Genetics and Evolution

I find much science fascinating, including my favourite areas of astronomy and cosmology, and occasionally indulge myself by buying a copy of New Scientist.

One edition contained a most interesting article entitled The Unselfish Gene. The title was a dig at Richard Dawkins’ book The Selfish Gene which claims that evolution takes place through natural selection only at the level of genes (tiny parts of human cells which pass on characteristics from parent to offspring).  Dawkins believes the environment provides challenges to genes and only those which successfully meet the challenges survive. 

Charles Darwin wrestled with the problem of why male births outnumber female births even though the work of his contemporary Gregor Mendel, the “father of modern genetics”, suggests the number of the two sexes should be equal.  Darwin speculated that maybe the countless generations who practised female infanticide had affected the genetic predisposition of parents to produce either a girl or boy.  

Many reject this idea. But the New Scientist article reported that “a small but growing band of evolutionary biologists, geneticists and psychologists” is beginning to think Darwin may be right.  They hold that natural selection operates not only on genes but on a combination of genes and culture.

An international research team led by Kevin Laland of the subdepartment of animal behaviour at Cambridge University researched the incidence of left-handedness and believes it is partly due to cultural factors. Some of their findings are consistent with these factors having a prenatal effect on a baby.  In other words it isn’t just obvious cultural factors such as parental example producing left-handed children, but the “culture” of left-handedness in a particular family has a genetic effect. 

Marc Feldman, a biologist at Stanford University, has researched milk drinking in humans.  Humans can only digest cow’s milk if they produce the enzyme lactase which allows them to absorb the milk sugar, lactose. Where people have drunk cow’s milk for many generations 90% of the population have lactase.  Those without a history of drinking cow’s milk have a different version of the enzyme and are prone to sickness if they drink it.

Laland with Jochen Kumm and Feldman claim their research shows female infanticide may indeed influence the genetic predisposition towards having boys.  

The technical term for this theory is gene-culture coevolution and it threatens to undermine Dawkins’ Selfish Gene thesis. We are, of course, here speaking of variation within the species, not evolution across the species.

All of this is controversial but if proved true would seem to have some fascinating and disturbing implications.  If persistent behaviour in a particular society can affect genetic predisposition does persistent sinful behaviour by human beings cause a genetic predisposition towards sin?  Are scientists about to discover original sin?  If the sin of female infanticide can have genetic effects, why not other sins?

Presumably this would mean that persistent homosexual practice could have genetic effects in society producing a predisposition towards homosexuality – a homosexual orientation?  Clearly, learned behaviour from the example of a particular culture has a powerful effect. But does it also have a genetic effect?  Currently though there is no reliable evidence that homosexuality is genetic. 

At present this is fascinating speculation, but stranger things have ultimately been proved.

However if a genetic cause or factor is discovered in any sinful tendency, that does not remove personal responsibility. Genetic causes are in the category of human weakness and temptation, not determinism which removes free will and means people are forced to behave in particular ways.

© Tony Higton: see conditions for reproduction