Shout out to the f-list

[chickenfeet]

This is a shout out to anyone who is familiar with current thinking on the "Daughters of Eve" and "Lucy" hypotheses. What's the current cutting edge thinking on the validity of mtDNA based analysis? I think I've seen heard/stuff that suggests that uncontaminated mtDNA is virtually impossible to find and that therefore the whole ball of wax needs to be treated with some scepticism but I might have been imagining it. Opinions and pointers to recent papers on the subject most appreciated.

Comments

[a-d-medievalist.livejournal.com]

Well, I'm of no help here ... I sat here for about 30 seconds before I could even think what mtDNA was. It is mitochondrial DNA, yes? IIRC, you are right in that there are problems, but I thought it was because it didn't remain intact as long as DNA. but like I said, I'm iggerant ever since I stopped living with a New Scientist reader.

[chickenfeet2003.livejournal.com]

It is mitochondrial DNA I'm thinking about. I think I read somewhere that any mtDNA from an ancient source is bound to be contaminated and that therefore little reliance should be put on conclusions drawn from it. OTOH, I'm still seeing it acceoted as gospel in works published as recently as 5 years ago. The implications are quite far reaching so I would like to know more.

[rhythmaning.livejournal.com]

I hadn't realised contaminated mitochondrial DNA had clouded the picture. The theory would probably hold, though - since mitochondria are passed down the female line.

But there may be two different types of analyses done. What I've read about are studies on current people, and drawing conclusions from that - there would probably be limited contamination.

Your comment above talks about analysing ancient DNA - pretty dodgy, I would guess.

[madamerotten.livejournal.com]

what level of contamination are you refering to?

[chickenfeet2003.livejournal.com]

I'm not at all sure. I guess I would have to say "a degree of contaminarion sufficient to put in doubt the sort of continuity hypotheses suggested by the 'Cheddar man' findings".

[madamerotten.livejournal.com]

Im not sure what kind of contamination hes refering to. i can think of two levels of contamination. contamination from nature and environment from the time of death to finding contamination from the lab proceedures. If hes referring to lab proceedures, that can usually be prevented and accounted for. i wish the original quoter was more specific

[chickenfeet2003.livejournal.com]

I'm going from memory here but I think the implication was that any handling of the object during or after excavation would result in enough mtDNA transfer to invalidate a result. So I guess this gives a spectrum of possible contamination from recent, extremely careful investigation with explicit steps taken against contamination to analysis of an artefact that's been kicking around a museum for a hundred years.

[madamerotten.livejournal.com]

i can see where some concern would arise with that. if you know you are going to be thinking about mtDNA analysis, then you can put on some tivex suits. or, you can get mt DNA profiles from everyone who worked directly with the artifact and screen for their contamination as controls in the lab. you can tell the difference between your DNA and that of the sample as long as there are differences, and there will be. from an older artifact in a museum, there would be more handlers and less control of contamination.

at least this is what i think.

[pyroclasticgrub.livejournal.com]

I had to learn this a couple of years ago, so I'll see what I can remember. Bear in mind that my prof remains very skeptical of DNA analysis because when you gather ancient DNA, you're only getting a tiny chunk of the genome that would have been present. Also, the Eve hypothesis paper (the one with the u-shaped population movement model) didn't include data from all available populations. I'll see if I can find that one for you, as well as the alternate Templeton paper.

Maybe I'll just give you refs because I'm really bad at explaining this stuff.

-Conroy, G. C. 1997. Reconstructing Human Origins: A Modern Synthesis. New York: Norton and Co. (See Pp: 387-401 for a specific discussion and criticisms of the Eve hypothesis.)

-Cann, R., Stoneking, M., Wilson, A. 1987. Mitochondrial DNA and Human Evolution. Nature: 31-36. (The first major paper on the topic)

-Templeton, A. R. 1993. The "Eve" hypothesis: A genetic critique and analysis. American Anthropology. 95: 51-72. (one of the main critiques of Eve hypothesis)

If I find more stuff, I'll let you know. I can also forward these questions to my friends who are more DNA-oriented.

Sorry, but I'm more of a bones kinds of girl. :)

[chickenfeet2003.livejournal.com]

Thank you