Before the Norman Conquest (1066) English people did not have hereditary surnames. They were usually known just by a personal name. If they had a nickname as well, this was not passed on to their children. It was the Norman barons who introduced surnames into this country, and the fashion gradually spread to other families, but it was a long drawn out process. Most English people and Lowland Scots had hereditary surnames by 1400.
The circumstances in which these names were passed on to their descendants were complicated. Fashion played a part, as did the new practice of keeping written records such as manor court rolls, but the inheritance of a name undoubtedly had much to do with the inheritance of property, status or occupation. [4a.]

Names were derived from a variety of sources:

• Nicknames such as Fox, from the animal, or White, perhaps from the hair or complexion
• A person's job or trade. Names such as Cook, Turner or Wright.
• Place names - Green, Hill or Wood

The name "Sykes," which means "spring," "stream," or "boundary ditch", could have originated in several places where people lived close to one of these land features.

In 1999, Bryan Sykes, the Oxford geneticist and author, got usable DNA samples from 48 Sykes' in West Yorkshire, Lancashire and Cheshire counties in England. He talked about his conclusions in a 2000 article in The American Society of Human Genetics and a 2001 BBC radio special.
Bryan states:
"around half of fifty male Sykeses had exactly the same Y chromosome, evidence suggesting that they came from a common ancestor. The Y chromosome patterns among the other half resembled those of the general population, and this was taken to mean that they had been introduced to the Sykes family by adoption, by assuming the name or by illegitimacy - the three causes being linked together as 'non-paternity events'."

This points strongly to one original Mr Sykes, but there are experts who put forward other theories. There may, for example, have been several founders, with one line being much more prolific than all the others. These less prolific lines, who simply had fewer sons, would be indistinguishable from non-paternity events.

Even if these lines do exist, the fact remains that the majority of present-day Sykeses can trace their origins back to a family living in Slaithwaite, just outside Huddersfield, in the fifteenth century, or, Bryan Sykes contends, further back to 1280 when William del Sykes held land nine miles east in Flockton.

Results of tests of 48 Sykes:
Bryan tested 4 markers (DYS #'s 393, 390, 19, 391). Mutations only occur every 250-500 generations. The distance is the sum of the differences in allele values. A difference of 2 or more would be a very low probablity for two people who were related. See: DNA Genealogy

#    Distance 
21     exact
 3       1
 7       2
17       3 or more	

Articles:
1. Redmonds G (1992) Yorkshire surnames series. Vol 2. GR Books, Huddersfield UK
2. "Surnames and the Y Chromosome", Bryan Sykes and Catherine Irven, The American Society of Human Genetics: 66:1417-1419, 2000.
3. In the name of the father: surnames and genetics, Mark A. Jobling, Trends in Genetics Vol. 17 No. 6 June 2001
4. BBC Radio Special "Surnames, Genes and Genealogy, 2001
  a. Origins of surnames
  b. Program 1 "There's Only One Mr. Sykes"
5. Sykes and Single-Origin Surnames, George Redmonds, New England Ancestors, 2002
6. Geanealogy, Genes & Geography, lingua franca, Australian National Radio, 2003
7. With Regard to DNA, 2005, Jerry Sikes

Links:
The Sikes / Sykes DNA Project at Sikes/Sykes Families Assn.
Alvin Sikes Family DNA Results
Sykes/Sikes Family Project at FamilyTreeDNA
DNA Genealogy

Books:
"Trace Your Roots with DNA: Use Your DNA to Complete Your Family Tree:", Megan Smolenyak, Ann Turner
Adam's Curse, Bryan Sykes