Wednesday, April 16, 2014

Oblique Transmission

The other day I was lucky enough to spend time with family in the Piney woods of Deep East Texas.  During that time I made a spear with my cousin Bradley and set off on a short romp around the woods. 

While Bradley observed the process that was being demonstrated to him for the first time, I couldn't help but think of role that cultural transmission played in forming patterns of stone tool production throughout the archaeological record. The material record, those artifacts measured by archaeologists, are the “hard parts” of culture (Dunnell 1978) and may be seen as the skeletal remains of culture, akin to bones that are the representation of the human phenotype that survive after death.


Cutting the main shaft and cleaning it prior to straitening

Ready to go!



Cultural transmission occurs when knowledge is passed to others.  There are multiple modes of transmission.  For instance, vertical transmission occurs with parent-offspring teaching.  Oblique transmission describes learning, in this case a craft skill, from a non-parent of the older generation.  If interested, Stephen Shennan (2009) has compiled a great edited volume on cultural transmission and cultural evolution.

In the following study Eerkens and Lipo (2005) focus on the effect of small unintentional changes in the shape of stone points through unbiased transmission from parent to offspring (vertical transmission).  In each subsequent generation a 3% error rate in reproduction is added to the length of a projectile point and is then transmitted to the next generation in a Markov chain manner such that change could be simulated over time. The extent of error could be positive or negative for each generation, meaning potentially longer or shorter points from the previous generation could appear.  The likelihood for length error will behave in a stochastic manner due to unintentional error during unbiased transmission such that projectile length will have a random probability of distribution.  The authors model the process across 400 generations of 10 lineages and allow no interaction or borrowing (horizontal transmission) between traditions of manufacture. 



Figure adapted from Eerkens and Lipo (2005).



                                                      

The results (Fig 1) show that simple copying error during cultural transmission may cause traditions of manufacture to drift quite far from the original form and may increase or decrease slightly per generation (Eerkens and Lipo 2005:322).

So cheers to oblique transmission, technological innovation and morphological drift! Well done Bradley.   

Out and about in beautiful East TX
Not exactly what we were hunting for, cool to look at though!


REFERENCES
Dunnell, R.C. 
(1978).  Archaeological potential of anthropological and scientific models of functoin. In: Dunnell, R.C., Hall. E.S., (eds.), Archaeological Essays in Honor of Irving Benjamin Rouse. Mouton, The Hague, pp 41-73.

Eerkens, J. W. and C. P. Lipo.
(2005). "Cultural transmission, copying errors, and the generation of variation in material culture and the archaeological record." Journal of Anthropological Archaeology 24(4):316-334.

Shennan, S.
(2009).  Pattern and Process in Cultural Evolution. In Pattern and Process in Cultural Evolution. S. Shennan (ed.). Univiersity of California Press. Los Angeles.          


Sunday, March 2, 2014

Handaxes and San Pedro Shootout




Hi all,

Recently, students of a Texas A&M anthropology course processed animals with Acheulean handaxes and also observed projectile point penetration on fresh animal hide.  I made the handaxes from chert nodules that I liberated from parking lot medians here in town and the San Pedro points from quartzite and obsidian.  Students conducted many other tests, including skeletal damage cause by blunt force trauma and burn patterning on animal bone.

Beginning in Africa. ca. 1.7 mya, and extending until ca. 100,000 years ago, Acheulean handaxes were in use for a staggering amount of time.  The production and use of these teardrop-shaped tools and associated flakes extends from South Africa to Northern Europe and Asia.  The Acheulean technological complex focused on the production of large cutting tools such as bifaces, large flake tools and large cleavers.  For this study we tested differences in applicability between a handaxe and the flakes produced during manufacture for the task of fleshing and separating sections of a carcass.  The flakes removed to produce the handaxe offered precision cutting tools while the resultant axe provided a sharp and heavy implement for separating joints and crushing bone to collect marrow.      



Students use Acheulean handaxes and observe cut mark patterning

For the next test we set out to see how San Pedro points perform as armed darts.  I have a bit of a soft spot for these after seeing one positioned over a much later stone-sealed offering pit in New Mexico.  The ease of production, durability and wide cutting edge makes this morphology especially attractive.  The darts performed quite well and roared through the fresh sheep hide without issue.  However, going home with a handful of unbroken darts would be boring so we kept shooting until the points broke.  The quartzite point was by far the most robust projectile, no surprise there.  The obsidian points performed well and left very clean puncture wounds.  The barbs created by the notched corners functioned fantastically well, so much so that the darts had to be pulled out through the target from the back.

The arrow I had made from river cane growing in the backyard felt better than the shorter version I had made the week prior.  The added length kept the foreshaft joint off of my hand while at full draw.  This arrow flew true and had no issue passing through fresh hide.

Lower half of target had hide and rib sections for impact tests. Upper portion had hide on cardboard backing
Arrow made from backyard river cane with turkey feathers
This Tularosa Corner Notched (ca.1100 B.P.) on composite arrow performed well

First in a set of San Pedro points ready for flight test (Southwest U.S.,ca. 3500-1700 B.P.) .

Quartzite San Pedro #1 impact on bone through hide
Dart #2, hafted obsidian San Pedro point
San Pedro #2 through sheep hide
Surprisingly, San Pedro #2 split through this branch with minimal tip damage

San Pedro #2 eventually struck bone directly under the hide and shattered

San Pedro #3
San Pedro #3 damaged tip after a few ground impacts and a glancing strike on bone through hide
This Pueblo Side Notched arrow point still pushed through after three resharpening events

Saturday, February 22, 2014

Making and Breaking

Hi all,

For the last few weeks I have been producing projectile points and armed darts for a Texas A&M course focused on taphonomic processes.  This course, led by Dr. Darryl de Ruiter, illustrates how animal bones found in the prehistoric record offer evidence of human behavior and natural post-depositional processes.  For instance, differences in impact damage from projectile points and cut marks on bone from butchering may show changing subsistence strategies over time.  We have used stone-tipped arrows, atlatl darts, metal spears...all sorts of fun sharp things.

My part in all of this is to provide a healthy supply of projectile points and other stone tools for use in these experiments.  I have been having a blast and thought I would share what we have been up to so far.

As always, it's been fun to make functional points and destroy them.



Producing stone tools with students for a butchering experiment
Angela Gore testing obsidian point damage on bone
Antler composite point without  binding or inset blades

The durability of this point style surprised us all

Antler point damage from impact with bone


Hafted Folsom point ready for impact damage test
Impact damage from cow head on Folsom
Similar damage pattern on Folsom from Kincaid Shelter, TX. Photo: Texasbeyondhistory.net


 
This Folsom point passed through the throat with no trouble
Josh Lynch launching a Folsom point. Look at the flex in that dart!
 
Clovis point wrapped and ready
Clovis point entrance wound

Clovis point impact damage on cow bone

Tuesday, February 4, 2014

Testing the Third Notch


Hi all,

 CLICK HERE TO SEE THE TEST VIDEO

The presence of a little third notch on Bonito Notched and Temporal points has interested me for a number of years.  I first saw these point types in person in 2011 while helping teach for the Archaeology Southwest Field School out in southwest New Mexico.  These points were made throughout the western half of New Mexico and into eastern AZ.  I wouldn't be surprised to see these points in northern Mexico given prehistoric interaction.  People made these points during the Late Prehistoric period, Pueblo II to III time frame, placing them around A.D. 950-1150.  Bonito points were in vogue in Chaco Canyon during the Classic Bonito phase (A.D. 1020-1120) when construction at the massive Pueblo Bonito was completed.  Check out Justice 2002:254 for info on how these relate to earlier Chaco point forms.  Bonito points were contemporaneous with non-triple notched points for some time, as both types have been found together in excavated arrow bundles at Pueblo Bonito (Judd 1954).
Temporal Point from Fornholdt Site, Mule Creek, NM
 
Temporal points occupy a more southerly region and are more or less restricted to southwest New Mexico and eastern AZ. These points also have a third notch along one margin and date to the Late prehistoric; around A.D. 900-1200 is a good ball park date range.

The points were typically made from flake blanks and often exhibit the original flake scar from core removal.  I can typically produce a point of this kind within 15 minutes.  They are thin, sharp, and a welcome asset to any quiver.

The third notch was not used as an additional element for hafting the point to a foreshaft as hafted points have been found at Pueblo Bonito with sinew wraps only around the lower two notches (Justice 2002:41; Cosgrove 1947).

So, is a third notch on one side a technological advantage, or should we look outside of technological function to explain this attribute?


Area of Fornholdt Site, NM with mule deer in distance

The Test

I wanted to see if the single third notch along one side aided in consistent and predictable fragmentation.  If the points failed to show a clear advantage over serrated points or normal point breakage patterns then we might start entertaining ideas of social, rather than technological function.  for a pilot study I created five hafted points with a single notch on one side.  These points were shot with a recurve bow into meat targets until breakage was achieved.  The broken points were observed for breakage patterning to understand technological function versus a more vaporous social marker.

Set of Bonito Notched and Temporal points ready for hafting

Hafted points with a third notch along one side

Results


All points functioned well and took several hard impacts prior to any sort of impact damage.  As always, I would want more data.  Only one point exhibited a break along the third notch.  All others broke at the tip or at the intersection of haft and point, where in my experience a majority of breakage occurs during impact.  At this point I cannot comfortably attribute the single third notch as a technological advantage over serrated points or straight-edged points.  The third notch did not make breakage patterns more predictable, nor did it make the point into some kind of frangible arrow point.

The remaining points show no strict breakage patterning
One point broke along the third notch

Temporal point going strong after several impacts
 Discussion

I can see why we would think the third notch functioned as as technological advantage.  for instance, perhaps the third notch was a quick way of making the point break apart on impact with bone, which is a good thing in some cases.  But, this was not the case.  The points broke in relatively normal order.  In fact, the points took just as much of a beating prior to breakage as any other point.  I had to shoot the points through sinew and light bone up to five times before any type of breakage occurred.  This is of course luck of the draw, as one major bone impact on the first shot would cause a break.  But, at the end of the day, shot after shot, the points did not show any superiority in breakage patterning to other points tested so far.  Perhaps in this case we have a social function or marker of time and place flaked into stone rather than strict technological choice.  More tests will help, but for now I have been persuaded to look at these types as a mark of identity, rather than technological/functional adaptation.  Possible social functions? Your guess is as good as mine.


 Happy Hunting



Refernences:

Cosgrove, Cornelius B.
    1947      Caves of the Upper Gila and Hueco Areas in New Mexico and Texas.  Papers of the peabody Museaum of American Archaeology and Ethnology, Harvard University 24(2).

Judd, Niel M.
    1954      The Material Culture of Pueblo Bonito. Smithsonian Miscellaneous Collections Vol. 124.

Justice, Noel D. Stone Age Spear and Arrow Points of the American Southwestern United States
     2002      Indiana University Press, Bloominton, Indiana.




Monday, January 27, 2014

Flake Tools and Deer Hide


Hi all,

The other day my friend Angela Gore shot an Axis deer near Fredericksburg, TX and brought the hide over to begin the fleshing and tanning process.  Angela is interested in Upper Paleolithic and Paleoindian archaeology focused on the peopling of Beringia and the Americas, specifically patterns of human dispersals, hunter-gatherer ecology, and human behavioral adaptation.

What's really cool is that she brought along a ton of raw chert local to the area where the deer was taken. This locally available raw material is commonly known as root beer chert and is a minor lithologic constituent of the larger Fredericksburg limestone, dolomite, marl, and chert group. High quality nodules from this group knap very well and offer a more durable alternative to obsidian.

Axis deer hide ready for work
Fredericksburg root beer chert nodules

 We decided to perform the task with local raw materials to see what it would have been like to process a deer hide as a Central Texas forager.  The abundant raw materials allowed us to use expedient flakes taken from a core to flesh the hide.  Informal tools are made when minor design constraints are present such that little to no reshaping of a flake is necessary to complete a task.  In an instance of raw material scarcity, our technological choice may have become centered around a more formalized flake core to preserve our stone.  In this case I created blade-like flakes (more than twice as long as wide) from a single-platform core and produced more as initial flakes became dull through use.

Flake core with parallel removal scars and partially fleshed hide


When lithic specialists think of hide processing we sometimes focus too much on formalized scrapers.  Formal scrapers are the most iconic implement, yet are only one member of a much larger tool kit.  Interestingly enough, for our task, sharp flakes comprised the entire usable assemblage for the initial stage of fleshing.  The scrapers that we tested did laughably little to separate the tough membrane from the hide.  Formal scrapers will play a dominant role in the next stage of scraping the residual tissue once the hide is salted and soaked.  Salting the hide removes fats and oils that decompose and lead to hair loss on the pelt.  In this way each step includes a dominant tool assemblage that plays a key role in the multistage process.  Overlap in tool morphology no doubt exists as trimming with sharp flakes will accompany the formal scraper use later.  As far as site formation process goes, the initial fleshing leads to the production and eventual discard of several large, sharp flakes while the ensuing hide scraping produces small retouch flakes as scrapers are resharpened.

Angela uses a sharp flake to cut flesh from the hide


Visible use wear on the fleshing flakes took the form of a dull continuous polish along the cutting margin with minor flakes removed to dull sharp areas that came in contact with hands.

This sharp curved flakes worked very well.  You can see residue along the working portion of the flake

All in all a very fun experience that reminded us both of the compound nature of tool production, use and discard during a single hide processing event.  Additionally the task helped to reinforce the usefulness of expedient flake tools and the importance of tailoring production techniques to raw material availability.

Happy Hunting!         

Wednesday, January 15, 2014

Oh, Snap! Obsidian Knife Breakage

Hi All,

I hafted the fluted obsidian knife from the other day and took it out for a test in the Piney Woods of Deep East TX.  I (unsurprisingly) did not manage to get a deer or wild hog this time.  I did, however happen upon a rabbit.  These rabbits have been a real hit at cookouts with the neighbors, no really.

The Test:

In keeping up with thrashing nice things, I used the hafted knife to process a rabbit in a similar method seen in the previous rabbit knife post. The materials used did not change: obsidian knife blade, antler handle and pine pitch glue.  Rather than keeping the cutting edge centered along the tool's cutting margin, this time I played with a slight bevel.  This was supposed to be used in a test of resharpening efficiency between beveled and mid-line margins.  I had misplaced my metal knife so i set out on another functional-recon experiment with what I had laying around.


Hafted knife with beveled edge created along lower cutting margin



Results:

Unfortunately, I had little chance to observe differences in beveled/centered cutting edge performance as the blade snapped during rib cage separation.  I had inverted the knife, using the curved edge in an upward direction to open the rib cage from the inside.  This task did not bode well for this specific tool.  The event was signaled by the broken blade flying across the workspace that left a spiral of blood stretched across the ground.  So...pretty cool to see actually.  Try it for yourself sometime as a party trick, no?

The catastrophe resulted in a strange hinge fracture that traveled from margin to margin and split the piece in half.  The crack initiated from the curved section of the tool as force was applied upward.  Bending stress increased upon the fulcrum created at the junction of blade and handle to a sufficient degree such that the applied stress overcame the performance capabilities of the tool.  The fact that this was a fluted knife may have something to do with the breakage, as the channel flake eliminated the typical lenticular cross-section that usually works so well under bending stress. 


Blade held as used during fracture.  Fracture initiated from top to bottom

Oblique distal view of vertical bending stress fracture



Discussion:

Is this type of breakage specific to knife use?  I have never seen a hinge fracture like this as the result of horizontal impact damage.  Perhaps this type of breakage is associated with vertical bending stress during butchering events.  More tests are needed, as usual, but his seems to be something special in the world of task-specific breakage patterns.

The following images illustrate how this piece broke.  I have found that inverting the image is a simple way to see flake scar patterns slightly better.  There are some great new imaging studies out there that are revolutionizing our ability to assess flake patterning.  Inverting the image colors on obsidian is a quick and dirty way to see a piece in another light, plus it looks cool.







Let me know if you have seen anything akin to this type of stress fracture.

Happy Hunting!