This article was originally published in The conversation and has been republished under Creative Commons.
HHumans are the only species to live in all of the world’s environmental niches, from ice caps to deserts, from rainforests to savannahs. As individuals we’re pretty puny, but when we’re socially connected we’re the most dominant species on the planet.
NOTNew Evidence of Stone Tools in Southern Africa show those social links were stronger and wider than we thought in our ancestors who lived about 65,000 years ago, shortly before the great migration “out of Africa” in which they began to spread to worldwide.
SOCIAL LINK AND ADAPTATION
EEarly humans weren’t always so connected. The first humans to leave Africa faded away without this migratory success and without leaving any genetic trace among us today.
BBut for the ancestors of today’s people living outside Africa, it was a different story. In a few thousand years, they migrated and adapted to all types of environmental zones on the planet.
AArchaeologists believe that the development of social networks and the ability to share knowledge between different groups was key to this success. But how do we observe these social networks in the distant past?
JTo answer this question, archaeologists examine tools and other man-made objects that still survive today. We assume that the people who made these objects, like people today, were social creatures who made objects with cultural meanings.
SOCIAL CONNECTIVITY 65,000 YEARS AGO
A small common stone tool gave us the opportunity to test this idea in southern Africa, during a period known as the Howiesons Poort about 65,000 years ago. Archaeologists call these sharp, versatile tools “backed artifacts,” but you can think of them as a “stone Swiss army knife”: the kind of useful tool you carry around to do various jobs you can’t do by hand. .
JThese knives are not unique to Africa. They are found all over the world and in many different forms. This potential variety is what makes these small blades so useful for testing the hypothesis that social ties existed more than 60,000 years ago.
Across southern Africa, these blades could were made in a number of different shapes at different locations. However, around 65,000 years ago, it turns out that they were made in a very similar pattern over thousands of miles and multiple environmental niches.
Je fact that they were all made to look like points so similar to the strong social bonds between geographically distant groups across southern Africa at that time.
IImportantly, this shows for the first time that social ties were in place in southern Africa just before the great migration ‘out of Africa’.
A USEFUL TOOL IN DIFFICULT TIMES
PPreviously it was thought that people made those blades in response to various environmental stresses because, just like the Swiss army knife, they are multi-functional and multi-purpose.
JHere is evidence that stone blades were often glued or tied to handles or shanks to make complex tools such as spears, knives, saws, scrapers and drills, and used as points and barbs for arrows. They were used to process vegetable matter, skins, feathers and furs.
OWhile making the stone blade was not particularly difficult, bonding the stone to the handle was, involving complex glue and adhesive recipes.
DDuring the Howiesons Poort these blades were produced in huge numbers throughout southern Africa.
Data from Sibudu Cave in South Africa shows that their peak production occurred during a very dry period, when there was less rain and less vegetation. These tools were made for thousands of years before the Howiesons Poort, but it was during this period of changing climatic conditions that there was a phenomenal increase in their production.
IIt is the multifunctionality and versatility that makes this stone tool so flexible, a key advantage for hunting and gathering in uncertain or unstable environmental conditions.
A STRONG SOCIAL NETWORK ADAPTED TO CLIMATE CHANGE
HHowever, the production of this tool at present can only be seen as a functional response to changing environmental conditions.
IIf their proliferation was simply a functional response to changing conditions, then we should see differences in different environmental niches. But what we see is the similarity in production numbers and the shape of artifacts over large distances and different environmental zones.
JThis means that increased production should be seen as part of a socially mediated response to changing environmental conditions, with the strengthening of long-distance social ties facilitating access to scarce, even unpredictable resources.
Jhe likeness of the stone ‘Swiss army knife’ across southern Africa provides insight into the strength of social bonds at this key time in human evolution. Their similarity suggests that it was the strength of this social network that allowed populations to thrive and adapt to changing climatic conditions.
JThese findings have global implications for understanding how the expansion of social networks contributed to the expansion of modern humans out of Africa and into new environments around the world.