Pharyngula

Silly and naive

Paul Nelson isn’t happy that I explained that W. Ford Doolittle is not denying common descent when he says there was a large and diverse pool of organisms swapping genes at the base of the tree of life, and he presents a very revealing counter-argument:

Before I respond to PZ’s baseless charge, let’s see what mental image the following proposition generates:

All organisms on Earth have descended from a single common ancestor.

I’ll bet “single common ancestor” caused you to picture a discrete cell. And if you opened a college biology textbook, to the diagram depicting Darwin’s Tree of Life, you’d find that same image.

Maybe among Nelson’s clique, they imagine a single cell; I don’t know of any biologists who would, though. Do they also imagine a single pair of humans giving rising to the modern population, too?

Lineages do not have descent through single individuals or pairs in any evolutionary explanation. It’s always populations. Humans arose as descendants of a group of our ancestors who also apparently maintained a loose and slowly weakening genetic contact with the root stock and closely related primates — there was a gradual separation of the lineage over time and embodied in many individuals. The rise of life in general was even less tidily bounded in the absence of strong isolating mechanisms — the little buggers were promiscuously sloshing genes back and forth among all kinds of cells.

I’m afraid that all Nelson has accomplished with his complaint was to reveal yet again how naive and simplistic the creationist view of biology is. And we already knew that … there’s nothing new there at all.

Oh, and do take a look at Nick Matzke’s mocking of his claim about textbooks. He seems to think the bars on a cladogram represents single, discrete individuals? I think Nelson has just flunked Evolutionary Biology 101.

Comments

  1. #1 saurabh
    July 12, 2007

    I’ll point out this insulting comment Doolittle leaves in his last paper for the likes of Nelson:

    Holding onto this ladder of pattern [i.e., the single-root tree of life] is an unnecessary hindrance in the understanding of process (which is prior to pattern) both ontologically and in our more down-to-earth conceptualization of how evolution has occurred. And it should not be an essential element in our struggle against those who doubt the validity of evolutionary theory, who can take comfort from this challenge to the TOL only by a willful misunderstanding of its import. The patterns of similarity and difference seen among living things are historical in origin, the product of evolutionary mechanisms that, although various and complex, are not beyond comprehension and can sometimes be reconstructed.

  2. #2 xebecs
    July 12, 2007

    Please pardon a naive question.

    Is the phrase “All organisms on Earth have descended from a single common ancestor.” used by evolutionary biologists or (at least) by lowest-common-denominator biology textbooks?

    Or is the phrase just a straw-quote from thin air?

  3. #3 anonymous
    July 12, 2007

    Paul must know that ID is not working out. Why can’t he admit it?

  4. #4 waldteufel
    July 12, 2007

    Of course Paul Nelson thinks that humankind can be traced to a single pair of humans: Adam and Eve 6,000 years ago. It says so, right there in Paul’s Wholly Babble.

  5. #5 Martin Brazeau
    July 12, 2007

    Nelson is confusing anastomosis with multiple origins. Nothing in Doolittle’s remarks suggests that he thinks life sprung up several times independently.

    Flunking Evolutionary Biology 101? Try flunking basic high school biology. Perhaps even flunking his primary school reading lessons.

  6. #6 386sx
    July 12, 2007

    Good job with exploring evolution Mr. Nelson. That’s pretty good. You’re a real good evolution explorer.

  7. #7 Jon
    July 12, 2007

    In the Selfish Gene, Dawkins presents, I think, one of the best narratives (I’ve read, at least) for how life probably began, starting with the very unlikely occurrence of those first replicating molecules. I just can’t fathom someone reading it and not finding it entirely plausible and at least somewhat explanatory. Then again, plausibility isn’t something that usually factors into most peoples’ beliefs about the world.

  8. #8 Ginger Yellow
    July 12, 2007

    xebecs, the point is that “ancestor” doesn’t mean organism. It means species.

  9. #9 JC
    July 12, 2007

    I’ll bet “single common ancestor” caused you to picture a discrete cell. And if you opened a college biology textbook, to the diagram depicting Darwin’s Tree of Life, you’d find that same image.

    In the same diagram you’ll also find lots of big arrows. Have the Darwinist fiends ever dug up an enormous fossilized arrow? Another nail in the coffin of eviloution, I think.

  10. #10 Rosie Redfield
    July 12, 2007

    Don’t forget that sexual reproduction (meiosis plus gamete fusion) is a recent and eukaryote-specific invention. If not for the processes that occasionally move pieces of DNA from one bacterial cell to another, common descent from a single ancestral cell would indeed accurately describe our early evolutionary history.

    This movement of DNA can obscure and confound attempts to track lineages of descent back into the orgins of the major groups of organisms. Doolittle’s claim (heavily hyped and I think exaggerated) is that this transfer has been so frequent that the concept of deep lineages must be discarded.

  11. #11 QrazyQat
    July 12, 2007

    Seems to me that if you zap a primordial puddle full of goo and this creates living matter, it’d be pretty hard for it to be just one cell. In fact, even assuming it was just a very local event, let’s say confined to a single drop of water, there’d still likely be thousands or millions of little living thingies. These bits are pretty small; even cells would be pretty small.

  12. #12 truth machine
    July 12, 2007

    Maybe among Nelson’s clique, they imagine a single cell; I don’t know of any biologists who would, though.

    Then who is Doolittle’s dispute with? He writes “Holding onto this ladder of pattern” — who is holding on? “is an unnecessary hindrance in the understanding of process” — hindrance for whom? “this challenge to the TOL” — what challenge, if all biologists already accept his view?

    Do they also imagine a single pair of humans giving rising to the modern population, too?

    Mitochondrial Eve and Y-chromosomal Adam (who lived in different eras, I know) were individuals. I don’t think it’s unreasonable to take “a single common ancestor” as referring to an individual, and if biologists don’t mean that, they should be a lot clearer. But this of course does not justify Nelson’s absurd claim that Coyne and Doolittle disagree over common descent which is, as Doolittle says, “a willful misunderstanding of its import”.

  13. #13 brightmoon
    July 12, 2007

    oh, paul nelson , my favorite creationist [insert eyeroll]

    figures

  14. #14 steve s
    July 12, 2007

    JC’s post above is my favorite blog comment in quite some time.

  15. #15 Nick (Matzke)
    July 12, 2007

    Mitochondrial Eve and Y-chromosomal Adam (who lived in different eras, I know) were individuals. I don’t think it’s unreasonable to take “a single common ancestor” as referring to an individual, and if biologists don’t mean that, they should be a lot clearer.

    There is a distinction in biology between species trees and gene trees. Gene trees provide information about species trees (= organismal phylogeny) but they are not the same thing.

    Your Mitochondrial Eve and Y-chromosomal Adam example is a good one actually. It is true that various universal features of extant human mitochondria or y-chromosomes trace back to a single individual, but this is just an inevitable product of neutral drift (google “coalescence evolution”). The individuals are different individuals, “Adam” and “Eve” lived in different places, tens of thousands of years appart. And many other genes would trace back to still different individuals — at no time was the human population down to 1 or 2 individuals.

    So when scientists discuss the “common ancestor” of e.g. humans and chimps, no one has in mind a single individual, they are all talking about a species or population. In fact we still have polymorphisms (variability in gene DNA sequences within a population) that are also polymorphisms in chimps, indicating that those particular alleles haven’t fixed yet.

  16. #16 phat
    July 12, 2007

    Holy crap!

    Light just dawned with the very biologically ignorant person.

    I love this blog.

    phat

  17. #17 phat
    July 12, 2007

    To be clear, I’m not saying that I’m biologically determined to be ignorant (although, I can’t prove either way I suppose).

    I’m saying I never learned biology.

    phat

  18. #18 Sophist, FCD
    July 12, 2007

    And if you opened a college biology textbook, to the diagram depicting Darwin’s Tree of Life, you’d find that same image.

    And another thing–when a biology textbook talks about a species like, for instance, tigers, they show a photo containing one or at most a handfull, not all tigers to ever exist anywhere, ever. What’s up with that?

  19. #19 Sophist, FCD
    July 12, 2007

    I don’t think it’s unreasonable to take “a single common ancestor” as referring to an individual, and if biologists don’t mean that, they should be a lot clearer.

    So, what, it’s the author’s responsibilty to make sure that any fragment of their text must clearly convey their meaning even when surgically excised from it’s context? Hmmm. Lets try that shall we?

    It’s unreasonable to take “a single common ancestor” as referring to an individual.

    Oops. Sloppy writing there, truth machine. I guess you need to work on clarity too.

  20. #20 Tom
    July 12, 2007

    Mitochondrial Eve and Y-chromosomal Adam (who lived in different eras, I know) were individuals. I don’t think it’s unreasonable to take “a single common ancestor” as referring to an individual, and

    Try reading Dennett’s Darwin’s Dangerous Idea for a really great englsh language explanation of how M. eve was only one individual of a population of other women who all shared very much the same suite of genes/alleles. At the time Dennett wrote it (1994-95) Y-Chromosome Adam had not yet been nailed down so he’s missing. Dennett can be pretty dense reading, but that is one of the clearest explanations of this particular comncept.

  21. #21 Ann Homily
    July 12, 2007

    Sort of related to this topic: I found this neat little video on YouTube showing the fossil evolution of vertebrates:

    http://www.youtube.com/watch?v=BBkRM4pSvgM

    (he needs to add more… it’s only up to mammal-like reptiles.)

  22. #22 Springheel
    July 12, 2007

    Does this jibe with the thesis of Dawkin’s “Ancestor’s Tale”?

  23. #23 YetAnotherKevin
    July 12, 2007

    One thing I remember from “Ancestor’s Tale” is that if you go back far enough in the history of a species, every single member of the ancestral population is either an ancestor of every member of the modern population, or not an ancestor of any member of the modern population.

    That’s still hard for me to wrap my mind around.

  24. #24 Shawn Wilkinson
    July 13, 2007

    The rise of life in general was even less tidily bounded in the absence of strong isolating mechanisms — the little buggers were promiscuously sloshing genes back and forth among all kinds of cells.

    I knew it. In the beginning was the Orgy, and the Orgy was with God, and God was the Orgy. The Greeks gave great praise not to language but sexual promiscuity. Now classical history makes significantly more sense.

    /joke\

  25. #25 Bob O'H
    July 13, 2007

    JC’s post [#9] above is my favorite blog comment in quite some time.

    Seconded.

    Bob

  26. #26 hf
    July 13, 2007

    This layman had to google ‘anastomosis’ before I was sure what y’all meant.

  27. #27 truth machine
    July 13, 2007

    So when scientists discuss the “common ancestor” of e.g. humans and chimps, no one has in mind a single individual

    Reading comprehension problem? What I said was that biologists need to be clearer about this. And it’s absurd to say that “no one has in mind a single individual”, as if non-scientists don’t exist. And I don’t believe it’s true for all scientists, not when it comes to abiogenesis, as opposed to elsewhere in the tree — a significant number of scientists really do believe that there was a single replicating molecule common to all our histories, and a single cell common to all our histories, and some of those scientists are even biologists.

  28. #28 truth machine
    July 13, 2007

    One thing I remember from “Ancestor’s Tale” is that if you go back far enough in the history of a species, every single member of the ancestral population is either an ancestor of every member of the modern population, or not an ancestor of any member of the modern population.

    That’s still hard for me to wrap my mind around.

    It’s shouldn’t be that tough. At any point in time, there’s a set of organisms that isn’t the ancestor of any member of the modern population, and the complementary set of organisms that are ancestors of at least one member of the modern population. If any of the latter set isn’t the ancestor of every member of the modern population, just go back further in time. Eventually you must reach either a set that qualifies, or a single organism that is a common ancestor of the entire population — which qualifies. QED

  29. #29 truth machine
    July 13, 2007

    Try reading Dennett’s Darwin’s Dangerous Idea for a really great englsh language explanation of how M. eve was only one individual of a population of other women who all shared very much the same suite of genes/alleles.

    Well duh. But that has no bearing on what I wrote, which is about the piss-poor way that biologists communicate. Mitochondrial Eve, who is a common ancestor of all of us, was an individual, and Y-chromosome Adam, who is a common ancestor of all men, was an individual. It is not, then, unreasonable for one to think (incorrectly) that the “common ancestor” of humans and monkeys, and the “common ancestor” of all life, is an individual. It’s elitist and insular for biologists to expect the population at large to understand that they are talking about populations or species when they don’t use those words.

  30. #30 Ichthyic
    July 13, 2007

    It’s elitist and insular for biologists to expect the population at large to understand that they are talking about populations or species when they don’t use those words.

    you’re still missing it.

    the question was asked early on:

    Is the phrase “All organisms on Earth have descended from a single common ancestor.” used by evolutionary biologists or (at least) by lowest-common-denominator biology textbooks?

    and the answer is emphatically NO.

    what is said is that all organisms share COMMON ANCESTRY.

    this is NOT THE SAME as saying all organisms share A common ancestor.

    so the confusion you continue to berate is all on you, TM.

    It’s also why PZ said he never hears biologists speak in the terms you describe.

    you’ve been entirely taken in by the strawman people like Paul have created of the issue. the confusion you suggest is perpetrated by biologists upon a poor ignorant public does not exist except in the strawmen created by the ignorant themselves.

  31. #31 Ichthyic
    July 13, 2007

    It’s shouldn’t be that tough.

    it sure was for you, given that you got it entirely wrong.

    I’m just going to steal Nick Matzke’s words to Paul Nelson in the thread on PT, as they are brief and to the point:

    So you *do* think that those nodes represent individual organisms! Incredible!

    Here’s a thought experiment for you. Take a species. Divide into two subpopulations via some catastrophe in the middle. In the first subpopulation, molecular character 1 arises on gene A. In the second population, molecular character 2 arises on gene B. Each character spreads to a high frequency in its respective subpopulation. Then, migration or environmental recovery brings the two subpopulations back together. Mating/conjugation occurs and suddenly 20% or so of the population now has characters 1+2, but without anyone ever having inherited 1+2 from an single individual organism with 1+2.


    In other words, a single character can trace back to a single organism, but the inference that ALL shared characters therefore trace back to the SAME single organism is wrong, wrong, wrong.

    I’m sorry, TM, that you seem to think that biologists are confusing the general public, as the way Nick parses it seems pretty damn clear to me. It’s also pretty much exactly the way I’ve heard it described by any biology instructor I’ve ever dealt with, myself included.

    OTOH, there’s no accounting for what any particular individual will get themselves confused about.

  32. #32 Ichthyic
    July 13, 2007

    a significant number of scientists really do believe that it is possible that there was a single replicating molecule common to all our histories, and/or a single cell common to all our histories, and some of those scientists are even biologists.

    I added the correction in bold. Also, you should catch yourself up on the research on abiogenesis that has occurred in the last 30 years or so, as a growing body of evidence is now weighing against the idea you note above.

    check the posts by Gary Hurd in the thread on PT for some good links.

  33. #33 truth machine
    July 13, 2007

    I won’t waste my time on the foolish fish and his numerous lapses of logic and reading comprehension.

  34. #34 truth machine
    July 13, 2007

    Well, just this:

    In other words, a single character can trace back to a single organism, but the inference that ALL shared characters therefore trace back to the SAME single organism is wrong, wrong, wrong.

    Listen, you stupid fuck, I don’t think any such thing and never claimed any such thing. That you think I do is because of your inability to comprehend logic or English.

  35. #35 truth machine
    July 13, 2007

    Is the phrase “All organisms on Earth have descended from a single common ancestor.” used by evolutionary biologists or (at least) by lowest-common-denominator biology textbooks?

    and the answer is emphatically NO.

    what is said is that all organisms share COMMON ANCESTRY.

    this is NOT THE SAME as saying all organisms share A common ancestor.

    You are emphatically a lying jackass and an idiot. Go google “common ancestor”. Among similar hits is this one at
    evowiki: http://wiki.cotch.net/index.php/Common_ancestor

    “According to the hypothesis of common descent, any two species on Earth living at any time share a most recent common ancestor (concestor1).”

    It notes that the phrase refers to species, but the claim that the phrase isn’t used is complete and utter bullshit. What does LUCA stand for? Last Universal Common Ancestry? Of course not, you stupid lying dipshit.

    Ok, now I’m really done with the stench of this rotting fish.

  36. #36 Ichthyic
    July 13, 2007

    I won’t waste my time on the foolish fish and his numerous lapses of logic and reading comprehension.

    IOW, you won’t admit that the way you attempted to explain common ancestry, or the berating you aimed at “biologists” were both wrong.

    got it.

  37. #37 Ichthyic
    July 13, 2007

    living at any time share a most recent common ancestor (concestor1).”

    you are obfuscating. do note the term included:

    MOST RECENT common ancestor.

    not the same.

    sorry, you’re still wrong, and you still don’t quite understand what is meant by common ancestry in an evolutionary sense, apparently. It’s kinda funny watching you get all flustered about it, rather than simply admit you were getting it slightly wrong.

    I remember that from the wiki-war we had a long while back.

    shake your fist all you want.

    Nick’s argument speaks for itself quite eloquently, which is why I quoted it verbatim.

  38. #38 Ichthyic
    July 13, 2007

    hey, maybe that’s it! you get your learning from wiki, and then project any confusion you garner from a wiki entry onto biologists in general?

    shall we argue over the value of online encyclopedias as teaching tools again?

  39. #39 Ichthyic
    July 13, 2007

    It notes that the phrase refers to species,

    I read the wiki article…

    it is made explicity clear in that very article how the term is used, and if you think wiki is the authority on how biologists teach evolutionary theory… well…

    In any case, the mere fact that the article YOU linked to explains clearly the usage of the term doesn’t exactly support your argument that biologists are confusing the issue in their presentation, does it?

    again, it’s not the biologists who are confusing the issue in their presentations, it’s those who don’t understand the issues to begin with trying to play at being biologists and themselves confusing the issue to the people that read what they write.

    I still rather think you are berating the wrong folk, and you need to be taking aim at the likes of Paul Nelson.

    It’s very likely one of the reasons PZ pointed to the thread about Paul on PT.

  40. #40 travc
    July 13, 2007

    Yep, it is all about populations. That is why _population_ genetics and _population_ biology are where the speciation research action is (mostly at least).

    Though, to be overly kind, a single founder is possible and probably has happened not too infrequently. A pregnant female for (effectively a pair for those silly sexual animals), or a single seed or bit of vegetation, or a bacterium drifting over to some unknown land.

    Of course, that isn’t what he meant.

    BTW: Thanks for pointing out Doolittle’s work. I’m a big fan of the “horizontal transfer as the norm in very early evolution” theory, but was most familiar with Carl Woese’s papers on it and some derivatives/expansions/supporting experiments.

  41. #41 astromcnaught
    July 13, 2007

    This is a fascinating if somewhat dangerous-to-err thread. As an interested layperson I was always under the impression that all extant humans had descended from M-eve. But now I think this is refering to a gene tree, not a species tree. I would not be surprised if the mis-understanding is commonly held.

    I know, I should really go buy a 101 style textbook rather than learn evolution from here and the wiki. Still, it makes a nice change from the bible studies of which I was becoming unaccountably fond.

  42. #42 truth machine
    July 13, 2007

    “I read the wiki article…

    it is made explicity clear in that very article how the term is used”

    I’ll say it again, asshole: your claim that the phrase isn’t used is complete and utter bullshit.

  43. #43 truth machine
    July 13, 2007

    if you think wiki is the authority on how biologists teach evolutionary theory… well…

    I don’t think that and I didn’t say that, moron. What I said is that biologists do a sloppy job of communicating. It doesn’t do any good to blabber about how you teach evolutionary theory in the classroom. That’s like the guy who goes through the intersection on a green light without looking and gets broadsided. “I had the right of way!”, he blabbers as they rush him off to the hospital.

  44. #44 Steve LaBonne
    July 13, 2007

    I think truth machine is overdue to become trth mchn.

  45. #45 Justin Moretti
    July 17, 2007

    The rise of life in general was even less tidily bounded in the absence of strong isolating mechanisms — the little buggers were promiscuously sloshing genes back and forth among all kinds of cells

    You paint early evolution as some sort of orgiastic frenzy – no wonder the Creationist Christians are offended. ;-)

    Mind you, in first year medicine we were shown a bacterium in the process of dividing while one of the daughter cells was being donated plasmids via a sex pilus; so the orgy continues, four and a half thousand million years later.

    Don’t those little bastards ever get tired? I’ll have some of what they’re taking.

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