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What follows is a general summary of the results of the Dewees(e) Surname Project.  A more technical summary can be found at

Posted 10-2-2013/ 7-17-2014/ 8-18-2014 / 4-7-2015

mmary can be found at  Proj

To review how this project came about, my fourth cousin Curtis Dewees and I (Andrew Dewees) were independently attempting to confirm our lineages back to the Joseph and Phebe Dewees family of Grayson County Kentucky.   Upon discovering our common interest, we agreed that results of a Y-DNA test would be informative and might help answer this question.  If in fact we are both descended from Joseph Dewees, we should share copies of his Y chromosome.  Therefore, our two Y chromosomes are expected to be identical to each other, except for the occurrence of rare mutations over the six generations back to our common paternal ancestor, Joseph Dewees.  Our results from Y-DNA 37 test kits showed that we were an exact match at 35 of 37 Y-DNA sites.  This agrees well with theoretical predictions for fourth cousins as calculated by the experts. (Actually, we are fourth cousins, once removed.)

As will be discussed below, our Y-DNA patterns also are very similar to other Deweeses in this project.   Therefore, Curtis and I very likely are fourth cousins descended from Joseph Dewees, as our paper records suggest. The Y-DNA results support this statement, but cannot prove with certainty that Joseph Dewees was our fifth great grandfather.  In general, DNA test results can only support or reject hypotheses about genealogical relationships based on paper records, but cannot prove them with certainty.

Dewees(e) family historians have shown that virtually all U. S. Dewees(e) families trace their paternal lineages back to 17th Century Dutch immigrant Garrett Hendricks deWees through one of his three sons.  (A well-documented review of this early Dewees Family, written by Dewees(e) family archivist Dr. Jack Vaughn and Ted DeWeese, can be found at this site:

We determined that Y-DNA testing provides an excellent opportunity to analyze this unique family structure; therefore, we initiated the Dewees(e) Surname Project in 2010. 

Through Y-DNA testing we hope to identify and group the different Dewees(e) family lineages, thus confirming or not the paper records of family genealogists.  Additionally, where paper records are incomplete, we might be able to place a Dewees(e) family, or even a non-Dewees(e) family,  into its proper Dewees(e) family lineage based solely on  their Y-DNA pattern. 

For this discussion, please view the Project Y-DNA Results (colorized) in a new tab at

Currently, there are 13 participants in the Dewees(e) Surname Project, 12 of whom are grouped  into family lineages under the three sons of Garrett Hendricks Dewees- Cornelius, Lewis (Lambert) and William.  This grouping is based on genealogical records submitted by each participant, which can be viewed at  One participant (DeWease) is ungrouped.

Presented in the Y-DNA Results table are the DNA test results for each of the 13 participants.  The outcomes of the 37 STR marker sites are shown for each participant.  Each number in the table is the number of repeating DNA segments for a given Short Tandem Repeat (STR) marker site.  For example, all grouped participants in this project have 14 copies of the DNA segment for the first STR marker site in the table, DYS393.  The numbers in blue and pink represent STR marker sites where a mutation has occurred at some generation in a participant’s lineage leading back to the common paternal ancestor of Dewees(e) participants, Garrett H. Dewees.  Moving across the table beginning at marker site DYS389I, one can observe nine marker sites for which a mutation has occurred in the various Dewees(e) lineages.  At the remaining 28 sites, all grouped participants are identical in their STR values.  The conclusion here is that all 12 grouped participants carry nearly identical copies of their common male ancestor’s Y chromosome, except for variation among  these nine mutational events which are spread over the various family lineages. (A technical discussion of the Deduced Ancestral Dewees(e) Y chromosome can be found at

As expected, the three family groupings (Cornelius, Lewis, William) show some distinct differences from each other.  For example, for marker DYS460, two of three descendants of Lewis have a value of 10 whereas descendants of William all have a value of 11 at this site. Among descendants of Cornelius, five have a value of 11 and one has a value of 10 for this marker.  For another marker, DYS570, descendants of William have a value of 19 whereas descendants of Lewis and Cornelius have values of 20 or 21. And, for marker CDY-a, descendants of William have a value of 35 and all other participants have a value of 34 or 33.

This type of information will be useful in the future to help assign a Dewees(e) male who lacks definitive genealogical records to his appropriate group.  For example, see Mr. Miles in the Cornelius group.  His assignment to this group is discussed below.

Participants who are descendants of the same son of Garrett are generally more similar to each other in their STR values than they are to descendants of other sons of Garrett.  For example, #181213 (William) and #181226 (William) are known to be fourth cousins and they differ at only 2 of 37 sites.  Whereas #181226 (William) and #N89299 (Lewis) are eighth cousins and differ in 4 of 37 sites.  This pattern is expected because the more closely related two Dewees(e) men are, the fewer mutations are expected to occur in their lineages back to their common ancestor.

A Non-paternal event (NPE) in genetic genealogy is said to have occurred in the paternal ancestry of a male whose Y DNA pattern differs greatly from the patterns  normally present in males having his surname.   Thus, NPEs are of concern in single family surname projects such as the Dewees(e) Surname Project.  It has been reported that the NPE rate might approach 25% of participants in a given surname project (“Towards improvements in y-DNA Surname Project Administration” by James M. Irvine, Journal of Genetic Genealogy, 6(1), 2010).

There are various explanations of NPEs.  A son may carry a different surname than his biological father due to illegitimacy, both in-wedlock and out-of-wedlock.    For a variety of reasons a male child may be given his mother’s surname rather than his father’s.  An adopted child is usually given the surname of the adoptive family which is most likely different than that of the boy’s biological father. 

We have three instances of non-paternal events in the Dewees(e) Surname Project:
1. As is evident in the Y Results table, the Y DNA pattern of Mr. DeWease, listed in the table as ungrouped, differs greatly from the typical Dewees(e) pattern. His Y-DNA pattern, in fact, is a perfect 37-site match to three men in the FTDNA database all having the Wilson surname. Mr. DeWease had some reservations about the accuracy of his family records a few generations back in his family lineage.  Upon learning of his Y-DNA results, and after further study of family records, he finds that he likely is a descendant of Peter Wilson.

2. Mr. Miles is shown in the results table as a descendant of Cornelius Dewees. Mr. Miles was identified as having a Dewees(e) Y-DNA pattern following a search in the FTDNA database for Y-DNA matches to the Dewees(e) pattern.  Originally, Mr. Miles was a participant in the Miles surname Project, but his Y-DNA pattern differed greatly from patterns of other Miles men. He was initially placed in the Cornelius group of this project because his Y-DNA pattern differs at only two marker sites (DYS570 and CDYb) from the Modal pattern for this subgroup.  However, with the addition of participant #340505, Mr. Miles also differs at only two sites from the modal pattern in the Lewis group.  Because Mr. Miles differs at four sites from the Modal pattern in the William group, he likely is not a descendant of William.  Due to the small number of mutational events in these data, we are unable to say with certainty from which of the three sons Mr. Miles descends, but most likely it is Cornelius or Lewis.  This Miles family has joined our project and is currently reviewing historical records for a possible intersection of the Miles and Dewees(e) families.

3.  This case is not represented in the Y Results table.  A Mr. DeWeese tested his Y-DNA with another company and sent me the results of 30 Y-DNA sites which were tested in our project as well. His results were highly divergent from the typical Dewees(e) Y-DNA pattern.  Subsequently, he explained that his DeWeese family surname came from his DeWeese grandmother who gave her son (the test subject’s father) her maiden name- DeWeese. Because Mr. DeWeese’s unknown paternal grandfather was not a Deweese, his Y chromosome differs greatly from the typical Dewees(e) pattern.

Y-DNA studies of single-surname lineages using STR markers are very useful in confirming family genealogies and in detecting unexpected family relationships. The Y-DNA results of the Dewees(e) Surname Project are in agreement with the historical structure of the U. S. Dewees(e) family- virtually all members of this family trace their paternal lineages back to the three sons of immigrant Garrett Hendricks Dewees.  Based on their Y-DNA patterns, the descendants of the three sons of Garrett fall more or less into identifiable family groupings. Caveat: the validity of these groupings rests on the accuracy of family genealogies submitted by the participants.

Although the Y-DNA data presented here support the findings of Dewees(e) family historians, it does not rule out other family structures.  To increase confidence in our conclusions, larger sample sizes are needed, both in the number of participants and in the number of Y-DNA marker sites tested (more than 37).

As shown in the Y-DNA Results page, three Dewees(e) males are confirmed by SNP (Single Nucleotide Polymorphism*) testing to belong to the I-M223 haplogroup, and #181226 belongs to I-Z190 haplogroup. Their haplogroup designation is colored green. The haplogroup designations for the remaining  Deweeses are in red and “have been predicted by Family Tree DNA based on unambiguous results”, primarily from their STR patterns (haplotypes). The I-M223 haplogroup identifies a group of people all of whom share the M223 SNP, a rare mutation that occurred in their common male ancestor several thousand years ago. Males having a Y chromosome with this mutation were present in northern Europe after the last ice age and today are concentrated in the countries of Denmark, Germany and the Netherlands. This is in agreement with the origins of the Dewees(e) family in that family historians report the family founder Garrett Hendricks deWee immigrated from the Netherlands to New Amsterdam (now NYC) in about 1663.  Information about this haplogroup can be seen at
The project administrator (kit# 181226) has tested several additional SNPs and is shown as belonging to haplogroup I-Z190.  This is a subgroup of the I-M223 haplogroup whose members have tested positive for a more recently occurring SNP, Z190.  It is very likely that all Deweeses are in the I-Z190 subgroup as well.
* SNP- Mutations at the single nucleotide level, for example T changed to C, are rare, occurring at a rate of 1/million.  Once a SNP mutation occurs on the Y chromosome it persists in all male descendants in the resulting lineage.   This group of men, all carrying the same unique SNP on their Y chromosome, represent a subgroup of the human population known as a Y haplogroup.

 Andrew Dewees
Administrator, Dewees(e) Surname Project