Above, MacMillan Ancient Weathered tartan. See more about Clan MacMillan tartan.
Below some links to more general information on the subject of DNA:
Wikipedia's definition of Single-nucleotide polymorphism
A technological development that promises to have profound consequences for the future of clan genealogy in the 21st century is the study of DNA. In theory every man passes to his son an exact duplicate of his own Y-Chromosone DNA, allowing us to say that every man alive who possesses an exact match of another man’s Y-Chromosone DNA must be descended from the same male ancestor; so, again in theory, every man called M’millan should have the same Y-Chromosone DNA.
In practice it’s rare for Y-Chromosone DNA to descend entirely unaltered for many generations, and tiny changes ("mutations") take place fairly regularly. DNA genealogists use these changes to track branches off a family line, and claim that it’s possible to say roughly when a branch came off that line using the nature and number of these mutations.
Since clans never have consisted just of direct male-line descendants of its namefather - especially the most powerful clans who conquer the lands of other clans and absorb their members into their own kindred (by marriage and/or or name-change) - we know that any clan Y-DNA project is going to show many different results. That is especially so in the case of a particularly old clan like the MacMillans, and its DNA Project (started in 2004 by Adhaniá McMullen Olson, and administered after her death by Gary McMillian and David W. McMillan) shows a vast range of results.
The Clan MacMillan DNA Project is recognized by Chief George MacMillan of MacMillan and Knap.
The Clan MacMillan DNA Project, hosted at Family Tree DNA (FTDNA), numbered 389 participants at the time of writing (January 2016). The Y-DNA test results have been organized into subgroups representing men who share the same haplogroup. FTDNA now identifies an individual’s haplogroup by the terminal SNP (Single Nucleotide Polymorphism). A SNP is a variation at a single position in a DNA sequence among individuals. The International Society of Genetic Genealogy (ISOGG) and others are developing a comprehensive Haplogroup Tree that defines the many branches of the human Y-Chromosome. The tree now has thousands of branches, each defined by a sequence of SNPs that have occurred over time. As more and more people have their Y-Chromosome sequenced, researchers are able to construct a more complete tree. Terminal SNPs are now being identified that occurred only a few hundred years before present, in the genealogical timeframe.
Chief George is in the haplogroup currently defined by the terminal SNP labeled FGC11672. There are currently over 65 members in this haplogroup. The next largest haplogroup is defined by the SNP labeled Z17620, and this haplogroup includes almost 40 members. There are several other haplogroups with 10 to 20 members. The largest haplogroup is defined by the SNP M269, however, this is the terminal SNP provided by FTDNA when they are unable to predict a more definitive terminal SNP and further testing is required to identify the terminal SNP.
For project participants that share the same SNP, Short Tandem Repeat (STR) markers can be used to compute the Time to Most Common Ancestor (TMRCA). STRs mutate at a faster rate than SNPs and the STR markers that differ between two men can be used to estimate the TMRCA. The TMRCA is actually a probably distribution that describes the likelihood that two individuals share a common ancestor within a given number of generations.
FTDNA offers STR tests for 25, 37, 67 or 111 markers. For SNP testing, FTDNA offers the BIG Y test, SNP packs, and individual SNP tests. For autosomal and X chromosome testing, FTDNA offers the FamilyFinder test. The FamilyFinder test can be used to identify matches between cousins that share DNA on the 22 autosomes and the X-Chromosome.
Chief George is kit number 35,953 and he has taken the BIG Y test, the 111-marker STR test, and the FamilyFinder autosomal DNA test. His testing was accomplished through generous donations from clan members.
For the DNA Project to become really significant it needs many more participants, particularly those with already proven paternal lines within or back to Scotland, with which others can compare their results. Financial support may be available to test individuals with known deep ancestral roots in Scotland.
Connections with other Scottish clans reflected in DNA studies.
In the meantime, it’s also interesting to compare the results of the MacMillan project with those of other clans claimed to have a shared descent with the MacMillans. The MacGregors in particular have had a DNA project going for some time that has thrown up one or two results showing possible connections with MacMillans and Macraes. These may be particularly significant in the light of the descent given the MacGregors in MS1467 (which has them also coming from the MacMillan’s progenitor, Cormac mac Airbertaich), and the legend in Lorn about Macrath, namefather of the Macraes, having belonged to the kindred of the MacCouls (MacDhughaills) of Craignish, who were probably named for Dugal the grandson of the Clan MacMillan namefather, Gilchrist "Maolan" mac Cormac.
For further information about the Clan MacMillan DNA Project, contact Gary or David, or go to the Project website. Another page of the website has Y-Chromosome DNA (Y-DNA) STR results for the project.