A comprehensive new study that looked at hominin fossils over a span of 4 million years suggests that early humans gained stature as they moved out of the forests and into the savannahs.
The study is published in the journal Royal Society Open Science.
The research, which is the largest-ever study of early human body sizes involving 311 specimens dating from the earliest upright species to modern humans, also found that early humans’ stature and weight increased at different speeds over time.
“An increase solely in stature would have created a leaner physique, with long legs and narrow hips and shoulders,” said lead author Dr. Manuel Will at the University of Cambridge’s Department of Archaeology and a Research Fellow at Gonville and Caius College, in a university statement. “This may have been an adaptation to new environments and endurance hunting, as early Homo species left the forests and moved to more arid African savannahs.”
Will explained that because a larger skin surface increases the ability to evaporate sweat, the higher surface-to-volume ratio of tall, lanky body would benefit the hunter forced to stalk animals for long hours in the arid heat.
“The later addition of body mass coincides with ever-increasing migrations into higher latitudes, where a bulkier body would be better suited for thermoregulation of colder Eurasian climates,” Will said.
While height increased dramatically between 1.4 and 1.6 million years ago, consistently heavier hominins do not appear in the fossil record until about a million years later.
“From then onwards, average body height and weight stays more or less the same in the hominin lineage, leading ultimately to ourselves,” added Will.