Most of these sites have issues related to either the artifacts recovered or their dating. There are good artifact asemblages at Meadowcroft, Cactus Hill, and Monte Verde but disagreement about the dates. At Meadowcroft, for example, the radiocarbon dates may have been thrown off by a coal deposit in the cave. At Big Eddy and Topper, the dates look secure but there are questions about the artifacts. The picture above is of artifacts from Topper. At both these sites the Pre-Clovis assemblages seem to consist of crudely chipped pebbles, like the ones pictured above.
I got the latest issue of American Antiquity this week, and wanted to share with you an article from it written by the researchers at Big Eddy: "Trampling Experiments in the Search for the Earliest Americans" by Neal Lopinot and Jack Ray of Missouri State University. I'm sorry but there really isn't anything I can link to.
Lopinot and Ray thought that the material they were recovering from their lowest levels looked suspiciously crude, and began to doubt they were made by human agency. They devised an experiment to find out.
They reasoned that "artifacts" like the ones at Big Eddy and Topper may have been made by animal trampling. Field archaeologists commonly see things like this, rocks flaked by cattle trampling or crushed by heavy construction equipment, that look like crude tools. They are commonly referred to by elegant terms such as "cow-facts" or "dozer-facts".
The researchers made beds of pebbles and cobbles of stone found at Big Eddy and placed them where they would be trampled by elephants and bison, stand-ins for common megafauna during the end of the Pleistocene. In the picture above you can see an elephant from a zoo in Missouri trampling on the stone. This experiment went well as three adult Asian elephants named Vicky, Patience and Connie were walked over the bed repeatedly. The bison used were from a herd in a nearby state park where a similar bed was set up. Things did not go quite as well there:
"The untamed bison herd could not be manipulated like the elephants, but park personnel attracted the herd to the experimental area with so-called 'bison candy', large grain pellets soaked in molasses. Unfortunately, the bison were skittish and, after many hours, only a few young calves and later a few cows stepped on the gravel in the experimental pit. A couple of large bulls in the herd sniffed around the gravel and walked over or stepped around the boulders, but they never were observed as having stepped direcly on these or the gravel pit."
I can just see the bison sniffing suspiciously at that pit. And leave it to the kids to go get the candy!
The bison experiment was continued for five days and eventually 29 modified pebbles and cobbles were recovered. A total of 228 modified pebbles and cobbles were recovered from the elephant experiment. Above is a photo of some of these that Lopinot and Ray call "zoofacts." They really look quite like the Pre-Clovis material from Big Eddy and Topper. The researchers analyzed the zoofacts just as they would real artifacts and came up with a number of attributes that can be used to differentiate them.
I suppose this shows that everyone should be a little suspicious when only very crude tools are found in Pre-Clovis contexts. Humans everywhere else had very sophisticated flaked-stone tool kits at this time period. Why should people here be any different? Lopinot and Ray say they are keeping an open mind, and admit that not absolutely everything from the Pre-Clovis levels at Big Eddy fit neatly into the zoofact category. But this shows we should be cautious.
And please understand, I am not invested in disproving Pre-Clovis claims. I am just trying to stand up for good science. I fully expect that within my lifetime we'll find a (some?) Pre-Clovis occupation we can all agree on.
I believe it is starting to appear that the paradigm we have been using for he last 50 years or so, of a single overland migration across Beringia about 14,000 BP, is impossibly simplistic. I think future research will likely show that (as Valerius Geist believes) there were many attempts to colonize the Americas from Asia over a long period of time, both overland and down the coast in boats. We aren't recognizing or haven't found the inland sites and sites along the coast have been drowned by the Holocene rise in sea level.
There is all sorts of evidence that currently doesn't fit together very well. Mitochondrial DNA evidence from Native Americans seems to indicate a single migration of a small number of individuals. But the morphology of the earliest Paleoindian skeletons we have is distinctly different from modern Native Americans. A recent review of all the radiocarbon dates from all the Paleoindian sites in Alaska shows that the oldest sites there are younger than the oldest good dates from further south in North America. That doesn't seem to fit with a Beringian migration. Time and more research will tell. I think we'll see that Clovis was the latest and most successful colonizing attempt.