The analysis of Y-DNA markers provides a new opportunity for genealogists to unravel their family history. This new tool is now producing results that can take some of the guesswork out of adding ancestors to our pedigree charts and connecting other lines that appear to be related but lack primary documentation to confirm these connections. With traditional research, our focus is heavily influenced by geography, family naming patterns, migration patterns, etc. This approach most often leads us to discover new ancestors but it can also lead us into wrong direction as well. Your particular oldest proven ancestor may have broken away from his family connections and traditions. Your oldest proven ancestor may not have named his children after his older generation of relatives and may have moved to new areas where no siblings or cousins lived. DNA assists genealogists in finding and verifying lines that are genetically related and warrant further traditional research.

Analysis of DNA markers allows us to identify which Casey lines look encouraging as potential relatives and reduces unproductive research on unrelated lines that ended up in the same county by chance. It can also determine relationships between previously unrelated lines due to shared mutations. The Casey surname is a clan based surname and has few original genetic origins (supports Casey family origin research of only six original septs of the Casey clan). With Y-DNA testing, it will be possible to determine which genealogical cluster (clan) that you belong to. With a lot of carefully selected submissions, common mutations will also assist us to determine which branch of each sept that you belong to.

DNA research provides its best fit by tracing your "all male" line of ancestors (Y-DNA) as basic biology limits our genealogical research for earlier ancestors to testing of all male lines. The female DNA does not enough known markers that pass from mother to daughter and mutate at rates that are useful to genealogists. The Y-DNA markers are by far the best fit for genealogical research and should be 90 % of all DNA tests purchased. These Y-STR markers mutate at reasonable rates that are useful to genealogists that pass from father to son for generations.

The deep ancestry of submissions can be verified by testing Y-SNP markers (deep clade testing). Many Y-DNA submissions have common Y-STR marker values and many genealogical clusters can overlap with other genealogical clusters. Y-SNP tests can assist in separating these genetic groupings that have common Y-STR values. Contrary to popular belief, having common Y-STR values (even at 37 or 67 markers) does not guarantee that you are closely related. However, if submissions have similar DNA but different deep ancestry (Y-SNP values), it is extremely unlikely that these submissions are closely related – even though their Y-STR markers imply a very close relationship. Y-SNP testing also provides a very easy first pass of grouping submissions that are possibly related.

The newest test available from Family Tree DNA is called Family Finder. This DNA test reveals all ancestries in one test as it does not use markers that are tied to either males or females. This test shows promise for those researchers that have a very contemporary brick wall due to an adoption or poor source documentation. It also shows promise to locate very closely related third and fourth cousins that have not been located by traditional research. This test is similar to an extended paternity test that but reaches back only four or five generations. This test is not applicable for extending your ancestry chart – unless you have less than five or six generations discovered via traditional research. For those that have seven or more generations already proven by traditional research, this test will probably not help break through any brick wall in that time frame.

Another test that is used is the female deep ancestry test, mtDNA. The mtDNA is only passed from mother to daughter over many generations. This could have been a good test but the markers mutate too slow for genealogists. mtDNA testing is very similar to Y-SNP testing as both only reveal deep ancestries. It does have very limited use for proving two women that may be the daughters of one of your ancestors. If you test descendants of the suspected sisters (all female descendants) and they do not share the same deep ancestry, it is extremely unlikely that they would be sisters. If tests show that both women have the same deep ancestry, it greatly increases the odds that they could be sisters – but this test only proves that they share a common deep ancestral connection that is 2,000 to 20,000 years ago. This is not in a genealogical significant time frame of 200 to 300 years ago. I do not recommend this test for genealogical purposes.

All females have X-STR markers similar to males having the Y-STR markers. This DNA is passed from mother to daughter through the generations in the same manner that Y-STR markers are passed from father to son. This could have been another test that could have been very useful to genealogists – but basic biology reveals that there are only a handful of these markers that pass from mother to daughter and mutate at rates that are useful to genealogists. The X-STR test is currently similar to the Family Finder DNA test is limited to showing relationships at only two or three generations. With the combination of current X-STR tests and mtDNA tests, there are no viable testing that works in connecting all female lines 200 to 300 years ago (where most of our pedigree charts end).

There are four major usages of Y-DNA testing to solve genealogical problems:

1) If you have been researching a family line that you believe is related to your line but can not find enough traditional proof to verify the connection, then Y-DNA testing can provide an quick and cost effective answer – Yes or No or Maybe. Testing well proven male descendants of each line could quickly answer this question and could eliminate a lot of unproductive research on a line that was found to be genetically unrelated. For very common surnames that have many genetic origins, this is a very new powerful tool. This is an extremely powerful new research tool that can produce very quick results. It is highly recommended that researchers sponsor the testing of lines that are good candidates for being related.

2) If you trying to add another generation to pedigree chart and have many possible candidates, Y-DNA testing can eliminate many lines that are not genetically related. Testing could reveal many new candidates that are worthy of additional research. Y-DNA is revealing many genealogical clusters of related individuals. By finding out which cluster that you belong, you gain solid source documentation on which lines are related and which lines can not be related. The success of this scenario depends on the maturity of the DNA Project and how common of the Y-DNA values that are found. For most DNA Projects, the majority of submissions belong to well established genealogical clusters but there are still many smaller clusters that have too few submissions to analyze. There also remains many groupings of submissions that are not that closely related but smaller groupings are elusive to determine.

3) If you suspect that several lines must be connected but just can not locate solid source documentation to prove how they are connected, Y-DNA can reveal connections via common mutations. This scenario is the real sweet spot for Y-DNA testing but requires a lot of submissions (multiple submissions per proven line) and a lot of marker values (67 Y-STR markers or 111 Y-STR markers). Unlike probate records that show how many individuals are related, Y-DNA testing slowly reveals one genetic branch of a cluster at a time. The most common DNA marker values of a cluster is called the Most Recent Common Ancestor (MRCA) haplotype and is an estimate of the DNA marker values of the oldest male ancestor of the genealogical cluster. Y-DNA testing is limited to living donors who are descendants and mutations can randomly occur anywhere between the donor and the common ancestor of the cluster. This requires multiple DNA tests for each well proven line to separate recent mutations from those closer to the oldest proven ancestor. Eventually, older mutations can be assigned to our male ancestors that are close to our oldest proven ancestor and will reveal branches within each cluster.

4) A new and exciting twist that is being uncovered with DNA testing is referred to as Non-Paternity Events (NPEs). This is where the surname fails to track genetics due to informal adoptions, out of wedlock births and outright name changes. This is a difficult scenario to analyze and there are a lot of misconceptions on this topic. Having common Y-STR DNA and different surnames does not normally imply a genetic connection as most suspect. However, this is a very powerful tool to assist in verifying connections where surnames change or are already known NPE events via traditional research. There are several weighting factors that increase the odds of a genealogical connection for different surnames: 1) sharing several rare DNA marker values (found by looking at tables that show how rare marker values are); 2) sharing common mutations within large group of DNA submissions that have similar DNA; 3) traditional geographical connections in the same time frame that would allow the NPE event to take place; 4) primary sources of traditional documentation that directly link the two surnames; 5) Secondary sources that support the connection such as unusual first names and middle names, common migration patterns and unsupported family lore that state connections between the two surnames.

Information obtained from the Casey DNA Project

Many who are interested in participating DNA Projects are not certain on what information will be uncovered by taking the plunge of testing DNA for genealogical research. The benefits of DNA testing vary widely between submissions based on how common the surname is, how many genetic origins the surname has, how many rare DNA marker values are uncovered and even how much traditional documentation exists for the lines being tested. Below is a list of the most significant discoveries to date and are representative of the results that most sponsors should expect:

1) The Casey surname has far fewer origins than most common surnames. With around 50 DNA submissions, only five genetic groupings have been determined to date. This supports traditional surname origin documentation that they were only six unrelated clan leaders that established septs of the Casey clan when our ancestors first started using surnames.

2) Four submissions have non-Irish deep ancestry (two different non-Irish haplogroups). The probable source of this variation is probably a non-paternity event in the last 200 to 400 years. These two unique haplogroups provide very unique Casey DNA fingerprints for these lines.

3) We have suspected that all Casey lines that originate from South Carolina were probably related. Of the sixteen Casey submissions with ties to South Carolina, fifteen were indeed closely related. However, the line of Elisha Casey, b. 1773, was found to be closer related to the Munster, Ireland cluster. Descendants of Elisha Casey should now concentrate on Munster, Ireland ties when looking for connections and should no longer research South Carolina lines where DNA evidence shows any connections would be very remote.

4) The South Carolina cluster appears to distantly related to the Munster, Ireland cluster (both clusters could share a common male Casey ancestor around 400 to 600 years ago). This has two major implications: a) the South Carolina cluster may have origins in southwestern Ireland vs. the family tradition of County Tyrone; b) the common genetic ancestor of both clusters combined probably lies somewhere between the two individual clusters. This greatly assists in determining which branches (mutations) occurred earlier and could influence connections in both clusters.

5) Common mutations have determined actual relationships between previously unrelated lines: a) The South Carolina cluster has two very early branches (about half in one branch and half in another branch). b) the Munster cluster has Dennis Casey, b. 1825 and Elisha Casey, b. 1773 with a common mutation that implies these two unrelated lines (via traditional research) must be more closely related than other submissions in this cluster; c) the Jesse E. Casey, b. 1797 and the Ambler Casey, b. 1790 share a common mutation unique in the South Carolina cluster (this supports undocumented sources that these two were brothers). There are several other branches and possible branches revealed to date.

6) The South Carolina cluster has many rare and very rare DNA marker values. These marker values are so unique that any individual (regardless of surname) with these rare marker values is probably genetically related to this Casey cluster. With only 67 markers tested, this is very uncommon to have such a unique DNA fingerprint.

7) There is a submission with the surname of Hanvey that is believed to be genetically related to the Casey South Carolina cluster. This Hanvey submission did not match other proven Hanvey submissions as expected and is now believed to be an adoption or out of wedlock son of a Casey male. Traditional genealogical documentation ties this Hanvey line to Casey families in South Carolina. Also, the Hanvey submission share a very unique DNA fingerprint that non-Casey lines are very unlikely to have.

8) DNA evidence discounts suspected connections due to geographical ties: a) Henson Casey was believed to a missing son of Ambler Casey; however, two submissions of Henson Casey do not have the common DNA fingerprint shared by Ambler Casey and Jesse E. Casey. b) John Casey, b. 1782 was believed to be closely related Ambler Casey, b. 1790 and Abner Casey, b. 1786. However, John Casey belongs to a different earlier branch of this cluster and can not be as closely related as geographical ties imply.

9) The Munster cluster currently ties five previously unrelated lines together genetically. Four of five in this cluster have ties to southwestern Ireland. However, one line has only early South Carolina ties – Elisha Casey, b. 1773. These lines now have genetic evidence that indicates that these lines are closely related and warrant further traditional research to connect these lines.

10) Not all Casey lines from the Munster area of Ireland are closely related. DNA is showing that 70 % belong to the Munster cluster but 30 % belong the R1b1a2 grouping. DNA evidence implies at least two separate Casey clusters originate from the Munster area of Ireland (southwestern Ireland). This divides Casey lines found in the Munster area into two different septs that are not related genetically.

11) Two submissions of John Casey, b. 1782 clearly establish a unique mutation associated with this line. If any new line submits DNA and has this unique DNA fingerprint, this new line would have a very close relationship to the line of John Casey, b. 1782. This mutation provides a DNA fingerprint (branch in the cluster) for this line. The lines of Ambler Casey and Jesse E. Casey also share a unique mutation that produce another branch within the South Carolina cluster. This mutation involves a very fast moving marker and additional testing is required to strengthen this branch.

12) There are many submissions that have unique mutations and currently do not match any other submissions in their cluster. As second submissions in each of these lines are tested, some of these new submissions will have the same mutations and will create new firmer branches in their cluster. These lines only have one submission for the oldest proven ancestor – this is insufficient testing to determine if the mutation is significant (close to the oldest proven ancestor) or not genealogically significant (close to the donor where connections are already well proven).

13) All of the submissions of the South Carolina cluster are very closely related and should be able determine connections in the 1700s. Given enough Y-STR markers being tested and enough submissions for this cluster, DNA could one day prove how many of these unrelated lines are connected. FTDNA has recently unveiled their 111 Y-STR marker test which will greatly benefit this cluster in establishing new connections. Since only 25 % of the known lines in this cluster have been tested to date, expanded coverage of these lines will reveal even more connections.

14) The Hanvey NPE submission exactly matches the DNA fingerprint of the Abner Casey, b. 1786. The Hanvey has known genealogical connections to Casey's in South Carolina (believed to be around 1830 after most Casey families left this area). Not only is this Hanvey line related to these 1830 Casey families but the Abner Casey, b. 1786 are also very closely related to the same 1830 Casey lines as well. This provides research direction for the Abner Casey line.

15) As with traditional research, you sometimes get very low odds scenarios. With traditional research, sometimes unralted men with the same name and age appear in this same area. This can lead to a lot of confusion in traditional research. These same low odds scenarios also appear with DNA submissions as well. The Henson Casey line has two submissions where the only explanation is that there must be a backwards mutation to the original DNA value. The South Carolina cluster has two very early branches where half of the submissions belong each of the two early branches. However, the two submissions of Henson Casey line show both values of this early branch. Another submission from a third son is required to determine which branch that Henson Casey belongs to. The only logical conclusion is that one of these Henson Casey submissions must have mutated back to the original DNA value.