DNA Testing Of Deep Ancestry

Randall Burns writes: " Oxford Ancestors, founded by world-famous University of Oxford scientist Bryan Sykes has announced the public availability of an inexpensive($US 180) service that will trace matrilineal ancestry using DNA tests. Applications include forensics, genealogy and research of history. Coverage includes a recent BBC story. The currently available test can trace matrilineal ancestry back to one of seven women who lived 150,000 years ago to which 99% of all people of European descent can trace their ancestry."

Comments

One of seven women?

[blogan]

99% of people come from one of these seven women? Man, they must have been huge sluts! :)

Seriously, I don't see the point of this. When people want to trace their ancestry, they're mostly concerned with who their great great grandparents were and who their relatives were that lived during the Civil war, not 150,000 years ago. Yeah, it's cool, but nothing I'd pay $180 for.

The new factions:

[hypergeek]

If 99% of Europeans were matriarchically descended from one of seven women...

(Scene opens with armored mercenary on horseback approaching a stone castle retrofitted out of the decaying hulk of the abandoned steel husk of an office building. Camera pans, giving audience a breathtaking view of the barren, wrecked skyline of a post-apocalyptic American metropolis.)

Guard (steel spear glinting as he shouts): "Halt! Who goes there? Know ye that this place be the realm of the descendents of Bertha the Bountiful. If thou be a son of Agnes the Prolific, begone from here, lest we slay thee!"

Mercenary: "Good soldier! Stay thine blade, for I, too am of the Tribe of Bertha!"

Guard (in stupid, low grunting Superbowl-commercial voice): "Whazzuuuuuuuuuuuuuuup!"

Mercenary pulls a flintlock pistol from his belt, cocks the hammer, and fires at Guard, killing him instantly. Audience cheers.

Guard (lacking the decency to just DIE): "Lo! I am sped! Dead am I! I am made as dust by the treacherous asp! Gone am I from this mortal coil! I am---"

Mercenary: "Why won't you DIE??!"

(Mercenary dismounts, then proceeds to kick Guard till he falls dead, and more importantly, silent. Audience cheers.)

Mercenary: Never underestimate the 1% descended from Jane Doe the Probably-Just-a-Rounding-Error-In-Our-Calculations !

Mercenary proceeds to singlehandedly storm the castle, raping and pillaging, stealing treasure, weapons, and office supplies.

Major weaknesses in mitochondrial lineage tracing

[orpheus]

Mixed population bacterial genetics may be a far better anology than eukayotic (nuclear) genetics for explaining the distribution and prevalence of mitochondrial populations

First, some much simplified background (I have a degree in molecular biology): Mitochondria are self-reproducing organelles (= cell 'organs') that many people believe were once independent organisms that entered into a symbiotic relationship with a host cell, and eventually became utterly dependent on the cell. They now function as the primary site for the production of ATP, the main cellular fuel. There may be hundreds or thousands in a single cell

Mitochondria reproduce (to some degree) independently of the cell, and contain their own DNA. The DNA for everything else is in the nucleus (the cell's brain) but the mitochondria 'live' and reproduce in cytoplasm (cell body). When we breed, the nuclear DNA does the whole dance of meiosis/mitosis we learned in school, but the mitochondria fission like bacteria. Most (if not all) of the mitochondria is from the mother because a) the egg has thousands of times as much cytoplasm as the sperm; and b) after first contact with the egg, the sperm's mitochondria go into hyperdrive ("the acrosome reaction") and burn themselves out.

Now for the Original Contributions

1. In the billions of years of symbiosis since the development of eukaryotes, many genes that are useful or essential to the mitochondria have 'migrated' into the nucleus.

2. Though the mitchondrial 'support' genes are fairly cosistent from person to person, they aren't identical in everyone. Those genes only got to the nucleus by accident (mutation, adaptation by mitochondria to the available cell resources, etc) and therefore not all strains may be able to live in all people, or certain strains may enjoy a competititve advantage in a given person

3. Some individuals are known to have multiple strains of mitochondria, due to the various flukes and accidents of biological history. I know of no study that states that *most* humans have only one strain, and doubt its the case. It's actually a good idea to have multiple strains, since anything that kills (or impedes the reproduction of) a solo strain would kill (or prevent the reproduction of) its host. Multistrain individuals should be slightly hardier.

4. Mitochondria became part of the cell when we were single celled organisms. The mitochondrial DNA variation we measure is presumed to be 'nonessential' because mitochondria have very little DNA, and most of it was largely fixed long ago. We presume we're sorting mitochondria by 'eye color', but we may not be.

4) Mitochondria must adapt to their host as the host changes. A cow's mitochondria is much less similar to ours than you'd expect, considering that cows and men didn't diverge very long ago on a mitchondrial timescale.

5) Suppose a type mitochondria in a remote tribe requires the (nucleus) gene PII'ase. This is fine if the tribe all carries the (nuclear) gene for PII'ase. However, this mitochondrial line may die out when interbred because outside populations may not carry the gene PII'ase.

6) I can think of a dozen other mechanisms, but let's not go overboard.

Conclusion:
Mitochondria are subject to many of the evolutionary and selection pressures as independent bacteria, symbiotes, etc. the finding that there are seven major strains of mitochondria in modern man simply suggests that seven mitochondrial strains are widespread and well-adapted to the core genome of humans

It doesn't mean there were only seven 'original women'

It may mean that there were only seven (mitochondrially) *undemanding* women [ducks!] and the truth may be far more complicated. (lesser strains may coexist with the support of the major strains, etc.) and probably are.