Do chimps have culture? a phylogenetic study
Over the last few years, the evidence has been accumulating that different populations of chimpanzees have different cultures. Field studies of chimp behaviors (e.g. Whiten et al 1999 (PDF)) have shown a wide range of behavioral variation across Africa.
For example, chimps at one site, Bossou, use stone hammers and anvils to open nuts, whilst at another site, the chimps use both wooden and stone hammers on anvils made of stone and root. More examples, from White et al, show some of the variation in types of behavior and how they differ across research sites:
| sites | |||||||
|---|---|---|---|---|---|---|---|
| Behavior | Bossou, Guinea | Taı̈ Forest, Ivory Coast | Gombe, Tanzania | Mahale (M-Group), Tanzania | Mahale (K-Group), Tanzania | Kibale Forest, Uganda | Budongo Forest, Uganda |
| Investigatory probe (probe and sniff) | Habitual | Customary | Customary | Habitual | Habitual | Present | Absent |
| Drag branch (drag large branch in display) | Habitual | Customary | Customary | Customary | Customary | Habitual | Habitual |
| Leaf-sponge (leaf mass used as sponge) | Customary | Customary | Customary | Present | Absent | Customary | Customary |
| Branch-clasp (clasp branch above, groom) | Habitual | Customary | Customary | Customary | Customary | Customary | Customary |
| Branch-shake (to attract attention, court) | Customary | Customary | Customary | Customary | Customary | Habitual | Customary |
| Buttress-beat (drum on buttress of tree) | Customary | Customary | Customary | Customary | Customary | Customary | Customary |
| Rain dance (slow display at start of rain) | Absent | Habitual | Customary | Customary | Customary | Customary | Habitual |
It has been suggested that this type of variation is representative of cultural traditions, and hints at a new field of study: cultural panthropology. However, not everyone is convinced that this is evidence of chimpanzee culture. This could just be the outcome of genetic differences between the populations.
To test this, Lycett et al, forthcoming in P.N.A.S., take the Whiten et al data, and analyse it within a phylogenetic framework (parsimony). This gave them a tree showing the cultural relatedness of these groups. If this behavioral variation is due to genetics, then this tree should conform to the groupings found in previous genetic analyses.
This is not the case - the behavioral data does not mirror the genetic data. Lycett et al conclude that:
These findings are inconsistent with the hypothesis that patterns of behavioral differences at the population level are genetically determined. Instead, they are in line with a growing number of studies involving captive groups (…) and wild populations (…) that suggest many chimpanzee behaviors are socially learned and can be considered cultural.
Reference:
Lycett et al: Phylogenetic analyses of behavior support existence of culture among wild chimpanzees
