Toca da Tira Peia is the new name of American prehistory, providing an OSL date for the layer of scattered stone tools of c. 22,000 years BP. Located near the also controversial Pedra Furada site, the date seems to give some support to those who dare to think outside the box on the early peopling of America.
Christelle Lahaye et al., Human occupation in South America by 20,000 BC: the Toca da Tira Peia site, Piauí, Brazil. Science 2013. Pay per view → LINK [doi:10.1016/j.jas.2013.02.019]
When and how did the first human beings settle in the American continent? Numerous data, from archaeological researches as well as from palaeogenetics, anthropological and environmental studies, have led to partially contradictory interpretations in recent years, often because of the lack of a reliable chronological framework. The present study contributes to the establishment of such a framework using luminescence techniques to date a Brazilian archaeological site, the Toca da Tira Peia. It constitutes an exemplary case study: all our observations and measurements tend to prove the good integrity of the site and the anthropological nature of the artifacts and we are confident in the accuracy of the luminescence dating results. All these points underline the importance of the Toca da Tira Peia. The results bring new pieces of evidence of a human presence in the north-east of Brazil as early as 20,000 BC. The Toca da Tira Peia thus contributes to the rewriting of the history of the peopling of the American continent.
There are slightly older sites in North America, however they are all surrounded into some degree of controversy: Topper in South Carolina is dated to c. 23,000 cal-BP (C14) while some sites in Alberta, located in the Mackenzie "ice-free corridor" have also dates under the LGM layer (i.e. > 21 Ka BP).
There's actually nothing impossible about such early dates in my understanding.