Weird things you never thought you’d have to write: man-made global warming is not going to make red-headed people disappear.
Here’s the hypothesis:
Dr Alistair Moffat, managing director of Galashiels-based ScotlandsDNA, said: “We think red hair in Scotland, Ireland and in the North of England is adaption to the climate.
“I think the reason for light skin and red hair is that we do not get enough sun and we have to get all the Vitamin D we can.
“If the climate is changing and it is to become more cloudy or less cloudy then this will affect the gene.
“If it was to get less cloudy and there was more sun, then yes, there would be fewer people carrying the gene.”
Dr Moffat meant, presumably, that in less sunny climates, dark-skinned genes are a disadvantage, and people with light skin (which happens to be associated with blond or red hair) tend to have more children, because they survive to adulthood without developing the problems associated with vitamin D deficiency. But if the weather becomes sunnier (not in fact a guaranteed outcome of man-made global warming, by the way), then that advantage will be eroded, and the disadvantages of pale skin – less protection from UV rays, largely – will become more important, leading to gingers having fewer children and the gene dying out.
There is a correlation between latitude and skin colour, but interestingly it’s far from clear exactly why that is. Darker skin protects against melanomas, but melanomas have next to no impact on reproductive fitness, since they don’t tend to kill people of childbearing age. It’s fairly well accepted that lighter skin protects against vitamin D deficiency in cooler climates, but quite why the skin gets darker again in sunnier ones is still the subject of debate, as far as I can tell.
But even if we accept that climate change will make everything sunnier (it won’t necessarily), it’s still far from clear that that would put any selection pressure on the ginger gene. In Canada and Alaska, the Inuit people – many of whom live in a climate even bleaker and moodier than Scotland’s – have kept a dark skin for thousands of years, apparently because they have a fish-rich diet which provides them with all the vitamin D they need. And in a reversed, but analogous, situation, whatever it is that causes light skin to be selected against in warmer climates can almost certainly be overcome by the simple application of sunscreen. Our selection pressures have changed. It is unlikely that many light-skinned people will fail to have children as a result of too much sun.
They might, of course. It’s possible that in a few hundred years, if the Northern Hemisphere gets sunnier, Dr Moffat will turn out to be right. It is a moderately plausible-sounding tale.
But it is equally plausible-sounding that red hair will become fashionable, driven by the raw and irresistible sexuality of Christina Hendricks, Damian Lewis and Isla Fisher, and that this will create a positive feedback loop of sexual selection. People with red hair will have more children; and because of that, people who are attracted to red-haired people will have more grandchildren, because they will tend to have red-haired children; and it will spiral out of control, with each generation both more ginger and more given to ginger-fetishism than the last, until dark-haired people are unable to find a mate, and all children are born with red hair, and the gingers inherit the earth.
Whose Just-So story will come true, mine or Dr Moffat’s? Probably neither. But we don’t know. Which is why reporting “scientist says thing”, instead of “this new research, if its results are repeated, adds this new information to the already established body of evidence”, is rarely a particularly informative way to report on science.
Anyway, rant over.