elt@astrovax.UUCP (11/10/83)
A rather astonishing discovery was announced by Allan C. Wilson of UC Berkeley at a meeting at Cold Spring Harbor Laboratory (NY) held in August '83. Another group led by Luigi Cavalli-Sforza of Stanford has verified this result. Briefly stated, their result is as follows: All living people (or at least ~99% of them) have a single common female ancestor on their purely maternal line. In other words, tracing back to one's mother's mother's mother's ... mother will bring everyone back to a single individual woman. She is estimated to have lived between 50,000 and 500,000 years ago. This result is based on comparisons of human mitochondrial DNA taken from very diverse populations all over the world. Mitochondrial DNA is passed along solely (i.e., asexually) by females to their offspring. The mutation rate for this process is very roughly known, and this together with delicate measurements of differences between two individuals' mitochondrial DNA, allows the determination of the interval since they shared a common pure female line ancestor. The technique is fairly new and is not yet completely accepted, but so far no one has suggested any specific reason for doubting its validity. The most serious uncertainties are associated with the estimate of the time scale involved but do not alter the basic conclusion of a single common ancestor. Explanations for this "fact" are not as difficult as they might at first appear given reasonable assumptions about population and reproduction statistics; however, all such explanations imply that the human species must have once (before!) had a close brush with extinction. Certainly it is a curious twist on the standard biblical story in which it is emphasized that people descended from a man through two sons. It appears that we actually descended from a woman through two (or more) daughters. (Note: Men are simply sterile offspring from the point of view of mitochondrial DNA.)
rlw@wxlvax.UUCP (Richard L. Wexelblat) (11/10/83)
Everyone knows that. Her name was Eve.
piet@mcvax.UUCP (Piet Beertema) (11/10/83)
>All living people (or at least ~99% of them) have a single common female >ancestor on their purely maternal line. In other words, tracing back to >one's mother's mother's mother's ... mother will bring everyone back to a >single individual woman. She is estimated to have lived between 50,000 and >500,000 years ago. Fine! But please explain: how comes the oldest fossil hominid skull is about 2,000,000 years old! Must have been only males then living at that time.... -- Piet Beertema Center for Math. & Comp. Science (CWI), Amsterdam ...{decvax,philabs}!mcvax!piet
elt@astrovax.UUCP (Ed Turner) (11/11/83)
----------------------------------------------------------------------------- Questions have been raised about my article on a single common female ancestor for everyone. Let me try to answer some of them: 1) It is not a joke. It wouldn't be funny if it were, would it? 2) As far as I know the result has not yet been published but only presented by the authors I cited in my original article at the Cold Spring Harbor meeting. Presumably it will eventually appear in the conference proceedings and probably elsewhere. I originally heard about it from colleagues here at Princeton who were not involved in the work; they regard the result with caution but not disbelief as far as I can tell. The work was reported in the August 13, 1983 issue of SCIENCE NEWS on page 101. 3) The interpretation of the mitochondrial DNA results in terms of a common ancestor is that of the original authors and certainly not my own (I am no expert on this subject). 4) Obviously there are possible natural selection biases which might account for some similarity in the mitochondrial DNA, but in this case the similarity is so great (i.e., at such a large fraction of the loci) that at least some experts reject this explanation. 5) On statistical grounds (a subject in which I am reasonably expert), I'm not sure if the result is all that surprising given that the total human female population was roughly constant at N individuals for of order N total generations.
wls@astrovax.UUCP (William L. Sebok) (11/11/83)
> All living people (or at least ~99% of them) have a single common female > ancestor on their purely maternal line. ... > > This result is based on comparisons of human mitochondrial DNA taken from > very diverse populations all over the world. Mitochondrial DNA is passed > along solely (i.e., asexually) by females to their offspring. The mutation > rate for this process is very roughly known, and this together with delicate > measurements of differences between two individuals' mitochondrial DNA, allows > the determination of the interval since they shared a common pure female line > ancestor. Could this trick be used on the Y chromosome to estimate the time back a single common ancestor on the purely paternal line? Any biologists or geneticists out there? -- Bill Sebok Princeton Univ. Astrophysics {allegra,akgua,burl,cbosgd,decvax,ihnp4,knpo,princeton}!astrovax!wls
fred@umcp-cs.UUCP (11/12/83)
From: wls@astrovax.UUCP > All living people (or at least ~99% of them) have a single > common female ancestor on their purely maternal line. . . . > This result is based on comparisons of human mitochondrial > DNA taken from very diverse populations all over the > world. . . . Could this trick be used on the Y chromosome to estimate the time back a single common ancestor on the purely paternal line? Any biologists or geneticists out there? Bill Sebok Princeton Univ. Astrophysics I'm neither, but based on my understanding of the original article, mitochondrial DNA has NOTHING to do with the DNA in the X and Y chromosomes, so the answer is: no. As a matter of fact: I recall reading a magazine article within the last year, which stated that the genetic code used in mitochondrial DNA is quite different than that used in all the other DNA in your body. That is: the mapping from the triples of the four chemicals which make up the code, to amino acids, is not the same. This has led some people to speculate that the mitochondria originally evolved as a separate life form, later forming a symbiotic relationship with other cells. Since I've taken this about as far from genealogy as it can go, I will now shut up. Fred Blonder harpo!seismo!umcp-cs!fred
rene@umcp-cs.UUCP (11/14/83)
Re: explain how the earliest hominid (sp? right word?) skull was found
approx. 2,000,000 years ago? I guess they were all males?
[I haven't yet learned to read in the original message!]
What's to explain? All that is meant is, there is supposed to be one
woman who lived about 50,000 - 200,000 years ago whose offspring gave
rise to most of the women alive today. This does not preclude other
women being alive at that time or earlier. Where did you get the idea
it did?
- rene
--
Arpa: rene.umcp-cs@CSNet-relay
Uucp:...{allegra,seismo}!umcp-cs!renewalsh@ihuxi.UUCP (B. Walsh) (11/15/83)
Rene- (Re: your response) When I first read the question about the skull, etc., I thought the same thing you did, but then I thought that this woman of 50-200,000 years ago obviously also had a mother, and HER mother had a mother, etc. I think that's where the confusion is. Apparently, they've only traced back so far, but not far enough. I'm confused! Unless this particular woman's traits are the only ones that have made it down this far, and her ancestors' traits were obliterated. Beats me! B. Walsh
dnc@dartvax.UUCP (David Crespo) (11/26/83)
the problem, my dear rene is that peoles have feelings too, no, what i mean is that if we were all descended from one female ancestor, but that other ancestors were possible, what happened to the offspring of these other wome? Did the guys just decide on this one lucky(?) lady and dump the rest, or were her genes so much stronger tha everyone else, or was it mass selective genocide? no, it seems ulikely that the article is anything but a clever plant by scientific creationists who have infiltrated Cold Springs Harbor's proceedings (BTW, this is where J. Watson of DNA repute is situated) (mebbe its Crick, but oe of them) . Be o the lookout, intruder alert, throw the book at em.