About us
Your mtDNA sequence is an heirloom that was passed down to you from generation to generation for thousands of years in an unbroken chain of direct maternal ancestors, as mothers passed down their mtDNA to their daughters who then passed it down to their daughters and so on . . . down to your mother and then to YOU. Sons inherit their mother's mtDNA too, but it is daughters who can pass it to the next generation.
Over centuries, as mtDNA is passed down over and over in a given lineage, occasionally a random change (mutation) occurs in the mtDNA sequence at some point among the 16,500+ base pairs/positions, creating a genetic variant that is passed down to all subsequent descendants in that direct maternal line. These mtDNA variants accumulate in a line over myriad generations, creating patterns in the mtDNA that can be recognized, identified, and tracked. These patterns are used to classify numerous large branches and smaller downstream branches referred to as haplogroups, clades, and subclades/subgroups.
In ancient times, a woman--often referred to as "Iris"--became the clan mother of mtDNA Haplogroup I. Everyone who belongs to Haplogroup I is her descendant through a solid line of daughters--our direct maternal ancestors. A pair of variants (the defining motif) that defines Haplogroup I is: T10034C G16129A. (The numbers and letters indicate that, at position 10034 of the mtDNA sequence, the original T switched to C, and at position 16129, the original G switched to A.)
Over time, as additional mtDNA variants accumulated in Iris' descendants, haplogroup I diverged into a series of distinct subclades and most of those led to a web of ever-younger downstream subclades. Some subclades are found in a wide geographical area, some are scattered in diverse locations, while others are found in a single region (such as I2b in Finland).
For years, the Phylotree was considered the official published mtDNA tree of humankind. It was last updated in 2016. In the subsequent nine years, a vast number of additional Haplogroup I subclades came to light but were not officially identified. On February 25, 2025, FTDNA released its beta Mitotree that catapulted development of the mtDNA tree forward. It used the Phylotree as a starting point, but then reanalyzed and reconstructed the tree using many thousands of additional mtDNA sequences that had become available. The PhyloTree had identified seven main branches of Haplogroup I, and the Mitotree has added ten more!
I1...I2'3 (I2...I3...) I4...I5...I6...I7...I9...I10...I13...I14...I17...I18...I19...I20...I21...I22
(The Mitotree is expected to undergo periodic updates. I, Martha Hicks, intend to update this page with changes.) A set of changes took place on April 14, 2025, and the subclade categories for members were updated.
Below are some stats about each main branch of Haplogroup I: (1) Number of individuals who had full-sequence mtDNA testing (2) List of main lettered subclades, (2) Total number of subclades to which our members belong in each main branch, (3) Total number of members in each main branch with mtDNA testing at FTDNA, and (4) Percentage of total project members in each main branch.
I1
Number of those in I1 with full-sequence testing at FTDNA: 2,372 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I1a, I1b, I1c, I1d, I1e, I1f … I1h, I1i, I1j, I1k, I1l, I1m, I1n, I1o, I1p,
I1q, I1r, I1s
Members of our project belong to 157 downstream subclades of those branches.
Number of project members in I1: 603
Percent of project members in I1: 32.12%
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I2
Number of those in I2 with full-sequence testing at FTDNA: 2,020 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I2a, I2b, I2c, I2d, I2e, I2f … I2h, I2i, I2j … I2l, I2m, I2n, I2o … I2q … I2u,
I2v, I2w, I2x, I2y, I2z, I2aa, I2ab, I2ac … I2ae, I2af, I2ag, I2ah, I2ai, I2aj,
I2ak, I2al, I2am, I2an, I2ao, I2ap, I2aq, I2ar, I2as … I2au, I2av, I2aw, I2ax,
I2ay, I2az, I2ba, I2bb, I2bc, I2bd, I2be, I2bf, I2bg, I2bh, I2bi, I2bj, I2bk, I2bl,
I2bm, I2bn, I2bo, I2bp, I2bq, I2br, I2bs
Members of our project belong to 145 downstream subclades of those branches.
Number of project members in I2: 495
Percent of project members in I2: 26.37%
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I3
Number of those in I3 with full-sequence testing at FTDNA: 587 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I3a, I3b, I3c, I3d … I3f … I3w, I3x, I3y, I3z, I3aa, I3ab
Project members belong to 43 downstream subclades of those branches.
Number of project members in I3: 154
Percent of project members in I3: 8.2%
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I4
Number of those in I4 with full-sequence testing at FTDNA: 1,139 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I4a, I4b … I4d
Project members belong to 75 downstream subclades of those branches.
Number of project members in I4: 284
Percent of project members in I4: 15.13%
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I5
Number of those in I5 with full-sequence testing at FTDNA: 329 (Feb. 2025)
Main branches on the Mitotree (Feb. 2025):
I5a, I5b, I5c … I5f
Project members belong to 44 downstream subclades of those branches.
Number of project members in I5: 117
Percent of project members in I5: 6.23%
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I6
Number of those in I6 with full-sequence testing at FTDNA: 21 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I6a, I6b, I6c
Project members belong to 4 downstream subclades of those branches.
Number of project members in I6: 6
Percent of project members in I6:
0.32%
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I7
Number of those in I7 with full-sequence testing at FTDNA: 13 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I7a
Number of project members in I7: 2
Percent of project members in I7: 0.10%
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I9
Number of those in I9 with full-sequence testing at FTDNA: 7 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I9a
Number of project members in I9: 1
Percent of project members in I9: 0.053%
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I10
Number of those in I10 with full-sequence testing at FTDNA: 3 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members in I10: 1
Percent of project members: 0.053%
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I13
Number of those in I13 with full-sequence testing at FTDNA: 2 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members in I13: 1
Percent of project members: 0.053%
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I14
Number of those in I14 with full-sequence testing at FTDNA: 3 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members in I14: 1
Percent of project members: 0.053%
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I18
Number of those in I18 with full-sequence testing at FTDNA: at least 2 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members in I18: 1
Percent of project members: 0.053%
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I19
Number of those in I19 with full-sequence testing at FTDNA: 2 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members in I19: 1
Percent of project members: 0.053%
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I20
Number of those in I20 with full-sequence testing at FTDNA: 15 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025):
I20a, I20b
Project members belong to 2 downstream subclades of those branches.
Number of project members in I20: 3
Percent of project members: 0.16%
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I21
Number of those in I21 with full-sequence testing at FTDNA: 2 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): None
Number of project members: 2
Percent of project members: 0.10%
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I22
Number of those in I22 with full-sequence testing at FTDNA: 3 (Feb. 2025)
Main lettered branches on Mitotree (Feb. 2025): I22a
Number of project members: 40
Percent of project members: 2.13%
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The following FTDNA page has useful information for understanding haplogroups, including explanations for the usage of symbols and various formats sometimes used for subclade labeling on the Mitotree: :
Understanding mtDNA Haplogroups
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Martha Jane (Schliesser) Hicks 2013-2025
mtDNA Haplogroup I Project: Background by Martha Jane (Schliesser) Hicks is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.