Genetic analyses of permafrost and temperate sediments reveal that plant and animal DNA may be preserved for considerable time periods, even in the absence of obvious macrofossils. In Siberia, five permafrost cores ranging from 400-10 thousand years (kyr) contained at least 19 different plant taxa, including the oldest authenticated ancient DNA sequences known, and megafaunal sequences including mammoth, bison, and horse. The genetic data record a number of dramatic changes in the taxonomic diversity and composition of Beringian vegetation and fauna. Temperate cave sediments in New Zealand also yielded DNA sequences of extinct biota, including two species of ratite moa, and 29 plant taxa characteristic of the prehuman environment. Therefore, many sedimentary deposits may contain unique, and widespread, genetic records of paleoenvironments. ; Eske Willerslev, Anders J. Hansen, Jonas Binladen, Tina B. Brand, M. Thomas P. Gilbert, Beth Shapiro, Mike Bunce, Carsten Wiuf, David A. Gilichinsky, Alan Cooper ; Copyright © 2003 American Association for the Advancement of Science