Sunday, 25 March 2012

Memes And Genes: A Small Difference

Reading the introduction to Susan Blackmore's "The Meme Machine" by Richard Dawkins, I came across a superb illustration of how memes can act just like genes and can give rise the a different phenotype.

Supposing a Martian geneticist visited Earth and carried out a study of humans, one thing would almost immediately recognised as a phenotypic difference between males. He would notice that some males have foreskins and some do not.

This set me thinking about how said Martian might interpret this and how this could lead to scientific discoveries maybe new to Martian science, some of which might be counterintuitive and hard for a Martian to believe.

To avoid some people's delicate sensitivities in these things, let's call these Type A and Type B males.

If this Martian geneticist knew nothing of human cultures and religions or about the memes by which we inherit these things, it would appear exactly as though this condition was genetically inherited. By and large, Type A males would have Type A fathers and, in those instances where they were not, looking at their grandparents might show interesting patterns of inheritance:
  1. Maternal grandfather has the same Type as the grandson but the paternal grandfather has the other Type.
  2. Paternal grandfather has the same Type as the grandson but the maternal grandfather has the other Type.
  3. Neither of the grandfathers has the same Type as the grandson.

So what would our Martian make of this?

He would probably conclude that there is a complicated pattern of inheritance which doesn't fit the simple dominance/recessive Mendelian pattern but, in the absence of intermediates between Type A and Type B, which might indicate several genes being involved, this would be puzzling.

One solution he might hypothesise is that there is some unstable genetic 'toggle' operating, switching between the two Types but neither of which has a strong advantage so is not being selected for or against. This unstable gene can fairly frequently mutates back and forth between the two.

This would explain why he sometimes found Type A men with Type B father and grandfathers, Type B men with Type A father and grandfathers but mostly it appeared to be a case of perfectly straightforward inheritance from father to son.

Now, suppose our Martian geneticist decided to broaden his study and look at the frequency of Type A and B males in different parts of the world. In some places like the Middle East he would find almost universally Type B. In fact he might think he was fortunate he hadn't just studied men from that part of the world in the first place otherwise he may never have come across Type A.

In other places like Japan he might have discovered they were all Type A with Type B being as common as hen's teeth.

But in some cultures, like India, he would have discovered a mixture of Types with a fairly strong pattern of inheritance where sons were almost invariably the same as their fathers.

And in other places like Europe and America there would have been a much more confused pattern like I have outlined above. The chances of finding a man for which there was no clear-cut (excuse the pun) pattern of inheritance would be much greater here. Does the hypothesised genetic toggle operate more frequently here yet hardly at all in India, China or the Middle East?

And even more puzzling would be the close link between the relative frequency of the two Types and skin colour in some areas but not in others. Puzzling indeed, and grounds for much more detailed research and testing of competing hypotheses, and even different schools of thought developing amongst Martian geneticists.

Until a genius Martian geneticist who had recently read a paper on 'culture' and suddenly made a connection, hit upon the idea of the condition not being a genetic condition at all but a cultural thing. Bingo!

But how does culture affect male genitalia?

A quick experiment to examine a large number of male children at birth and again after a few days, a few weeks and a few months and problem solved. It's the child's parents who are getting someone to mutilate some of their sons, and usually because his fathers had been mutilated - but not always. It's not genetic at all but cultural. No matter how absurd the idea of parents having their children mutilated for no particular biological reason might seem, the evidence for it is clear. All that remains now is to explain why on Earth (sorry) they are doing it.

What's happening here is that mother and father usually have the same culture as their parents had and that is mostly the predominant local culture. In areas like India where there are mixed cultures but intermarriage is rare there can be a mixture of Type A and Type B but they are usually inherited from their parents particular culture. In other places like Europe and America, intermarriage is more common and, in those cases there is no clear rule about which parent's culture will predominate.

And then there is the fact that cultures themselves change, so, in a rapidly-changing culture, such as we have in the developed world, although the grandparents may have believed in mutilation there is no guarantee that their children will. And this illustrates the difference between memetic and genetic evolution. We can choose which memes we pass on and we can change our own memes. Our genes are fixed for us by our parents who have no control over which they pass on to us.

The Martian equivalent of a Nobel Prize for the discovery of replicators which are not genes but can closely mimic them. And a whole rash of research papers and books on the development of childhood mutilation in response to culturally inherited superstitions in a sentient species, and then on the development of superstitions in an evolving memetic culture.

Of course this is just a fantasy. Any alien species capable of getting to Earth and carrying out scientific research on us would almost certainly be aware of memes and how they can induce otherwise bizarre behaviour like religions in an otherwise rational and sentient species.

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