The contribution of genetic and environmental factors to IQ, “hyperactivity,” height, and weight, varies considerably by geographic region, according to a new study.
The research was done by the Twins Early Development Study at King’s College London’s Institute of Psychiatry and involved the study of data from 6700 different families and 45 different childhood characteristics. The researchers found that the genetic and environmental contributions to the different characteristics depended largely on geographic region.
Development, health, and behavior, are determined by the complex interactions between genetic make-up and the environment. “For example, we may carry genes that increase our risk of developing type 2 diabetes, but if we eat a healthy diet and get sufficient exercise, we may not develop the disease. Similarly, someone may carry genes that reduce his or her risk of developing lung cancer, but heavy smoking may still lead to the disease.”
The Twins Early Development Study is UK-based and follows more than 13,000 pairs of twins, including identical and non-identical, born between 1994 and 1996. The researchers did a broad survey to assess a wide range of cognitive abilities, behavioral and physical traits, environments, and academic performance in 6759 pairs of twins when they were aged 12. They then designed an analysis to find the genetic and environmental hotspots for the surveyed traits.
“These days we’re used to the idea that it’s not a question of nature or nurture; everything, including our behaviour, is a little of both,” explains Dr Oliver Davis, a Sir Henry Wellcome Postdoctoral Fellow at King’s College London’s Institute of Psychiatry. “But when we saw the maps, the first thing that struck us was how much the balance of genes and environments can vary from region to region.”
“Take a trait like classroom behaviour problems. From our maps we can tell that in most of the UK around 60 per cent of the difference between people is explained by genes. However, in the South East genes aren’t as important: they explain less than half of the variation. For classroom behaviour, London is an ‘environmental hotspot’.”
The maps give an overview of the fact that the environment interacts with the genome, without focusing on specific genes or environments. Patterns emerged from the data though.
“The nature-nurture maps help us to spot patterns in the complex data and to try to work out what’s causing these patterns,” says Dr Davis. “For our classroom behaviour example, we realised that one thing that varies more in London is household income. When we compare maps of income inequality to our nature-nurture map for classroom behaviour, we find income inequality may account for some of the pattern.”
“Of course, this is just one example. There are any number of environments that vary geographically in the UK, from social environments like healthcare or education provision to physical environments like altitude, the weather or pollution. Our approach is all about tracking down those environments that you wouldn’t necessarily think of at first.”
In addition to the environmental hotspots, there are genetic hotspots too. The researchers think that these genetic hotspots are just the environments that make genetic differences stand out more.
As an example, researchers searching for gene variants that increase the risk of hay fever may study populations from two different regions. In one region, people might live among fields of wind-pollinated crops, and, in another region, they may be miles away from anything similar. In the second region, where no one is exposed to pollen, no one will develop hay fever regardless of susceptibility.
But in the first region, where people live among the fields of crops, everyone will be exposed to pollen, and the differing levels of genetic susceptibility will stand out. That would make the region appear as a genetic hotspot for hay fever.
“The message that these maps really drive home is that your genes aren’t your destiny. There are plenty of things that can affect how your particular human genome expresses itself, and one of those things is where you grow up,” says Dr Davis.