Early humans living in Africa almost two million years ago came in a range of shapes and sizes just as people do today, evidence suggests.
Some were distinctly vertically challenged, measuring around 1.5 metres, while others would have held their heads high in the modern world.
Another possibility, thought to be less likely, is that there were numerous species belonging to the human family Homo that varied in appearance.
Researcher Jay Stock, from Cambridge University’s Department of Archaeology and Anthropology, said: “If someone asked you ‘are modern humans six-foot tall and 70kg?’ you’d say ‘well, some are, but many people aren’t’, and what we’re starting to show is that this diversification happened really early in human evolution.”
The study is the first in 20 years to compare the body size of humans who shared the earth with mammoths and sabre-toothed cats between 1.5 million and 2.5 million years ago.
Measurements of fossils from sites in Kenya, Tanzania, South Africa, and Georgia in eastern Europe, revealed significant regional variation in the size of early humans during the last Ice Age.
Some groups, such as those living in Olduvai, Tanzania, measured just 1.5 metres on average, while those from the Koobi Fora region of Kenya grew to heights of almost 1.8 metres.
The evidence also suggests that big bodies and long legs were not pre-requisites for spreading out of Africa into Europe and Asia.
The main increase in body size occurred tens of thousands of years after the small, primitive human Homo erectus migrated out of Africa.
Fossils show that Homo erectus, which averaged less than five foot in height and weighed less than eight stone, was living in Georgia 1.77 million years ago.
“The evolution of larger bodies and longer legs can... no longer be assumed to be the main driving factor behind the earliest excursions of our genus to Eurasia,” said co-author Manuel Will, from Tubingen University in Germany.
The scientists, whose findings are reported in the Journal of Human Evolution, developed a method of calculating the height and body mass of individuals from small fossil fragments, some no bigger than toes.
Stock said: “In human evolution we see body size as one of the most important characteristics, and from examining these ‘scrappier’ fossils we can get a much better sense of when and where human body size diversity arose.
“Before 1.7 million years ago our ancestors were seldom over five foot tall or particularly heavy in body mass.
“When this significant size shift to much heavier, taller individuals happened, it occurred primarily in one particular place – in a region called Koobi Fora in northern Kenya around 1.7 million years ago.
“That means we can now start thinking about what regional conditions drove the emergence of this diversity, rather than seeing body size as a fixed and fundamental characteristic of a species.”