Why did our ancestors grow taller? Science sheds new light on the question

For decades, the exact time when human height underwent its evolutionary leap has been a subject of debate among researchers. A recent international study, published in the journal Proceedings of the National Academy of Sciences (PNAS), has now reconciled the various theories.

By studying 386 fossil specimens (estimating their body mass) from 21 distinct taxa, the scientists were able to demonstrate that human stature had in fact evolved at two parallel rates. To confirm their hypotheses, they also repeated their analyses using 1,000 different phylogenetic trees and 1,000 distinct datasets.

On the one hand, our lineage has followed a modest but steady increase in body size over millions of years, gaining approximately 0.9 kilograms per million years. On the other hand, a much more abrupt acceleration occurred among the more recent members of the genus Homo, particularly among the species that succeeded Homo habilis.

This interpretation aligns directly with major changes in our ancestors’ way of life, such as the adoption of a more efficient bipedal gait (walking on two feet), the occupation of a larger territory, and increased meat consumption. According to the researchers, human body size was thus as much a cause as a consequence of these profound ecological and behavioral changes, reports Slate.