Before Out of Africa….

Share on FacebookShare on Google+Email this to someoneTweet about this on Twitter

A new paper, The Dawn of Human Matrilineal Diversity, is out in AJHG. I read too much John Hawks to really be all that excited about mtDNA based studies, and this paper is Mitochondrial Eve to the nth power. But…I do think it is indicative of a trend which suggests a rollback from the most extreme Out of Africa scenarios; i.e., that one band somewhere in Eastern Africa arose ~100,000 years ago and expanded demographically so that they were the exclusive ancestors of all human beings.1 The introgression story is one angle; but the likelihood of preexistent population substructure within Africa itself is another. If you don’t read the paper (which is Open Access), just check out Figure 1 and the map. Breathless description of the study over at ScienceDaily of course….

Related: Kambiz comments in more detail.

1 – Some of this was more about public perception than reality; just like the one mtDNA ancestor was conflated with one female ancestor (the same trick of course applied to the NRY).

Labels:

5 Comments

  1. The likelihood of preexistent population substructure within Africa itself is another. 
     
    This is the bugaboo any origin (in linguistics, for example). For purposes of exposition origins are presented as simple, but if you look at them closely, they never are. (The same is true of parts, of course).

  2. I was just about to post this in the open thread.

  3. Breitbart and Yahoo unfortunately delivered unto us some VERY garbled articles here, which I must assume are summarising Science Daily. 
     
    The dates in question would appear to be: 
    -200000 ybp: Eve 
    -150000-90000?: Khoi-!San diverge 
    -135000: drought (rather, series thereof) begins 
    -90000: droughts end 
    -70000: populations start to recover 
    -60000: out of Africa for us (ancestors of Razib, me, other gnxp addicts) 
    -40000: intermingling in Africa for Africans (ancestors of African gnxp addicts) 
     
    That would imply that the divergence of humanity, already beginning 150000 ybp from spreading out over the vast north/south distances of east Africa, was enforced by the brutal conditions of 135000-90000. Any band that found an oasis was stuck there. 
     
    [begin rant about bad Yahoo summaries] 
     
    But that article begins with the number 70000, which in the context of Yahoo’s summary seems pulled out of a … hat, until we learn that Meave Leakey said this: “Who would have thought that as recently as 70,000 years ago, extremes of climate had reduced our population to such small numbers that we were on the very edge of extinction.” Who indeed would have thought of the year 70000 ybp, reading a body of text which says nothing of it? I certainly didn’t; Leakey’s comment implies that the bottleneck event was a single disaster, over a relatively small span of time. 
     
    Quite a few of us self-described “morons” at Ace of Spades were wondering if Leakey was confusing this event with the Toba eruption. 
     
    [/end rant] 
     
    Instead I’ve got to ask if Toba happened before or after the exit from Africa, if it bottlenecked our populations, if a Toba event could put genes under selection which a drought event couldn’t and how we could tell, if it had anything to do with the invention of clothing / bodylice to which N Wade refers….

  4. Kambiz seems to be implying that among the results of the population rebound at 70000 ybp: that pygmy females (“mtDNA”) split from a proto-Bantu (ie. “black”) population. here
     
    (He calls them “pygmy Khoisan” but I am unsure why he calls them Khoisan. The real Khoi and !San speakers, called “Bushmen”, had long since – so the articles are saying – gone their way as of 70000 ybp. Pygmies don’t speak Khoisan and look nothing at all like the orange-skinned, narrow-eyed Bushmen. Maybe Khoisan is a shorthand for “not-typically-black southern African”? If so I’d like that shorthand to vanish away.) 
     
    Anyway, I had thought the pygmies broke off rather earlier than 70000; same time as the Bushmen. I guess we just flat know more detail than we once did…

  5. I had thought the pygmies broke off rather earlier than 70000; same time as the Bushmen. 
     
    At least by Y-DNA, Pygmies clearly “belong” to the YxA branch that has many (at least 6) mutations separating it from A. Instead B nd CR (or CT, as some cal it now) are separated by only 2/3 mutations, what suggests that Pygmies and other B-Africans are much closer to the Afrasian CR bunch than to Khoisan (most directly associated with A).  
     
    Maybe it was earlier than 70K but not much earlier anyhow, specially if mtDNA studies are convergent into this kind of genealogy. Not as old as Khoisans in any case.

a