Geneticist Steve Jones on obesity, biology of Homos and genetics’ influence on people’s lives
How does genetics influence the way we live? Why is obesity dangerous for people? How does genetics fail to understand human height? Professor of Human Genetics Steve Jones describes the specifics of human nature.
The way we die has changed. We used to die of things like cholera, of cold, of starvation, in London – of the terrible air and the fog, and that’s more or less been conquered. But we all have to die in the end. And what we die of now is our own inborn weaknesses. So that might suggest that genetics is some kind of terrible fate, and you can be told, when you’re young, what you’re gonna die of. But it’s not really like that at all, because actually genetics simply tells you what kinds of environments, what kinds of nurture you are most at risk at.
What’s amazing about the obesity plague is how recent it’s been. If you look at the figures for the United States for people who are very fat, not just a little too fat but morbidly obese, who are really almost circular, and almost certainly have difficulty walking, and might even have difficulty standing up, some of them. The number of those people in the United States has gone up in proportional terms by something like 10 times in the last 30 year. So if you go back to 1985 and you draw a map of american obesity there’s only about four or five states, mostly in the South, where more than 1 person in 10 has that problem. If you look at the figures for 2015 there are now more than half of states where more than 1 person in 3 has this problem of morbid obesity. And that’s really important for health because if you are obese you have all kinds of problems and the biggest and the most intractable problem is a condition called type 2 diabetes.
One of the great failures of modern genetics is its failure to understand most of the things in human society which are inherited, things like human height. It’s obviously the case that tall parents have tall children, short parents have short children. There’s obviously a lot of genes out there, the environment’s evolved too. But we haven’t been able to find those genes, or, to put it another way, we found too many of them. The last time I looked there was something like a 150 genes whose variation was behind human height. Altogether they only explained about 5 to 10 percent of the variation. So it was this big surprise to find that there are a number of genes in the audience to this program of people who have different genes which don’t appear to be abnormal, like leptin deficiency, but which alter the extent to which they feel hungry.