Hi ray In contrast to your other message, Frith probably doesn't always indicate "viking blood", although in the case of Friths from around West Lancashire, or Firths from Sheffield (as in another post) or Orkney, it might turn out so.Have you been tested? What have you found?
I am interested in showing which families are related to each other, and where they came from. This question can sometimes be answered by DNA testing. For this, the Y chromosome (which only males have, passed down from the father, like surnames, conveniently enough) is currently being tested.
(Mitochondrial DNA or mtDNA, which both males & females have but is only passed down from the mother, can be studied also. mtDNA typically doesn't give much information on the relatively recent past, such as Vikings -the type of DNA studied in the Y-chromosome mutates faster than most other DNA, so is useful for tracing these more recent events.)
If you are a British male and have your DNA tested, and are found to be in haplogroup R1a, Q, or certain subgroups of haplogroup I1a, you can be fairly sure you were descended from a Viking (or perhaps a Norman.There is probably a way to tell the difference; I'm still learning). Other subgroups of I1a can be traced to Anglo-Saxons. The vast majority of men in the British Isles are from haplogroup R1b; most of these are likely to be Celtish/Pictish. None of this is absolute, there is always some uncertainty, since for example there are many R1b's among Norwegians & there must have been R1b Vikings as well.
The most recent scientific paper from the group at Nottingham University uses the fact that older families of Wirral and W. Lancashire have an unusually high proportion of R1a males, to show that the area must have been settled by Vikings expelled from Ireland in AD 902. see http://mbe.oxfordjournals.org/cgi/reprint/25/2/301.pdfhttp://mbe.oxfordjournals.org/cgi/reprint/25/2/301.pdf and http://www.nottingham.ac.uk/-sczsteve/survey.htmhttp://www.nottingham.ac.uk/-sczsteve/survey.htm Look at the maps with mostly purple "pies" on them. The yellow "pie slices" show the proportion of R1a in the population.The purple shows the proportion of R1b.
This is a rapidly changing field, more is being pieced together as DNA testing becomes cheaper. Y chromosome haplogroups are in a sense like tribes, and trace back to paleolithic times, before the ice ages. However, because Y-DNA can mutate over just a few generations, it is useful for showing whether two families with the same or similar surnames are related, even when this can't be documented by birth records. If two families have identical mutations then they are likely to be related. This can be tested now.
I am trying to do this, to show which familes are related to which. I have started a DNA project for Firth, Frith, Thrift, and related surnames. (The results can also be used to show viking ancestry etc.) The test can be done for free! (Of course better results are available from the testing companies if more money is spent.) Please look into this at http://www.familytreedna.com/public/Thrift-Frith-Firth/http://www.familytreedna.com/public/Thrift-Frith-Firth/. Or contact me directly.