Clovis-Culture lasts only for 200 years?

Before reading "Science" I was very sceptical concerning this news. But the data seem to be very uniformly:

... Of the remaining 11 sites, Waters and Stafford found that five had been recently dated by higher-precision techniques. The pair decided to redate the others, succeeding in all but one case. The results, Waters says, "were a real surprise." All of the new dates--as well as all of the previous acceptable dates--occurred within, at most, a 450-year band. Indeed, they say, Clovis probably existed for as little as 200 years, between 11,050 and 10,800 radiocarbon years B.P.--a cultural flowering both somewhat later and considerably shorter than thought.

... other cultures, including one in Monte Verde, Chile, dated to 1000 years before Clovis.

... Meltzer stresses that the dates used are from a minority of North American sites, most in the west, whereas most Clovis points have been found in the east. Until more data are compiled, he says, researchers "can't know whether this is a real effect or simply a consequence of sampling."