Recently we published several Blog posts in Updates on DNA, and as the blog scrolls, to keep the content easily accessible we have consolidated them into one page on DNA information with some specifics that may be of interest to MacLeods.

Scientific Background

Deoxyribonucleic acid (DNA) is really just four chemicals: Thymine (abbreviated as T) pairs with Adenine (A), and Guanine (G) pairs with Cytosine (C).  DNA was discovered in 1953, but the first Human genome (3200 Million base “Letter” pairs, all the Human DNA in one person) was not sequenced (reading each letter) until 2003, and findings first published in 2007. Only about 2% of DNA encodes proteins, and 99.5% of any two random people’s genomes will be identical.

Aside from sequencing a genome (which was on pace to cost $100,000,000 each in 2001, dropped to $10,000,000 in 2007, and was now just above $1000 in 2015, projected to go below in the next few years), there are some inexpensive (by comparison- costs run $39-$750) consumer level tests one can take by mail order. 3 “Kinds” of DNA can be tested from home easily, in 2 Main “Types” of tests.

Y-DNA, Passed on the male line only

Y-DNA tests can be taken only by genetic males, and one type (usually done first) looks at Short Tandem Repeater (STR)- phrases of repeated alleles, for example ‘GATAGATAGATAGATA’ would be “4” at a particular location, called a “DYS” (DNA Y-chromosome Segment). DYS are usually designated with a unique number. Used in Y-DNA to statistically decide what SNP (explained below) to test for, and based on known drift rates, can mathematically estimate number of generations between two men. Changes in STRs is basically a “copy error” that drops off or adds a set of repeats. An average rate is 1 per 500 generations, and there are up to 111 locations or “Markers” that are looked at for current Y-DNA tests.

One section of a Y-DNA STR test result may look like this

One section of a Y-DNA STR test result may look like this- Without comparing to others, it doesn’t really tell you much. But in a spreadsheet with other people’s results, you can count the “Genetic Distance” to estimate how many generations since a common male-line ancestor

Another type of Y-DNA test looks for specific Single Nucleotide Polymorphisms (SNP)–When a base pair of chemicals at any given location randomly changes from one chemical to another (like C becomes T, G becomes A, etc).


This mutation is inherited by all descendants of the individual in which the SNP occurred. SNPs occur very rarely, so they can be used to split a “Haplogroup” (think tree trunk) into “Subclades” (think branches). Because you have to know the specific location and mutation to test for, you usually need to have done an STR test to find someone within a comparable amount of generations that has already tested SNPs to know where to start from. Some testing companies like FamilyTreeDNA will also make a prediction of a Haplogroup, and even some subclades for you if you are very “close” to someone with a confirmed SNP. Other than copy error insertion and deletions, and SNPs, Y-DNA is passed unchanged from father to son, since there were humans. By tracking the branches in the tree through the errors, we have learned a lot about male-line-specifics.

(New 2018): Here’s an example from FTDNA’s new Big-Y 500 SNP discovery test, showing the SNP L21 (A common Gaelic SNP) as a change from a Reference value “C” to a “G”, at Hg38 position 13542548.

L21 Y500 copyOlder tests from some companies may give you just a + or – Result for SNP test taken, like the result below.

SNPs Taken

Or they may present it in a tree as is known today (testing company trees lag behind the ISOGG tree and Hobbyist trees by quite a bit however), with options they offer for testing further

testipFor an excellent video that explains much more about how to use Y-DNA in trying to close the top-down anthropology approach with the bottom-up genealogy approach, see Maurice Gleeson’s video from 2015’s Genetic Genealogy Ireland conference

Also see John Cleary from University of Edinburgh’s lecture on Y-STR use and tests like FTDNA’s Big-Y
A second kind of DNA test looks at Autosomal DNA (atDNA), which is the 22 non-sex chromosomes that are recombined between mother and father when passed on to children. Test can show cousinship within 6-7 generations, and also distant ancestral admixtures. Genealogy DNA atDNA test are for SNPs (Family Tree’s  atDNA test looks for ~700,000 SNPs). The forensic DNA you hear about is also atDNA, but it looks at STRs, so it is totally different. X-DNA (genetic males have one X chromosome, females two) is often tested at same time as atDNA, but the data not used in most genealogy matching systems.

The third kind looks at DNA that is only inherited from the mother– Mitochondrial DNA (mtDNA). mtDNA is non-nuclear DNA, so it is not part of your chromosomes or “genes” and is passed “unchanged” (except for SNP mutations that occur) from mother to all children, but can only be passed on by a mother, so a mtDNA shows the distant female-line descent. Genealogy mtDNA tests are for SNPs. mtDNA SNPs are not very numerous, so the branches are quite infrequent. Perfect matches may still not have had a common female-line ancestor for 500 or 1000 years.


Y-DNA Branches and mtDNA branches in a timeline

 Y-DNA, Male-line descent

Y-DNA data has been around a while now, and growing exponentially as more people test. Current test companies have many more British Isles and European American samples than any other single group, but the diversity is growing as more people test.

Clan MacLeod is a very diverse group as our DNA project has shown, but there are 3 Main Y-DNA Haplogroups of interest. This is not at all to say anyone with a different Haplogroup doesn’t belong – Just that the biggest 3 groups so far in the clan project are R1b, R1a, and I1; the Next Generation Sequence tests like FTDNA “BIG-Y” have started to leap the gap between ancient populations and historic time-frames, now it is almost within grasp, given enough testers, to actually assign terminal SNPs to certain clans and lineages! The heavy lifting is the NGS testers and Researchers like Alex Williamson, who has one of the most cutting edge trees for Scots DNA/R-P312 research online at: ytree.net

  • R1b (Most of Western Europe is R1b, there are many sub-groups)

In the 3rd Millenium BCE, there was a mass migration from a R1b-carrying (Pre-Yamnaya) Culture on the North Pontic Steppe into Europe, and the following Neolithic/Copper Age Bell Beaker Culture in Europe was confirmed as R1b, with P312 present! This means in summary, the Hebrides residents were (primarily): Summary: Hunter-Gatherer 12,000BC-3500BC, Grooved Wares 3500BC-2000BC, Bell Beaker->Celts->Gaels 2000BC-800BC, Viking Gall-Gael 800-1200AD, and the Scots from 1200 on

A paper known as the “Beaker behemoth” has established that the Beaker people were the direct fore-runners of the Celts


Bell Beaker finds

Bell Beaker Person.JPG

Artistic render of a Mittle-Saale Beaker Culture person by Karol Schauer

    • R1b-L165: Leod (Belongs to the DF27, marker of maritime expansion of the Beaker peoples into an Ibero-Atlantic Celt branch–boat-mobile coastal people found from Spain to Denmark–He plausibly could have been either have been Viking or Hebridean native by Y-DNA, but was certainly Gall-Gael in culture! It is now looking like the Nordic BY456 samples has a MRCA of 800AD so more likely Hebridean slaves taken back to Scandinavia rather than indigenous Scandinavians. With additional Hebridean branches of L165 having a MRCA of 2400BC, Leod’s paternal ancestors look more Hebridean than proto-Norse)
      • Potential Leod SNP path below:
        • R-M207 (ex: Mal’ta boy DNA, 22,000BC)
        • >R1-M173/M306 (Proto-Indo-European Western Asia origin, 22,000BC, ex: Afontova-Gora-2, 15,000BC)
        • > R1b-M343 (16,500BC, Paleolithic)
        • >L278>P297 (Samara/Orenburg-Yamnaya culture)
        • >M269 (4500BC, Bronze Age, Yamnaya/Kurgan culture- Pontic Steppe & Between Black and Caspian Seas– later that area will be called Cimmeria 1300-600BC, Scythia 1100-200AD (See the Arbroath Declaration for significance of that to Scotland), and Sarmatia 500BC-400AD)
        • >L11>P312/S116 (2900BC Formation, Time to Most Recent Common Ancestor (TMRCA) 2500BC, Middle Bronze Age migration to Europe–Bell Beaker Culture; Proto-Italo-Celto-Germanic; Quedlinburg DNA sample)
        • > ZZ11
        • > DF27/S250 (Ibero-Atlantic Celt)
        • > Z195/S355
        • > Z198
        • > L165/S68 (Most recent common ancestor of all L165 lived ~2400BC)
        • > FGC29987/BY456
        • > BY3224
        • > BY3253
        • > BY3210 (This SNP has only been found in MacLeods to date per ytree.net, and there is a further 2 branches:
          • BY13703 Branch with 2 MacLeod testers, possible association with Harris
          • BY19718 – Found in a descendant of Donald MacLeod or Galtrigal, the “Faithful Palinurus” that assisted Bonnie Prince Charlie’s escape from Scotland
          • Quedlinburg

            One of the Quedlinburg Men

  • R1b-L21: Significant percentage of non-chief’s lines of MacLeod and MacDonald, Is the dominant Y-DNA line of much of Scotland and Ireland, and is represented slightly less heavily in Iceland and Norway; Currently associated with Gaelic origins, and many down-stream SNPs are known; An ancient DNA sample from Hinxton-4, a 2000 year old Briton, tested as R1b-DF25, a subclade of L21
    • New Info! (2016):(picking up after P312 above)> L21 (2500BC; North Atlantic Celt, Ancient DNA found in Rathlin-3 sample)>DF13 (2500BC formation, 2300BC TMRCA, found in Rathlin-2)
    • Under DF-13, there are Several SNP trees that have been mapped to historical groups:
      • DF21>S5488>S7200>L720Clan Chattan (Documented as having signed a bond of Manrent with the Chief of MacLeod on 15 Jan 1588AD)
      • DF21 (2300BC formation, 2100BC TMCRA ex: Rathlin-1)> S5488 (2100BC formation, 1700BC TMCRA) >Z16294 (1700BC formation, 200BC my own personal TMCRA with the Ely O’Carroll Irish Kindred)
      • DF21>FGC3213>ZZ1>S3058/FGC3188 –“Little Scots Cluster” postulated as the SNP marker for the Celtic Maetae tribe (located near what is now Stirlingshire)
      • Z39589>DF41>S775>L746–“Royal Stewart” descendants of Sir John Stewart of Bonkyll who died at the Battle of Falkirk on 22 July 1298
      • Z39589>L1335 (Pictish/Scottish Cluster) >FGC17595/Z17612>FGC17611/Y5080–descendants of Christopher MacRae, chief of the MacRaes of Kintail in 1511AD, Constable of Eilean Donan Castle)
      • Z39589>L1335 (Pictish/Scottish Cluster) >FGC3221>FGC3263McClure (MacLeod Sept)

Tribes of Scotland 150AD

  • R1b-U106: (Proto-Germanic, est 2500BC; In our context, potentially Danish Viking)
  • R1a (Most of Eastern Europe is R1a, with some wide outliers)
  • R-M207 (ex: Mal’ta boy 22,000BC)
  • >R1-M173/M306 (Proto-Indo-European Western Asia origin, 22,000BC ex: Afontova-Gora-2, 15,000BC)
  • >R1a-M512/M17/L168>M459 (formed 16,000BC, TMCRA 2,400BC)
  • >M198>M417 (formed 6500BC, TMCRA 3500BC ex: Corded Wares, BattleAxe Culture 2900-2300BC)
  • >Z645>Z283>Z282 (TMCRA 3000BC)
  • >Y2395 (TMCRA 2500BC)
  • >Z284>S4458 (TMCRA 2000BC)
  • >S5301 (TMCRA 1300BC)
  • >S5153>L448 (TMRCA 1000BC)
  • >CTS4179>YP276>YP275>YP280>YP330 (TMRCA 150AD)
  • >YP327 (TMCRA 1150AD)
  • >FGC11892/YP326–multiple branches all descended from Somerled
  • (New 2018): John the Good, Lord of the Isles (1336–1386), chief of Clan Donald – CLD 56/57, clan branches below:

    • Keppoch – CLD28, FGC11911
    • Sleat – CLD18/49
    • Glengarry – YP6398
    • Clanranald – CLD50
  • I1-M253 (pre-dates Indo-European incursion into Europe)
    • I1: First inhabitants of the Hebrides, Northern Europe (Especially North Highlands, Norway, Sweden, Denmark)
    • I1-M253>DF29>CTS6364>L22>P109: A Viking Y-DNA marker

Looking at the Clan MacLeod DNA project, of 229 participants 78% were R1b, 11% R1a, 9% I1, 2% Other. 136 of the R1b were not SNP tested, 32 were R1b-L165, and 11 were R1b-L21. About 14% of the participants were potential direct male line descendants of Leod (R1b-L165 Leod Modal)

An interesting comparison is the Clan MacDonald DNA project where 1225 participants were 70% R1b (519 not SNP tested, 337 R1b-L21, and 19 R1b-L165). 20% were R1a; 14% of the participants were potential direct male line descendants of Somerled (R1a-L176 Somerled Modal) and 8% I1, 2% other

In the Isles of the Hebrides DNA Project, 70% were R1b 15% R1a, 15% I (10% I2, 5% I1

There is a striking similarity in percentages: In both cases, 3/4 of the clan appear to have Gaelic male-line ancestors, with approximately 14% having potential male-line descent from a clan founder of non-Gaelic origin, and just under a tenth of pre-Gael indigenous male lines present. For more details on how I arrived at this conclusion, going much further back in time is required.

A heat map of modern atDNA admixture compared to atDNA of an 24,000 year old ANE Central Siberian mammoth hunter (sample known as MA-1), who was Y-DNA haplogroup R and mtDNA haplogroup U

In prehistoric Europe, there were though to be three populations, Northwestern Hunter-Gatherers (WHG), Ancient North Eurasians (ANE), and Early European Farmers (EEF).

A heat map of modern atDNA admixture compared to atDNA of an 8000 year old WHG person found in a Cave in Loschbour, Luxemburg. He had genetic markers for dark skin and blue eyes. He was Y-DNA I2-L460 and mtDNA haplogroup U5. He is loaded on GEDmatch.com as kit# F999918

One theory holds that the WHG group had Y-DNA of the I1 and I2 haplogroup, and the EEF had the Y-DNA G2 haplogroup.


A heat map of modern atDNA admixture compared to atDNA of an 7500 year old EEF person found in a Linearbandkeramik (LBK) culture grave in Stuttgart, Germany- she is in GEDMatch.com as kit# F999916

Much is still being learned, but recently some academic papers have suggested that expansion of horse and chariot riders from the Steppes, North of present Ukraine brought proto-Indo Europeans of Y-DNA R1b and R1a into Europe.

Additional groups of R1a folks went East into China, where the Tocharian Mummies have tested R1a, and others became Scythians, while still others moved into Eastern Europe and a small minority heading further north into Scandinavia.

World modern distribution of R1b Y-DNA

World modern distribution of R1b Y-DNA

Other R1b groups headed to the middle East, where Hittites and Trojans are thought to have been R1b, yet other R1b headed to Africa, with R1b-V88 found commonly in Cameroon, the Housa tribe of Sudan, and the Herero tribe of Niger-Congo area of West Africa.r1btree

The R1b that went to Europe, (R1b-M269) split into two main trunks about 5000 years ago, R1b-U106 which has some association with some Germanic tribes, and R1b-P312 which is thought to be proto-Celtic.



R1b-P312 further divided into DF27, which is concentrated in the Iberian Peninsula, U152 (also called S28, discovered around 2005) is thought to be Italo-Gaulish and may have been the Hallstat and La Tene Celts that interacted with the earliest Romans, and L21 (also called S145), which is centered on the British and Irish Isles.

Picture4A subgroup of DF27, only identified only in the last few years is L165. The larger group R1b-DF27, is thought to have had a maritime expansion north from Iberia.
R1b-L165, Also known as S68 by it’s first discoverer Jim Wilson of EthnoAncestry in 2007, was found in parallel by FTDNA in 2010 before it was published.
It is about 3,500 years old, and in a Scots context is tightly coupled to the Hebrides. It is the probable haplogroup of Leod, and another cluster of L165 was the progenitors of MacNeil of Barra, Lindsay of Jura, Buie of Jura, some families in the Uists, and more being discovered monthly (see the project at: http://www.familytreedna.com/public/r-l165project/)

R1b-L21, The Haplogroup that best approximates North Atlantic Celt is defined by the SNP where the “C” at rs11799226 changed to a “G” in a man about 4,000 years ago. Many further SNP subdivisions have recently been discovered, some with geographic localization.


David Vance, participant in the L21 Project has charted all the new L21 sub-clades:


Perhaps due to the Scots and Irish cultural interest in genealogy, there has been an explosion of new subdivisions discovered in L21. The map below shows the population of modern males carrying L21 in Europe today.

Picture6This heavy sampling of Scots and Irish Y-DNA has made some SNPs start coming closer in time to becoming regionally identifiable, and in some cases Clan and surname associated in confluence with STR comparisons.

British Celt Tribe maps

Roman Names for the Celtic Tribes of the Isles- Most will be R1b-L21 dominant in Y-DNA

R1a  was thought to be dominant haplogroup among the northern and eastern Proto-Indo-European language speakers, which evolved into the Indo-Iranian, Thracian, Baltic and Slavic branches.

R1 Proto-Indo-European expansion is linked to an early adoption of bronze weapons, the domestication of the horse in the Eurasian steppes and the invention of the chariot. The first expansion of R1a into Europe probably occurred with the Corded Ware Culture, sometimes called the battle-axe people because of the corded-impressed pottery and polished battle axes found at sites associated with the Corded Ware culture. Testing bone from archaeological digs confirmed R1a1a in samples from: Corded Ware culture in Germany (2600 BCE), from Tocharian mummies (2000 BCE) in Northwest China, Andronovo culture (1600 BC) in southern Russia and southern Siberia, and finally various Iron-age sites from Russia, Siberia, Mongolia and Central Asia.

Picture7R1a1 is defined by SNP M17. In a UK or Scots context, the R1a-M17 found is usually the sub-group R1a-L176.1, associated with Norwegian Vikings (30% of modern Norway) and the Gall-Ghàidheil, particularly in it’s appearance in the Chiefs of MacDonald and their claimed descent from Somerled (See confirmed SNPs for the Lords of the Isles earlier). However, Many Gall-Ghàidheil descendants are also of R1b haplogroup, often L165 and L21 subclades, and R1b still comprises 28% of the Y-DNA lines of modern Norway.


I1 is the Y-DNA hapolgroup associated with the Mesolithic (Stone Age) to early Chacolithic (Copper Age) dominant inhabitants of Europe. Some archeological cultures that have been postulated to belong to haplogroup I1: Linear Pottery Culture (LBK) (5600-4240 BCE), Ertebølle culture (EBK) (5300-3950 BCE), Funnelbeaker culture (4000-2700 BCE) and Pitted Ware culture (3200-2300 BCE). Grooved Ware peoples, inhabitants of Skara Brae ~3100-2500BCE and builders of the Neolithic Megalith stone circles of Lewis (Callanish 2900-1000BCE) and Orkney (Stones of Stenness 3100BCE, Ring of Broadgar 2500-2000BCE, Ness of Broadgar 3500-2000 BCE , Maeshowe 2800BCE, etc)

I1 makes up 35% of the Y-DNA lines of modern Norway, and a majority of Fenno-Scandian Vikings. I1 is found in higher concentration on Lewis than Skye. Some subgroup SNPs such as I1-M253, P109, L1301, L1302, M307 are though to be Viking markers, but could just as easily be the aboriginal people of the Hebrides.

Picture10One last Y-DNA haplogroup not showing up in the ACMS project that is interesting to note, especially for North Americans: Y-DNA Haplogroup Q, the Y-DNA signature of many Native Americans. Since some missionaries in Canada used McLeod as an English cognate of the indigenous Cree language name Mahkiyoc, some Canadian people of Cree heritage have the surname McLeod, and presumably would test Y-DNA Haplogroup Q.

Autosomal DNA, Recombinant between parents

Autosomal DNA (atDNA) is recombined randomly between atDNA of both parents. The unit of measurement of shared segments is the CentiMorgan (cM): “It is defined as the distance between chromosome positions (also termed, loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01”. Just think of it as the amount of shared DNA, either in a single block (a “segment”) or all segments added together.

Segments below 5cM might be identical by state (IBS), not identical by descent (IBD). Identical twins have a total of 6722.2cM match, Parents a 3400cM match; Siblings average 2640cM match; Grandparents, Aunts, Uncles, ½ siblings- 1700cM; Great Grand Parents, 1st Cousins, Great Uncles- 850cM; 1st Cousins once removed- 425cM; 2nd Cousins, 1st Cousins 2x Removed- 212.5cM; 3rd Cousins, 2nd Cousins 2x Removed- 53.13cM; 5th Cousins- 3.32cM; 8th Cousins- .05cM


Percent of shared atDNA with different relatives

atDNA Products include FTDNA ‘s “FamilyFinder” and 23andMe, AncestryDNA, etc. Most of these companies sell Cousin matching (reliable to 5th Cousins and very occasionally out to 7th and 8th), and usually offer a very generic Biogeographic Analysis or “Ethnic Composition”

Picture12Where this becomes interesting is where you can download your raw data, and use at a site like GEDmatch.com against population genetics databases, and ancient DNA to make chromosome paintings like these:




Ethiohelix African dataset

The only problem is, the percentages vary depending on what was in the source/comparison database, so you can never take the percentage as universal- it’s just what percent was shared with that group in the comparison database. This has also led to an under-reporting of Native American heritage, as for various legal and sociological reasons many of that culture are opposed to testing and are therefore not found in many comparison data sets. The previous 5 graphics were all made with the same person’s autosomal data, just against different databases- you can see how results can differ by what you compare them against!

One further complication is that due to recombination, all of your true genealogical ancestors are not going to be found in your atDNA. Since you can picture atDNA as two decks of cards that are shuffled between your parents, then half discarded, leaving only one 52 card deck going forward- repeat that with 2 more decks over many generations and shuffles the two hybrid decks and discard half gain, repeat with another 2nd gen hybrid deck, etc.. and there may be no cards from one of the original decks left in the many-many times descendant deck. Random chance determines some of this, so mixed population people like many Americans will have this problem with confirming distant ancestors admixtures.

1cM to ancents

Matching 1cM segments from the same Autosomal data as above with some excavated anceint remains tested for DNA. Segments below 5cM can be IBS, so very small segments are still considered conjectural at this point

MtDNA, female line descent

Mitochondrial DNA (mtDNA) as we mentioned earlier, is DNA that is only inherited from the mother. It is not the X chromosome, it is actually in the mitochondria of a cell.  mtDNA is non-nuclear DNA, so it is not part of your chromosomes or “genes” and is passed “unchanged” (except for SNP mutations that occur) from mother to all children, but can only be passed on by a mother, so a mtDNA shows the distant female-line descent. Genealogy mtDNA tests are for SNPs. mtDNA SNPs are not very numerous, so the branches are quite infrequent. Perfect matches may still not have had a common female-line ancestor for 500 or 1000 years. It is most useful on very old specimens, as samples have remained stable to test for many thousands of years.

Polar Representation of the spread of mtDNA Haplogroups

Polar Representation of the spread of mtDNA Haplogroups, color coded by thousands of years ago

At first mtDNA was compared by mutations against the revised Cambridge Reference Sequence (rCRS), which is the Haplogroup H2a2a, but now uses Letter and number Haplogroups just like Y-DNA.

Some of the Y-DNA groups we mentioned earlier have equivalents in mtDNA–  Y-DNA R1a and R1b  is probably the same population source as mtDNA H, and specifically H2a1 mtDNA may be same population as R1a Y-DNA. 50% of Europe today is mtDNA H.  Y-DNA Haplogroup I is probably the same population source as mtDNA U Haplogroup as well.

Tree of mtDNA Haplogroup H

Tree of mtDNA Haplogroup H


Tree of mtDNA Haplogroup U

To read more, check out:

http://www.ftdna.com (The recommended testing site for ACMS)
http://www.gedmatch.com (Source of the Chromosome Paintings)

FTDNA’s Isles of the Hebrides DNA Project

FTDNA’s ACMS MacLeod DNA Project – Test 67 or more markers, and especially consider Big-Y if you have well documented MacLeod branch genealogy!

http://www.eupedia.com (Maker of many of the excellent Y-DNA ‘Heat Maps’, and one of the best amateur level reads on ancient European population genetics)


The Big Tree (Alex Williamson’s P312 Tree)

Articles about mtDNA found in Viking graves:


Any requests for more specific information? Email us at texasmacleods@gmail.com or post a comment here


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