Author and journalist, Tom Wolfe, made the claim that "Evolution came to an end when the human beast developed speech! As soon as he became not Homo sapiens, 'man reasoning,' but Homo loquax, 'man talking'!" (Quoted in the Chronicle of Higher Education, May 11, 2006 on-line at http://chronicle.com/daily/2006/05/2006051103n.htm) . Wolfe, by his own admission has been highly influenced by the thinking of sociologists like Max Weber and anthropologists like Clifford Geertz.
As a sociologist (with extensive anthropological training), I too have often pondered this idea, and come to a similar, but more limited conclusion.
First, and foremost, there is an entire world of species other than man, without language, for whom evolution continues unabated. Indeed, one could argue that evolutionary pressures (adapt or go extinct) are greater than ever for species other than man, because of human cultural impact upon the environment. The most famous or infamous (depending upon what side of the evolution/creationism divide on sits) example of human economic activity impacting evolution is Kettlewell's study of the relative preponderance of light and dark variants of the peppered moth (Biston betularia) in England published in March 1959 in the Scientific American (Vol. 201, No. 3, pp48-53).
A digression: while using Google to check the exact reference above, I found that most of the recent citations of this article are by creationism/intelligent design advocates, and I noticed a fascinating lacuna in the understanding of such people of the concept of "evolution." One page in particular made the knowledge gap crystal clear, stating that the example of the peppered moth showed "NATURAL SELECTION in action. The problem is that there is NO EVOLUTION occurring (no increase in complexity)!" [empahsis in the original]. Source: http://emporium.turnpike.net/C/cs/basics/sld014.htm (note the link at the bottom of the page back to the "Creation Science home page." Since when (in science) are "natural selection" and "evolution" two different things? Evolution is change, any kind of change, even change to a less complex level of organization. Human's losing the function of the appendix (a lessening of complexity) is just as much evolution as the changes that gave birth to language.
Back to Tom Wolfe, and the relationship between evolution and culture. Putting aside the continued presence of evolution among other species, can we argue that evolution disappeared from human kind, when language and culture appeared? Certainly humans have made use of cultural knowledge and creativity to adapt culturally to environmental conditions (clothing, fire, agriculture, electricity, engineering technology, etc.). I would argue however, that our reliance on increasingly complex culture has made us more suceptible to environmental extremes and evolutionary pressures, and will lead to our eventual extinction. (Exctinction is evolution, too). The Europeans who settled Greenland during the Medieval Warm Period , depdent on European technology, went "extinct" (at least in Greenland) when the Younger Dryas (Little Ice Age) came along. We too are likely to become extinct when global warming pushes the climatic envelop to extremes, and our technology is unable to make the transition.