It appears natural selection is forcing the appearance of "education genes" rarer. Although the effect corresponds to a small drop in IQ every few decades, the impact could be big in a few centuries.

Although the study does not go far as to claim that each generation will be dumber than the last, though scientists did clarify that it's more complicated than it appears.

A study from Iceland is perhaps the latest to raise the idea of a downward trend of IQ numbers. According to The Guardian, the research from deCODE, a genetics firm based in Reykjavik, finds that groups of genes that predispose people to spend more years in education are becoming rarer in the country from 1910 to 1975.

The scientists used a previous database of more than 100,000 Icelanders to see how dozens of gene variants that affect educational attainment have appeared over time in the population. According to the Guardian, they found a decline over the 65 year period, implying that there's a downturn in the natural inclination to rack up qualifications.

However, these genes involved in education affected fertility as well. Those who carried more "education genes" tended to have fewer children than other people. This led to scientists proposing that the genes are becoming rarer in the population because better educated people had contributed less than others to the Icelandic gene pool.

Spending longer times in education and the career opportunities that provides is however not just the only reason that the better educated people tend to have fewer children. The study explained that if one is predisposed genetically to have a lot of children, the opposite could happen as well.

However, according to the Proceedings of the National Academy of Sciences, its immediate effect is small. The research estimates that a drop of IQ of about 0.04 points per decade can be observed. Nevertheless, Stefansson explained that if the trend continues to centuries, the impact could be big.

It was also explained that perhaps genetics have a small role on education. There is perhaps a larger role in the form of societal and environmental constraints on people.