The term ‘pedigree collapse’ was coined by Robert Gunderson of the Genealogical Society of Utah. Essentially, it refers to a reduction in the number of ancestors a person has due to the relationship of their parents. For example, if two first cousins marry and reproduce, their child will have, at most, six great-grandparents rather than the usual eight. Without pedigree collapse a person’s ancestral tree would become impossibly large – going back to the Middle Ages my family tree would show about a billion ancestors (two parents, four grandparents, eight great grandparents and so on) which is more than the population at that time.

My research, thus far, has thrown up a single example of pedigree collapse, and that is on my maternal grandmother’s maternal line. Selina HARDIE nee SUTTON 1877-1912 was the daughter of Julia Ann GRIGGS and Henry SUTTON. Her mother was a granddaughter of Sarah Ann HAWKES and John CULMER; her father was a grandson of Sarah HAWKES and William SUTTON.

Sarah Ann (my 4x great grandmother) and Sarah (also my 4x great grandmother) were first cousins – Sarah Ann’s father William was born in Ash parish in 1754 and Sarah’s father was William’s older brother John, born in Ash in 1747. It took me a good few years to sort out the connection! And I’m certain there must be several more instances just waiting to be uncovered.