Basis for cumulative cultural evolution in chimpanzees: social learning of a more efficient tool-use technique.
Shinya Yamamoto, Tatyana Humle, Masayuki Tanaka
DOI: 10.1371/journal.pone.0055768Read full text
Abstract
Background: The evidence for culture in non-human animals has been growing incrementally over the past two decades. However, the ability for cumulative cultural evolution, with successive generations building on earlier achievements, in non-human animals remains debated. Faithful social learning of incremental improvements in technique is considered to be a defining feature of human culture, differentiating
human from non-human cultures. This study presents the first experimental evidence for chimpanzees’ social transmission of a more efficient tool-use technique invented by a conspecific group member.
Methodology / Principal Findings: The chimpanzees were provided with a straw-tube, and spontaneously demonstrated two different techniques in obtaining juice through a
small hole: “dipping” and “straw-sucking”. Both the “dipping” and “straw-sucking”
techniques depended on the use of the same tool (straw-tube) for the same target (juice)
accessible from exactly the same location (small hole 1cm in diameter). Therefore the
difference between “dipping” and “straw-sucking” was only in “technique”. Although the
two techniques differed significantly in their efficiency, their cognitive and
perceptuo-motor complexity were comparable. All five chimpanzees who initially
performed the “dipping” technique switched to using the more efficient “straw-sucking”
technique upon observing a conspecific or human demonstrate the more proficient
alternate “straw-sucking” technique.
Conclusions / Significance: The social learning mechanism involved here was clearly not
local or stimulus enhancement, but imitation or emulation of a tool-use technique.
When there is no biologically relevant difference in cognitive or perceptuo-motor
complexity between two techniques, and when chimpanzees are dissatisfied with their
own technique, chimpanzees may socially learn an improved technique upon close
observation of a proficient demonstrator. This study provides important insights into
the cognitive basis for cumulative culture in chimpanzees, and also suggests possible
conditions in which cumulative cultural evolution could arise even in non-human
animals.