elturner@phoenix.Princeton.EDU (Edwin L Turner) (10/09/87)
In 1983 ther ewas a fairly extensive discussion of the above referenced topic started by an article I posted which I reproduce, in part, below: -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. If anyone is now or still interested, an update is given in the Research News section of the Oct. 2 issue of SCIENCE (vol. 238, pp. 24-26). The upshot is that the basic result now seems to be generally accepted with the experts falling to arguing about better dating estimates and detailed mechanisms. It remains true that the result suggests that our species has had at least one rather close brush with extinction, direct or statistical. Ed Turner "Does one really have to fret phoenix!elturner About enlightenment? No matter what road I travel, I'm going home."
dhesi@bsu-cs.UUCP (Rahul Dhesi) (10/10/87)
In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU (Edwin L Turner) writes: All living people (or at least ~99% of them) have a single common female ancestor on their purely maternal line.... I wonder why Creationists haven't picked up on this. -- Rahul Dhesi UUCP: <backbones>!{iuvax,pur-ee,uunet}!bsu-cs!dhesi
dd@beta.UUCP (Dan Davison) (10/10/87)
In article <1248@bsu-cs.UUCP>, dhesi@bsu-cs.UUCP (Rahul Dhesi) writes: > In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU > (Edwin L Turner) writes: > > All living people (or at least ~99% of them) have a single common > female ancestor on their purely maternal line.... > A small correction: this refers ONLY to mitochondrial DNA, not nuclear DNA, and so for the vast majority of the population says nothing about a single common female ancestor. Nor does it imply a population bottleneck 200,000 years ago. It seems to me this "Eve" business has been really messed up by the media. (1) She's the "eve" for mitochondria only. (2) It makes no statement about the human population because 200,000 years is *tiny* relative to the tempo and mode of primate mitochondrial evolution. [See the paper by Wesley Brown et al., J. of Molecular Evolution, 18:225-239 1982, "Mitochondrial DNA sequences of Primates: Tempo and Mode of Evolution"] Note that the other women alive at the time could have left mitochondria in their descendants who did not have female offspring as recently as 2 generations ago, thus making it look as though there is an "Eve". I'd suggest those interested in this topic who want a more intelligent handling of the topic see the September/October issue of The Sciences, pp. 30-37. Note, though, that even The Sciences blew it: the cover says "Who was the mother of all mankind?". Amazingly fuzzy thinking! I am quite amazed at the degree of misinformation this work has caused. By the way, "molecular clock" fans: this may be one of the few cases where a molecular clock has been claimed and there is a clear cut case which supports the argument. For those non-biologists reading this, the "molecular clock" was proposed by Allan Wilson in a review in the Annual Review of Biochemistry in 1977. The argument goes that the rate at which base changes occur ("mutation") happens, on average, regularly over long periods of time. If you can determine the "tick" of the clock, you can do phylogenetic work to determine the divergence time of two species from sequence comparison alone. This idea has so many holes in it I must admit I do not understand the apparent general acceptance of the idea. dan davison/t-10 ms k710/theoretical biology/los alamos national lab/ los alamos, nm 87545/dd@lanl.gov/...cmcl2!lanl!dd/dd@lanl.uucp
emigh@ncsugn.ncsu.edu (Ted H. Emigh) (10/11/87)
In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU (Edwin L Turner) writes: > >In 1983 there was a fairly extensive discussion of the above referenced >topic started by an article I posted which I reproduce, in part, below: > >-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. >- [Material left out] >... It >remains true that the result suggests that our species has had at least one >rather close brush with extinction, direct or statistical. Just because we have common ancestors does not mean that we have had a "close brush with extinction". Not even close. No more so than any other organism on this planet. Notice that the time from divergence was measured by the accumulation of mutations. It is this accumulation (among other factors) that keep the genetic diversity of the species. Also, remember that the size of the human mitochondrial DNA is about 65K bases, while the entire genome is about 3 BILLION (US Billion, really 1000 Million) bases. While the EVE model is an interesting 'fact' it is hardly the stuff to force us to rethink human evolution. I teach it in my General Genetics and Population Genetics classes to drive home the point of the extreme difficulty in understanding MACRO evolution by completely understanding MICRO evolution. -- Ted H. Emigh, Dept. Genetics and Statistics, NCSU, Raleigh, NC uucp: mcnc!ncsuvx!ncsugn!emigh internet: emigh%ncsugn.ncsu.edu BITNET: NEMIGH@TUCC @ncsuvx.ncsu.edu:emigh@ncsugn.ncsu.edu
falk@sun.uucp (Ed Falk) (10/12/87)
In article <1248@bsu-cs.UUCP>, dhesi@bsu-cs.UUCP (Rahul Dhesi) writes: > In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU > (Edwin L Turner) writes: > > All living people (or at least ~99% of them) have a single common > female ancestor on their purely maternal line.... > > I wonder why Creationists haven't picked up on this. They will, once they've explained away the fact that "Eve" lived at least 50,000 years ago; kinda goes against the biblical version. Also, bear in mind that "Eve" wasn't *the* common ancestor, she was *a* common ancestor. All they know is that we can all claim direct descendancy from her somewhere in our past. I remember something about there being a very small population (as few as six) of women from whom we all come. "Eve" was the only one of this group who we *all* can list in our ancestry. -- -ed falk, sun microsystems sun!falk, falk@sun.com terrorist, cryptography, DES, drugs, cipher, secret, decode, NSA, CIA, NRO.
zgel05@apctrc.UUCP (George E. Lehmann) (10/12/87)
In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU (Edwin L Turner) writes: >remains true that the result suggests that our species has had at least one >rather close brush with extinction, direct or statistical. Rather than a close brush with extinction, this suggests to me support for either evolutionary or creationist beginnings (whichever you subscribe to). Consider that there must be a beginning to the line for both scenarios, and the 'single-ancestor' seems to be a requirement. -- George Lehmann, ...!uunet!apctrc!zgel05 Amoco Production Co., PO BOX 3385, Tulsa, Ok 74102 ph:918-660-4066 Standard Disclaimer: Contents are my responsibility, not AMOCO's.
throopw@dg-rtp.UUCP (Wayne A. Throop) (10/12/87)
> dd@beta.UUCP (Dan Davison) >> dhesi@bsu-cs.UUCP (Rahul Dhesi) >> All living people (or at least ~99% of them) have a single common >> female ancestor on their purely maternal line.... > A small correction: this refers ONLY to mitochondrial DNA, not nuclear DNA, > and so for the vast majority of the population says nothing about a single > common female ancestor. How does the fact that mitochondrial DNA was used in this evaluation escape the conclusion of a single common female ancestor (SCFA for short)? Mitochondrial DNA comes exclusively from the female parent, and if there was a single common original human mitochondrial DNA, it must (barring unusually bizarre co-incidences) have come from a single female at some point in time. The evidence supports a single common ancestral mitochondrial DNA, hence an SCFA. > Nor does it imply a population bottleneck 200,000 years ago. True. There may have been any number of male ancestors, and the fact that only one maternal line survived doesn't mean that it was the only maternal line *at* *that* *time*. > Note that the other women alive at the time could have left mitochondria > in their descendants who did not have female offspring as recently as > 2 generations ago, thus making it look as though there is an "Eve". Not only does it *look* as if there is an "Eve", there *IS* an "Eve" in the sense meant -- that is, all *surviving* humans have an SCFA. The point is that the lines of descent of Eve's "competitors" may have died out only recently, but they *DID* die out. (Note that this Eve isn't much like the biblical Eve, which may explain why creationists don't try to exploit the cute naming of this hypothetical individual.) > Note, though, that even The Sciences blew it: the cover > says "Who was the mother of all mankind?". Amazingly fuzzy thinking! > I am quite amazed at the degree of misinformation this work has caused. Um.... why is this "fuzzy thinking"? In the sense meant, she *would* be the mother of all mankind. In the same sense that, say, your maternal grandmother is the "mother of" you, your siblings, and your maternal cousins. It doesn't mean that she was the only female ancestor of yours in that generation, just that she is a common one to the group of people in question. -- "What are we going to do?" "S-s-s-simple," said Inigo after a while. "Are you frightened too?" asked Fezzik in the darkness. "Not... remotely," Inigo said with great care. "And before, I meant to say 'easy'; I don't know how the 's-s-s-s' got in there." --- from the book The Princess Bride by William Goldman
werner@aecom.YU.EDU (Craig Werner) (10/13/87)
In article <1248@bsu-cs.UUCP>, dhesi@bsu-cs.UUCP (Rahul Dhesi) writes: > In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU > (Edwin L Turner) writes: > > All living people (or at least ~99% of them) have a single common > female ancestor on their purely maternal line.... > > I wonder why Creationists haven't picked up on this. > Rahul Dhesi Two reasons why Creationists haven't picked up on it: 1. It was discussed in the scientific literature on evolution, and if you reject evolution, you don't tend to keep up with the literature. 2. "Eve," so called, is far too old. She is anywhere from 50,000 to 500,000 years old, and as everyone knows, the world was created in 6 days and nights, oh, about 5000 years ago (I'm not whether Bishop Usher's calculations agree with the Jewish calendar, which would put the Earth's age at 5248 years plus 4 1/2 weeks.) -- Craig Werner (future MD/PhD, 3 years down, 4 to go) werner@aecom.YU.EDU -- Albert Einstein College of Medicine (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517) "If I don't see you soon, I'll see you later."
pell@boulder.Colorado.EDU (Anthony Pelletier) (10/13/87)
I'm confused here. Would anyone have suggested that humans evoloved more than once? As in there were several different times and different places on the planet where humans arose from other primate forms. It seems to me that an event as momentous as that in evolution would have occured only once. I think far more about molecules than I do about organisms (they're too complicated), but it seems obvious to me that if we evolved only once, we have one common ancestor. -tony Molecular etc. Biology Boulder, Co. 80303=0347
leonard@bucket.UUCP (Leonard Erickson) (10/13/87)
In article <1248@bsu-cs.UUCP> dhesi@bsu-cs.UUCP (Rahul Dhesi) writes: <In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU <(Edwin L Turner) writes: < < All living people (or at least ~99% of them) have a single common < female ancestor on their purely maternal line.... < <I wonder why Creationists haven't picked up on this. Easy, the same evidence also shows that this common ancestor was too far back to fit in with the Bible. And this (and similar) evidence also shows "recent" common ancestors with gorillas (and very slightly les recent with chiimps). As I recall, human DNA is similar enough to gorilla that a hybrid would quite likely be viable! Of course, no one is going to try it. It is a real can of worms ethically.... -- Leonard Erickson ...!tektronix!reed!percival!bucket!leonard CIS: [70465,203] "I used to be a hacker. Now I'm a 'microcomputer specialist'. You know... I'd rather be a hacker."
jenkins@arthur.cs.purdue.edu (Colin Jenkins) (10/14/87)
in article <2545@sigi.Colorado.EDU>, pell@boulder.Colorado.EDU (Anthony Pelletier) says: > > I'm confused here. Would anyone have suggested that humans evoloved more > than once? As in there were several different times and different > places on the planet where humans arose from other primate forms. > It seems to me that an event as momentous as that in evolution would have > occured only once. > > -tony I recall from my genetics courses that many genes mutate in similar ways with significant statistical frequencies. Of course, this doesn't *prove* anything about the existance of multiple or singular ancestors, but I should think it would leave the door open for the consideration of multiple individuals distinctive enough as ancestors to be called Homo Sapiens. My impression of evolution is not that a single momentous event could have occurred, but rather a series of such events. If, after each significant mutation, a large quantity of offspring was produced, then the next step in the sequence would have a significant statistical likelihood in a large base of individuals, not just one, and so on for each significant mutation. Colin
dino@ddsw1.UUCP (Laura Watson) (10/14/87)
In article <1367@aecom.YU.EDU> werner@aecom.YU.EDU (Craig Werner) writes: > > 2. "Eve," so called, is far too old. She is anywhere from >50,000 to 500,000 years old, and as everyone knows, the world was >created in 6 days and nights, oh, about 5000 years ago (I'm not >whether Bishop Usher's calculations agree with the Jewish calendar, >which would put the Earth's age at 5248 years plus 4 1/2 weeks.) Not so, my esteemed Mr. Werner. I don't have a Bible handy for an exact quote, but the verse which says something like: "The earth was without form and void" could be *equally* *as* *well* translated from the original Hebrew as "The earth became a waste and a desolation." This comes right before the bit about the world being created in 6 days and nights, implying that God *RE*created the world in 6 days and nights after wiping out an older failed model. Everybody knows the earth is older than 5248 years. People who believe in evolution don't keep up with creationism. -- Laura Watson ...ihnp4!ddsw1!dino Contentment is the smother of invention.
pell@boulder.Colorado.EDU (Anthony Pelletier) (10/14/87)
(Colin Jenkins) writes: (in response to me) >> >> I'm confused here. Would anyone have suggested that humans evoloved more >> than once? >> >> -tony > Colin: >I recall from my genetics courses that many genes mutate in similar ways with >significant statistical frequencies. Of course, this doesn't *prove* anything >about the existance of multiple or singular ancestors,but [it is possible] > >My impression of evolution is not that a single momentous event could have >occurred, but rather a series of such events. If, after each significant >mutation, a large quantity of offspring was produced, then the next step in >the sequence would have a significant statistical likelihood in a large base >of individuals, not just one, and so on for each significant mutation. > > Colin Of course we are arguing in the dark here--proof would be hard to come by. In the early-going of a rather good book called "Molecular Biology of the Cell" (Alberts, Bray, Lewis, Raff, Roberts et al.), the authers admit there bias that each major event in evolution occurred only once, one primordial cell, one eukariote, one metazoan on down the line. Our mitochondria should be direct decendants of not only the first Human, but also the first euk. It seem logical that, given speciation of a new mammal has not been observed as long as man has been keeping track, it is a rare event. I find it hard to believe that it happened more than once, let alone more than once in a small enough area that these different H. sapiens could make one breeding population. I always assumed that the reason archiologists argue over whose fosil is older has to do with the assumption that the younger ones are Decended from the older, not different lines that are co-incident. I imagine speciation in the following way (here I am way out of my line): Some event occurs (eg. a chromosome re-arrangement) such that an offspring can not mate productively, or, at least not have fertile offspring, with any members of the group except its parent or perhaps its siblings. Offsping of these matings are also constrained in there mating. You now have a separate breeding population. If the new population has a selective advantage, you have a new, meta-stable species. Now, the new species might well co-exist with the old for some time, amassing some numbers of individuals that would seem to be in one population with the parent species. But they would be a separate breeding population. The notion of a group of organisms going off into a secluded area and evolving together into a new species seems absurd to me. I can buy that selection on all of them is the same, but the random element of evolution, mutation, cannot possibly occur in them all. More likely, the mixed population, such as the one I describe exists until some selective pressure kills off the parent species. just rambling -tony
rs55611@ihlpl.ATT.COM (Robert E. Schleicher) (10/14/87)
In article <548@bucket.UUCP>, leonard@bucket.UUCP (Leonard Erickson) writes: > In article <1248@bsu-cs.UUCP> dhesi@bsu-cs.UUCP (Rahul Dhesi) writes: > <In article <894@phoenix.Princeton.EDU> elturner@phoenix.Princeton.EDU > <(Edwin L Turner) writes: > < > < All living people (or at least ~99% of them) have a single common > < female ancestor on their purely maternal line.... > > As I recall, human DNA is similar enough to gorilla that a hybrid would > quite likely be viable! Of course, no one is going to try it. It is a real > can of worms ethically.... > > -- > Leonard Erickson ...!tektronix!reed!percival!bucket!leonard > CIS: [70465,203] Amazingly, I read a short article in the newspaper some time ago (which I'm trying to recall from memory, so please bear with some vagueness) about some researchers in Italy who had been experimenting with fertilization of human eggs with either gorila or chimp sperm (or the other way around). They were able to cause fertilization, as evidenced by the start of cell division, but only for a very short time (on the order of days), so there was never anything resembling an embryo. After someone revealed to the press the nature of the experimentation, it was called off. However, this does raise some very critical ethical questions. At the present rate of advances in genetic engineering, many of the ethical questions need answers quickly. The scariest part of the article was a quote from one of the researchers who said something to the effect of: (paraphrasing) "Just think! We could create a race of human/ape hybrids that we could use for manual labor!" The article concluded with the following food for thought (perhaps far-fetched; perhaps not): To what extent would/should human civil rights be "granted" to such a human/ape hybrid? As of now, there is a relatively clear distinctionmade between humans (with rights, at least ideally), and all other animal forms, who have essentially no rights. As we learn more about ape and porpoise intelligence, we may decide we are in need of animal rights in some cases. Even if apes never have rights, what about a half-ape/half human? Do they get a sub-set of human rights? What about the inevitable combinations like 3/4 human-1/4 ape or other mixes of human/ape genes. How about voting rights (1/2 vote for a half-human?) What about the exceptional half-human that's more intelligent than some full-human? The cans of worms that this would create are incredible. Barring some sort of control or legislation over genetic experimentation, we are bound to see something shocking occur within 10 years. Of course, how to control things (ie., legislate ethics) is also a difficult question. Frankly, I don't expect to see anything happen in this area until something dramatic happens, causing some amount of public outcry. Bob Schleicher ihlpl!rs55611 (Perhaps someone who remembers the article more clearly can elaborate. The article I read was in the Chicago Tribune quite a few months ago.)
daver@sci.UUCP (Dave Rickel) (10/15/87)
In article <548@bucket.UUCP>, leonard@bucket.UUCP (Leonard Erickson) writes: > As I recall, human DNA is similar enough to gorilla that a hybrid would > quite likely be viable! Of course, no one is going to try it. It is a real > can of worms ethically.... I don't believe this is correct, but of course, i could be wrong. I remember that humans, gorillas, and chimpanzees all seem to be about equidistant from some common ancestor on the evolutionary tree--that gorillas are as closely related to man as they are to chimpanzees; ditto with chimps. I do recall reading that human hemoglobin is close enough to gorilla hemoglobin (the difference is one amino acid in one protein chain) that it is virtually certain that some human has the equivalent of gorilla hemoglobin in his veins. david rickel decwrl!sci!daver
hildum@iris.ucdavis.edu (Eric Hildum) (10/15/87)
Hello, I suspect that the matter of voting is already solved in the US by a clause in the constitution - something to the effect that 5/8 of a vote is assigned to "others". Eric
jenkins@arthur.cs.purdue.edu (Colin Jenkins) (10/15/87)
in article <2567@sigi.Colorado.EDU>, pell@boulder.Colorado.EDU (Anthony Pelletier) says: > (Colin Jenkins) writes: (in response to me) >>> I'm confused here. Would anyone have suggested that humans evoloved more >>> than once? > Colin: > >>I recall from my genetics courses that many genes mutate in similar ways with >>significant statistical frequencies. Of course, this doesn't *prove* anything >>about the existance of multiple or singular ancestors,but [it is possible] >> >>My impression of evolution is not that a single momentous event could have >>occurred, but rather a series of such events. If, after each significant >>mutation, a large quantity of offspring was produced, then the next step in >>the sequence would have a significant statistical likelihood in a large base >>of individuals, not just one, and so on for each significant mutation. > > Of course we are arguing in the dark here--proof would be hard to come by. Sure, but it is interesting to kick around a bit... [ Describes good Bio book where authors believe each major event in evolution happened once ] > Our mitochondria should be direct decendants of not only the first Human, but > also the first euk. It seem logical that, given speciation of a new mammal > has not been observed as long as man has been keeping track, it is a rare event. I'm not sure that logic supports you here. I would guess that man has been "keeping track" for not more than 2000 years (probably a lot less). Evolution is thought to require millions of years, so not seeing a new mamal recently is not a good foundation to base a claim about evolution on. > I imagine speciation in the following way (here I am way out of my line): > Some event occurs (eg. a chromosome re-arrangement) such that an offspring can > not mate productively, or, at least not have fertile offspring, with any > members of the group except its parent or perhaps its siblings. > Offsping of these matings are also constrained in there mating. On this point (and I am just as far out of my line at this point) I have trouble because such a breeding incompatibility would probably only come about through radical genetic changes, rather than small ones. I don't think that evolution supports an idea of radical change, rather gradual changes selected by the environmental factors to be passed on through reproduction. The other problem with this thought is that it seems to presuppose that the mutant will be somehow aware of its reproductive incompatabilities and make the fortunate choice of breeding with its relatives. More complicated is the fact that the none of the other relatives may have received the mutations, so they should have just as much difficulty mating with the mutant as any other normal organism. I saw a National Geograpic or Nova on the "Eve" issue and I thought that particular program went on to suggest that Cro Magnums may have interbred with Neanderthols, considered to be seperate species. (Did anyone see it? I was in the kitchen suffering through meal preparation and could only hear the television. My memory is only sketchy on the show). > -tony Colin
emigh@ncsugn.ncsu.edu (Ted H. Emigh) (10/16/87)
In article <2052@arthur.cs.purdue.edu> (Colin Jenkins) writes: >> I imagine speciation in the following way (here I am way out of my line): >> Some event occurs (eg. a chromosome re-arrangement) such that an offspring can >> not mate productively, or, at least not have fertile offspring, with any >> members of the group except its parent or perhaps its siblings. >> Offsping of these matings are also constrained in there mating. > >On this point (and I am just as far out of my line at this point) I have >trouble because such a breeding incompatibility would probably only come about >through radical genetic changes, rather than small ones. I don't think that >evolution supports an idea of radical change, rather gradual changes selected >by the environmental factors to be passed on through reproduction. Evolution "supports" whatever mechanisms are needed. I know of no evolutionist that requires ALL changes to be small and gradual. In particular, the speciation "event" most likely is quite radical (environmental if not genetic). > >The other problem with this thought is that it seems to presuppose that the >mutant will be somehow aware of its reproductive incompatabilities and make >the fortunate choice of breeding with its relatives. More complicated is the >fact that the none of the other relatives may have received the mutations, so >they should have just as much difficulty mating with the mutant as any other >normal organism. > Here comes my yearly description of the comparison of chromosomal arrangements among the great apes (which includes man). If you have heard this before, there is no need to read the rest, you can just send your flames automatically. I have before me a diagram (SCIENCE 1982, 215:1525-1530) which shows gives a comparison of the banding patterns of humans, chimpanzee, gorilla, and orangutan. There are several remarkable things about the diagram. 1) The chromosomes match up very nicely with the exception of human chromosome #2, which matches up with TWO chromosomes of each of the other great apes. This suggests that a our #2 is a fusion of two chromosomes of our (the great apes) common ancestor or that the great apes chromosomes arose from a fission of on chromosome from our common ancestor (and humans retained the single chromosome). 2) If you look at each chromosome, the banding patterns are quite similar. However, for all but the smallest chromosomes (19-Y) there are obvious inversions. Now recalling your elementary genetics class, the important features to remember about inversions are: Inversions have no detectable effect on the individual with an inversion (with the possible exception of regulatory groups, etc); Individuals who are heterozygous for the inversion (that their two chromosomes have one "normal" and one inverted) have a much lower reproductive fitness (crossing over within an inversion lead to large chunks of chromosomes either deleted or duplicated). What this means is the populations with small effective size can quickly become effectively reproductively isolated from their neighbors -- one of the conditions for speciation to occur. (Obviously speciation can occur in other ways -- this describes just one way). -- Ted H. Emigh, Dept. Genetics and Statistics, NCSU, Raleigh, NC uucp: mcnc!ncsuvx!ncsugn!emigh internet: emigh%ncsugn.ncsu.edu BITNET: NEMIGH@TUCC @ncsuvx.ncsu.edu:emigh@ncsugn.ncsu.edu
jenkins@arthur.cs.purdue.edu (Colin Jenkins) (10/18/87)
in article <677@ncsugn.ncsu.edu>, emigh@ncsugn.ncsu.edu (Ted H. Emigh) says: > In article <2052@arthur.cs.purdue.edu> (Colin Jenkins) writes: << <<On this point (and I am just as far out of my line at this point) I have <<trouble because such a breeding incompatibility would probably only come about <<through radical genetic changes, rather than small ones. I don't think that <<evolution supports an idea of radical change, rather gradual changes selected <<by the environmental factors to be passed on through reproduction. < < Evolution "supports" whatever mechanisms are needed. I know of no evolutionist < that requires ALL changes to be small and gradual. In particular, the < speciation "event" most likely is quite radical (environmental if not genetic). OK, however I wasn't talking about environmental changes, but rather individual biological ones. Radical changes of environment are easy to imagine as contributors to evolution. I did not mean to imply that all processes that contribute to evolution *must* be small. When someone says a "radical" change perhaps it should be qualified. Change in genotype, or change in phenotype? I was thinking strictly in terms of genotype. The impression I get from the idea of "radical" change is some new organism with a number of differences, rather than a few. Kind of like a snake born with legs and feet one day giving rise to a whole new species of snakes with legs and feet (I presume that a complicated change such as this would require many genetic mutations, rather than a few). Is such a "jump" viewed as a frequent and major contributor to evolution? (That wasn't a facetious question, I'm really asking) <<The other problem with this thought is that it seems to presuppose that the <<mutant will be somehow aware of its reproductive incompatabilities and make <<the fortunate choice of breeding with its relatives. More complicated is the <<fact that the none of the other relatives may have received the mutations, so <<they should have just as much difficulty mating with the mutant as any other <<normal organism. << < I have before me a diagram (SCIENCE 1982, 215:1525-1530) which shows gives a < comparison of the banding patterns of humans, chimpanzee, gorilla, and < orangutan. There are several remarkable things about the diagram. [Description of close chromosomal matching and differences, and comments on inversions and some of their effects in differing combinations on offspring ] < What this means is the populations with small effective size can quickly < become effectively reproductively isolated from their neighbors -- one of < the conditions for speciation to occur. (Obviously speciation can occur < in other ways -- this describes just one way). < -- < Ted H. Emigh, Dept. Genetics and Statistics, NCSU, Raleigh, NC What you posted was very interesting, but I'm not sure what it says about the correctness or incorectness of what I posted. If the inversions you talked about do produce radical genetic changes that can reproductively isolate populations, what mechanism ensures that breeding takes place between compatible mates? Perhaps a definition of terms would be instructive. What do you mean when you say "radical" change? Colin
rmr@chefchu.SGI.COM (Robert Reimann) (10/19/87)
In article <10107@sci.UUCP>, daver@sci.UUCP (Dave Rickel) writes: > > I remember > that humans, gorillas, and chimpanzees all seem to be about equidistant from > some common ancestor on the evolutionary tree--that gorillas are as closely > related to man as they are to chimpanzees; ditto with chimps. > This was a matter of contention until recent comparisions of human, chimp, and gorilla DNA showed that gorillas were closer, as in the diagram below. If I remember correctly, the point where the gorilla/human ancestor split from chimps is not very far from the point where gorilla and human lines split. ------- chimps | ------- ---- gorillas | | ---- | ---- humans Robert Reimann.
throopw@dg-rtp.UUCP (Wayne A. Throop) (10/20/87)
> rmr@chefchu.SGI.COM (Robert Reimann) > If I > remember correctly, the point where the gorilla/human ancestor split from > chimps is not very far from the point where gorilla and human lines split. > > ------- chimps > | > ------- ---- gorillas > | | > ---- > | > ---- humans Um. I don't think this is correct. In the "Eve" episode of Nova last year, the diagram was resolved by molecular similarity studies in the opposite way (that is, "chimps" and "gorillas" should be exchanged in the above diagram). If *I'm* remembering the program correctly, the human-chimp common ancestor existed about 5 million years ago, and the human-chimp-gorilla common ancestor existed about 8-12 million years ago. Molecularly, gorillas are an equal distance from either humans or chimps (about 95% similarity according to the Nova episode mentioned), while chimps are closer to humans than to gorillas (about 98% similarity). -- "It was just paper before and it's still just paper." --- Sam Walton, Oct 19, 1987 -- Wayne Throop <the-known-world>!mcnc!rti!xyzzy!throopw
hyland@esosun.UUCP (Steve Hyland) (10/20/87)
In article <7034@sgi.SGI.COM> rmr@chefchu.SGI.COM (Robert Reimann) writes: >This was a matter of contention until recent comparisions of human, chimp, and >gorilla DNA showed that gorillas were closer > Robert Reimann. An article in Monday's Los Angeles Times indicated that extensive gene mapping resulted in chimps having more common genomes (is that the correct term?) with humans than gorillas. Now, could we start talking about something other than this in soc.women ? Steve Hyland SAIC "There's a seeker born every second" -- The Firesign Theater
wcalvin@well.UUCP (William Calvin) (10/21/87)
The DNA hybridization method, which has been nicely calibrated against the fossil birds, gives the gorilla branch at 10-11 Myr, the chimp- hominid split between 7.7 and 6.3 Myr. This method is the most accurate so far because it utilizes all the nuclear DNA, not just what is expressed (and is thus under various rates of natural selection). The 90+ percent junk DNA isn't under selection and so probably has a constant clock rate compared to proteins. William H. Calvin University of Washington NJ-15, Seattle WA 98195
daver@sci.UUCP (Dave Rickel) (10/22/87)
In article <343@dg-rtp.UUCP>, throopw@dg-rtp.UUCP (Wayne A. Throop) writes: > > rmr@chefchu.SGI.COM (Robert Reimann) > > If I > > remember correctly, the point where the gorilla/human ancestor split from > > chimps is not very far from the point where gorilla and human lines split. > Um. I don't think this is correct. In the "Eve" episode of Nova last > year, the diagram was resolved by molecular similarity studies in the > opposite way (that is, "chimps" and "gorillas" should be exchanged in > the above diagram). I sent mail to rmr saying more or less the same thing. He wrote back, saying that he rechecked his sources, and he got gorillas and chimps transposed, and also that his news access has been flaky and to go ahead and post the correction. My source says that gorillas and chimphumans diverged about 6 million years ago, and chimps diverged from humans about 4.5 million years ago. The article goes on to suggest that perhaps humans should be reclassified as Pan Sapiens (interesting idea, but i would give long odds against). david rickel decwrl!:19:ebahei