As of July 2011, the primary host for the Y-DNA surname study is now Family Tree DNA.
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The English de Havilland family: We have proven that the de Havilland family of Guernsey (from whom Olivia de Havilland descended) and the Havilands of America (that can be traced back to the immigrant William Haviland, and a few other branches) are in fact the same family.
A grandson of Major Piers de Havilland (the last member of the family to own Havilland Hall on Guernsey) and 4th great grandson of Peter de Havilland (Bailiff of Guernsey in 1810; also an ancestor of actresses Olivia and Joan, and of airplane inventor Sir Geoffrey), has participated in our Y-DNA project. He matched 42 out of 43 markers with a majority of the Havilands in our study, despite that he is a 13th-15th cousin.
The MRCA (most recent common ancestor) between this de Havilland branch and the Haviland branch that emigrated to America is Thomas, Sieur de Haveilland himself, a Jurat of Guernsey in 1470 who is the earliest paternal ancestor from whom any Haviland can be traced. This means that we now know at least 42 of the Y-chromosome alleles that belonged to a man who lived in the late 1400's and from whom over 8000 known persons are descended!
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The Irish Havlin family: The Haviland/de Havilland Y-DNA Project has proved that the Irish Haviland / Havlin family is a genetically different family tree than the Haviland / de Havilland family from Guernsey and England. A Haviland participant of our study who descended from the Irish had at least 13-14 different alelles than the other Haviland or de Havilland subjects. So we have positively identified 3-4 distinct family trees bearing variations of the name Haviland which have no relationship to one another.
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The Germanic Haverland family: At least one Y-DNA project participant bearing the name Haverland has 25 different alelles than any Haviland or de Havilland subject, proving he is definitely not of the same family. However his genealogy is unknown. Adoption in his branch could also explain these differences. We need someone with a deep Haverland genealogical ancestry to participate in order to conclusively prove whether this family is related to the de Havilland stock originating in Guernsey.