team from the company deCode Genetics reports today in the journal Nature that a father's age determines how many new DNA mutations a child inherits, and that this may explain a recent rise in the number of children being diagnosed with autism.

The chance substitution of one DNA letter for another—a mutation—is what allows bacteria to become resistant to drugs and, over the stretch of ages, the human species to evolve. Such changes can be dangerous in the short term, however, as they may disrupt the function of genes, including those involved in cognition.

In Iceland, where deCode is based, the age of fatherhood has risen sharply over the last few decades. Along with it, the number of mutations being inherited by newborn Icelanders is also rising, says Kari Stefansson, deCode's CEO.

Technology Review interviewed Stefansson recently in Boston about the results.

TR: Tell me about your latest paper.

Stefansson: We did a study of the mutation rate in the Icelandic population, and what we found is that it's determined by the father's age. Hardly anything else influences it. Astonishing. For each added year in the age of the father, there are 2.1 mutations added to the offspring.