Icelandic phone app stops you dating close relatives
30 September 2013 Last updated at 08:46 BST
In Iceland, there has been little immigration over the years.
This means there is not as much genetic diversity as on larger land masses. Go back a few generations and most Icelanders will find they are related to each other.
Spencer Kelly explores how Icelandic people are using technology to make sure genetic similarities do not get too close by using an app called Bump and literally bumping their smartphones together.