Sunday, 14 September 2014

10 ideas about genetic differences between human groups

Nicholas Wade's book, A Troublesome Inheritance, has created huge controversy by claiming that race is real and explains human differences in economic performance. Here is a response from many genetic scientists, which also includes links to comment around the web. I don't wish to jump into that debate, but just to give a set of thoughts about the issue of genetic differences between races. (Disclaimer: I am not an expert biologist, just an interested amateur.)

1. The fundamental truth of biology is that humans are basically the same.

Humans make up a single species, which interbreeds with itself. When two people reproduce, a new viable human is created, with DNA that results from combining their DNA, more or less at random. This is like taking parts from two cars and building a new car with it: you can't mix a Maserati and a Ferrari, only two Maseratis of the same model. So, all humans are basically the same.

That is not to deny that the differences between humans have profound social consequences - for example, in deciding who gets rich and poor - and are therefore of great interest to us. But a Martian biologist would probably find two humans as hard to tell apart as we find two sheep. Our similarities vastly outweigh our differences.

2. Races are statistical facts, not buckets.

This also follows from the "single species" idea. To say that I am Caucasian or you are African does not imply that everything about us differs, or that any single gene we have is certain to differ. People interbreed. "Race", if it means anything genetically, is shorthand for having (probably) had many ancestors from a particular area of the world. This may result in someone possessing a particular allele with more likelihood; but that is a matter of probability, not certainty.

Socially, people often treat race and ethnicity as buckets, and that can become self-fulfilling. But this is a fact about society not biology.

3. Within that interpretation, there are real genetic differences between races.

This is now uncontroversial. For example, people from some parts of the world are more likely to have the allele linked to sicke cell disease than others; partly because the allele helps protect against malaria.

4. There are also differences between races in genes that affect behaviour and/or psychology.

For example, different alleles of the MAOA gene exist in different proportions among different racial groups. The MAOA gene is linked to risk-taking and violence. Here's a rather long summary of recent research.

5. These differences do not necessarily add up to "differences between groups in psychology being caused by genes".

Most geneticists think that any given social behaviour is influenced by many genes - there is no neat 1-1 link. So, a group that possesses more of one allele (say MAOA-2R) could possess less of another, undiscovered gene which pushes them the opposite way.

There are reasons this could be true. For example, suppose that over an evolutionary timespan there has been an optimal level of risktaking, and that risktaking is increased by (alleles of) two genes. It is entirely possible for one group to evolve to have the risk-taking allele at one locus, while another group evolves to have the allele at the other locus. The different genes will then not add up to different behaviour, which is instead kept similar by evolutionary pressure.

6. Or, some group differences in behaviour may have genetic causes. We will find out soon either way.

Nevertheless, there is no general reason to think that intergroup genetic differences will cancel out 100% in this way. On the face of it that seems unlikely - as Cochran and Harpending say in The 10,000 Year Explosion, it's like expecting a coin to land on its edge.

Science is progressing fast in this area, with new statistical methods and databases coming online. Whether genetics matters a lot or a little, the debate can and will be settled by empirical data - which is one reason I am writing this.

7. Genetic differences are multi-dimensional.

Think of genetics and most people think of IQ. IQ is politically salient because it is linked to economic outcomes, and because it threatens to array racial groups on a continuum, with higher IQ being better. But real differences will be more complex than that. Think about MAOA: aggression is bad, right? But risk-taking, for example in entrepreneurship, isn't always bad. If there are differences between groups, we will not be able to order them hierarchically.

8. Genes are not destiny, in the large.

OK, here I am disagreeing with Nicholas Wade's position in the speculative second half of his book. Think about Caucasians versus Asians. In the 19th century, British gunboats were knocking on China's door. In 2014, China is the second power in the world, and pushing for first place. These changes happen too fast for genetics to be a useful explanation.

9. Genes are not destiny, in the small.

Genetic does not mean unchangeable. To take a simple example, many genetic diseases have simple cures. More generally, human choices, including human culture, can make up for - or perhaps sometimes amplify! - genetic differences. (Culture itself, by contrast, can be very hard to change.)

10. Liberal equality does not require us all to be identical.

Why don't we deny the vote to stupid people? We are equal not because we are all the same in every way, but because - as Christianity would put it - we are all possessors of a living soul. Similarly, we have a duty to judge individuals as individuals, and not on the basis of belonging to an ethnic group. Doing the former is usually efficient, since ethnicity is at best a weak predictor of someone's behaviour. It is also morally right.

It may be - I think it is quite likely - that genetic differences will account for many of the differences between people. They may also account for some of the differences between groups. Given the rate at which the science is developing, we would be very unwise not to start thinking about this. I do not want to be too sanguine about its consequences: obviously it would be, in some sense, "bad news" for human equality. At the same time, it is not a cause for liberal despair, or for racism and intergroup contempt to triumph. Whatever differences there are will be probabilistic not deterministic, multidimensional and complex; and morally outweighed by our underlying shared humanity - a truth supported equally by religious tradition, and by modern biology.