Cyclical selection in cultural evolution

Cyclical selection is an important concept from ecology. It involves organisms which have lifecycles involving environments that vary cyclicly. Cyclical selection is sometimes called "alternating selection". It is sometimes described in terms of "switching environments". Cyclical selection is part of a more general phenomenon - known as "fluctuating selection". Some examples of cylical selection:

• Seasonal variation - organisms may face one environment in the summer and another one in the winter.

• Male gametes - these spend most of their lives inside male testicles - but must periodically run an obstacle course inside female organisms - where they face very different selection pressures.

• Parasites - many pathogens reproduce inside host organisms and must repeatedly find new hosts. Thriving within a host present systematically different set of challenges to spreading between hosts - and so the pathogens face an alternating selective pressure.

This brings us to cultural evolution. Cultural symbionts behave similarly to organic pathogens - in that they can reproduce within a host as well as find new hosts. Different selection pressures apply inside minds compared to outside them. Inside minds memes must compete for attention - so that they can persist by being repeatedly rehearsed in short-term memory. Outside minds, memes need to get shared on social media sites and avoid spam filters. It's a different environment with different sources of selection. Memes multiply within minds as well as spreading between them. This may not be completely obvious - but the idea is supported from many directions. Some mental illnesses are explicable in terms of overgrowths of thoughts relating to fear, paranoia, negativity, anxiety or obsessions. Memories fairly plainly involve copying and creativity often involves making copies with variations. Again, copying criteria inside minds are different from copying criteria used by computer systems in the external world.

For parasites there's the risk that adapting to the environment inside a host will result in the loss of the ability to spread between hosts. Memes face much the same problem - adapting to survive within a host can result in the loss of the ability to spread between hosts. Too much intracranial selection can lead to intercranial sterility.

Parasites may resist evolution within hosts - since this may destroy their ability to spread between hosts. Resisting evolution within hosts has the disadvantage of reducing their fitness there. Parasites that are not able to rapidly evolve within a host are more likely to be obliterated at the hands of the immune system - or by other existing residents. Memes face the same dilemma. They don't want to lose their ability to spread between hosts - but may be under considerable pressure to evolve and adapt to their host's internal environment.

Intracranial selection may suggest some theraputic strategies to help deal with virulent memes. Cylical selection suggests that an extended period of selection within a host might result in reduced virality. The parasite may appear to make peace with its host. This suggests - for example - that the memes from old evangelicals might help to pacify young ones.