This study documents and interprets adaptive postcranial morphology among prehistoric Jomon period foragers from Hokkaido, Japan (HKJ). The Hokkaido climate is differentiated from other Japanese islands by freezing winters with sea-ice accumulation in the northern regions. Increased brachial and crural indices are, however, observed among HKJ foragers, while body mass (BM) has not yet been estimated for these groups. Based on previous observations and paleoclimatic reconstructions, it was predicted that increased BM and increased distal relative to proximal limb lengths would typify HKJ foragers. Similar BM was observed between HKJ foragers and groups from colder environments. Intralimb indices do, however, suggest similarity between HKJ foragers and groups from high-latitude, warm environments. It is likely that HKJ foragers retained cold-derived BM in association with Pleistocene migrations to Hokkaido via Northeast Asia. That is, enlarged BM among HKJ foragers is associated with long-term evolution in a colder environment. Relatively elongated distal limbs may represent morphological response to a slightly warmer environment. Following migration to Japan from a colder environment, elongation of distal limb segments resulted in elevated brachial and crural indices. Relatively elongated distal appendages may also reflect positive nutritional status as HKJ people experienced lesser rates of systemic stress than other Jomon groups. It is also possible that elongated distal relative to proximal limbs are associated with neutral mutation and genetic drift. This interpretation suggests a neutral mutation associated with relative limb length in some HKJ ancestor with subsequent spread of this allele through isolation and drift. Ontogenetic and temporal studies of intralimb indices among Jomon people are necessary to further evaluate these interpretations. Copyright © 2009 John Wiley & Sons, Ltd.