////The Curious Origin of mtDNA Haplogroup B2 in the Americas

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The Curious Origin of mtDNA Haplogroup B2 in the Americas

Since the publication of Paternal origin of Paleo-Indians in Siberia: insights from Y-chromosome sequences I have found myself contemplating the migration or migration of maternal lineages to the Americas.

Quick refresher: Our maternal lineages trace from each one of us along our direct maternal line. Eventually, all people alive today connect to a woman known as mtDNA Eve. From her, the line continues back to our common ancestor with the Neanderthals. Beyond that, it connects to the first peoples and then to our common link to our primate cousins. This line is traced with our DNA. The DNA used is our mitochondrial DNA (mtDNA). It is passed from mother to child each generation. The connecting branches of this DNA tree are called mtDNA haplogroups.

One of the mtDNA haplogroups to reach the Americas with first peoples is B2. It is believed to have traveled over the frozen Beringia landmass that connected Asia to modern Alaska.

Generally, researchers have considered the timing to be deep, around 18,000 years ago. They have also considered it to be a single migration of the four major lineages: A, B (really B4'5), C, and D. However, they admit, reluctantly, that there is not a clear common place of origin for all four lines in Asia.

I also am working on an update to the mtDNA B4'5 story page. Thus, I looked again at some rather old papers I had not read in over 10 years. Goodness! I missed something before.

Here is the ancestral path from our RSRS (mtDNA Eve) ancestor to Native American B2. It is not intuitive.

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    • RSRS
      • L1’2’3’4’5’6
        • L2’3’4’5’6
          • L2’3’4’6
            • L3’4’6
              • L3’4
                • L3
                  • N
                    • R
                      • B4’5
                        • B4
                          • B4b’d’e’j
                            • B4b
                              • B2

Yah. Complicated, right?

Here is the final branch before B2 alongside B2's sister branch B4b1.

  • B4b Age 28,712.2 ± 4,821.5; CI=95% (Behar et al., 2012b)
    • B4b1 Age 25,156.8 ± 5,049.0; CI=95% (Behar et al., 2012b)
    • B2 Age 16,818.5 ± 2,619.9; CI=95% (Behar et al., 2012b)

This puts the timing of B2's birth just before or just after her line's likely migration from someplace in Asia to the Americas.

Where was the location in Asia? Well, we can look first at a map of all B4'5 lineages in modern populations. Here is one created by Dr. Balanovsky and his team. The lower frequency places are dark green, and the higher frequency places are dark purple. Middle frequencies are yellow.

mtDNA Haplogroup B4'5 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

mtDNA Haplogroup B4'5 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

Over almost 30,000 years, B4'5 lines have spread a good deal. Where in all of that was B2 or her mother line born?

Well, we can look at where her sister branch B4b1 is found today. Here is the B4b1 map. It is clear right away that there is one population in Siberia. However, most are toward the east in modern China. B4b1 is not found in the part of Asia closest to ancient land bridge.

mtDNA Haplogroup B4b1 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

mtDNA Haplogroup B4b1 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

Finally, let's look at where B2 is found today. Here something becomes really clear. B2 is not part of Alaskan populations. It is also not common in most of modern Canada. Why could this be?

mtDNA Haplogroup B2 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

mtDNA Haplogroup B2 – Geno 2.0 Author: Balanovsky, O. et al., 2011 Copyright: National Geographic

What does that tell us so far? B2's ancestors came from Asia. However, an origin in the Northeastern Siberian region is unlikely. Central Asia or Eastern Asia are possible. Then, there is the puzzling issue of B2's absence from Alaska.

This brings me back to that paper I reread. That was Patterns of mtDNA diversity in northwestern North America, Malhi et al., 2004. In it, the authors tested teeth mostly found in rivers/creeks from the North American Northwest. There were:

  • Plateau Salish (Salisham language family) dating to about 200 BP: 6 out of 11 samples were B.
  • Vantage dating to between 500 and 1500 BP: 0 out 7 samples were B.
  • Plateau Sahaptian (Sahaptian language family) dating to about 200 BP: 4 out of 8 samples were B.
  • Wishram (Chinook language family) samples dating to about 200 BP: 17 out of 33 samples were B.

This tells us two things. First, around 200 years ago, B2 lineages were about 50% of Northwestern North American lineages. Second, about 500 to 1500 years ago, B2 lineages were ether absent or very uncommon in the area. That looks like B2 arrived in the Northwest after 500 years ago?

That gives me more questions. Why doesn't B2 look like a Beringia migration? Is B2 into the North American Northwest a relatively recent migration from someplace else? Does B2 look like a South to North migration to you? B2 looks to have one of the oldest split-times from Asian lineages in the Americas. Is this accurate? Could it be a completely separate migration from A, D, and C lineages? Did something happen to shift A, B, C, and D lineages in Asia such that B4b in modern Asia is shifted?

I don't have answers. I want them though.

2018-11-10T07:24:53+00:00October 27th, 2018|Categories: mtDNA Quarterly|Tags: , , , |
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