Quantcast

«

»

Oct 24 2012

What the embryologists really say

The anti-choice advocates are always citing a handful of embryologists in order to claim that scientists say human life begins at fertilization. The one fellow who is always getting cited in these claims is Keith L. Moore, a very familiar name in embryology circles, because he wrote several introductory texts on human embryology. I thought I would quote what Moore and Persaud actually wrote in the 4th edition of Before We Are Born: Essentials of Embryology and Birth Defects in 1993 (this text has been around since 1974, so it really has trained a generation in medical embryology, and there is also a 2012 edition, which I don’t own…it’s a bit on the elementary side for my interests).

The section on the first week of human development begins:

Human development begins at conception or fertilization when a male gamete or sperm fuses with a female gamete or ovum to form a zygote (Br. zygotos, yoked together). This highly specialized, totipotent cell is the primordium of a new human being. By birth the zygote has given rise to millions of cells [that's an underestimate --pzm]. Although large, the zygote is just visible to the unaided eye. It contains chromosomes and genes (units of genetic information) derived from the mother and father.

Odd…it doesn’t say we have a human being at fertilization, but instead says we have a totipotent cell that is a primordium that will become a human being.

By golly, I think the anti-choicers stretch the truth as much as creationists do!

52 comments

Skip to comment form

  1. 1
    abb3w

    Err… looking at the on-line OED definition of “primordium”, it gives “The very beginning, the earliest stage; a starting point, an introduction; (also) a source or origin” and “An organ, structure, etc., in its earliest discernible stage of development (often as a group of cells)”. This seems to mean that if the “totipotent cell is the primordium of a new human being”, then the “totipotent cell is the earliest stage of development of a new human being”. Whether that such earliest stage is itself “a new human being” or not seem a bit ambiguous.

    A more detailed lecture on the exact use of primordium in biology might clear that up, but it looks like you may be overplaying the degree of clarity of counterargument from the Moore and Persaud implications. It seems exceptionally unlikely to convince any pro-lifer who looks up primordium.

  2. 2
    jesus

    I’d be curious: In what capacity is Moore being cited by “anti-choicers”? Do they take some quote from him? Or simply attribute a position to him based on an interpretation of something he said?

    I mean, I don’t imagine any serious biologist would suggest that a zygote with about as many cells as a bag of skittles has skittles constitutes a human life, but it might help to understand their thinking if you can give a bit more context on the argument they’re using.

  3. 3
    Randomfactor

    a primordium that will become a human being.

    I think “could become” would be a more accurate statement.

  4. 4
    dianne

    The version of Moore that I used explicitly stated that the question of when a human life began was a subjective one and that the author would put it no sooner than 8 weeks when organ formation was completed (i.e. 10 weeks by conventional methods of counting pregnancy which starts at LMP and after the majority of elective abortions) and that there were numerous arguments to be made for a later date. In short, not supporting the “pro-life” position in any appreciable way.

  5. 5
    Inaji

    jesus:

    it might help to understand their thinking if you can give a bit more context on the argument they’re using.

    It helps if you read all the posts on the front page. Try here and here.

  6. 6
    holytape

    Wait, are you expecting pro-lifers to read and be familiar with the stuff they quote? Silly silly. Next you’ll be expecting creationist to understand the laws of thermodynamics, or expecting republicans to care about women who aren’t in the kitchen.

  7. 7
    ChasCPeterson

    It’s not exactly a scientific question, so why would either side try to argue from scientific authority? Dr. Moore’s opinion is just that.

    I don’t imagine any serious biologist would suggest that a zygote with about as many cells as a bag of skittles has skittles constitutes a human life

    for one thing, any serious biologist would know that a zygote is a single cell by definition. One cell.
    A skittles-bag of cells is an embryo.

  8. 8
    Nepenthe

    Eukaryote cells are definitely more like Peanut M&Ms than Skittles.

    This is important because if fetuses were made out of Skittles they wouldn’t be so delicious.

  9. 9
    robro

    holytape: They care about women who are in the kitchen? I’m thinking there’s another member that they care about more than the little woman in the kitchen.

  10. 10
    jesus

    Caine, Divisitrix du mal,

    Thank you. I read Bad Argument #3 when it was posted earlier this week, so I did not remember Moore being mentioned, so I didn’t connect it with this post. As for the video of the debate, I did not watch it, at PZ’s suggestion that only sadists would enjoy it. How was it?

  11. 11
    jesus

    ChasCPeterson:

    for one thing, any serious biologist would know that a zygote is a single cell by definition. One cell.
    A skittles-bag of cells is an embryo.

    Heh, shows what I know. Eh, can’t blame me, I received my biology education from American high-school and Pharyngula exclusively.

  12. 12
    Thomathy, Gay Where it Counts

    Nepenthe and ChasCPeterson, they are like a box of smarties; anything else and they wouldn’t be good.

  13. 13
    F [i'm not here, i'm gone]

    Where does life begin? Hm. The woman with the fertilized egg is already a live human. I’d be looking there.

  14. 14
    unclefrogy

    I thought that creationists and anti-choicers were the same but the posts about the debate the other day seemed to indicate differently that they were not but I find that hard to believe. I would think that most are.
    is there any data or is it a case walk like a duck

    uncle frogy

  15. 15
    Giliell, professional cynic -Ilk-

    Really, what those people constantly fail to understand is the difference between something being a necessary condition and something being a sufficient condition.
    The fact that everybody’s existence started with egg and sperm fusing doesn’t mean that every time egg and sperm fuse you get a somebody.
    First the blastocyte has to implant, something about 50% of them (not very) spectacularly fail to do. Then it has to make it through the first trimester, something another big proportion fails to make. Then there’s the rest of pregnancy, the fact that not everything that’s a viable pregnancy results in a viable newborn, the big obstacle of birth…

    It’s like claiming that I’m a millionaire because I play the lottery. Surely everybody who won the jackpot started by buying a ticket, but nobody would be so stupid to make the other claim…

  16. 16
    chigau (違う)

    Smarties aren’t available in the USA.

  17. 17
    robro

    Off topic news, but appropriate enough: another Republican Senate candidate, Richard Mourdock of Indiana, has blessed rape pregnancy as a gift from God.

    http://www.guardian.co.uk/world/2012/oct/24/richard-mourdock-rape-remarks-romney

  18. 18
    ChasCPeterson

    Smarties aren’t available in the USA.

    wut

    link

  19. 19
    ChasCPeterson

    ah, now I see.
    different
    Smarties

  20. 20
    vaiyt

    @14:

    There’s a lot of atheists, skeptics and rationalists who are anti-choice. Is it a surprise, considering the rampant mysoginy within the subculture?

  21. 21
    davidb54

    Randomfactor gets it right. A fertilized egg could become a human being. It’s not guaranteed. The odds are close to 50:50. About half of fertilized eggs (actually, blastulae by the time they reach the uterus) do not implant in the uterus. Instead, they become part of the woman’s menses. Now, if you believe that life begins at fertilization, then all of those teensy balls of cells are stillborn babies. About 5 million of them a year in the US. Is it OK to toss those dead people into landfills along with the used tampons and sanitary napkins? The anti-abortion folks go bonkers about in vivo fertilization clinics tossing frozen fertilized eggs. Why aren’t they equally adamant about all those deceased blastulae?

  22. 22
    robertbaden

    I’ve wondered for a while why fertilization is called a fusing of two cells and not a case of predation.

  23. 23
    jeroenmetselaar

    This part of the abortion debate is also avoiding the only question that matters. This question is of course: Is it your uterus where the fetus is growing?

    If yes then it is your choice. If no then bugger off, it is not your business.

  24. 24
    Thomathy, Gay Where it Counts

    Yeah, ChasCPeterson, Smarties are delicious but Smarties are disgusting abominations.

    What we need are qualifiers. Hey! This could help the anti-choicers, if they would ever listen. What they need are qualifiers for human. That way the can tell the difference between something merely alive and something that constitutes a person.

  25. 25
    infraredeyes

    @20:

    There’s a lot of atheists, skeptics and rationalists who are anti-choice.

    Citation needed.

  26. 26
    Worldtraveller

    By golly, I think PZ’s right!

  27. 27
    Thomathy, Gay Where it Counts

    infraredeyes:

    @20:

    There’s a lot of atheists, skeptics and rationalists who are anti-choice.

    Citation needed.

    Agreed.

    Vaiyt:

    Is it a surprise, considering the rampant mysoginy within the subculture?

    It’s trivial at this point to say and to provide evidence that there exists a rampantly mysoginist subculture within the atheist/sceptic/rationalist communities. It’s another thing to say that there is rampant mysoginy. It needs to be reiterated that it is, by all appearances, a vocal minority of the meta-community who are mysoginists, but no one knows (I’d dearly like to know).

    Further, mysoginy and anti-choice don’t necessarily correlate. Your response to Gilliel seems to be a non sequitur, stupidity is sufficient to be anti-choice, mysoginy isn’t necessary.

    That said, I regard anti-choice stances as inherently anti-woman, so perhaps it’s not far off to positively link mysoginy with anti-choice. Although, I can imagine some MRAs being pro-choice, in a sick way, exactly because of their mysoginy. Stupidity, again.

  28. 28
    Thomathy, Gay Where it Counts

    Damnitall. I read misogyny spelled incorrectly once and then run with it!

  29. 29
    Storms

    @#15 Giliell and #21 davidb54
    Oddly I was doing some research on this yesterday to satisfy my curiosity and inform my arguments. I was truely startled by the facts:

    About 30% of blastula don’t implant, about 30% more implant but spontaneously abort before the first missed period, and 12-18% abort or miscarry after that. The rate of loss dimishes to under 1% at 26 weeks. A whopping 72-78% of fertilized ova never achieve live birth in 20-29 year old women. According to the first study linked below:

    Human embryos are remarkably prone to errors in genetic and epigenetic programs with more than 80% of embryos carrying numerical and/or structural chromosomal abnormalities and at least 30% are characterized by errors in global epigenetic modification and abnormal gene expression.

    Of those that that spontaneously abort, 75-90% show chromosomal abnormalities.

    This is natural error correction folks. It actually makes me question if the quest to support earlier and earlier pre-mature births is ethical in cases without maternal cause. Certainly we need stronger informed consent and secondary biology education on these subjects. What young woman (or voter) shouldn’t know how error-prone human development is?

    “Human pre-implantation embryo development”
    “Conception to ongoing pregnancy: the ‘black box’ of early pregnancy loss”
    “Genetic and Nongenetic Causes of Pregnancy Loss”

  30. 30
    Storms

    s/blastula/blastulea/

  31. 31
    Storms

    s/blastul?+/blastulae/

  32. 32
    vaiyt

    Further, mysoginy and anti-choice don’t necessarily correlate. Your response to Gilliel seems to be a non sequitur, stupidity is sufficient to be anti-choice, mysoginy isn’t necessary.

    There is a link between not treating women as full human beings and wanting to legislate over their basic rights. Not all the atheist anti-choicers have that position because of misogyny – some of them are just squeamish about abortion or have other reasons – but if they are misogynists, there’s a good chance they don’t approve of women making choices.

  33. 33
    Thomathy, Gay Where it Counts

    but if they are misogynists, there’s a good chance they don’t approve of women making choices.

    Well, I agree with that …

  34. 34
    Pierce R. Butler

    Kevin Dugan @ # 29: Human embryos are remarkably prone to errors in genetic and epigenetic programs …

    Does that mean other species function better in this regard?

  35. 35
    sharkjack

    It is basically an equivocation fallacy. First, they make it seem like they’re arguing for the fact that an embryo/zygote is part of the human species. I’m okay with that under very strict definitions of the human species. However once this is acknowledged the next step is to get as much leverage as possible into the position that the embryo/zygote should be seen as a human being, equivocated with a person. Arguing from the position of the zygote as a person is far easier, at least on an emotional level. After all it gives more impact to the idea that women murder their unborn children by having an abortion and it makes the idea of ageism sound more legitimate.

    In the end it doesn’t matter. Women have the right to end pregnancies by virtue of bodily autonomy, the fetus, even if granted a right to life has no right to parasitize the body of a woman. In the Dillahunty debate debate debate abortion was equated to killing a baby left on the porch of your house, or killing a baby while you’re on a boat in the middle of a lake. I’d liken it more to jumping into rapids to save a person from drowning myself, but that would defeat the point of the analogy (because you know, pregnancy isn’t exactly risk free, nor is it a minor inconvenience).

    Anyway, even if we were to grant that women don’t have this right, you don’t stop abortions by making them illegal and you don’t stop people from getting pregnant with unwanted children. That would require better anticonception medication/treatment, better education and good access to these things for all women. If you’re pro life, that is what you should be fighting for.

  36. 36
    Storms

    The first source listed in my post above indicated that human eggs significantly more prone to defects than other (smaller?) organisms. 1/20 to 1/5 human eggs contains chromosomal or epigenetic defects compared to 1/100-1/200 for mice.

    Estimates of meiotic error rates in humans are high (5-20% of oocytes) compared with other species (1/10,000 meiotic yeast cells, 1/2000-1/6000 Drosophila germ cells and 1/100-1/200 murine germ cells)

    I can’t (quickly) find a study on relative frequency of aneuploidy (chromosomal errors) across species. If someone knows of one, please link it. I did find a reference (below) that seemed to indicate it’s not that prevelant in pigs. However, I hesitate to make a larger inference as different methods were used.
    Aneuploidy Detection in Pigs Using Comparative Genomic Hybridization: From the Oocytes to Blastocysts

    Focus is directed on in vivo porcine blastocysts and late morulas, 4.7% of which were found to carry chromosomal abnormality. Further, ploidy abnormalities were examined using FISH in a sample of porcine embryos. True polyploidy was relatively rare (1.6%), whilst mixoploidy was presented in 46.8% of embryos, however it was restricted to only a small number of cells per embryo. The combined data indicates that aneuploidy is not a prevalent cause of embryo mortality in pigs

    A google search also turned up a fragment of a text book I can’t afford that indicates humans and sheep are the only species so far found with very high rates of aneuploidy.
    Embryonic Mortality in Farm Animals

  37. 37
    Stacy

    @unclefrogy

    I thought that creationists and anti-choicers were the same but the posts about the debate the other day seemed to indicate differently that they were not but I find that hard to believe. I would think that most are.
    is there any data or is it a case walk like a duck

    There are anti-choicers who aren’t creationists.

    And, believe it or not, I personally know a creationist (an evangelical Christian who believes in creationism) who is pro-choice. I don’t suppose he can be the only one.

  38. 38
    Pierce R. Butler

    Kevin Dugan @ # 36 – thanks for the follow-up!

    [insert lay-level speculation about relatively recent major evolutionary changes here]

  39. 39
    otrame

    The first source listed in my post above indicated that human eggs significantly more prone to defects than other (smaller?) organisms.

    That is very interesting. I wonder why. What with us being intelligently designed and all.

    But think about this. If there had not been a pretty serious chromosomal defect a while back, we would still have 48 instead of 46. Pretty sure we wouldn’t be us if that little mistake hadn’t happened.

  40. 40
    Colin J

    Yeah, but, no, but… Human. It’s the very first word in the quoted paragraph!

    What, you expect me to read further than that?

  41. 41
    RFW

    At least in medieval times, the Church (i.e. RCC) held that the soul did not enter a (fetus? embryo? zygote? baby? unborn child?) until it “quickened” – that is, until Mom could feel it moving. I don’t know if this position in turn led to legal distinctions in the handling of abortions and murder of pregnant women. before and after “quickening”.

    The anti-intellectual bias of the anti-abortion movement is thus attested by their (possibly willful) ignorance of religious history.

    When and if the RCC changed its position on the matter, I do not know.

    Sorry, but I can’t give a reference. This is one of those many snatches of knowledge I’ve held onto from general reading years ago in my mare’s nest of a memory. Perhaps someone can provide a trustworthy citation?

    [Cripey: a posting full of "I don't know". And here I strive for a reputation for omniscience! Some omniscience!]

  42. 42
    Pierce R. Butler

    RFW @ # 40 – I don’t have a citation handy, but “the church” in this case was relying on the writing of T. Aquinas, who in turn was cribbing from Aristotle.

    Part of their doctrine, iirc, was that souls enter male feti 40 days after conception – but take 80 days to make it into females.

  43. 43
    Jafafa Hots

    Life begins at spermatogenesis.

  44. 44
    vaiyt

    @43: Life begins with the first living being. We’re direct descendants from it in an unbroken chain of cell divisions.

  45. 45
    Jafafa Hots

    @43: Life begins with the first living being. We’re direct descendants from it in an unbroken chain of cell divisions.

    Well, I’m breaking my strand of that chain. No reproducing for me.
    Trillions of ancestors since the beginning of life, all leading up to me… and I’m turning around and giving them the finger.

  46. 46
    khms

    @43: Life begins with the first living being. We’re direct descendants from it in an unbroken chain of cell divisions.

    Exactly. You might perhaps argue that spermatozoa lack some aspect of life, but ova certainly don’t.

    Similar for human – all involved have human genetics, and so are human.

    Gedankenexperiment: cut of a finger. Freshly cut of, it’s still alive (for example, you could sew it back on and it would keep on living). So, that finger is human, and alive. Is it a person, or a human being? I’m assuming even those rabid anti-choicers wouldn’t want to say so. But what does make the difference?

    At our current tech level, that doesn’t matter all that much, for the reasons already given. (Well, not to the abortion debate. Presumably it is relevant in other situations, such as determination of death, or euthanasia, and so forth.) It becomes a relevant question, though, if our tech ever reaches the level were we could routinely take the embryo out of the mother and into an artificial womb, without serious risk to either. Then, if we should come to the conclusion that personhood begins at some point before birth (I personally don’t believe it does), then and only then we might want to rule that under certain conditions (which I certainly won’t try to predict), abortion is not an option and removal to artificial womb must be used instead. Of course, that still removes the embryo from the woman, so it’s not clear that this hypothetical situation actually makes a significant difference wrt. bodily autonomy. (Well, it might make the decision easier for some women.)

  47. 47
    Storms

    @#39 otrame & #38 Pierce R. Butler

    Interesting conjectures. I’d be interested in a similar study of aneuploidy in other homonids to see if it’s human (and sheep) specific or started earlier in our evolution.

  48. 48
    Tuválkin

    PZ, is «a zygote (Br. zygotos, yoked together)» (my emphasis) a typo? Yours or the sources’? Or does "zygote" actually come from Breek? (Who knew?)

  49. 49
    Ichthyic

    Gedankenexperiment: cut of a finger. Freshly cut of, it’s still alive (for example, you could sew it back on and it would keep on living). So, that finger is human, and alive. Is it a person, or a human being? I’m assuming even those rabid anti-choicers wouldn’t want to say so. But what does make the difference?

    take it a step further (entering the world of futurama…). cut off a head and keep it alive in a jar.

    which is the person? the body or the head. both can be kept alive.

    Is the headless body of Agnew less of a person than the head of Nixon?

  50. 50
    Ichthyic

    ) It becomes a relevant question, though, if our tech ever reaches the level were we could routinely take the embryo out of the mother and into an artificial womb, without serious risk to either.

    this is why the choice should ALWAYS remain with the mother.

    It should ALWAYS be a mother’s choice at all times, whether or not she wants to bring another life into the world. IT SHOULD NEVER EVER BE LEFT TO THE STATE TO DECIDE.

    period.

    exclamation mark.

  51. 51
    Tigger_the_Wing, Back home =^_^=

    With the genetics thing – I have knowingly lost half the embryos I have conceived; likely I have lost more without knowing it. It suddenly occured to me the other day that my mitochondrial genetic line is about to go extinct. My mother, and her mother, had no sisters. My sisters have no daughters. My daughter has only sons. With them, the line peters out.

  52. 52
    Ichthyic

    With them, the line peters out.

    “You still wake up sometimes, don’t you? You wake up in the dark and hear the screaming of the mitochondria.”

    ;)

Comments have been disabled.