...Although the researchers found traces of ancient human DNA in one pigmented calcite crust sampled in Escoural Cave (Portugal), to their surprise they also found ancient human DNA in several nonpigmented parts of the cave wall in Escoural as well as in Covarón Cave (northern Spain), which had initially been sampled as negative controls.The study shows that human DNA can be preserved on cave walls long after the populations that visited the cave have disappeared...Of the 54 samples collected, only five yielded authentic ancient human mitochondrial DNA...two of these samples showed no detectable faunal mitochondrial DNA, a rare finding that...