Spread of Scottish family names

[kerrand]

Scottish clan sites love to claim that everyone in a clan is descended from a single family and hence carry the family name. This seems unlikely to me.

For example, the first Ker (or Kerr) recorded in Scotland was in about 1250 or so (apparently descended from a de Ker who was a Norman who came over with WIlliam the Conqueror). Are all Kerrs descended from this family or (as seems more logical) did some of their tenants just take the name? Does anyone know of statistical or popultation studies which have looked at this kind of thing?

Between 1650 and 1700 there were about 3552 Kerr (and similar) births recorded in Scotland (FamilySearch.org). If I build a very naive model assuming 50% births as male and 3.5 births per family per generation and a 25 year generation time starting in 1250, curiously I get a number in the 3000-4000 range by 1700.

I know the model is very simplistic but at least it's in the same ball park. Any thoughts?

[Shona]

Clan stuff is a bit simplistic, to be honest. I always thought that Kerr was an Old Norse surname in Scotland which predated the Norman Conquest (although from France, they has Norse roots). Comes from Kyarr and Kier is also a variant - also appears as Carr. Scottish Gaelic 'cearr' which means 'wrong-handed' (or left-handed) as a surname origin is also in the mix. Yes, come people took on clan surnames to show allegiance, but just because people had the same surname does not mean there are links. In Kintyre, where my dad's lot are from, Brodie crops up as a surname. They are not connected at all to the Brodies of Moray. The name in Kintyre comes from Brolachan or O'Brolachan - whch also appears as Bradley.

[HarrysMum]

I went to a Scottish genealogy day ages ago. I don't know how true it is, but the fellow talking told us a lot of family names were given to workers as well, so the surname Gordon could have come from a blood related family member or a person who worked for the Gordon family.

The, there is my Kellas lot. They just appear neat my Gordon's and Grants, but apparently belong to the Farquarson clan. I'm sure that spelling is incorrect....lol