 In 2011, a large group of scientists challenged the Younger Dryas impact hypothesis on the basis of claims that most of the conclusions could not be reproduced and were a misinterpretation of data.The article claimed that no nanodiamonds were found and that the supposed carbon spherules could be fungus or insect feces and included modern contaminants.In response, in June 2013 some of the original proponents published a re-evaluation of spherules from eighteen sites worldwide that they interpret as supporting their hypothesis.