Mar 28 2011

A Pre-Clovis Find?

I love scientific mysteries of all kinds – ones where competent experts can legitimately disagree on the interpretation of the evidence, and all agree on what evidence would most likely settle the debate. It’s like a cliffhanger of a great mystery series, except you don’t know when the new season will begin. You just have to wait for new episodes to pop up unexpectedly.

One such debate is the question of how and when were the Americas peopled. This is a story of our recent pre-history. Knowledge of this time has not survived to the present, so we have to reconstruct the past from the clues left behind. And it is recent enough in the past that there is likely to be good physical evidence for archaeologists to find.

For a time the Clovis culture was considered to be the first people in the Americas. They likely crossed the land bridge from Asia to North America about 13,500 years ago, and then worked their way down to South America. They are called the Clovis culture because they are defined by the artifacts they left behind – their projectile points have a very distinctive feature that defines the Clovis. They are fluted at the base on both sides – the stone is precisely carved to be made thinner at the base to allow for better hafting to a wooden spear. These points were designed to hunt the large game of North America, like mammoths. Wherever Clovis points are found – you have Clovis culture.

Unfortunately, there are no sites that have both human remains and Clovis points, so we cannot be sure about the genetic heritage of the people responsible for the Clovis culture. This is definitely a site, somewhere out there, waiting to be found. It is possible that the Clovis culture was not the product of a single population of humans, but was in reality a culture that could have spread to different populations. In other words – Clovis may track a technology, but not a specific people. This is an intriguing idea that also makes it all the more important that we find human remains and Clovis points together.

In any case, there were people widely distributed in the Americas from 13,500 to about 11,000 years ago using Clovis technology. This technology then disappears and is replaced by later paleo-Indian cultures. Another mystery is what, exactly, happened to the people using Clovis technology. Did they die out and were replaced by later migrations? Did they become the later cultures, or merge with them? Perhaps they simply changed their tools after the extinction of much of the megafauna of North America, switching to points better suited to smaller game.

Another question is whether or not the Clovis culture truly represents the first people in the Americas. Is there any evidence of a pre-Clovis culture? Now a new find adds potentially significant evidence to the claim that there were pre-Clovis people in the Americas.

A large find of stone tools and evidence of tool crafting was found north of Austin, Texas – over 15,000 individual pieces of stone. They are largely small tools, which has led archaeologists to suspect that this was a mobile assemblage – made to be picked up and carried. Most importantly, the tools date to about 15,000 years ago, a full 1,500 years or more before the earliest Clovis culture.

In addition to the dating, the find is located beneath a later Clovis site. If the arrangement of these finds represents that order in which they were deposited (and not later mixing) then the tools farther down must be older than the Clovis points found further up.

That is the straightforward interpretation of the find, and by all accounts the authors did a thorough job of presenting their data. Of course, the interpretation of this evidence is not without its controversy also. Other scientists have done their job by thinking of all the possible weaknesses in the evidence.

According to interviews done by the BBC it has been pointed out that the dating method used, optically stimulated luminescence (OSL), while considered a reliable dating method may not be as accurate as carbon dating. If the dates are off by a couple thousand years then this would not be a pre-Clovis find.

Further the assigning of the tools from the two layers to Clovis and non-Clovis can be questioned on the basis that neither contains the projectile points that are diagnostic of the Clovis culture – they contain only other kinds of stone tools.

Perhaps most problematic is that the tools were found in a flood plain. They are buried in clay, which is a good thing in that the clay is hard and not easily disturbed. So from that point of view there was probably not later mixing of the dirt layers. But the clay also indicates that these tools may have been deposited in their current location from somewhere else by flood waters. If the tools were moved around by water, then their relative positions may be deceptive.

While this is clearly an important find, scientists will need to carefully examine the evidence and explore alternate theories before we can know what the definitive answer is.

From reading the article and interviews I was also left a bit confused as to the current status of the theory of a pre-Clovis population in the Americas. From my discussions with archaeologists it seemed to me that the pre-Clovis theory was speculative and not confirmed. However, some of the archaeologists interviewed for the BBC report indicate that the “Clovis-first” hypothesis is dead, and that other sites already clearly establish the existence of pre-Clovis people in the Americas.

I often find it challenging to find out what the consensus is within a specialized field – it seems like you will get a different picture depending on which experts you talk to. What is clear is that there remain two schools of thought regarding pre-Clovis people in the Americas. As an outsider, I am currently unsure which side has the upper hand, in terms of evidence and consensus.

It does seem likely, given how testable the claims of each side are, that eventually opinion will yield to more definitive evidence.

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20 responses so far

20 Responses to “A Pre-Clovis Find?”

  1. amy jacksonon 28 Mar 2011 at 10:19 am

    How can I read that link Dr.Novella? It seems to be for members only.

  2. amy jacksonon 28 Mar 2011 at 10:21 am

    ”explore alternate theories before we can know what the definitive answer is”

    Exactly, well said.

  3. SARAon 28 Mar 2011 at 10:38 am

    So what is going to convince everyone that this is a pre-clovis find? Carbon dating? How can you carbon date an arrowhead? Wouldn’t you just be dating the rock, which would be far, far older than the tool itself. That would appear to be the only objective evidence possible to define this particular set of artifacts.

  4. bjzaon 28 Mar 2011 at 11:38 am

    Sara, radiocarbon dating itself is 1) only one form of radiometric dating and 2) only useful in dating items of organic origin. According to the BBC article, the team used optical dating, which essentially fixes a date on when the tools were last exposed to sunlight. An archeologist quoted in the BBC article raises doubts about the methodology, but someone with expertise and access to the original will have to step in to comment on that.

    As is the case with evolution and the silliness of demanding evidence of “missing link,” a single test on a single find isn’t going to be wholly convincing since it can’t lead to much of a theory. The data points are so few that the best theory to explain them is necessarily going to be modest (or risk wild speculation). In the end it’s the entire body of evidence that will matter here, and there are still hugely important unanswered questions.

  5. Michael Meadonon 28 Mar 2011 at 11:48 am

    Wikipedia has a list of pre-Clovis archaeological sites.

    I’m not an expert but I read the paper in question, and I think the evidence they present convincingly rules out mixing. Also, Steve, the authors themselves don’t make much of the fact that the Buttermilk Creek complex was found underneath a Clovis site. They rely on the absolute date from OSL, and a couple of indirect lines of evidence (magnetism in the clay, etc.) to rule out mixing.

    It is worrisome, though, that the margin of error brings it so close to the Clovis dates. (But, then again, the technology is far less sophisticated than Clovis fluted points).

  6. Steven Novellaon 28 Mar 2011 at 12:17 pm

    Michael – I know that mixing is not the issue here. It’s how the tools were originally deposited in their current location.

    I am going to interview an archaeologist (Kenny Feder) on this story for this week’s SGU.

  7. eeanon 28 Mar 2011 at 12:45 pm

    great :)

    American archaeology is probably a field that could use more skepitcal scruntiny in general. I remember the museum at Cahokia talking about how they worshipped the sun. But really they have no idea and its just an educated guess (their monuments do line up with sun). I think this sort of thing isn’t uncommon, done in the service of creating a narrative about a people we know little of.

  8. jreon 28 Mar 2011 at 4:17 pm

    The best popular work I’ve come across on dating methods is Bones, Rocks and Stars by Chris Turney. In it, techniques such as optically stimulated luminescence are described in the context of important puzzles (such as the dates of extinction for large animals in Australia) they have helped to solve.

    One institution that ought to be a premier educational resource on Paleoamerican culture is the National Museum of the American Indian in Washington, D.C.– but it is worthless on the subject of dating. In one beautiful exhibit of arrowheads and spear points, the words “Clovis” or “Folsom” are nowhere to be found. Indeed, those words, and any reference to the dating of artifacts from this period, are conspicuously absent throughout the museum. You get three guesses as to why this is.

  9. Zhankforon 28 Mar 2011 at 6:54 pm

    I think it’s important to point out that the vast majority of the 15 000 artifacts found at the site are not in fact tools, but are known as “debitage;” the tiny little flakes of flint that are the result of the sorts of advanced flintknapping processes that modern homo sapiens have been using for a few tens of thousands of year. Debitage is not entirely useless – in fact, the flakes knocked off the “main” tool being produced can often be quite a bit sharper than the tool itself – but mainly they’re important because they are clear evidence of human activity; that sort of stone chip doesn’t occur without intent.

    The about.com (OK, not exactly authoritative, but I’ll go with it, it’s the first one I found) says that only 56 of the artifacts are in fact what are generally classified as “tools.”

    Still awesomely cool, though! Pre-Clovis sites can sort of be the scientific equivalent of Atlantis or Noah’s Ark claims, in that they get made every couple years and rarely hold any water, but this one looks pretty good so far.

  10. Zhankforon 28 Mar 2011 at 6:59 pm

    Correction for above: Atlantis and Noah’s Ark claims never hold any water. Sorry.

  11. bachfiendon 28 Mar 2011 at 8:16 pm

    Now I’ve got yet another reason to be looking forward to next week’s SGU, and it’s only Tuesday morning.

    Atlantis could hold a little water if it’s a vague allusion to an unknown civilization destroyed by the eruption of the Santorini volcano.

  12. Zhankforon 28 Mar 2011 at 8:38 pm

    That’s a good point, but I’d still call it a trace amount of water.

  13. Davdoodleson 28 Mar 2011 at 9:46 pm

    We need to concentrate on divining what pre-scientific medical behaviors they engaged in, so we can make money peddling Clovis and pre-Clovis folks’ “ancient wisdom” on late night TeeVee… ;)
    .

  14. SARAon 28 Mar 2011 at 11:57 pm

    @Davdoodles
    I don’t think we need any actual information. The ‘divining’ process allows us to make it up as we go along. So whatever readily available cheap product we can make and then sell as Pre-Clovis ancient wisdom will work.
    Documentation can be manufactured as needed.

  15. Michael Meadonon 29 Mar 2011 at 3:31 am

    @Steve – awesome. Looking forward to the interview. My take is in all likelihood unreliable and too rosy… :-)

  16. BillyJoe7on 29 Mar 2011 at 5:46 am

    “I think it’s important to point out that the vast majority of the 15 000 artifacts found at the site are not in fact tools, but are known as “debitage”, the tiny little flakes of flint that are the result of the sorts of advanced flintknapping processes that modern homo sapiens have been using for a few tens of thousands of year…56 of the artifacts are in fact what are generally classified as “tools.””

    250 flakes per tool!
    …anyone find 3D jigsaw puzzles interesting might like to try their hand :D

  17. bachfiendon 29 Mar 2011 at 7:35 am

    Zhankfor,

    A homeopathic trace of water perhaps?

    In which case, according to homeopaths, Atlantis would more exist than if we found it well preserved sitting on an island somewhere.

  18. Zhankforon 29 Mar 2011 at 10:28 am

    @BillyJoe7

    Not necessarily a huge ratio of debitage per tool, but keep in mind that more tools may have been produced at the site then were deposited and recovered. The jigsaw puzzle analogy is good way to think about it, though!

  19. azmzon 29 Mar 2011 at 12:25 pm

    I’m surprised that Waters, in the BBC article, is arguing as if there was still major opposition to pre-Clovis occupations. There have been known credible pre-Clovis occupations (or sites) since the late 1970s with acceptance growing since the mid-1980s.

    The question for archaeologists was whether these occupations before Clovis had a population large enough to sustain itself. Granted my training is somewhat dated, but I was taught a population needed roughly 500 individuals to be self-sustaining. Below that threshold a population would eventually be extinguished.

    From the archaeological record, we can assume that the Clovis culture had the minimum threshold whatever it is. The pre-Clovis occupations that have been accepted as credible do not appear to have attained that minimum, so the culture or cultures died out.

    Zhanfor, concerning debitage you stated, “[T]hat sort of stone chip doesn’t occur without intent.” There is a category known as geofacts as opposed to artifacts. Geofacts are items that can be produced through natural processes without human intervention. For instance, the force of flooding waters can be enough to smash together rocks of the right type at the right angle to produce stone flakes that are indistinguishable in their physical properties from debitage.

    The possibility of geofacts is one reason why one pre-Clovis site, the Calico Site, has not been accepted by consensus among archaeologists. Pre-Clovis occupations at the site are dated roughly 18,000 years ago and somewhere between 100,000 and 200,000 years ago. Wikipedia has a summary of the site and discusses geofacts: http://en.wikipedia.org/wiki/Calico_Early_Man_Site

  20. Zhankforon 29 Mar 2011 at 1:05 pm

    azmz, true, and good point; maybe I should have said that debitage in those numbers and in that concentration don’t occur without human intent. There’s still an assumption implicit in that statement, but I’d call it a safe one.

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