GENOME CHANGES EVERYTHING
RIDLEY:) For the first time in four billion years a species on this
planet has read its own recipe, or is in the process of reading its
own recipe. That seems to me to be an epochal moment, because we're
going to get depths of insight into the nature of human nature that
we never could have imagined, and that will dwarf anything that philosophers
and indeed scientists have managed to produce in the last two millennia.
That's not to denigrate what's gone before, but the genome changes
everything. We know that just because the first one or two glimpses
inside this box, the first lifting of the lid of the human genome,
reveals to us enormous insights into what's going on, and just from
the first few genes we're looking at.
What I've set out to do, both in Genome and in Nature via Nurture is
to try to put these in historical context, because I think it is important not
only to understand how the old debates are going to be refracted through the
new genomics, but also to simply tell some of the stories that are coming out
of the genomics labs and other psychology and evolution labs that are using genetic
information. The sheer leverage that genomic science now has, compared with sciences
that went before, is very striking. What I mean by that is that with a small
amount of effort you can get really big results. You can get stuff that doesn't
need statistics to prove that it's significant in molecular biology in a way
that you can't, necessarily, in brain imaging or particle physics studies or
something like that, which requires a lot more effort to get a small amount of
of what I'm interested in is that it's the genes that are related
to behavior, and how they work. The big insight is that genes are
the agents of nurture as well as nature. Experience is a huge part
of a developing human brain, the human mind, and a human organism.
We need to develop in a social world and get things in from the outside.
It's enormously important to the development of human nature. You
can't describe human nature without it. But that process is itself
genetic, in the sense that there are genes in there designed to get
the experience out of the world and into the organism. In the human
case you're going to have genes that set up systems for learning
that are not going to be present in other animals, language being
the classic example. Language is something that in every sense is
a genetic instinct. There's no question that human beings, unless
they're unlucky and have a genetic mutation, inherit a capacity for
learning language. That capacity is simply not inherited in anything
like the same degree by a chimpanzee or a dolphin or any other creature.
But you don't inherit the language; you inherit the capacity for
learning the language from the environment.
That's a good example, because for the first time we've now got a gene, the
FOXP2 gene on chromosome 7, which looks like it may be an important cog in
that machinery. It would be surprising, given it's the first gene that we've
been able to look at, if it was the most important cog, but it's certainly
one of them. What happens is that if that gene is broken you get, essentially,
a human being with a great difficulty in generalizing grammatical rules and
in developing fluent speech. You get a general language disorder. But what's
interesting about that gene is that although you might say, "Well, here's the
language gene, and humans have got it and nobody else has it," this is not
so—it's present in mice; and chimpanzees, orangutans and every other
mammal has this gene. Indeed, it's a very highly conserved gene with very little
change over the past few million years.
So you might say, "How can it be important in language?" If you take Svante
Pääbo's work on it and you look at what's been going on in it, it
appears that it's had very little evolutionary change in it until you get to
the human lineage. And then, since the common ancestor of the chimpanzee there
have been two amino acid changes in the gene, which is as much in the whole
of the rest of the mammalian pedigree. Those two sense-changing alterations
in the gene have happened in the past 200,000 years. It was probably about
200,000 years ago they happened, and they've elbowed aside all other versions
of the gene. There's been a selective sweep of these mutations through the
species. So what we're looking at here is a gene that was under very strong
selective pressure around 200,000 years ago, which is around the time that
we think human beings first started using language in something like the form
that it is today. How that genetic change changes the wiring of the brain in
order to enable language learning I don't know, and nobody knows the answer.
But the point is the word enable there. Genes are enablers and not constrainers.
People tend to think about genes as being constraints on what human beings
can do. In fact, that's a very misleading way of looking at it. What's happened
is that genetic changes are necessary to enable kinds of learning, to enable
kinds of nurture, and to enable kinds of experience to get into the organism.
In that sense genes are just as important a part of the story of nurture as
they are the story of nature. When you start to see it that way, you can resolve
the old nature-versus-nurture debate, and you can instead start to talk about
nature via nurture instead.