Coyne and Embryonic Development…Wrong AGAIN!

A student recently sent me a question based on a statement made in Dr. Jerry Coyne’s book, Why Evolution is True. Since there doesn’t seem to be much written about it for a general audience, I thought I would summarize the issue. Here is Dr. Coyne’s statement:

One of my favorite cases of embryological evidence for evolution is the furry human fetus. We are famously known as “naked apes” because, unlike other primates, we don’t have a thick coat of hair. But in fact for one brief period we do – as embryos. Around sixth months after conception, we become completely covered with a fine, downy coat of hair called lanugo. Lanugo is usually shed about a month before birth, when it’s replaced by the more sparsely distributed hair with which we’re born. (Premature infants, however, are sometimes born with lanugo, which soon falls off.) Now, there’s NO NEED for a human embryo to have a transitory coat of hair. After all, it’s a cozy 98.6 degrees Fahrenheit in the womb. Lanugo can be explained ONLY as a remnant of our primate ancestry: fetal monkeys also develop a coat of hair at about the same stage of development. Their hair, however, doesn’t fall out, but hangs on to become the adult coat. And, like humans, fetal whales also have lanugo, a remnant of when their ancestors lived on land.1 (emphasis mine)

Note the strong words by Dr. Coyne. Embryos have “no need” for such hair, and thus its presence can “only” be explained as a remnant of our primate ancestry. Not surprisingly, Dr. Coyne is wrong on both counts.

Let’s start with the first mistake Dr. Coyne makes. He seems to think that the only reason a human embryo would need hair is for insulation. Since the embryo is obviously kept at a constant temperature in its mother’s womb, there is no need for insulation, so there is obviously no reason for it to have hair. This, of course, is amazingly narrow thinking, as hair can have functions other than that of insulation. For example, in adults, hair provides sensory information. Not surprisingly, this kind of narrow thinking led Dr. Coyne to the wrong conclusion about lanugo.

Perhaps Dr. Coyne should have asked a few embryologists to look at his book before he published it. If he had, he would have learned that lanugo has a very important function in the human embryo. To learn about the function of lanugo, however, you must first learn about something else embryos have during the same stage of development: the vernix caseosa. This name comes from two Latin words that mean “cheesy varnish,” and it is a waxy coating made from dead skin cells and oil produced by the embryo’s sebaceous glands.

While it sounds pretty gross, this “cheesy varnish” serves at least three very important functions for the embryo. As Tortora and Grabowski say in their book, Principles of Anatomy and Physiology,

This substance covers and protects the skin of the fetus from the constant exposure to the amniotic fluid in which it is bathed. In addition, the vernix caseosa facilitates the birth of the fetus because of its slippery nature and protects the skin from being damaged by the nails.2

So what does this have to do with the lanugo that Coyne highlights in his book? Well, the “cheesy varnish” that is so important to the embryo is produced slowly, and since there is a lot of motion in the womb, it could be easily pulled off the skin in its initial stage of formation if there weren’t something to hold it in place That’s the job of the lanugo.

Indeed, if you look at a developing human embryo, you find that the “cheesy varnish” first accumulates where there is a lot of lanugo.3 It then spreads out, coming into contact with other patches that are spreading out from other regions of lanugo. So lanugo performs a very important function in the development of the vernix caseosa: it anchors this important “cheesy varnish” to the skin while the varnish is being formed.

Of course, this fact is taught in most classes that deal with embryology in depth. For example, students at the University of Michigan Medical School are taught:

The fine hair on a newborn infant is known as lanugo. It helps to anchor vernix caseosa (“cheese-like varnish”), a waxy substance that protects the fetus from maceration by the amniotic fluid.

Dr. Mark Hill at the University of New South Wells describes lanugo hair as follows:

From about the third month lanugo hair (Latin, lana = wool) hair is initially formed and it has a role in binding vernix to skin.

Indeed, this is such a well-known fact that review materials for the U.S. Medical Licensing Exam discuss it. For example, Philip R. Brauer in his review book, Human embryology: the ultimate USMLE step 1 review says:

Vernix caseosa is a culmination of sebaceous gland secretions and dead epidermal cells, and the lanugo hair helps retain it on the outer skin surface.4

Now remember, Dr. Coyne stated that the “only” explanation for lanugo hair in human embryos is as a remnant from our primate ancestry. Of course, we know that is not correct. Lanugo hair is present in human embryos because it serves an important purpose: Without lanugo, the embryonic skin would not form the protective layer that it needs while in the womb.

This, of course, is exactly what you would expect in a creationist framework: embryonic structures form for a reason, not because of some leftover vestige of an imagined evolutionary process. As is usually the case, then, the more you learn about science, the stronger the case for creationism becomes.


1. Jerry A Coyne, Why Evolution is True (Viking), 2009, p. 80.
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2. Gerard J. Tortora and Sandra Reynolds Grabowski, Principles of Anatomy and Physiology (John Wiley and Sons, Tenth Edition), 2003, p. 154.
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3. Susan Tucker Blackbur, Maternal, fetal, & neonatal physiology: a clinical perspective (Saunders, Third Edition), 2007, p. 530.
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4. Philip R. Brauer, Human embryology: the ultimate USMLE step 1 review (Hanley & Belfus), 2003, p. 95.
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6 thoughts on “Coyne and Embryonic Development…Wrong AGAIN!”

  1. Dr. Jay:

    Super post. Nice to see the word getting around showning Coyne for his lack of comprehension. Your observations are apparently beyond reasonable rebuttal. The features you concentrated on are just the bare “tip of the iceburg” in terms of Coyne’s almost ludicrous explanations of why Darwin’s hypothesis is true.

    You might be interested in my web site that slowly works through the book’s main concept errors and, although “tedious” (to say the least),tries to build reasonably plausible rebuttals.

    Thanks for your work,


    1. Thanks for your comment X Prof! Your site looks thorough, not tedious. I look forward to reading your thoughts.

  2. I must say, fairly good post, considering its source. Your small point is correct – lanugo serves a function. This fact doesn’t prove creationism however, as evolution accounts for features serving functions as well. Especially when a present feature is co-opted to perform a new function, like anchoring vernix. (BTW, I’m assuming vernix developed later than lanugo. Do other primates also have vernix?)

    But even this small point doesn’t do much against Jerry’s quote. Your first emphasis: “Now, there’s NO NEED for a human embryo to have a transitory coat of hair.” Notice he didn’t say there is no need for lanugo. He said a transitory coat of hair. Why couldn’t the hair that replaced the lanugo accomplish it’s function? Wouldn’t an engineered development not produce any hair that is later replaced, especially by more sparse hair? Or at the very least, only some of the lanugo would fall out and the rest would be our post-birth hair?

    Second emphasis: “Lanugo can be explained ONLY as a remnant of our primate ancestry: fetal monkeys also develop a coat of hair at about the same stage of development.” Taken in the context of vernix, and “explained” as a what (what is its function), not a why (why do humans have embryonic transitory hair), you are granted the small point. But that is not how Jerry wrote the passage. Can you agree this is true: “Embryonic transitory hair can be explained only as a remnant of our primate history*: fetal monkeys also develop a coat of hair at about the same stage of development.”

    And the larger point – human embryos share features with other species’ embryos – is still best explained by evolution, not creationism. For instance, what is the function of the tail of the human embryo? Please forgive me if I don’t know the creationist answer to this, no matter how spread across the internet it is.

    * Notice that my re-write says “primate history”, not “primate ancestry”. That is what the book says, and on page 85, not 80. I know you have a man crush on Dr. Hunter, but you could at least quote the original rather than his old posts. But still, your vernix comments make much more sense than his epistemology blathering.

    1. Shooter, I know you desperately want to believe that the function of lanugo was co-opted. Of course, there is no evidence for such an assertion, but since evidence means virtually nothing to you, that’s not surprising. Certainly this post doesn’t “prove” creation. Science, in fact, cannot “prove” anything. However, it does demonstrate that Coyne doesn’t know what he is talking about, yet again.

      You are assuming many, many things, most of which are not true. Since lanugo and vernix work together, it is most reasonable to assume they were designed to appear together as well. Yes, all primates of which I am aware have vernix during their embryonic development, and it is best explained as the result of design.

      It seems you know as little about human embryonic development as Coyne does. Lanugo is transitory because it is REPLACED by either vellus or terminal hair, depending on position in the body. Vellus hairs are too small to hold on to the vernix, and terminal hairs require pigment, the chemical machinery for which develops later. Thus, embryos DO need a transitory coat of hair in order to hold the vernix in place.

      You ask, Can you agree this is true: “Embryonic transitory hair can be explained only as a remnant of our primate history*: fetal monkeys also develop a coat of hair at about the same stage of development.” Of course not. First, we don’t have a primate history, and second, it can be (and is much better) explained as a result of design. Lanugo and vernix are designed to go together, so the necessary genes for them both were in the baranomes of most mammals.

      You definitely know nothing about human embryonic development, since you actually believe the nonsense that human embryos have tails. Of course they don’t have a tail. Human embryos have a caudal eminence. It has nothing to do with a tail, once again demonstrating how incredibly deceptive the talkorigins site is. As this paper in Cells, Organs, and Tissues puts it:

      The eminence produces the caudal part of the notochord and, after closure of the caudal neuropore, all caudal structures, but it does not produce even a temporary ‘tail’ in the human.

      Thus, just like lanugo, it serves a very important purpose and has nothing to do with some imaginary ancestry with apes.

      It is very easy to see why you are an evolutionist, as you leap to conclusions so quickly! Of course I did not quote from Dr. Hunter’s website. First, if you could actually read, you would see that my quote contains more words than Hunter’s quote. Thus, I could not have gotten it from his site. Second, if you would actually do some investigation rather than simply take on faith the words of a commenter, you would find that the quote is exactly how it appears in the book (with ANCESTRY, not HISTORY), and it certainly does appear on page 80, as my reference indicates. Of course, if you had actually read the book, you would have been able to check it out for yourself.

      Once again, I have to go back to the trailer quote from Land of the Lost

      You ever get tired of being wrong?

  3. Hi Dr Wile,

    you say above?

    ‘Since lanugo and vernix work together, it is most reasonable to assume they were designed to appear together as well.’

    What evidence do you have that they were designed atall?

    1. Hi Rich. Thanks for the comment! The entire process of embryonic development screams of design. It is a pre-programmed process that has an incredibly parsimonious use of both energy and information. When we see a computer run a program that produces incredible results on very little power and a very compact information source, it is clear that the program is the result of design. From a scientific perspective, then, it is most reasonable to assume that the embryonic development process is the result of design as well.

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