The systematic investigation of these records is ongoing.

Cave sites remain important as well.

Caves provide the kind of stable, dark, dry conditions that maximize preservation of organic material, and the cave record of human occupation in the Americas extends back well into the pre-Clovis period at multiple sites.

The recovery of additional ancient DNA from cave sites — either from human remains or from sediment that preserves traces of ancient occupation — has the potential to add significantly to the genetic picture of early Americans.

Underwater archaeology along the submerged continental shelf is perhaps the most challenging but potentially most rewarding frontier.

The coastlines of the Last Glacial Maximum are now under water, but the seafloor preserves sedimentary records that extend back through the glacial period.