Obsidian blades as surgical tools

In my recent post on #hipsterscience, the quote that struck closest to home was the one about the obsidian blade. See, most of my analytical work has been focused on stone tools (aka lithics) and how they were manufactured, used and managed by people in the past. Whenever it was available, obsidian seems to have been one of the preferred materials to make sharp flakes of, mainly because it is incomparably sharp among lithic raw materials!

Just how sharp is obsidian? Extremely damn frikkin' sharp! I often regale students about the first time I knapped stone myself, a sad, sordid story that ends with a fountain of blood gushing from the tip of my index finger (not that I would ever exaggerate for dramatic effect or anything). Well, that bloody geyser was unleashed by a flake of coarse flint - and obsidian is much, much sharper than that. When I've given knapping demos using obsidian and inadvertently nicked myself with little obsidian flakes, they're so sharp that I usually didn't notice I was bleeding until I smeared blood all over myself - this made knapping look pretty bad-ass to at least one group of sixth graders I once gave a demo to.

But don't take my word for it! Lithic specialists often refer to the story of Don Crabtree (one of the people directly responsible for the rebirth of knapping in the 60's and 70's) insisting that he be operated on by surgeons using scalpels tipped with obsidian blades he had expressly knapped for the purpose. Buck (1982) reports some observations on this episode, as well as on experiments comparing the obsidian to steel scalpel blades, concluding that, at 30 angstrom (i.e., 3 nanometers; that's three billionth of a meter) obsidian is much sharper than even the sharpest steel blade, the cuts it produces heal just as well if not better than those made with a steel surgical blade, and contrary to some concerns, it doesn't chip or leave residues when employed to operate on soft tissue. Specifically, he observes that

In most fields of surgery, of course, a modicum
of sharpness suffices, and one feels comfortable
with the convenience of the modem disposable
steel blade. However, in many specialized areas,
scalpel blades and razor blades leave much to be
desired. Examples that come to mind are the
debridement of nerve ends for repair, microvascular
surgery, fine plastic work on thin skin (blepharoplasty,
for example) and ophthalmologic surgery.
Though one with faith in modem technology
cannot imagine that instruments equal to these
various tasks cannot be produced today, the fact
remains that no honed metal edge has matched
that of the glass blade to date. (Buck 1982: 269)

Since the results of that brief experimental study were published almost thirty years ago, however, there hasn't been much of a push for obsidian tipped surgical instruments. My guess as to why this might be the case, beyond inertia in surgical equipment trends, is that some of the practical aspects of making obsidian blades might have been underestimated by Buck, especially those concerning standardization in shape and thickness, along with the properties of various grades of obsidian.

Edit (03/03/2001, 10:45AM): Hey! This post was included in this week's ResearchBlogging 'Editor's Selection' for the social sciences! Sweet!

References:

Buck BA (1982). Ancient technology in contemporary surgery. The Western journal of medicine, 136 (3), 265-9 PMID: 7046256

Quote of the day: Bears, scrapers and points, oh my!

I'm co-teaching a seminar on Neanderthals and the origins of modern humans at UCD this fall, and so far having a really good time. Today, I introduced the topic of Mousterian stone tool technology to my students, including this classic tip on how to distinguish convergent scrapers from Mousterian points...

"In fact, the major problem in classifying Mousterian points is distinguishing them not from other point types but from convergent scrapers... Bordes (1961) himself offered a light-hearted "functional" criterion, writing that the best way to decide is to haft the piece and try to kill a bear with it. If the result is successful, then it is a point; if not, then it should be considered a convergent scraper. One of the problems with this approach is that it can quickly exhaust the available supply of bears or typologists, depending on the nature of the assemblage." (Debénath and Dibble 1994: 62).

Reference

Debénath, A. and H.L. Dibble. 1994. Handbook of Paleolithic Typology Volume One: Lower and Middle Paleolithic of Europe. University Museum of the University of Pennsylvania, Philadelphia.

Ape-man the hunter?

Well, at least the butcher, if not the tool-maker... McPherron et al. (2010) report the discovery of four bone fragments bearing marks left by stone tools from the the Dikika-55 locality in Ethiopia (dating to between 3.24-3.42 million years BP), a stone's throw from where the juvenile Australopithecus afarensis dubbed Selam was found. This is a pretty monumental discovery, in that it pushes back the evidence for the use of stone tool technology by about 800,000 years, and associates it fairly convincingly with A. afarensis (or, at least, as convincingly as can be done for those time frames). John Hawks and Greg Laden have interesting posts on some of the more salient aspects of the paper, which you should read if you're interested in this.

In a nutshell, McPherron and colleagues analyzed the bones using secondary electron imaging (SEI) and energy dispersive X-ray (EDX) to establish that the marks were, in fact, made in deep time before the bones fossilized. Having determined this, they then examined the morphology of the marks on the bone using ESEM (environmental scanning electron microscopy) and optical microscopes to establish that it was most similar to those of experimentally replicated marks made with stone tools used to cut flesh off a bone and crack bones open. I've looked at my share of cut marks over the years, and like Greg, I also agree with the authors that the DIK-55 cut marks look like marks made by stone tools. You'd have to never have looked at cut marks to argue with a straight face that the marks on the DIK-55 specimens look more like croc tooth marks than cut marks.

Given that the marks really seem to be genuine stone tool cut and percussion marks, the question then becomes one of establishing the age of the mark-bearing bones. As Hawks underlines, we're dealing with only four bones here, out of an unspecified total sample. So, we don't really know how common they were at DIK-55, since they do not meet the criteria usually used for collection - basically, they were collected because field observations suggested they might bear cut marks. And as Laden mentions, it'd be better if the bones in question had been collected in primary context, as opposed to from the surface next to their associated depositional context. This is important because there's always the possibility that they might have washed in or been somehow transported from another, potentially younger locality. That said, based on the absence of adhering sediment and the location of the specimens, their most likely provenience is from a sandy formation with a minimum age of 3.24 million years and a maximum age of 3.42 million years. The sample size issue is an interesting one to consider, but really, in this case the noteworthy feature of these bones is that they bear unambiguous traces of modification with stone tools, so their proportional importance is somewhat secondary.

OK, so, we have bones bearing marks made by stone tools that are older by some 800ky than the earliest known stone tool assemblages, which date to about 2.6-2.5mya (Semaw et al. 1997). What does it mean? Well, the most obvious conclusion is that the use of stone tools must be quite a bit older than has generally been assumed, and since A. afarensis is the only hominin associated with deposits that age in the region, they are the best candidates for having used them.

Here's the rub, though: there are no stone tools at DIK-55. Furthermore, the closest source of rocks that could have been used as stone tools is about 6km away. What does that mean? It means that, if A. afarensis really did use stone implements to process these remains, they must have brought them from a little ways away. That, in and of itself, is not earth shattering an observation. Sea otters, for instance, are known to carry rocks in skin folds next to their forepaws to use them in area where clams, crabs and abalones are present but rocks aren't. In that sense, the DIK-55 provide evidence for some basic planing depth, though not much more than in some other tool-using animals.

The big question relating to the stone tools here is whether A. afarensis made some or opportunistically used naturally occurring sharp pieces of stone. McPherron et al. (2010) remain agnostic on that one, as well they should given that they've already rocked the boat enough with this discovery and speculating would undermine their case. I also remain undecided on the issue, though I will say that there could be a case for the evidence presented in the paper to indicate that A. afarensis manufactured stone tools. This is based on two lines of observation: 1) there are no large rocks at DIK-55, the largest rocks found there being about 8mm in maximum size; and 2) the bones described in the paper bear both cut marks and percussion marks. Now, cut marks need to be made with a sharp stone edge, something like a flake, or a cobble with at least one flake knocked off. In contrast, percussion marks are made by blunt objects, usually a hammerstone similar to those used to knock flakes off of cobbles or cores. This distinction is usually not given much thought in discussion of human agency on bones because, by and large, if humans have flakes, they have a hammerstone to knap them off with. In fact, even at Gona, the earliest known stone tool assemblage, hammerstones, cores and flakes co-occur (Semaw et al. 1997; Stout et al. 2005).

In this case, however, the distinction is noteworthy because it implies that at least two different implements were brought in to DIK-55 to process the tools. Remember that there are no stones larges than 8mm at this locality, and try as it might, not even a Floresian hobbit would be able to use such small pebbles as tools with much success. It also means that there could be no 'crime of opportunity' in which an australopith just picked up a large rock that was just lying there to smash open a bone. In short, it means that both a blunt stone object (i.e., a hammerstone) and a sharp one must have been transported to DIK-55. Granted, it might simply be that hominins were carrying both unmodified cobbles and naturally occurring sharp pieces of stone with them. But if you understand that whacking a bone with a hammerstone will break it open (and create sharp edges on the bone as a result) and that sharp objects can be helpful in slicing meat off a bone, a parsimonious explanation might be that your lithic technological behavior includes the use of hammerstone to produce stone flakes. This would also make sense from the perspective of lithic technology where percussors and flakes are part of even the simplest toolkits.

Granted, this last bit is speculative, but what is certain is that people will be looking at 3.4-2.6mya deposits with renewed interest and attention in the coming years. What comes out of these investigation should allow us to flesh out the range of possible scenarios brought up by this new discovery from Dikika, which is proving to be an immensely rewarding area from a paleoanthropological standpoint.

References:

McPherron, S., Alemseged, Z., Marean, C., Wynn, J., Reed, D., Geraads, D., Bobe, R., & Béarat, H. (2010). Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia Nature, 466 (7308), 857-860 DOI: 10.1038/nature09248


Semaw S, Renne P, Harris JW, Feibel CS, Bernor RL, Fesseha N, & Mowbray K (1997). 2.5-million-year-old stone tools from Gona, Ethiopia. Nature, 385 (6614), 333-6 PMID: 9002516

Stout D, Quade J, Semaw S, Rogers MJ, & Levin NE (2005). Raw material selectivity of the earliest stone toolmakers at Gona, Afar, Ethiopia. Journal of human evolution, 48 (4), 365-80 PMID: 15788183

Lower-Middle Paleolithic island living?

There's a lengthy report describing some preliminary findings of Middle and perhaps even Lower Paleolithic artifacts on the Greek island of Crete that Thomas Strasser presented earlier this week. The report stresses especially that "ancient Homo species — perhaps Homo erectus — had used rafts or other seagoing vessels to cross from northern Africa to Europe via at least some of the larger islands in between."

If they're correct, Strasser's interpretations agree exactly with the results of work reported by Mortensen (2008) and which I already discussed a couple of years ago. Specifically, Mortensen argued that the implements he discovered "suggest that the first humans reached the island across the sea from Libya. That an early contact between northern Africa and southern Europe existed already during the Palaeolithic periods is a hypothesis now supported by most scholars."

Archaeoblog is skeptical about the findings, especially since no illustrations are provided that would help assess how 'Paleolithic' the implements look, while Hawks is also skeptical but suggests that fleeting human occupation may have occurred on Crete in the Middle Pleistocene as it may have on other large Mediterranean islands.

I'm of two minds about this. On the one hand, apparently large numbers of artifacts appear to have been found, on at least four distinct terraces as well as some rockshelters. Given that the team comprises a bona fide Paleoltihic archaeologist (C. Runnels), I see no reason to challenge the human-made nature of these implements. And, by referring to the Mortensen report, the current report certainly suggests that there was some sizeable human population on Crete at least during the Late Pleistocene (i.e., after ca. 130kya). That said, based on the description in the report, the stone tools in question appear to be handaxe-like things made on quartz (I recently discussed handaxes here). Quartz can be an impractical material to work, mainly because of its coarse crystalline structure, though in some cases, it can be fine-grained enought to yield decent knapped products. In other words, the structure of quartz often limits the range of formas that can be made from it, usually restricting them to relatively 'coarse' ones similar to some Lower Paleolithic types, which may account for some of the similarities mentioned in the text. Without some good illustration and photographs of these artifacts and of the quality of the quartz used to manufacture them, it's hard to make any kind of definitive statement.

Moving to the issue of the colonization of Crete, the whole 'they came straight from Africa' model is unconvincing to me. For one thing, the Greek mainland is much closer to the island than North Africa, and lower sea levels during cold periods of the Pleistocene would have made Crete more visible and accessible from there than from, say, Lybia. For another, the amount of finds and their time-transgressive nature (that is, they were found on four terraces spanning at least 90,000 years) suggest that people permanently settled the island for long stretches of the Middle Paleolithic. Both of these observations argue for hominins arriving to the island purely by chance. The question is whether or not they reached through seafaring. If they came from Europe, complex seafaring is unlikely to have been critical, whereas if they came directly from Africa, it would have been essential.

In a recent post, I detailed how seafaring - as inferred from the colonization of islands - has been argued by some to represent evidence of 'modern human behavior' (Norton and Jin 2009). However, in that case, colonization through seafaring was demonstrated by the presence of foreign lithic raw materials at specific site. If I understand the report about the finds by Strasser's team, however, the raw material of the Cretan finds appears to be exclusively local. The report states that

... hand axes found on Crete were made from local quartz but display a style typical of ancient African artifacts.

“Hominids adapted to whatever material was available on the island for tool making,” Strasser proposes. “There could be tools made from different types of stone in other parts of Crete.”

Strasser has conducted excavations on Crete for the past 20 years. He had been searching for relatively small implements that would have been made from chunks of chert no more than 11,000 years ago. But a current team member, archaeologist Curtis Runnels of Boston University, pointed out that Stone Age folk would likely have favored quartz for their larger implements. “Once we started looking for quartz tools, everything changed,” Strasser says.

This local provisioning of raw material, in my view, argues against colonization by seafaring to a degree. Reference to the stylistic similarities of the Cretan handaxes and those from Africa is, again in my view, a non-argument, since handaxes are very similar in morphology and technology pretty much throughout the Old World (McPherron 2000).

References

McPherron, S.P. 2000. Handaxes as a Measure of the Mental Capabilities of Early Hominids. Journal of Archaeological Science 27:655-663.

Mortensen, P. 2008. Lower to Middle Palaeolithic artefacts from Loutró on the south coast of Crete. Antiquity 82(317): http://www.antiquity.ac.uk/ProjGall/mortensen/index.html.

Norton, C.J., and J.J.H. Jin. 2009. The evolution of modern human behavior in East Asia: current perspectives. Evolutionary Anthropology 18:247-260.