Fresh evidence rebuts the theory that an asteroid wiped out prehistoric humans known as Clovis, or caused abrupt climatic changes, says a new study. 

Researchers from the Royal Holloway University, Sandia National Lab and 13 US and European universities, argue that no appropriately sized impact craters from that period have been discovered, and no shocked material or any other features of impact have been found in sediments.

They also found that samples presented in support of the impact hypothesis were contaminated with modern material.