However, this method of identifying relatives depends on the existence of population-scale variation. Population bottlenecks can destroy such variation - and may promote cooperation.
Similarly, the founder effect might also produce local regions with little variation.
These effects have been demonstrated experimentally:
- Population Bottlenecks Promote Cooperation in Bacterial Biofilms
- Kümmerli R., Gardner A., West S. & Griffin A. S. Limited dispersal, budding dispersal, and cooperation: an experimental study. Evolution 63, 939–949 (2009).
Humans are among those species that have experienced a relatively recent population bottleneck - in the form of the Toba catastrophe. It is intriguing to consider the scale of the resulting increased levels of cooperation between humans that might be the result of this.