The Age of Clovis (Waters et al. 2020) does a very good job of showing when some particular sites were used by people who also used Clovis points. It doesn’t really tell us all that much about the Age of Clovis, but it is a solid paper. Rather than the more ambitious and expansive “The Age of Clovis”, I might have titled the paper “The age of a group of Clovis points for which the find contexts and associated carbon dates fit a very specific set of conservative assumptions.” This is a valid way of approaching this kind of study, and this one is well done.

Perhaps the biggest issue with the paper, and it is far from fatal, is that there is occasional slippage between the broader claim of revealing the Age of Clovis, with all that the title conjures up in the reader’s mind, and the narrower focus on accurately estimating the age of particular sites securely associated with Clovis points.

There are several subtle examples of this slippage, and a few more obvious ones. In the subtle category, we find the authors claiming that “Only the two ages on XAD-purified collagen from two different mammoth bones found with artifacts in stratum B3 date the Clovis activity at the site [Lange-Fergusson].” It would be accurate to say something like only those two ages fit the appropriately conservative criteria for inclusion in our sample, without drawing broader conclusions about the age of the site itself.

More obviously, the title, abstract, and introduction, allow the reader to suppose (imply is too strong a term) that the paper is about an age and a people, rather than about a very small, very particular set of stone tools. This may account for at least some of the media interest in the paper. The authors, for example, talk about a Clovis complex, which definitely suggests something broader than a small group of Clovis points. Too late, I think, the conclusion finally reminds us that “Clovis – the technology – abruptly ends at ~12,750 cal yr B.P.” Even Clovis – the technology – is too broad a name for the object of study here, which is literally one single kind of object.

There is a bit of a missing discussion of the basic approach taken by the authors. They are very concerned with creating a criterion of demarcation that will allow them to include in their analysis the most accurate, best, and most reliable dates and associations with Clovis points, and to reject others completely. This is a defensible approach, but it is undefended in the paper. There is also a rather extreme concern for precision reflected right in the title of the paper. The alternative approach, which is also defensible, is to consider a larger set of observations of various reliability and confidence levels, and to estimate based on all of them.

The discussion of the Paleo Crossing site in Ohio gives a good example of appropriate outright rejection of a date. Dates which were originally reported as being on charcoal from a pre-contact structure are in fact on bulk sediment from post-hole fill in a recent structure. Fine. But other rejected dates are not quite as obviously rejectable, while not being quite acceptable either. In any case, the authors are very clear about the criteria they use for rejection, which is good, whether one favours their approach or the alternative.

Finally, in their conclusion the authors grant that “Archaeological evidence from many sites now indicates that people were in the Americas by ~16,000 to 15,000 cal yr B.P.” I have to note that if they applied the criteria they use for Clovis to the dates on which this estimate is based, they would have to revise it quite a bit toward the 14k range.


Waters MR, TW Stafford Jr, DL Carlson 2020. The Age of Clovis – 13,050 to 12,750 cal yr B.P. Science Advances 6 (43).

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