A psychologist in Wales explains why we do what we do:
Leo Hendry, professor of psychology at the University of Glamorgan, said people were keen to trace their roots out of a sense of self-identity.
"They begin to piece together a part of their identity that they didn't know about," he said.
"Some people dream about being the illegitimate great-grandson of a nobleman. It adds another dimension to who you are.
"It's an extension of the kind of fantasy daydreaming you did in childhood. I was convinced as a child that Gregory Peck was my grandfather." [Link]