The use of DNA testing for genealogical purposes is known as genetic genealogy. Genetic genealogy is not an end in itself, but rather complements traditional genealogical research. DNA results of two individuals can be compared to determine if they are related. If the traditional
paper trail research results indicate two individuals are related, then DNA testing is a useful tool for verifying they share a common ancestor. Conversely, if two people are believed to be related, but there is no documented evidence to support that conclusion, genetic genealogy can be used to support (or refute) the conclusion.
The McCorkle Surname Project, as with all surname projects, tests DNA from the Y chromosome of its participants, which means all participants must be male. This limitation is due to two basic facts: first, only males have a Y chromosome, and second, in most societies, children take the surname of their father (not their mother). In other words, when a man has a son, the son inherits both the surname and the Y chromosome of the father. Therefore, if two males have matching DNA results, and they have the same surname, then they share a common ancestor. Given that surnames have only been commonly used in Western societies for the past 500-1000 years, one may conclude that these two men have a common ancestor born at most 1000 years ago (a period of time is known as the genealogical time frame).
Occasionally, two people have matching DNA results, but they don't share a surname. In these cases, any of several explanations apply. It may be that the most recent common ancestor (or MRCA) was born prior to the genealogical time frame. Or, there could have been a non-parental event (NPE) such as an adoption, out-of-wedlock birth, a change of surnames, etc.
More commonly, two people will have the same surname, but not match genetically. If traditional research led to a conclusion that the two people are related, then genetic genealogy would prove the conclusion to be incorrect. Regardless, this project seeks to explore the ancestry of all McCorkle’s worldwide; therefore, all males with surname McCorkle, or with a documented McCorkle ancestor along their patrilinneal (all-male) ancestral line, are welcome to join.