Vegetation during the glacial period, post-glacial warming and the Younger Dryas does not seem to have been affected by human activities to any appreciable extent. Forest expansion at the beginning of the Holocene occurred independently of human agency, though early Neolithic farmers were able to take advantage of improved climatic conditions. Absence of macrobotanical remains precludes discussion of possible drought from 6,000 to 5,500 ВС. By farming, herding, and fuel-cutting, human populations began to have an impact on the landscape at different times and places. Deleterious effects of these activities became evident in the Tigris-Euphrates drainage during the third millennium ВС based on macrobotanical evidence from archaeological sites. Even more widespread, permanent deforestation did not occur until the Iron Age.