The misleading concept of Mitochondrial Eve.

I’ve just discovered a major breakthrough in the Mitochondrial Eve story.

Apparently, and this is surprisingly important, Mt DNA is not a neutral gene. This means it is subject to natural selection. Less efficient Mt DNA types will get selected out. Suddenly, a lot of conflicting information from various sources stars to make sense. It also means that the absence of wildly different Mt DNA types that could have come from Neanderthals or Homo Erectus is totally meaningless, as they would have been selected out by the newer, better Mt DNA type from Africa. Multi-regionalism and the hybrid hypothesis are suddenly back in play.

The only thing the spread of Mt DNA now tells us, is it’s own spread. Think of the difference between a small twig in a stream, it is at the mercy of the currents (like a neutral gene). Then think of an insect or fish in the same stream. It can move in any direction, with the movement of the water only exerting a pressure to move in one way. This is the effect natural selection would have. What this means is that Mt Eve was probably NOT the result of a population bottleneck, she just had a mutation for a more effective energy conversion in her cells. And, as beneficial mutations tend to, this spread all over the world. What it doesn’t mean is that one group of Africans spread out all over the world, and that we are all really closely related. 

It also raises the question, “are Y chromosomes neutral genes?”. I’m going to go out on a limb and say, probably not. There are genes for various functions on the Y chromosome, Adam could just have produced more motile sperm. This would mean that Y chromosome Adam simply had a mutation that gave his DNA an advantage, so that it spread. Maybe it made him taller, or faster. It could be anything. It doesn’t mean he was at the head of a small bunch of intrepid pioneers colonising the planet.

Add this to the fact that some very ancient X chromosomes have been discovered in Asia and Africa, that date back one to two million years, and you can see how the recently out of Africa theory is look very shaky indeed.

Adam and Eve….never existed.

6 responses to “The misleading concept of Mitochondrial Eve.

  1. Can you post a citation for this? I was exposed to this topic at as a graduate student a long time ago. I’ve enjoyed lurking and reading your blog.

  2. I have at least two studies here somewhere discussing the evidence of natural selection on mt DNA. Good luck finding them though…

    Try loooking for them in a couple of days, as I’m having a blog-editing session and a lot of stuff is not available right now.

    Nice to hear from a regular🙂

  3. I don’t understand. How do mitochondrial genes spread through the general population? By descent. It isn’t as if an individual inherits several different sets of mitochondrial DNA and then there’s some sort of selective struggle among them in that individual’s cells. Different mitochondrial genes might contribute to the differential fitness of different people (women?), but I’m not following how that negates the idea of a mitochondrial Eve?

    Can you expand a bit, please?

  4. Having reread your post, I honestly think that you are just muddled about the different implications of MT genes being selected — which could affect the ticking of the molecular clock, but not necessarily — and the broader question of a single origin for modern Homo, which is not in the least bit affected by whether the MT genes are selected or not.

    clock hypotheses depend on testing against an outgroup, and if the mutation rates in the two lines are not equal, well then you don’t have a clock.

    I’ve just read a new article in Scientific American, The Migration History of Humans: DNA Study Traces Human Origins Across the Continents and I don’t honestly think that a multiregional hypothesis for human origins has much left going for it.

    There is so much more than merely MT DNA all telling a very similar story.

  5. Jeremy..
    There’s a few DNA studies and geneticists pointing out that the out of Africa theory is impossible, as well as plenty of anthropologists. I archive a lot of the arguments against it here.

    I understand the concept of Mt Eve pretty darn well. The whole dating and use of it is rather dependent on it being a neutral DNA marker. It means that whole Mt lineages can waste away to nothing, and studies on ancient Euroepan remains suggest the frequencies of various clades has been rising and falling, some even go extinct.

    It means that there’s plenty of room for a ‘weak Eden’ scenario, and that’s supported by a LOT of anthropologists and some DNA studies.

    I am NOT a multiregionalist, BTW.

    Oliver..
    Mitochondrial DNA, not a ‘neutral marker’ but DNA under selection’, is on here somewhere…
    As is ‘the out of Africa deception’.

  6. Aaargh. Your links to me and to Oliver are bust.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s