20929–20934. Available from: http://dx.doi.org/10.1073/pnas.1013711107
    Tags: 
    Dikika
    Ethiopia
    stone tools
    Pliocene
    Africa
    Oldowan
    A. afarensis
    Synopsis: 
    The claim of stone tool use by A. africanus comes under fire.

  • Australopithecus afarensis used stone tools

    Wed, 2010-08-11 15:13 -- John Hawks

    UPDATE (2011-09-06) Note: The conclusions of the research were later critiqued, I posted on that criticism after this post.

    Shannon McPherron, Zeresenay Alemseged and colleagues working at the Dikika field site in Ethiopia have found evidence of stone tool use 3.39 million years ago [1]. That's 800,000 years earlier than the previous first-known tool use, and occurs during the existence of Australopithecus afarensis.

    The evidence is a series of cutmarks and one percussion mark on two bovid bones. One is a piece of rib from a large "cow-sized" animal, the other a femur fragment from a smaller "goat-sized" bovid. The analysis goes through several microscopic comparisons to rule out alternative causes for the cutmarks, such as trampling. The key paragraph of the results:

    The cut marks demonstrate hominin use of sharp-edged stone to remove flesh from the femur and rib. The location and density of the marks on the femur indicate that flesh was rather widely spread on the surface, although it is possible that there could have been isolated patches of flesh. The percussion marks on the femur demonstrate hominin use of a blunt stone to strike the bone, probably to gain access to the marrow. The external surfaces of ribs have thin sheaths of flesh, so the scraping marks on the fossil rib suggest stripping off of these sheaths.

    I have some lingering doubts, none of which are very serious, but that point out the need to look harder at other sites. It sure would have been nice if they'd found an anomalous sharp-edged rock nearby.

    The two bones are compelling, but the study does not give much indication of how representative they are. How many similar-sized bone fragments were left at the site? How many were collected? What fraction of "cutmarked" bones does that make? What fraction show signs of trampling and various kinds of post-depositional damage?

    Those questions are essential to answer the "green car" problem. If you don't know this one, it's fairly simple -- a witness reports a green car leaving the scene, and green cars are very rare -- the police think this is a great lead. But blue cars are very common in the city, and there is a small chance that the witness mistook a blue one for a green one. Whether it actually was a green car depends on the actual proportion of green to blue cars, and the actual probability that the witness was wrong.

    In this case, I think there is a very small chance that the marks on these bones could have been produced by processes other than deliberate cutting by a stone tool. But in a sample of hundreds or thousands of bone fragments, a small chance might well happen a couple of times. It's very difficult to quantify this, because archaeologists don't collect every bone fragment. The only real way to address the problem is to find more cutmarks and do other statistics on them -- do they occur where flesh is attached to bone, etc.

    It does seem odd that nobody's identified clear stone tools, which are in later sites a lot more common than cutmarked bones. A tool-user will make many artifacts during her life. (Why "her"? Well, in chimpanzees, it's the females who dominate technology transmission...) We have a lot of australopithecine bones. If this was a long-lasting tradition, we should have found a lot of stone tools by now.

    Maybe it wasn't a long-lasting tradition. Chimpanzee technology is significantly clustered geographically, some of the most interesting behaviors have been observed only at a single field site. If Australopithecus had a similar pattern of cultural diversity, tool use may have been innovated many times without "catching on" over a wide geographic or temporal extent. Here's what McPherron and colleagues conclude along similar lines:

    Whether A. afarensis also produced stone tools remains to be demonstrated, but the DIK-55 finds may fit with the view that stone tool production pre-dates the earliest known archaeological sites and was initially of low intensity (one-to-a-few flakes removed per nodule) and distributed in extremely low density scatters across the landscape such that its archaeological visibility is quite low (16).

    Or maybe we just haven't noticed. Fluvial contexts may have been bad places for Australopithecus to hang out. McPherron and colleagues allude to this explanation for the local absence of tools at Dikika:

    However, stone tool production and consequently archaeological accumulations are not expected at this locality given the sedimentary environment characterized by the palaeo-Awash River emptying into a nearby lake (3, 4). In this relatively low-energy depositional environment, clasts suitable for stone tool production are not present (few particles larger than fine gravel, 8 mm diameter). Within the exposed SH Member, the distance from DIK-55 to cobble-sized raw materials (>64 mm) is ~6 km (at Gorgore; Fig. 1). Thus, in this instance the absence of evidence for stone tool production in the immediate vicinity of the cut-marked bones may reflect landscape-level raw material constraints.

    The research article is accompanied by an essay by David Braun reviewing the find [2]. He stretches a bit, but I think the interpretations he suggests are worth airing. One -- why are there cutmarked bones 6 km from any good source of stone raw material?

    The meat and marrow of large animals must have been a valued resource, because McPherron et al. conclude that the tool users incurred the cost of transporting stones 6 kilometres from where they occurred naturally to the site where the butchery took place. Further costs that were associated with the consumption of carrion, and were apparently worth the risk, include exposure to parasites and competition with large carnivores.

    Two -- what about the "meat-brain" connection?

    This provides exciting evidence of how A. afarensis behaved. At one time, the species was considered to be a relatively primitive hominin, but this perception is being redefined. For example, it now seems that Lucy's kin had body proportions that were more similar to those of humans than of apes (6). Analyses of the hand of A. afarensis show that it had relatively short fingers that would allow the kind of fine-scale manipulation necessary for tool use (7). A recently discovered skeleton from the Woranso–Mille area of Ethiopia suggests that A. afarensis did not have the ape-like, 'funnel-shaped' thorax usually associated with a large digestive tract and low-quality diet (8). Perhaps the findings that these hominins used tools and had a carnivorous component to their diet should not have been so unexpected.

    A 2.6-million-year-old butchery tradition should already have refuted the hypothesis that meat-eating caused the expansion of brain size in Homo. But it was still possible to maintain that the initial Oldowan was insufficiently dedicated, or that the anatomical specializations (e.g., small guts) allowing brain expansion took time to develop, or that as-yet-undiscovered large-brained hominins would be found. Any of these are still possible, but the observations Braun points out pretty much demolish the 15-year-old story of "expensive tissue." Australopithecus seems to have had a small gut, and a bigger brain than chimpanzees. If there was a tradeoff, A. afarensis had already made it.

    Braun didn't mention A. sediba, which adds another wrinkle. A late species of Australopithecus with human-sized teeth. Or (as some prefer), a pre-habilis species of Homo with an Australopithecus-sized brain. What was its diet like? I have a feeling we'll know before too long.

    Meanwhile, I'll be floating for the rest of the year, since I included this as the far-out "bonus" entry in my 2010 New Year predictions! You know, the one that's so bizarre that it seems like it'll never happen. Heh.

    UPDATE (2010-08-11): John Noble Wilford got ahold of some skeptics for his NY Times story on the discovery:

    Still, the discoverers are already being pressed to defend their interpretation that the cut marks on the bones are evidence of stone-tool butchery. Tim D. White of the University of California, Berkeley, one of the foremost investigators of early human origins, said flatly that their “claims greatly outstrip the evidence,” and noted, “We have been working sites in this area for 40 years, and not a single stone tool has been found in deposits of this antiquity.”

    Sileshi Semaw, a paleoanthropologist at Indiana University who was a discoverer of the oldest confirmed stone tools, from 2.6 million years ago, noted in an e-mail message from Ethiopia that researchers had often been misled by bone markings left by trampling animals and other natural causes. “I am not convinced of the new discovery,” he said.

    UPDATE (2010-08-12): Maybe some are looking for more about australopithecine diets. My post from 2005, "Chemistry and early hominid diets" has a good compilation of stable isotope observations and what may explain them. With the cutmark evidence, you can read through the discussion of C4 plant contributions, and think about the grazers that A. africanus may have been eating.

    UPDATE (2010-08-16): Science Friday with Ira Flatow covered this story last week, including commentary by Alemseged and David DeGusta, who suggests that the marks may be crocodile bite marks. Doesn't look like it to me, but as I wrote above, I'd like to see statistics on a few hundred damaged bones to see the probability that an arbitrary one will look like stone cutmarks.

    References

    1. McPherron SP, Alemseged Z, Marean CW, Wynn JG, Reed D, Geraads D, Bobe R, Bearat HA. Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia. Nature [Internet]. 2010;466:857–860. Available from: http://dx.doi.org/10.1038/nature09248
    2. Braun DR. Palaeoanthropology: Australopithecine butchers. Nature [Internet]. 2010;466:828. Available from: http://dx.doi.org/10.1038/466828a
    Tags: 
    Dikika
    Lower Paleolithic
    Pliocene
    A. afarensis
    taphonomy
    archaeology
    Ethiopia
    Oldowan
    stone tools
    Africa
    zooarchaeology
    Synopsis: 
    A report finds cutmarks on fauna from Dikika, Ethiopia, 3.4 million years ago.

  • High-tech honey extraction, chimpanzee-style

    Mon, 2009-10-26 23:56 -- John Hawks

    Most people know that hunter-gatherer men hunt meat. Fewer people know the major secondary target for male foraging in many hunter-gatherer societies: honey. The resource is so highly valued that some men spend as much effort foraging for honey as they do hunting.

    Chimpanzees also forage for honey. The use of tools to dig for, bash into, and dip honey out of bee nests or hives has long been known from many chimpanzee field sites. For example, Craig Stanford and colleagues (2000) described how chimpanzees in Bwindi-Impenetrable National Park, Uganda, use small sticks to forage for honey from the small nests of stingless bees, while they use much bigger sticks to get honey out of honeybee nests.

    Two papers from this year have illustrated a new appreciation for the complexity of chimpanzee toolkits used for honey raiding. Crickette Sanz and David Morgan (2009) describe honey gathering by chimpanzees at the Goualougo, Congo field site, while Christophe Boesch and colleagues (2009) describe the technology used by chimpanzees at Loango, Gabon. Both are relatively new field sites, in which researchers have arrived recently or are still habituating the chimpanzees to their presence. Thus, the variations in chimpanzee behaviors at these sites are still being recognized and just starting to be reported.

    Loango National Park is a relatively new field site. As the researchers there continue to habituate the chimpanzees, they have been gathering a series of observations on behaviors that occur differently in Loango compared to other field sites. According to Boesch et al. (2009:2), chimpanzees at the Loango field site do not crack nuts despite a local abundance of them. But far from being simpler in their material culture than other chimpanzees that do crack nuts, the Loango chimps make up for their lack of nutcracking with a complex package of tools for honey extraction:

    Gathering honey from underground hives, similar to underground termite fishing in Goualougo, is special in the sense that chimpanzees cannot see where the resource is hidden and use the first tool, the perforator, as an exploratory tool to “feel” where the resource is located underground. In both cases, external indirect signs of food sources are visible (e.g., large termite mounds or small fragile Melipone-made tubes), but the nest itself is not visible and its exact location cannot be inferred. Therefore, chimpanzees have to investigate the soil in order to locate food that can be, in the case of Melipone underground nests, as much as 1 m deep and 70 cm lateral to the visible tube. Locating the underground chamber can take a human between 20 to 40 minutes (Boesch, pers. obs.). The successful locating of honey is apparent from honey sticking to the ends of perforators. To extract honey, a tunnel needs to be dug sideways so as to reach the underground chamber and prevent soil from getting mixed with the honey once the membrane of the chamber is broken (in general, the intact upper membrane of the chamber in the emptied hole can be felt). We think that such tunnels are dug with the help of perforators to loosen the soil. These tunnels are sometimes barely large enough to let a human arm through, and therefore indicate that chimpanzees know exactly where they are aiming. This cannot be done by simply following the bee tube, as it is much too fragile to resist the tool-assisted digging process. Thus, an elaborate understanding of unseen nest structure, combined with a clear appreciation that tools permit the location of unseen resources, and a precise three-dimensional sense of geometry for reaching the honey chamber from the correct angle, is demonstrated by the chimpanzees when extracting underground honey. It has been proposed that an elaborate understanding of causal relationships between external objects is required for flexible tool use to evolve (Boesch and Boesch-Achermann, 2000), and the fact that such exploratory tools are only seen in chimpanzees and humans supports this proposition (Boesch et al. 2009).

    I liked the authors' description of how they defined tool types and categorized objects on the basis of signs of use. WIth quite a simple technology, this differentiation appears nevertheless to be of a similar extent to the stone toolkits used by early Homo. What is different is the complexity of manufacture of (some of) the elements of the toolkit.

    That topic of basic manufacturing method versus within-toolkit differentiation is addressed by a new study by Thibaud Gruber and colleagues (2009):

    Here, we present the results of a field experiment [20] and [21] that compared the performance of chimpanzees (P. t. schweinfurthii) from two Ugandan communities, Kanyawara and Sonso, on an identical task in the physical domain—extracting honey from holes drilled into horizontal logs. Kanyawara chimpanzees, who occasionally use sticks to acquire honey [4], spontaneously manufactured sticks to extract the experimentally provided honey. In contrast, Sonso chimpanzees, who possess a considerable leaf technology but no food-related stick use [4] and [22], relied on their fingers, but some also produced leaf sponges to access the honey. Our results indicate that, when genetic and environmental factors are controlled, wild chimpanzees rely on their cultural knowledge to solve a novel task.

    The finer points of tool use lie atop a technological substrate. For one group of chimpanzees, this substrate may be sticks, for another stones (in nutcracking), for another leaves. Social learning may tend to associate some raw materials with manipulatory processes -- a chaïne operatoire, at a very simple level. The complexity of the honey-extraction kits appears to show that, at least for highly valued purposes, chimpanzees can bring together distinct elements into a single technological solution. It's nothing that a three-year-old human can't do, but it's another point in favor of Wynn and McGrew's "Ape's view of the Oldowan" argument.

    References:

    Boesch C, Head J, Robbins MM. 2009. Complex tool sets for honey extraction among chimpanzees in Loango National Park, Gabon. J Hum Evol 56:560-569. doi:10.1016/j.jhevol.2009.04.001

    Gruber T, Muller MN, Strimling P, Wrangham R, Zuberbühler K. 2009. Wild chimpanzees rely on cultural knowledge to solve an experimental honey acquisition task. Curr Biol (in press) doi:10.1016/j.cub.2009.08.060

    Sanz CM, Morgan DB. 2009. Flexible and persistent tool-using strategies in honey-gathering by wild chimpanzees. Int J Primatol 30:411-427. doi:10.1007/s10764-009-9350-5

    Stanford CB, Gambaneza C, Nkurunungi JB, Goldsmith ML. 2000. Chimpanzees in Bwindi-Impenetrable National Park, Uganda, Use different tools to obtain different types of honey. Primates 41:337-341.

    Tags: 
    tool use
    chimpanzees
    Oldowan
    diet
    apes
    technology

  • Plant processing with early Oldowan tools

    Tue, 2009-05-05 00:24 -- John Hawks

    Ann Gibbons was at the AAPA meetings early last month, and she reports in the current Science on some of the research. Her article about the use of early Oldowan tools from Kanjera, Kenya focuses on the evidence for plant processing:

    To find out just what early Homo was doing with the tools, [archaeologist Thomas] Plummer enlisted archaeologist Cristina Lemorini of the University of Rome, "La Sapienza." She studied replicas of the Kanjera tools, made with the same kinds of stone, that modern Hadza hunter-gatherers of Tanzania had used to butcher animals, process wild tubers, cut grass, and work wood. Then, using confocal and metallographic microscopes, she compared patterns of wear on the edges of the Kanjera tools with those on the replicas. She reported that the ancient tools had telltale signs of being used to process plant materials, such as cutting grass, and the distinct striations made by sediment as tools were used to clean and section fibrous tubers. She also saw patterns consistent with defleshing carcasses and woodworking, possibly to make wooden tools.

    Kanjera has been the subject of some very interesting raw material analyses over the last couple of years, by David Braun and colleagues (2008, 2009), documenting the selectivity of the Oldowan-makers for particular kinds of raw materials -- studies that have counterparts at other early Oldowan sites, including Lokalalei (Harmand 2009).

    Meanwhile, the analysis of use-wear and plant residues on stone tools has advanced markedly in the last ten years. Use-wear analysis considers the kind of microwear produced on artifacts by repeated use against materials like wood, hide, meat, and bone. For many years, archaeologists have worked on microwear -- for example, Lawrence Keeley and Nick Toth (1981) showed that wear patterns on the edges of Oldowan tools from Koobi Fora are consistent with use in both meat and plant processing. But use-wear analysis has undergone recurrent debate over the years, as people questioned the qualitative assessments of similarity between reference tools -- used by experimenters on known materials -- and archaeological artifacts. A short review of this history is given by Evans and Donahue (2008).

    A certain ambiguity about use-wear studies remains unresolved -- how much of the results are in the eye of the analyst? It helps a lot to have additional evidence. Plant residues and phytoliths have increasingly provided such evidence -- the actual parts of plants adhering to stone tools with use-wear that looks like plant materials makes it look pretty likely that the tools were used on the plants. To list some highlights, we have:

    1. Nuts and nutcracking at Gesher Benot Ya`aqov (Goren-Inbar et al. 2002).

    2. Woodworking, as documented by phytoliths and plant fibers adhering to initial Acheulean tools from Peninj (Dominguez-Rodrigo et al. 2001).

    3. Starch grains also can adhere to stone tools, and starch processing is clear in the Middle Stone Age of Mozambique (Mercader et al. 2008).

    4. A range of starchy and woody plant materials were processed by Mousterian (presumably Neandertal) people from Starosele and later Upper Paleolithic people from Buran Kaya III -- similar between the two sites despite their difference in time (Hardy et al. 2001). Some tools had both mammalian hair and feather barbules attached.

    There's an endless range of such studies; a deep literature, so that a few highlights don't really do it justice. A few studies, like the last one here, actually consider enough artifacts to start to develop an idea of the activity patterns of people. When you're only studying three or four artifacts that preserve any microwear, you've got evidence that a few things did happen sometimes, but you really don't have a full pattern.

    References:

    Braun DR, Plummer T, Ditchfield P, Ferraro JV, Maina D, Bishop LC, Potts R. 2008. Oldowan behavior and raw material transport: perspectives from the Kanjera Formation. J Archaeol Sci 35:2329-2345. doi:10.1016/j.jas.2008.03.004

    Dominguez-Rodrigo M, Serrallonga J, Juan-Tresserras J, Alcala L, Luque L. 2001. Woodworking activities by early humans: a plant residue analysis on Acheulian stone tools from Peninj (Tanzania). J Hum Evol 40:289-299. doi:10.1006/jhev.2000.0466

    Evans AA, Donahue RE. 2008. Laser scanning confocal microscopy: a potential technique for
    the study of lithic microwear. J Archaeol Sci 35:2223-2230. doi:10.1016/j.jas.2008.02.006

    Gibbons A. 2009. Of tools and tubers. Science 324:588-589. doi:10.1126/science.324_588b

    Goren-Inbar N, Sharon G, Melamed Y, Kislev M. 2002. Nuts, nut cracking, and pitted stones at Gesher Benot Ya`aqov, Israel. Proc Nat Acad Sci USA 99:2455-2460. doi:10.1073/pnas.032570499

    Hardy BL, Kay M, Marks AE, Monigal K. 2001. Stone tool function at the paleolithic sites of Starosele and Buran Kaya III, Crimea: Behavioral implications. Proc Nat Acad Sci USA 98:10972-10977. doi:10.1073/pnas.191384498

    Harmand S. 2009. Variability in Raw Material Selectivity at the Late Pliocene sites of Lokalalei, West Turkana, Kenya. Pp. 85-97 in Hovers E, Braun DR, Interdisciplinary Approaches to the Oldowan. Springer, Amsterdam. Amazon

    Keeley LH, Toth N, 1981. Microwear polishes on early stone tools from Koobi-Fora, Kenya. Nature 293:464-465.

    Mercader J, Bennett T, Raja M. 2008. Middle Stone Age starch acquisition in the Niassa Rift, Mozambique. Quatern Res 70:283-300. doi:10.1016/j.yqres.2008.04.010

    Tags: 
    diet
    Kanjera
    archaeology
    stone tools
    use-wear
    Oldowan
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