Pre-Clovis archaeological sites of the Americas 4: Buttermilk Creek, the Debra L. Friedkin site

Buttermilk Creek, Bell County is situated in the hills of Central Texas, 40 miles northwest of Austin.

 
The site has been excavated by Dr. Michael R. Waters and graduate and undergraduate students from Texas A&M University since 2006. It was discovered when Walters was involved in excavating the Gault Site 250 upstream. This Paleo-Indian site excavated in 1998 was found to have deeply stratified deposits including a Clovis horizon. Walters therefore decided to investigate the area further and discovered the new Buttermilk Creek sometimes referred to as the Debra L. Friedkin site.
 
As Pringle¹ noted in 2011

“Early humans would have been attracted to the area surrounding Buttermilk Creek due its favourable climate, abundance of food resources, a year-round water source, but most importantly because the area was a source of very high quality Edward’s Chert.”

 

 

 

Graduate and undergraduate students excavating at the Debra L. Freidkin site. Photo credit: Michael Waters, TAMU

 

Reporting on the excavation Waters’ et al² begun thus:

“Nearly 80 years ago, Clovis was identified as the oldest archaeological horizon in

North America [~12.8 to 13.1 thousand years ago (ka)]. Decades of subsequent research have advanced our understanding of Clovis chronology, adaptations, and technological organization. Whereas genetic studies indicate that the first Americans hailed from northeast Asia, no fluted Clovis points or other diagnostic characteristics of Clovis have been identified there. Additionally, fluted points in Alaska are rare, are technologically different, and postdate Clovis. These lines of evidence suggest that, although the ultimate ancestors of Clovis originated from northeast Asia, important technological developments, including the invention of the Clovis fluted point, took place south of the North American continental ice sheets before 13.1 ka from an ancestral pre-Clovis tool assemblage.”

 

Basically the authors were saying “We have a Pre-Clovis site to explain to you based on a simple toolkit that is a pre-cursor to Clovis points.”

 

To make an unassailable case the authors needed to demonstrate an uninterrupted stratigraphy and date their finds.

 

To address the first of these issues the authors excavated with extreme care and evidenced the stratigraphy in a number of ways.

Firstly they characterised it thus:

“..The high clay content and pedogenic characteristics—including slickensides, surface cracking, and evidence of subsurface microlow and microhigh topography—indicate that the floodplain deposit containing the Buttermilk Creek Complex artifacts is a Vertisol.. Although Vertisols were once thought to be well mixed by argilliturbation processes, more recent pedologic studies show this is not true and that Vertisols are minimally mixed. At the Friedkin site, the vertic features of the soil are weakly expressed.”

A vertisol is a soil in which, the high proportion of heavy clay, within it, can cause deep, wide cracks during dry periods of the year. The soil material is therefore subject to significant internal turnover. This would cause the stratigraphic position of artifacts to be disturbed. Hence the authors elect to address this point first. To really settle the issue of stratigraphic integrity they continue:

“Horizonation is preserved within the soil with the amount of clay, organic carbon, and calcium carbonate, as well as color, soil structure, and pH varying systematically with depth (Fig. 2C).”

The authors show a number of important measures vary as expected down the stratigraphic column. They go on:

“Crack infills constitute a minor portion of the soil volume with diameters rapidly decreasing from 2 cm near the surface to <1 cm at a depth of 1 m. Soil material between the crack infills is intact with few rodent burrows and limited root penetration (<2 mm diameter). Only a few cracks reach the Clovis and Buttermilk Creek Complex levels, and crack apertures are <1 mm diameter, smaller than the microdebitage (sizes 6 to 7, table S15) from these levels (Fig. 2D). There is no sorting of artifacts by size from the surface through the Buttermilk Creek Complex layers (fig. S11). Refitted artifacts occur in the Paleoindian and Buttermilk Creek Complex levels (table S16).”

In other words the distribution of artifacts by size does not show that artifacts have fallen down the small cracks.

Therefore their stratigraphic position is secure. Continuing the reinforcement of the the site’s stratigraphic integrity they say:

“The number of artifacts with pedogenic calcium carbonate adhering to them (sizes 1 to 5, table S15) increases with depth. No calcium carbonate accumulated on artifacts in the Late Prehistoric and Archaic levels, about 40 to 60% of the artifacts from the Paleoindian levels are coated with CaCO₃, and about 90% of the artifacts in the Buttermilk Creek Complex levels have CaCO₃ coatings. The percentage of calcium carbonate coatings on artifacts parallels pedogenic CaCO₃ occurrence and concentration within the soil horizons."

The artifacts have the right amount of calcium carbonate coating for their depth throughout.

“Measurements of mass-normalized magnetic susceptibility show a smooth decrease through the floodplain clays with depth, typical of uninterrupted soil development (14, 15) (fig. S7).

The authors use the correlation between soil formation and magnetic susceptibility to confirm the depositional sequence is undisturbed.

“Further, the magnetic mineralogy gradually changes from an assemblage dominated by magnetite in the upper 40 cm to an assemblage dominated by hematite and/or goethite at depths >40 cm. This trend of increasing oxidation with depth is indicative of undisturbed, nonsaturated, modern soils. Measurements of natural remnant magnetization are all of normal polarity, and magnetic inclinations are consistent with the latitude of the field site.”

The oxidation of iron minerals also confirms the intact stratigraphy. The authors conclude:

“Thus, on the basis of multiple lines of evidence—pedologic, magnetic, chronologic ordering of dates and diagnostic artifacts, artifact size distribution, and distribution of artifacts with and without calcium carbonate accumulations— we conclude that the artifacts from block A lie in undisturbed contexts and have not worked downward or displaced upward by soil-forming processes.”

 

The authors now need to date their finds. To do so they take 49 soil samples spanning the artifact baring levels and beyond, and subject them to obtained optically stimulated luminescence (OSL) dating.

For block A of their excavation, the block containing pre-Clovis artifact they provide two diagrams showing the positions of the OSL samples in column 1 and 2 and their associated dates:

 

 

The figures shown above are adaptations of the originals. The upper diagram and the left hand part of the lower diagram are from their fig. 2. The right hand part of the lower

diagram is adapted from fig. 1.

Original captions read:
Fig. 1. Geomorphic surfaces and excavation areas and trenches (black rectangles and squares) at the Friedkin site.
Fig. 2. Block A stratigraphy, archaeological complexes, and OSL ages (one sigma)
from column 1 (A) and column 2 (B). BP indicates years before the present.

A selection of the 15,528 lithic artifacts from the site is shown below:

Original caption from Waters et al.² read:

Fig. 4. Buttermilk Creek Complex artifacts: (a) lanceolate point preform, (b) chopper/adze, (c) discoidal flake core, (d) radially broken flake with notch, (e) graver, (f) flake tool with retouch on a radially broken edge, (g and h) flake tools with marginal edge retouch, (i) polished hematite, (j) bifacially retouched flake, (k) radially/bend broken flake, (l) radially broken biface, (m and n) blade midsections, (o to s) bladelets.
 
The authors conclude that the dates for the site are as follows:

“Below the Clovis horizon is a 20-cm-thick layer containing artifacts that represent repeated visits to the site and together define the Buttermilk Creek Complex.
Eighteen OSL ages, ranging from ~14 to 17.5 ka, were obtained from this layer, and all but three overlap at one standard deviation (Fig. 2, A and B, and table S2). The most conservative estimate of the age of the Buttermilk Creek Complex is ~13.2 to 15.5 ka, on the basis of the minimum age represented by each of the 18 OSL ages.”
 
Verdict:

Artifacts found were of 17500 years BP, long before the Clovis period and during a period of significant glaciation. Where and when did these people enter America?

 
Overall a meticulous excavation followed up by an exemplary paper with all possible sources of objection covered in great detail.
 
However there were STILL some unfavourable comments made by, of all people Tom Dillehay! He really ought to know better..

“I have a mixed opinion,” Dillehay told The Why Files³, proceeding to list some shortcomings in the study. “It would be most convincing if there was standard radiocarbon dating, and even better if those dates were taken from features like hearths and food stains. OSL dating has become more reliable, but it’s still not as reliable as carbon-14, although the sequences do line up very nicely with sediment dating.”

Dillehay has questions about the three-layer sandwich of pre-Clovis, Clovis and post-Clovis material. “I’m not saying the materials are mixed. Geologists, to identify the strata, applied these excellent, meticulous sediment and particle analyses, but there was no clear visible stratigraphy to distinguish Clovis from pre-Clovis, and again this does not meet standard archeological criteria.”

Dillehay also points to the lack of “diagnostic, complete projectile points in either, the Clovis and pre-Clovis material. In a discipline that has placed incredibly heavy emphasis on formal projectile points as the primary criteria for acceptance of a site, along with C-14 [radioactive carbon] dating, and geologic stratigraphy, I find this sort of acceptance, which seems to be uncritical, to be a major shift in the discipline.”

Still, Dillehay says “the interdisciplinary work is first rate, and I admire the multidisciplinary approach. But had there been C-14 dating and diagnostic projectile points, all this extraneous analysis would probably not be needed.”

 
In reply Waters had this to say³:

"It certainly would be nice to find arrow- or spear-points, says Waters, but “You can’t dictate what you will find. You have to roll with the punches.” Further excavation may or may not reveal a “smoking gun projectile point,” Waters adds. “We don’t know what kind of weaponry they used. In Siberia and Alaska, people were using a lot of bone, ivory and antler weaponry, and it might be that early folks in North America were using this as well.”

But due to heat and humidity, such organic material would not be preserved in the Texas site, he says.

 
I had to laugh when I read Tom Dillehay’s comments! After all the trouble he had getting his Monte Verde site accepted by the Clovis Mafia, I would have thought he would have been a little more positive about the paper, site and authors’ achievements. All I can think is it sounds like sour grapes, As he had yet to publish his Monte Verde paper describing man in southern Chile at 18.5 Kya.
 
James Adovasio of Meadowcroft fame, who had also experienced a decades long fight with the Clovis Mafia (his name for the Clovis-first proponent by the way), was a little more positive⁴:

 “It would appear the assemblage of artifacts is enough different from typical Clovis to be a distinct technology,” Dr. Adovasio said in an interview. “But it is not as much different as not to be ancestral to Clovis material.”
 

In other words one of the main implications of this discovery is that, with a pre-Clovis occupation of North America as proved by this study (and those of Adovasio and later  Dillehay) people had more time to settle in North America, colonize South America by more than 14,000 years ago.

 

He continued:

“Finally, we are able to put Clovis-first behind us and move on,”

Dr. Adovasio noted that the Clovis model had been “dying a slow death.” He recalled that “Waters himself was a Clovis-firster, but changed years ago.”

Adovasio finally finished somewhat disappointedly:

“The last spear carriers [for Clovis-first] will die without changing their minds,”

 

References

1.Pringle, H (2011).Texas Site Confirms Pre-Clovis Settlement of the Americas

Science 25 March 2011: Vol. 331 no. 6024  p. 1512 

DOI: 10.1126/science.331.6024.1512 

2. Michael R. Waters et al (2011). The Buttermilk Creek Complex and the Origins of Clovis at the Debra L. Friedkin Site, Texas. Science 331, 1599 (2011)

DOI: 10.1126/science.1201855

 

3. Tenenbaum, D. (2011).  The Why? Files 7^th April 2011:
Peopling the Americas — New evidence.

Retrieved from http://whyfiles.org/2011/peopling-the-americas-new-evidence/

 

4. Wilford J. N. (2011) Spear Points Found in Texas Dial Back Arrival of Humans in America. The New York Times March 24th, 2011

Retrieved from: http://www.nytimes.com/2011/03/25/science/25archeo.html?_r=0