The evolution of extreme altruism and inequality in insect societies
- 12 November 2009
- journal article
- Published by The Royal Society in Philosophical Transactions Of The Royal Society B-Biological Sciences
- Vol. 364 (1533), 3169-3179
- https://doi.org/10.1098/rstb.2009.0129
Abstract
In eusocial organisms, some individuals specialize in reproduction and others in altruistic helping. The evolution of eusociality is, therefore, also the evolution of remarkable inequality. For example, a colony of honeybees (Apis mellifera) may contain 50 000 females all of whom can lay eggs. But 100 per cent of the females and 99.9 per cent of the males are offspring of the queen. How did such extremes evolve? Phylogenetic analyses show that high relatedness was almost certainly necessary for the origin of eusociality. However, even the highest family levels of kinship are insufficient to cause the extreme inequality seen in e.g. honeybees via ‘voluntary altruism’. ‘Enforced altruism’ is needed, i.e. social pressures that deter individuals from attempting to reproduce. Coercion acts at two stages in an individual's life cycle. Queens are typically larger so larvae can be coerced into developing into workers by being given less food. Workers are coerced into working by ‘policing’, in which workers or the queen eat worker-laid eggs or aggress fertile workers. In some cases, individuals rebel, such as when stingless bee larvae develop into dwarf queens. The incentive to rebel is strong as an individual is the most closely related to its own offspring. However, because individuals gain inclusive fitness by rearing relatives, there is also a strong incentive to ‘acquiesce’ to social coercion. In a queenright honeybee colony, the policing of worker-laid eggs is very effective, which results in most workers working instead of attempting to reproduce. Thus, extreme altruism is due to both kinship and coercion. Altruism is frequently seen as a Darwinian puzzle but was not a puzzle that troubled Darwin. Darwin saw his difficulty in explaining how individuals that did not reproduce could evolve, given that natural selection was based on the accumulation of small heritable changes. The recognition that altruism is an evolutionary puzzle, and the solution was to wait another 100 years for William Hamilton.Keywords
This publication has 67 references indexed in Scilit:
- Structure and function in mammalian societiesPhilosophical Transactions Of The Royal Society B-Biological Sciences, 2009
- Lifetime monogamy and the evolution of eusocialityPhilosophical Transactions Of The Royal Society B-Biological Sciences, 2009
- Beyond society: the evolution of organismalityPhilosophical Transactions Of The Royal Society B-Biological Sciences, 2009
- Formalizing Darwinism and inclusive fitness theoryPhilosophical Transactions Of The Royal Society B-Biological Sciences, 2009
- Unicolonial ants: where do they come from, what are they and where are they going?Trends in Ecology & Evolution, 2009
- Darwin's ‘one special difficulty’: celebrating Darwin 200Biology Letters, 2009
- Ancestral Monogamy Shows Kin Selection Is Key to the Evolution of EusocialityScience, 2008
- Are mistakes inevitable? Sex allocation specialization by workers can reduce the genetic information needed to assess queen mating frequencyJournal of Theoretical Biology, 2007
- Optimization of inclusive fitnessJournal of Theoretical Biology, 2006
- The genetical evolution of social behaviour. IJournal of Theoretical Biology, 1964