Humans 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.
New evidence of stone tools in southern Africa shows that these social ties were stronger and broader than we thought in our ancestors who lived around 65,000 years ago, shortly before the great “out of Africa” migration in which they began to spread across the world.
Social bond and adaptation
Early 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.
But for the ancestors of today’s people living outside of Africa, it was a different story. In a few thousand years, they migrated and adapted to all types of environmental zones on the planet.
Archaeologists 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?
To 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, at a time known as the Howieson Poort about 65,000 years ago. Archaeologists call these sharp and versatile tools “backpack 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 at home. hand.
These 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.
Throughout 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.
The fact that they were all designed to look alike indicates strong social ties between geographically distant groups across southern Africa at this time.
Importantly, this shows for the first time that social ties were in place in southern Africa just before the great ‘out of Africa’ migration.
A useful tool in difficult times
It used to be thought that people made these blades in response to various environmental stressesbecause just like the Swiss army knife, they are multifunctional and multi-purpose.
There is evidence that stone blades were often glued or tied to hilts or handles 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, hides, feathers and fur.
While making the stone blade was not particularly difficult, bonding the stone to the handle was, involving complex glue and adhesive recipes.
During the Howiesons Poort these blades were produced in huge numbers across 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.
It is the multi-functionality and multi-use 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 a changing climate
However, the production of this tool at present cannot be considered solely as a functional response to changing environmental conditions.
If 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.
This 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.
The similarity of the “Swiss army knife” in stone across southern Africa provides insight into the strength of social bonds in this key period for 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.
These 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.