Why humans started using symbols

A series of innovative experiments at COBE Lab sheds light on the evolution of early symbolic behavior in humans ca. 100,000 years ago. 

 

Some of the earliest evidence of humans using symbols stems from about 100,000 years ago in Africa.

A central site of interest is the Blombos Cave, where patterns engraved in ochre pieces have been found. Another is the Diepkloof Rock Shelter, where engraved ostrich eggshells have been found.

The engravings at both sites were made over a period of more than 30,000 years.

The first engravings were simple configurations of parallel lines, but over time they grew more complex, with greater symmetry and crossing lines.

A group of researchers headed by Kristian Tylén wanted to understand why the engravings evolved over time in the way they did

They explored this through a series of experiments at COBE.

Experiments

1) In one experiment, participant had vivid flickering colors presented to their dominant eye and outlines of the engraved patterns presented to their other eye. This meant that the more dominant visual of flickering colors would initially override their perception of the engravings.

The researchers found that the later engravings entered participants’ conscious perception faster this way than earlier engravings. This suggests that the engravings evolved over time to be more salient, standing out to our visual perceptual system.

2) Another experiment had participants reproduce engravings from memory. They were more accurate in reproducing later rather than earlier engravings.

This suggests that the engravings evolved over time to be easier to remember and reproduce.

3) In a third experiment, participants rated later engravings more likely to have been made by a human than earlier engravings.

This suggests that the engravings evolved over time to look more intentional.

4) A fourth experiment found that later engravings were easier to recognize as coming from the same or different caves than earlier engravings.

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This suggests that the engravings evolved distinct elements of style over time, potentially signifying group identity.

5) In a fifth experiment, participants did not find it easier to distinguish later engravings from each other on an individual basis than earlier engravings.

The fact that the engravings did not evolve to be more easily distinguishable from each other suggests that they did not function as fully developed referential, denotational symbols—that is, they did not function like words or signs that have specific meanings and refer to specific things.

Conclusions

The results of the experiments suggest that these early examples of symbols did not function like words or signs with specific meanings. Instead, they may have served as aesthetic decorations and as socially transmitted traditions marking the sociocultural identity of the people who made them. This would explain why they evolved over time to be more salient, memorable, and expressive of human intent, and to reflect a particular site-specific style.

There is thus reason to believe that these were the original purposes that first drove humans to use symbols some 100,000 years ago.

The study was called "The Evolution of Early Symbolic Behavior in Homo Sapiens" and was published in the journal PNAS in 2020.