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Monday, September 10, 2012

Genes, memes and obesity

I have blogged several times about the uniqueness of obesity to the human race. Notwithstanding the fact that we share 98% of our genes with our nearest biological relatives, the chimpanzees, we alone get fat. It therefore follows that our obesity has origins in the basic biology of energy metabolism and storage but that it also has origins in the society we have constructed. For hard-nosed reductionist biologists, sniffing around the causes of obesity outside the laboratory is most unattractive because it brings us into the world of psychology, of human behaviour and of social organisation and these are all seen as “soft sciences”. If this view persists, then the so-called ‘hard sciences” of genetics and its associated disciplines, will wane in importance. Consider the brouhaha that greeted the discovery of cafeteria feeding of rats to induce obesity, the discovery of genetically obese rodent models, the incredible discovery of the appetite regulating plasma protein leptin and now, the flavour of the month, the gut microbiota. All have hit the front covers of Nature and Science and all have been the flavour of the months at key scientific conferences. But when all of these are added up, the best they can do is explain bits and pieces of the “how” of obesity. They cannot some of the “why” such as genetic predisposition but they cannot explain the “why” of individual obesity and overweight.

What makes humans so different from other species is that we alone have mastered the ability to learn from one another by imitation. This imitation can be vertical such as what we learn from our parents. It can be horizontal such as what we see others doing. Of course, we actually don’t have to see others doing something to imitate it. A third party can describe what he or she saw and we can have a shot at it, maybe getting it right first time, maybe having to go back for another look at the person who has mastered this act and eventually, we will be able to do it. These acts of imitation spread through society at a rate vastly greater than that of natural selection of genetic potential. To the biological scientist, this is interesting but seriously wooly. It is poorly defined, poorly characterised, impossible to measure and impossible to attribute origins of imitated acts.

In 1976, Richard Dawkins wrote a book which to this day remains a best seller entitled the ‘Selfish Gene’. Dawkins did not mean that there was a gene for selfishness but rather that all genes were utterly selfish in competing with other genes to be included in the blue print of the next generation, the one after that and so on. The human body is the vehicle and the gene is the “replicator”. But Dawkins stepped boldly out of biology in coining the term ‘meme” to explain the basic unit that is involved in the vertical and horizontal transmission of human knowledge. The exact quote is thus: “ We need a name for a new replicator, a noun that conveys the idea of a unit of cultural transmission, or a unit of imitation. ‘Mimeme’ comes from a suitable Greek root, but I want  a monosyllable that sounds a bit like ‘gene’. I hope my classicist friends will forgive me if I abbreviate mimeme to meme[1]”.

A meme is any concept or idea that is replicated by imitation. It can be verbal (rote, word-of-mouth, sung or chanted), written (prose, verse or music) and it can be an action (the Maori Haka, the handshake, the Christian blessing). The private thoughts and fantasies you have lying in bed or day dreaming on the bus to work are not memes since there is no expectation of transmission to others. Dawkins saw memes as being identical to genes in their characteristics with the three prerequisites of the latter: replication, variation and selection. Memes compete with one another for retention within our brains and there are far more meme than there is storage space in our brains  for them so the memes that win out to to be transmitted  vertically are no different from the genes that win out for retention in the next generation.

The development of obesity is a passive event over time since nobody really sets out to gain weight. But once we gain weight, we access memes that are implanted in our brains: “Fat isn’t pretty”; “Being fat is bad for health”. But when it comes down to the decision to “do something”, what is the behaviour we imitate? For some, especially among young professionals, the imitated behaviour fights the passive gain in weight, a life-time commitment of watching and weighing, of eating carefully and of exercising diligently. This behaviour is also true for some who lost weight and who want to imitate that behaviour that retains weight loss. For others, and it is a fact of life that it is the majority, the imitated behaviour is to do nothing. The meme to do something about overweight has to compete with memes that govern other activities in daily life and the modeled meme is one of the status quo. Fat people don’t die on the streets. They grow old. They are no sadder and no happier, no poorer and no richer and no more loved or feared than lean people.

The future of cell biology will reside in the cell since the latter is the raison d'ĂȘtre of cell biology. Human obesity can be studied by the geneticists and the memeticists on different planets as is presently the case. Those who bring these disciplines together will be the future. Memes are neither angels nor demons, which flit around some unique ethereal space entering our head for good or bad. Memes are ultimately connected to a neuronal network in the brain, unique to that meme. Thus they do have a biological base but not a genetic base. The biological base must connect to the phenotype. I wish I could sing like the late Luciano Pavarotti or swing my golf club like Tiger woods but I cant. Why not? I can cut the grass and I’m good at figuring out complex scientific concepts and at designing experiments to test these theories. Why so? Is our phenotype where our genotype meets our ‘memotype’? Complex questions indeed but valid complex questions.

[1] For those of you who would like a quick tour of memes, try the review by McNamara in Frontiers of Evolutionary Neuroscience May 2011 (volume 3): “Can we measure memes”. For a truly fantastic introduction to memes, buy Susan Blackmore’s book “the Meme Machine”, Oxford University Press.

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