Dr. Jim Wilson, a genetic genealogy researcher, is dubious that Norse raids are to blame for Scotland's profusion of red hair. "There are redheads in Scandinavia, and there were definitely redheaded Vikings," stated a senior academic at Edinburgh University. He added: "I think it's more likely that they're descended from Iberians or Gauls who settled in Scotland after Rome collapsed." Wilson also disputes the idea that Iceland was once part of Norway saying: "Iceland became independent in AD 930, so if anyone was raided it would have been long before that date." Redheads are common among other nations too, including Ireland, England, France, India, and America. So although redheads probably did occur within Viking populations, this doesn't mean they were dominant. The idea that redheads might be linked to Norse ancestry stems from studies of DNA markers called R1b and R0r. These markers are found in particularly high frequencies within some European populations. Analysis of DNA from individuals with known family histories of red hair discovered that they tended to inherit these markers from their parents. This suggested that those people were genetically more likely than others to have Norse ancestors. However, researchers need to take into account other factors which may influence whether someone carries these markers.