I wrote a while back about the Buttermilk Creek site in Texas, a site that has produced dates that may make it the oldest confirmed in the Americas if they are, in fact confirmed, making it a pre-Clovis site if it is, in fact, as old as the dates show. The data from this site comes in addition to the debated early dates from Monte Verde in Chile, Meadowcroft Rock Shelter in Pennsylvania, Paisley Caves in Oregon, the temporally borderline Arlington Springs remains from California's channel Islands, and a number of other sites with various pre-Clovis claims of various reliability. And hell, while we're at it, how about this rock art that nobody is claiming is pre-Clovis, but is claimed to be pretty damn old.
All of these sites together would seem to imply that humans have been in The Americas alot longer than had previously been thought, and that the Clovis Cultures were likely not the first peoples of the Americas. In fact, you will sometimes hear people, both archaeologists and members of the lay public alike, claim that the matter is settled, and that those who claim that there weren't pre-Clovis people are being stubborn or stupid.
The people making such charges are, of course, wrong.
Now, don't get me wrong, here. I do think that there is pretty good evidence for pre-Clovis occupation of the Americas. Hell, I think that the fact that the Clovis Cultures appear more or less out-of-the-blue without any clear precursors in the Old World is pretty good evidence that they developed in the New World, necessitating pre-Clovis peoples to develop into the Clovis peoples. While the evidence from the sites listed and linked-to above are a mixed bag (some of the ones in the Wikipedia link are complete fantasy, others are actually pretty good), none of them are, as of yet, clinchers. None seal the deal, proving the existence of pre-Clovis peoples in the Americas.
As a result, it is not being stubborn or wrong-headed to point out that no unambiguous evidence of pre-Clovis peoples exists. To be certain, there are individuals who will take the stance of "we've long known that Clovis was first, therefore you can stuff contrary evidence!" But most of the people who don't buy into the pre-Clovis arguments do so simply because the evidence for specific pre-Clovis claims isn't as solid as many pre-Clovis proponents, including myself if I am to be honest, would like to think it is.
One of the problems that we encounter is that, until fairly recently, and especially until the late 90s, most of the evidence that we like to claim in our favor is circumstantial: look at my own reasoning above - it holds together, it's internally consistent, and it seems reasonable...but it lacks anything in the way of actual physical evidence to support it, it's simply a statement of "X makes sense because of Y."
There are, of course, legitimate explanations as to why there would be little evidence of pre-Clovis peoples even if they were here. There's the fact that they likely were largely nomadic (though there may have been regional sedentism) and probably travelled in small bands, leaving little impact on the landscape. There's the natural destructive processes (erosion, for example) that routinely eliminate portions of the already ephemeral archaeological record. There's the simple fact that we don't know what the pre-Clovis sites would look like, and without datable materials (organics for radiocarbon, obsidian for hydration measurements, etc.) we might be writing them off (though as new dating methods are developed, this is becoming less of a good reason).
But all of these are excuses for why physical evidence is hard to come by, not proof of the existence of such evidence. It is frustrating to see many pre-Clovis proponents fail to grasp this point.
As earlier dates from more sites come to light, the argument gains physical support. But the support isn't sufficient to move the null hypothesis (that is, the position that is assumed to be true in the face of the lack of supporting evidence otherwise) in favor of the position of myself and my fellow pre-Clovisians just yet. It looks like it's getting there, but it isn't at the moment. Some of our favorite sites turned out to be not as old as previously thought, on further examination. Others may, in fact, be that old, but for various reasons the dates are legitimately being called into question (Monte Verde, I'm looking at you!).
There is also something of a cultural shift. As much as we like to claim that archaeology is all about the evidence all of the time, the fact of the matter is that personalities, training, and long-held beliefs and concepts do have influence. And the older generation of archaeologists have long held to the notion that Clovis is the earliest-known culture in the Americas. Now, many of these people will be overjoyed when something earlier is proven beyond question, but many will still be skeptical of the new data, no matter how solid, because that is human nature.
Archaeologists in my generation seem to be a little more open to the pre-Clovis hypothesis - many open to the point of gullibility anytime a pre-Clovis claim is made (again, sometimes human nature trumps actual evidence). Indeed, the generation immediately proceeding mine even developed new hypotheses for the populating of the Americas (the most popular of which is probably the Coastal Migration Hypothesis) that are now often taught to archaeology undergraduates. This indicates that interest in very early sites is more popular than it has been in at least a few decades, though some would dispute that assertion.
But, nonetheless, pre-Clovis hasn't yet been proven in any meaningful way. I think that it will be, it's just a matter of time, but when you see reports claiming otherwise, taken them with a grain of salt.