Directly dated Cucurbita from archaeological sites near Lake Huron expand the range and human usage of adventive, cultivated wild gourds or squash into the Great Lakes region, USA, by 4000 14C yr BP. The data also show that domesticated C. pepo squash was cultivated there by 3000 14C yr BP. Although milder Hypsithermal climate may have been a contributing factor, squash and gourds expanded northward during the mid-Holocene mainly by human agency and may be the first human-introduced adventive plant in temperate North America. Even after 3000 14C yr BP, when domesticated squash generally replaced wild varieties at northern sites, squash stands were probably informally managed rather than intensively cultivated.

A wetland deposit from the southern Appalachian mountains of North Carolina, USA, has been radiocarbon dated and shows continuous deposition from the early Holocene to the present. Non-coastal records of Holocene paleoenvironments are rare from the southeastern USA. Increased stable carbon isotope ratios (?13C) of sedimentary organic matter and pollen percentages indicate warm, dry early- to mid-Holocene conditions. This interpretation is also supported by n-alkane biomarker data and bulk sedimentary C/N ratios. These warm, dry conditions coincide with a mid-Holocene hypsithermal, or altithermal, documented elsewhere in North America. Our data indicate that the southeastern USA warmed concurrently with much of the rest of the continent during the mid-Holocene. If the current "warming hole" in the southeastern USA persists, during a time of greenhouse gas-induced warming elsewhere, it will be anomalous both in space and time.