About 800 years ago, an ancestor lived in Great Britain, whose descendants now live on at least three continents and carry the same gene that increases the risk of childhood epilepsy, scientists from the University of Melbourne have found.  The results are published in the American Journal of Human Genetics. The authors used the results of genotyping several dozen people with a point mutation in 121 positions of SCN1B gene from biobanks. It turned out that this mutation originated about 800 years ago in a common ancestor of the people involved in the study. This mutation had previously been associated with an increased risk of autosomal dominant epilepsy in children (GEFS+). Scientists believe that this mutation predates the settlement of Australia. They suggested that the genetic variant originated in England, and then its carriers moved to Australia and America, thus populating the three continents. The persistence of the mutation, which is associated with a severe autosomal dominant disease, may have been helped by the fact that in many carriers of the gene, the disease occurs in a mild form or does not occur at all.