I'm looking for a word to signify the ancestor from which a family tree is derived. They would be the first, from whom all other family members are descended. Does such a word exist? I imagine, given the long history of creating family trees, that someone at some point decided on a word other than 'the first guy'.
The word that popped into my own head was progenitor, which the OED gives as sense 1 the following:
A person from whom another person, a family, or a race, is descended; an ancestor, a forefather.
One advantage of progenitor over forefather is that it works for either sex. Well, in my opinion, at least, it does. The words progenitress, progenitrice, and progenitrix do exist and would in theory be available for an ancestral female, just as ancestress would. But I’m not sure that the explicitly female versions of these words get much currency these days.
I think forefather is the word you are looking for:
- the founder of a family; "keep the faith of our forefathers"
Found it — the term is the apical ancestor. See Wikipedia for details.
I've seen the word "proband" used in genealogy as the person of interest when either all descendants of the person, or all ancestors of the person are being studied.
This term is also used in genetics as the person being studied who has a trait of interest that may be passed to any descendant, and may have come from any ancestor.
See also What is the name of a "role" in a family tree? on Genealogy and Family History Stack Exchange.
"Patriarch" or "matriarch" also might be of use.