For those who might be interested, but know nothing or little about epigenetics, I will explain in what follows. This might turn out to be rather lengthy but, to my mind, it is the most important essay I have ever tried to write, and the most carefully considered one in its composition. I hope those of you who read to the end may also consider it important. Feedback would be welcomed.
The new, rapidly burgeoning science of epigenetics—a close cousin to genetics—is already becoming hugely important in medicine, particularly in cancer treatment. It also gives us significant insights into historical changes that occur in civilizations, even in interpreting modern events such as what is now occurring in North Africa and the Middle East.
Each of us has exactly the same number and types of genes (around 20,000 of them, the number not yet precisely known) in our DNA (in 23 separate chunks or chromosomes). Each gene has many variations (or mutations) within them making for billions of possible combinations. The number of possibilities is greater than all the individuals in the world and thus each of us has one unique set. However, our genes occupy only about 5% of our total DNA and are separated from their neighbours by much longer sections of other, almost identical, DNA material. This used to be called “junk” DNA because, until recently, it was considered to be useless and was only tugged along accidentally from one generation to the next by the genes. It is now called “non-coding DNA”.
Within the non-coding DNA there is another 5% of special ‘somethings’ which, for our purposes, we can call epigenes. No-one knows what the remaining 90% of our DNA is for—if anything—but no doubt all will be revealed in the coming years. However, even in the case of epigenes, very little is yet known about them except that they are like orchestral conductors which not only turn our genes on and off for specific periods of time but also instruct individual genes, or whole sections of them, to be active at the same time. In a newly fertilized egg, epigenes start orchestrating the genes to operate in strict sequence until the baby is born. Some of the epigenes then close down but many of them continue for the rest of the life of the individual as tissue is made and hormones are developed.
In turn, it is now realized that the epigenes are themselves affected by circumstances outside the individual. They can be caused by either the general chemical environment, or the food we eat, or our behaviours. Our behaviours may be voluntary ones, or those we adopt (consciously or not) from those around us, or even those which are forced on us by others who are more powerful. However, the precise biochemical pathways by which these external stimuli are fed back to our epigenes, and thus in turn to the operation of our genes, is as yet unknown.
According to our precise life circumstances each of us develops particular orchestras or setting of epigenes. Even in the case of identical twins when both are born with identical gene variations and identical epigenetic settings, the slightly different circumstances that each experiences from then onwards gradually change their epigenetic settings. Even though, at first, parents can find it impossible to tell them apart, parents can’t handle or speak to the twins in absolutely identical ways and the twins’ epigenetic settings, as they affect behavioural genes, gradually drift apart. Parents soon learn to tell them apart from their slightly different behaviours. Their behaviour continues to diverge from then onwards and throughout life. Later, as the each twin enters entirely different environments (in different classrooms, or in different jobs, or eating different diets) more and more epigenetic settings are affected differently and the twins even begin to change their appearances — in middle and old age particularly.
Although identical twins tend to have the same diseases throughout life (because their immune systems were identical to start with), their different chemical environments or diets might cause an epigenetic setting in one of them to change to the control of a dangerous combination of genetic variations. One may get a cancer, say breast cancer or prostate cancer, while the other doesn’t. However, the new epigenetic settings acquired in life don’t get passed on to the next generation. Predispositions may be inherited (particular gene variations and particular epigenetic settings) but not necessarily their inevitable fulfilment.
With one exception—boys until puberty. Some of his newly-acquired epigenetic settings can, in fact, be transferred into his germ-line cells—those which will actually make his sperm when he reaches maturity. Thus new epigenetic settings which affect his behavioural genes or his body-making genes are passed on in his sperm and there’s a 50:50 chance that they will be incorporated in any of his children. The classic case of this is the way food affects body size and weight. When we changed from hunter-gathering to agriculture we also changed to a diet with much more carbohydrate and less protein. The epigenes of a boy brought up on such a diet will change so that his genes will produce a smaller adult body — so that a better balance between carbohydrates and proteins is maintained. Half of his children will also tend to have slightly smaller bodies than they would otherwise have based on genes alone. All of these will then pass on the new epigenes settings to their children. If the high carbohydrate diet is maintained then, within a few generations, every single person in the population will have acquired the new epigenetic settings and, indeed, the settings can intensify in their effect.
But such epigenetic settings can also revert to their original state within a few generations. Thus when the much undersized people of Western Europe started to have adequate protein diets at around 1850 and onwards, the previous extreme epigenetic settings were gradually unwound from generation to generation via the males. Within about three or four generations—about 50 years ago—the average size and weight of West Europeans, males and females, are now back to that of hunter-gatherers in Neolithic times. We know that from their skeletons. The same is now happening among Japanese, Chinese and other Asian peoples as their millet- and rice-dominated diets acquire more protein.
But gross bodily effects such as size and predispositions to particular cancers are not the only effects of inherited epigenetic settings. Epigenes that affect behavioural genes even at a subtle level, can also be passed on. Predispositions to depression, suicide, violence, created in prepubescent boys have already been shown to be passed on to their children. In the case of girls, they can’t pass on any individually-acquired epigenetic changes because they are born with a complete set of eggs that will be used in her lifetime. A whole new scientific area of psychological epigenetics is now opening up in which a thousand and one personality and intellectual predispositions, too sophisticated to be explained by genes alone, are being investigated.
Some epigenetic predispositions, occurring within a family, say, can die away within a generation or two. Others, however, can spread widely in a population if produced by a much broader band of psychological circumstances which is maintained for long periods of many generations. Thus behavioural scientists within the biological research field are now perceiving that whole cultures can become endemic in particular regions of the human population if the psychological as well as the physiological environments remain much the same.
But only if the environments remain the same. Given some big and wide environmental shock, such as climate change, or the invasion of a foreign culture, or the dawn of science and a rash of innovations which offer new behavioural opportunities, then epigenetic settings will immediately start to change in at least some prepubescent boys. If the new circumstances are maintained in the next generation then the new epigenetic settings will sweep more broadly until, after a few generations, everybody is affected. Every individual will still have his or her own unique set of genetic variations and also epigenetic variations due to their individual life experiences, but there’ll be some epigenes that will be shared among them all, or at least, a substantial majority—no different from the effect of poor diet on body size during the agricultural era.
And, just as physiological changes due to epigenes have been proved to take about three or four generations to become widespread, and another three or four generations to subside if circumstances change back again, then we cannot expect that any substantive cultural changes due to epigenes can be made in any less a time period. And this is where the historian steps in. If a culture is overthrown violently—let us say, the Russian Revolution of 1917—then its successor tends to carry forward many of the characteristics of the former culture. As it happened the new communist culture there became a travesty of their ideological hopes and became even more repressive than the previous Tsarist one. And even though the post-1917 culture proved to be economically bankrupt and failed completely in 1989, the latest Russian culture is still violent—criminally more than statist this time—and it will probably be another two generations before Russian culture settles down into reasonable docility and justice for all the people.
And we now have another classic case in the attempted cultural changes now going on within the Islam countries. Their young people are able to see on TV and the Internet the sort of way of life that goes on in the West and some of their better educated middle-class youth have actually travelled or further-educated there. Whether our present way of life is desirable or not — goodness knows we have immense problems of our own — the Islamic youth want the same consumer goods and career opportunities that we have. This is quite as much a shock to the culture imposed by their elders, particularly their religious leaders, as is climate change, or the invasion of a foreign culture.
The necessary two- or three-generational cultural change had started to take place in Iraq under the secular culture imposed by Saddam Hussein. Brutal though he was to minorities such as the Shias (with its own hierarchical power system) he’d largely persuaded the Sunnis (with their individually governed mosques) to go along with the secular Baathist Party. A significant professional and scientific middle-class was already growing. If the no-fly zone strategy had continued—by which method the Great Powers were preventing him from growing a large army—then there was every likelihood that Iraq’s Westernization could have continued into a second generation. When Hussein died, or was overthrown, then there was every chance that the cultural change would have continued and spread more widely. We’ll never know.
What can be said, therefore, about the apparently successful (but, I think, doubtful) revolutions in Tunisia and Egypt, the more violent eruptions that are taking place in Bahrein and Yemen, the 2009 attempt in Iran, and the civil war that is now taking place in Libya? What the science of epigenetics is telling us is that, if any one of these attempts at culture change is successful in the short term, it is highly likely that real psychological and cultural changes will still take another two or three generations before the burden of Islam (as presently practised) is finally put out to pasture and a Western-type culture—warts and all—takes its place.