Read more: 鈥�Instant Expert: Evolution of selfless behaviour鈥�
Darwin鈥檚 problem is an unavoidable fact of life for all species, including our own: prosocial adaptations usually put individuals at a disadvantage relative to other members of their group. The only way for them to evolve is if there is another layer to the process of natural selection. That layer is group selection. More prosocial groups robustly outcompete less prosocial groups, which means a prosocial trait鈥檚 between-group advantage can make up for its disadvantage within groups. It鈥檚 that simple.
If scientific history had taken a different path, multilevel selection could have become the theoretical foundation for studying the evolution of social behaviour, or sociobiology. Instead, after the 1960s biologists tried to explain all social adaptations as forms of self-interest. When an entire scientific discipline decides something is wrong, it is difficult to persuade people to reconsider their position.
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Today, though, there is near-universal agreement among those familiar with the subject that the wholesale rejection of group selection was mistaken and that the so-called alternatives are nothing of the sort. Some, such as William Hamilton, reached this conclusion as early as the 1970s, but decades were required for others to follow suit. However, many people who do not directly study the subject, including many biologists, have got the impression that group selection was conclusively disproved and that nothing has changed since. As a result, there is widespread confusion.
It is probably not an accident that the individualistic swing in evolutionary theory coincided with similar swings in economics, the human social sciences and western culture at large. While evolutionists were interpreting all social adaptations as varieties of self-interest, economists were explaining all human behaviour as individual utility maximisation, and British prime minister Margaret Thatcher was declaring that 鈥渢here is no such thing as society 鈥� only individuals and families鈥�.
Science does not take place in a vacuum. Just as Darwin and his contemporaries were influenced by Victorian culture, we should be prepared to acknowledge 鈥� and correct for 鈥� the influence of a highly individualistic culture on the theories put forward during the second half of the 20th century.
The new consensus states definitively that the individual organism is not a privileged level of the biological hierarchy. The harmony and coordination associated with the word 鈥渙rganism鈥� can exist at any level and individuals can lose these properties when selection takes place within them, such as when cancers evolve. Social groups can become organisms, and organisms are highly regulated social groups 鈥� not just figuratively but literally.
Group selection has been an exceptionally strong force in human genetic and cultural evolution. Accepting it at face value and exploring its consequences will have implications for all branches of the biological and human-related sciences, from the origin of life to the regulation of human society at large spatial and temporal scales.
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