One small step, one giant stride in our understanding of our ancestors as scientists analyse prehistoric footprints

Discovery suggests some very early human ancestors may have been more like us than previously thought.

Previous analysis showed evidence of just three individuals walking across that tephra-covered land almost 3.7 million years ago

Prehistoric ape-men, living some three and a half million years before the first anatomically modern humans, walked like us – according to remarkable new research, carried out at a UK university.

The discovery has substantial implications for more fully understanding key aspects of subsequent early human evolution – and means that some very early human ancestors may have been more like us in some respects than has often been thought.

By extracting additional data from a series of 3.66 million year old footprints from Laetoli in northern Tanzania, archaeologists at Bournemouth University have succeeded in demonstrating that our distant ancestors developed a modern gait much earlier than has often been thought.

Because a modern-style gait is much more energy-efficient than that of our ape ancestors, the new discovery means that all or some of the group of species (the so-called australopithecines) who almost certainly made these footprints, would have been able to survive, reproduce and adapt better than other rival types of ape-man that had not developed a modern gait.

The energy saved by developing a modern way of walking could then have been spent instead on things like reproduction, personal defence, food acquisition and the protection and expansion of territory and resources. Those advantages would, in turn, have helped our distant ancestors to adapt more easily to different types of habitat – a crucial early step to expanding geographically.

In terms of reproduction, the modern-gait-induced additional energy availability is likely to have resulted in women experiencing less nutritional and other stress (and consequently more frequent pregnancies) and in babies being born with higher birth weights (which would, in turn, have led to higher infant survival rates).

The footprints being analysed by the Bournemouth scientists were preserved because of particularly unusual environmental circumstances. They survived courtesy of a nearby volcanic eruption. The normally grass-covered savanna had been covered by a thick layer of tephra (volcanic ash). It had also been raining (as well as footprints, rain-drop marks were also found) – and this had made the tephra damp and therefore much firmer and more able to register footprints.

A scan of one of the footprint tracks

As the group of australopithecines, probably somewhat bewildered by the ash fall, walked across this transformed alien landscape, they left their footprints. Further ash falls then buried the prints – and they then lay hidden there until British archaeologists discovered them 41 years ago and made accurate casts which have now been used for the Bournemouth research. However, up till now, archaeologists had only been able to study in detail the footprints of one individual, although they had been aware of two other individuals’ footprints which overlapped each other. However, using new specially developed computer software, the Bournemouth scientists, led by sedimentologist Professor Matthew Bennett, have succeeded in disentangling the many superimposed footprints from each other, so enabling the detailed study of them. In the process they identifyied a previously unknown individual.

The new data therefore suggests that there were four individuals walking across that tephra-covered land almost 3.7 million years ago.

They appear to have been walking in two pairs – probably one pair immediately in front of the other.

The examination of their footprints suggests that they were walking at around 2 miles per hour – in the direction of what may have been wooded terrain several miles to the north-west. It is conceivable that they realized that a forest would provide shelter from the ash falls.

The leading pair were probably a male and a female, while the second pair are likely to have been two males.

Because modern gait and modern body proportions are closely associated, the new discovery raises the possibility that the latter developed much earlier than currently thought. At present, most experts think that modern body proportions only appeared sometime after 2 million years ago.

“Our newly developed computer software has enabled us to increase the number of footprints we can identify. This gives us better insights into the range of individuals present, their sizes and their gaits. Understanding a range of footprints tells us more about a species and the variations within its population”, said Professor Bennett of Bournemouth University's Institute for Studies of Landscape and Human Evolution.

The extraordinary software, developed by Bournemouth University, is able to create and analyse a ‘multi-point’ 3D image of each footprint. Each 3D image consists of up to 300,000 points (each with two horizontal coordinates and one vertical one). Armed with this mass of data, the software is then able to disentangle overlapping prints and decide which prints were made by which individuals.

Near the site in Tanzania, where the footprints were found, the local Olduvai Museum has a small permanent exhibition dedicated to the discovery.