How Many Friends Does One Person Need? (12 page)

The fact that dread diseases are more common in the tropics than at higher latitudes may in part explain a curious feature of how languages are distributed: near the equator, language densities are much higher, and language communities (the number of people speaking a given language) very much smaller, than they are at higher latitudes. One explanation for this might be that it is a culturally evolved strategy to reduce the risk of cross-infection in areas where pathogens are more densely concentrated. Language barriers significantly reduce the opportunities for contact between different populations, thus minimising the risk of contamination. Creating smaller, more inward-looking, xenophobic societies may thus help to reduce exposure to diseases to which one has no natural immunity. It turns out that religion has a similar distribution: Randy Thornhill and his colleagues at the University of New Mexico found that people living in areas with high parasite loads (mostly those in the tropics) are much more religious than those living in areas with low parasite loads (mainly those at high latitudes).

Nonetheless, despite the fact that many new diseases seem to have their origin in the tropics, it is often in the subtropics that the major outbreaks occur. This seems to be explained by the fact that human population density is the single most important factor relating to disease outbreaks. In part, that reflects the historical development of the more successful economies of Eurasia and North America, creating denser populations of susceptible individuals. In addition, of course, language communities are significantly larger outside the tropics, thus facilitating
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mutual intercourse (in all senses of the word) between larger numbers of individuals.

In the end, however, the high proportion of these new diseases that have their origins in wildlife (so-called zoonoses) means that the single best predictor of where these diseases originate is local wildlife biodiversity. And that is a tropical issue. What should concern us is the fact that most of these biodiversity hotspots are in developing countries in Africa, Asia and Central America – the ones where the investment in disease monitoring and control is least well developed. It raises the question as to whether we in the developed world are investing our resources as wisely as we should because, once such diseases have moved from the developing to the developed world, they are invariably much more difficult to deal with. It’s a very good reason for putting more money into the developing nations.

If you suffered with morning sickness in early pregnancy, it may be little consolation to know that you are not alone: four out of five mothers-to-be experience vomiting or food aversions in the first three months. The medics, as usual, have tended to see only the symptoms and settle for offering palliatives of mostly questionable value – thalidomide, which blighted so many lives in the 1960s, was just one of the least sensible: it stopped the symptoms of morning sickness, but no one really took the trouble to look beyond that. In the medics’ considered view, morning sickness is just an unfortunate side effect of the hormonal changes that happen during pregnancy, so there is every good rea-
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son to get rid of it. But evolution doesn’t often produce things that are mere side effects. So why on earth should we experience such awful side effects from what is, after all, a perfectly natural process of everyday life?

In fact, it seems that morning sickness might actually be good for you – or at least, for your baby. Women who experience nausea in the first trimester of pregnancy have greatly reduced chances of losing the baby by spontan-eous abortion, and are likely to give birth to bigger, bonnier bairns. This has prompted evolutionary biologists to ask why this should be. One suggestion is that it is the outcome of a tussle between baby and mother over what the mother should eat. The argument is very simple. We eat lots of things that are mildly toxic, sometimes even downright poisonous, often because they taste good or give us a kick of one kind or another. These include things like alcohol, coffee, chilli, pepper and even broccoli. Many of these are carcinogens (cause cancers) if taken in large enough doses, and not a few are teratogens – substances that cause abnormalities in developing babies if ingested too often during pregnancy.

Adults can tolerate these poisons because the small doses we eat are diluted when dispersed around our relatively large bodies. But foetuses are tiny, and to receive even a small dose of one of these via the mother can have very adverse effects. In effect, morning sickness is the baby’s way of trying to prevent the mother from eating too much of what is not especially good for baby.

An alternative suggestion has been that the vomiting associated with morning sickness gets rid of harmful bacteria ingested with foods that are prone to going off. Adults can usually cope with a little rotting meat in small doses
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– it may cause an upset stomach, or at worse a spot of diarrhoea, but that passes pretty quickly. But, once again, what may be a tolerable dose for mum may be just too much for baby. The obvious candidates are meats and dairy products.

In a recently published study, Craig Roberts and Gillian Pepper of the University of Liverpool looked at the frequency of morning sickness across the world in relation to the kinds of diets typically eaten. They found that morning sickness frequencies were indeed correlated with the frequency with which stimulants (such as coffee) and alcohol were consumed. However, the frequency of morning sickness was most strongly associated with the amount of meat, animal fats, milk, eggs and seafood eaten, and least with the importance of cereals and pulses in the diet.

This suggests that it might well have been the risk of damaging infections that has played the major role in the evolution of morning sickness. The association between morning sickness and the amount of meat and dairy produce in your diet makes sense if the real problem is to avoid poisons. Meat and dairy produce are, after all, among the most nutritious foods available: they are rich in easily digestible nutrients. Why should one avoid them? The answer can only be the fact that they are prone to being infected with bacteria, and the load that these place on mother and baby may be enough to trigger a sponta-neous abortion. Most cereals don’t have this problem, so the more cereals you have in your diet, the less trouble you get.

One curious bit of evidence against the poisons hypothesis is the fact that the frequency with which spices are used in food also correlates negatively with morning sick-
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ness rates – which is surprising since many spices are well-known carcinogens. However, as every traveller to the Far East knows, a good hot curry kills off everything including all the bacteria inadvertently ingested with your food. Spices, it seems, are good for you. They also happen to be quite good at triggering the release of endorphins – the brain’s own painkillers – and these in turn seem to ‘tune up’ the immune system, thereby making you better able to cope with illness.

So, if you are thinking of getting pregnant, it seems that avoiding meat and dairy produce may be the best way of reducing the risk of morning sickness. That age-old Scots remedy for everything, porridge, is suddenly especially attractive. But maybe you should consider a drop of chilli to spice it up for good measure?

Pregnancy reminds me that if there is anything that we worry more about than death, it must be not being able to make babies. More anguish, time and money is spent on fertility treatments than anything else except making ourselves smell nicer. And so it was that, in the summer of 2006, thanks to the wonders of science, Patti Farrant became the proud mother of a bouncing baby boy at the age of sixty-two, acquiring at the same time the privilege of being the oldest mother in Britain. But as the latest in a trickle of post-menopausal IVF pregnancies, she raises a more fundamental issue than the mere question of whether grandmothers make good mothers.

We are the product of evolution, and the processes of evolution inevitably instil in us a complex set of motiva-
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tions and emotions that are designed to serve the principal function of doing evolution’s business – ensuring that, as best we can, we each make our contribution to the next generation’s gene pool. Because the evolutionary processes are blind to long-term consequences, they operate through emotions that have been tuned over evolutionary timescales to achieve the ends that best serve evolution’s interests.

For this reason, we are bedevilled by emotional shortsightedness. It often requires enormous self-control to resist satisfying our cravings in a world where technology can transform craving into actuality. Obvious everyday examples include our tendency to eat too much – and especially too many sugary and fatty foods – to enjoy the momentary pleasures of substances that inevitably harm us in the long run (I need not list these by name... ), to take risks (of both a sexual and a physical kind) for the thrill of the moment, to over-fish the seas or cut down the forests despite the fact that we all agree that such behaviour is inevitably self-destructive in the long run.

The hardest of these cravings to resist are, surely, those that have to do with our children. Parents are deeply ingrained by evolution to care desperately about their babies. We have to be, otherwise human babies would never survive, given that they are born so prematurely by monkey and ape standards. The problem is – as every parent knows only too well – it doesn’t stop with weaning. The need for parents to invest in their children goes on and on and on... seemingly for ever.

We tend to forget that successful child-rearing is not just a matter of making sure the little darlings survive childhood. We are an intensely social species, and, from
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an evolutionary point of view, placing our children advantageously in the adult social world is more important than their mere survival. That involves a great deal of social training in the teenage years, not to mention looking after their economic interests as young adults and providing them with the right kinds of social opportunities, marriage partners or even business breaks. It may begin with finding them godparents; it runs on into finding them jobs with friends or relations, and ends (or so one always fondly hopes) with lavish weddings. And then the grandchildren arrive, and the cycle starts again. Not to put too fine a point on it, it’s the first forty years of childcare that are the worst.

The problem is that the wonders of medical science have meant that babies who once would never have survived can now do so. The emotional investment of both parents and medics converge, and a ‘can do, should do’ culture prevails for what are surely the most understandable of reasons. But is it always in everyone’s best interests? In the heat of the moment, parents cannot see beyond the immediacy of their emotions, doctors cannot see beyond the exhilaration of achieving a result against the odds. The pressure is to push the boundaries further and further back, but the consequences down the line get overlooked. This is most serious where babies have more problems than just prematurity: the pressures of coping with the severely disabled all too easily result, during the decades that follow, in intolerable family burdens even for saints. Divorce rates are higher than average, and disabled children are at much greater risk of physical and mental abuse, and even death, when the patience of saints finally cracks under the strain.
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Life, and especially growing up, is a risk at the best of times. So is it morally right for those who dabble in this area to take the view that just because it is possible, it should be done? Is it really in our best interests for medical science to be driven by the desperation of our cravings? The lesson of evolution is that, more often than not, the answer is a resounding ‘no’.

Not all evolutionary slaps in the face come from the medical profession’s activities, of course. Just as many come from politicians and the social policies they try to impose on us, even if often for the best of political motives. But the consequences of trying to interfere politically with the biological world can be just as problematic. Two decades ago, for example, China worried so much about the population explosion looming over its head that it instituted its now infamous one-child policy: couples were allowed to have only a single child, and any extra conceptions that followed had to be aborted. Draconian as this may sound, it pretty much saved China from demographic disaster. It cut the birth rate overnight, and all but reversed the population growth rate.

However, they had reckoned without the effects that evolution has had on human nature. Lurking unseen in the wings was a completely different demographic disaster. What the government demographers had not anticipated – and demographers in general have never been noted for their understanding of, or even interest in, evolution – was the average couple’s overriding preference for boys, especially in rural populations where boys are
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essential as labour on the farm. The availability of cheap means for sexing babies
in utero
allowed parents to selectively abort girl foetuses.

Now, less than two decades down the line, the hidden timebomb created by an imbalanced sex ratio is beginning to reveal itself. The hundred largest cities in China have a sex ratio of around 125 boys to every hundred girls – against a normal sex ratio at birth of about 108 boys for every hundred girls. Current estimates suggest that there are around eighteen million more men than women of marriageable age in China, and the forecast is that this will rise to thirty-seven million by 2020. This is just a tad ominous, because boys without girls are seriously bad news.

One recent study demonstrated a strong correlation across mainland US states between the divorce rate and the frequency of rape: the significance of this is that many more divorced men than women remarry, and high divorce rates thus result in large numbers of other males being left without partners – and, hence, a large number of excessively frustrated men. And in case you need any more persuasion about the civilising influence of a ‘good woman’, consider the fact that one of the strongest predictors of recidivism in young male criminals in the UK is whether or not they settle down with a long-term partner after release from prison. Boys without girls are, to be blunt, a menace.