Memes and host lifespan

Cultural evolution has led to increased lifespans among many modern humans.

Symbiology has some basic models of how symbiotes affect host lifespan which seem likely to be applicable to cultural evolution. When a symbiont usually dies with its host, it can sometimes pay for it to divert resources from host reproduction into host maintenance processes. That makes the host live for longer and results in more opportunities for the symbiont to reproduce before it perishes with its host. Copies of individual memes do perish with their hosts - and this model is broadly consistent with the observed longer lifespans produced by cultural evolution to date.

However, there's an alternative scenario described by the same kind of model. If there's a lot of horizontal transmission of symbionts between hosts, the symbionts can sometimes profit by converting the hosts' resources into copies of their own heritable material as quickly as possible. This is the strategy employed by the Ebola virus, for example. Rather than increasing host lifespan, these types of parasite dramatically decrease it.

When does this latter scenario arise? The models are fairly specific about when this type of scenario is likely. It happens when the host density is high or when there's a lot of opportunities to spread between hosts.

The ability of memes to leap from host to host has dramatically increased over the last century. These days, mobile phones deliver memes pretty directly into peoples' brains in a near-constant stream. Horizontal meme transfer has increased dramatically in modern times - and it looks set to continue to rise. Our ability to pack humans together in huge cities has also continued to rise.

This raises some questions. What can be done to avoid going into an era in which memes shorten host lifespans - and rip through host resources like the Ebola virus does? Also, we have been seeing a lot of horizontal meme transmission for a while now. Yet if you look at the most meme-rich areas of the planet - such as Japan - host lifespans are excellent. Why are we not in an Ebola-like era already?

The most obvious answer is that memes that quickly kill their human hosts are selected against in various ways - by host immune systems, and by active suppression by groups of humans. People do get sucked into meme-spreading cults that rip through their resources Ebola-style - but education defends against this fate - and so do nearby friends and relatives.

An important reason for studying these dynamics is to see whether we can avoid problems. Will we see plagues of parasitic memes mirroring the 1918 flu epidemic? Will we see persistent draining influences - mirroring the effect of the HIV virus on lifespan in Africa? What about mixed bag pathogens? For example, smallpox helped Europeans to conquer native American tribes - while simultaneously killing many Europeans.

So far the influence of memes on lifespan seems consistent and positive. More memes are strongly correlated with longer lifespans. However I think it is too early to say whether this positive trend will continue without interruption. We should strive to understand these dynamics in order to help us to avoid problems in the future.

Cities as blisters

Cities can be usefully seen as being cultural blisters on the planet. Here is New York City:

As with many blisters, cities contains swarming organisms that are capable of spreading the blisters to new areas - in this case, meme-infected humans. Roads act as the main vessels through which the infection is spread. Ships can spread the infection across the oceans.

It's hard to avoid epidemiological terminology in this sort of discussion, but I don't mean to imply that humans or cities are bad or undesirable. They spread like a plague on the planet, but that doesn't mean that we need a cure for the pox. Instead, encouraging the spread of the phenomenon - using education - seems more appropriate. In the glorious future it seems likely that the whole planet, including the oceans, will be covered.

To the right, is a picture of Europe at night:

Memes and the Holocene extinction

The invasion of the biosphere by memes has had some rather negative consequences - as well as some positive ones. In particular, memes are primarily responsible for the ongoing Holocene extinction event. Without memes, humans would have remained minor players in the biosphere - and nobody would have obliterated the megafauna of South America and Australia.

If you look at the proximate causes of many of the extinctions you often find that a newly-introduced parasite or predator is involved. So: superficially, it looks like ordinary genetic evolution - and not to do with memes. However, appearances can be deceptive - and if you ask why the parasite or predator involved has recently appeared on the scene, the answer almost always involves human transportation technologies: planes, trains and automobiles. So, memes really are implicated.

The meme's eye view suggests that we ask: "what is in it for the memes?" There are several answers to this question. Sometimes memes just create a new environment, with different winners and losers. Some creatures can hitchhike on memetic creatures better than others can - and these get spread around, while the things they prey on or parasitize suffer. In such cases, extinction seems like an accidental byproduct of meme activity.

In other cases, competition is involved. Creatures with DNA genomes compete with memetic creatures for resources. Memes at first promote a human world - since humans can host memes better than other animals can. Then, after the development of computers, memes promote them instead - since computers are better hosts for memes than humans. Its not that the memes are out to get other forms of life - it is just that they need the same resources, and the memes are fitter and more viable.

One issue is whether the current extinction event will turn into a mass extinction - with most species dying out. This may depend on the scale of our conservation efforts - which are difficult to predict. However, it seems quite likely that most species will either die or be confined to much more restricted ranges.