The incidence of children born with Down’s Syndrome is not evenly spread. For example, there was a cluster of children with DS born to mothers who had attended a school in Dundalk, Ireland. You can...

The incidence of children born with Down’s Syndrome is not evenly spread. For example, there was a cluster of children with DS born to mothers who had attended a school in Dundalk, Ireland. You can read about the cluster following the reference provided in the nearby Connect and Extend feature. Why do you think clustering might naturally happen? What reasons are suggested in the paper by Dean et al. , for this kind of clustering?