Long-term patterns of body mass and stature evolution within the hominin lineage.

Body size is a central determinant of a species' biology and adaptive strategy, but the number of reliable estimates of hominin body mass and stature have been insufficient to determine long-term patterns and subtle interactions in these size components within our lineage. Here, we analyse 254 body mass and 204 stature estimates from a total of 311 hominin specimens dating from 4.4 Ma to the Holocene using multi-level chronological and taxonomic analytical categories. The results demonstrate complex temporal patterns of body size variation with phases of relative stasis intermitted by periods of rapid increases. The observed trajectories could result from punctuated increases at speciation events, but also differential proliferation of large-bodied taxa or the extinction of small-bodied populations. Combined taxonomic and temporal analyses show that in relation to australopithecines, early is characterized by significantly larger average body mass and stature but retains considerable diversity, including small body sizes. Within later , stature and body mass evolution follow different trajectories: average modern stature is maintained from 1.6 Ma, while consistently higher body masses are not established until the Middle Pleistocene at 0.5-0.4 Ma, likely caused by directional selection related to colonizing higher latitudes. Selection against small-bodied individuals (less than 40 kg; less than 140 cm) after 1.4 Ma is associated with a decrease in relative size variability in later species compared with earlier and australopithecines. The isolated small-bodied individuals of ( 0.3 Ma) and ( 100-60 ka) constitute important exceptions to these general patterns, adding further layers of complexity to the evolution of body size within the genus . At the end of the Late Pleistocene and Holocene, body size in declines on average, but also extends to lower limits not seen in comparable frequency since early .