The Mesolithic period is characterized by a number of behavioral changes among human groups.While some of these changes, such as the reduction of hunting territories and the development of the bow, appear strongly linked to environmental modifications resulting from post-glacial warming (the return of forests, disappearance of large migratory steppe herbivores like mammoths and reindeer in favor of forest-dwelling herbivores like deer, boar, roe deer, and small game), others involve upheavals in artistic and symbolic representations.