The Ark Encounter: Depicting a Real Flood with Unrealistic Images

Online press article as flagged at Sensuous Curmudgeon:
http://www.wsj.com/articles/a-full-scale-ark-adrift-on-a-flood-of-speculation-1470777841

(Nothing especially stands out for me but others might disagree. Ham might decide to ignore the article though SC hopes otherwise!)

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Haeckel was basically right. Vertebrate embryos do indeed resemble each other during development. This is nothing to do with “recapitulation theory” (explained below), which has rightly been dead for well over 100 years.

I’m going to justify that statement below, and also explain a little bit about the scientific facts about vertebrate development. I know that many of you on here are YECs, and that’s just fine —– I don’t care what people believe, I only care if they distort the science to justify those beliefs, and when people do that I will call them on it and correct them. Because if, as a creationist, you want to challenge science, you have to at least know what the science is, and the way that scientists have interpreted the data. That is, even if you disagree with the interpretation, you have to know the facts. It does no good at all to muddle the facts up and then present them (especially to a scientist who both reads and writes the primary literature) as some sort of “look how absurd evolution is” claim, as Chuck so graciously mansplained to me the other day about scientists saying that whales evolved from hippos.

Back to Haeckel: Creationists use Haeckel as a scapegoat to discredit the entire field of developmental biology, and its use by evolutionary biologists. This would have been absurd enough 100 years after his death, when developmental biology hadn’t really progressed all that much, but it’s particularly absurd today when the discipline has merged with molecular biology and genomics to form “evo-devo”, and all of the morphological evidence is being supported and extended by information at the molecular level. I can’t tell you the number of times that I’ve tried to give creationists some information from this area of science, only to be told that I’m simply out of date because I apparently don’t realize that Haeckel was disproved.

Did Haeckel’s drawings contain errors? Yes. Was he accused of fraud in his time? Yes, but not for those embryo drawings (for the woodcuts that Chuck mentioned — which were also the ones that Gould was talking about). Did Gould/Garstang/de Beer decry some of Haeckel’s ideas? Of course — but note that they’re decrying recapitulation theory, not the notion of developmental similarities. Should those drawings have been removed from the textbooks? Yes, and they mostly were after the Richardson pointed out the errors. Of course, some creationists still maintain that any pictures of embryos at all are now verboten.

In the bigger picture, none of this matters. Text books are full of inaccurate drawings that get repeated from copy to copy, either because the writers haven’t spotted the errors, or because the publishers don’t want to pay for a new figure (you’d be surprised at how common that is). As time goes on, those figures get replaced by better representations, or photographs. Haeckel’s embryos haven’t been used to justify recapitulation (the notion that vertebrates, in their development, go through the adult stages of the phylogenetic tree —- i.e., that a human is first a fish, then a reptile, then chicken, then a pig, etc.) for over 100 years. They’re used to illustrate the notion that we share developmental processes with other vertebrates. So, the drawings had some serious errors and they got replaced. End of story. But not to the creationists, who still insist on using Haeckel as a justification for dismissing all of developmental biology.

I am going to present some very basic, undergraduate level, facts about what we know about developmental biology in terms of what scientists think constitutes evidence for common descent. (Note that these nested interrelationships are backed up by other evidence: genomic DNA, mitochondrial DNA, etc.) Again, these are the facts. If you differ with the interpretations, then fine. Just get the facts straight.

All animals develop from a ball of cells. In all animals except sponges, that ball of cells invaginates during development (a process called gastrulation) to produce an inner layer of endoderm, and outer layer of ectoderm, and an internal gut cavity (different from the original hollow in the middle of the ball of cells).

In all animals except sponges, coelenterates (sea anemones/jelly fish) and cnidarians (comb jellies) that development proceeds further. A third layer of cells, mesoderm, forms between the ectoderm and endoderm, and forms many complex body organs (heart, kidneys, etc.), as well as muscle tissue. These animals are now mobile as adults. Their gut also breaks through to the other end, so that they have both a mouth and an anus. These animals are called “bilaterians”, and they are the phyla that radiate in the Cambrian.

In most bilaterians, the original hole that formed from gastrulation gives rise to the gut. They are called “protostomes” (= mouth first). In a few phyla, the original hole forms the anus, and the mouth breaks through later. These are the deuterotomes (= mouth second), and they include our own phylum, Chordata, the Echinodermata (starfish, sea urchins, etc.) and a couple more obscure phyla. Some sort of gill slits in the pharynx for filter feeding in water are also a general feature of deuterostomes, although they have been secondarily lost in modern echinoderms.

All chordates are distinguished by a further stage of development. A portion of the mesoderm differentiates early and forms a stiff cord running along the length of the body, the notochord (seen in us in embryos, and remaining in the adults as the intervertebral discs). The line of ectoderm along the top of the animal infolds and then buds off along its length, making a hollow tube of ectodermal cells that will go on to form the nerve chord.

All vertebrates are distinguished by a further developmental stage, in which they derive a fourth layer of basic tissue called “neural crest”. This makes a number of unique features in all vertebrates, including most of the front part of the head, and the cartilaginous bars that make up the skeleton supporting the gill slits (i.e, the pharyngeal arches). There are many, many other similarities between all vertebrates, including a trunk region in the embryo where the mesoderm is segmented on the top portion (somites) and unsegmented on the bottom portion (lateral plate). The various fates of the different portions of the portions of the mesoderm is the same in all vertebrates. E.g., the somites make the striated muscle, dermis of the skin, and the backbone. The lateral plate makes the smooth muscle of the gut, the heart muscle, and the limb bones.

So now we are at that dreaded “pharyngula” stage, where we get to consider the similarities in the developing pharynx. “Humans never have gill slits” the creationists will cry, and they are largely correct, but see one exception below. In the pharyngeal region a series of six pouches form (no, they are not just folds in the skin, as some creationists claim). Each pouch contains a cartilaginous pharyngeal arch (which in fish later develops into supports for the gills), and a set of developing nerves, blood vessels, and muscles which have an extraordinary specificity to each pouch and which are homologous among all vertebrates. The clefts between the pouches are what will form the gill slits in fishes.

Pouch 1 is innervated by cranial nerve 5, pouch 2 by cranial nerve 7, pouch 3 by cranial nerve 9, and the rest by cranial nerve 10. In jawed fish, the cartilaginous arch goes to form the jaws. It goes to form our own embryonic jaws, which are later replaced by dermal bone except for the back ends of the jaw halves, which end up as bones in our middle ears.

These homologies between vertebrates have been known about for many years. The middle ear bone homologies were figured out by Reichart in 1837, years before either Darwin or Haeckel. There is no room here to explain the extraordinary similarities in the developing pharynx of all vertebrates, but I will refer to Troy Brittain’s blog on this, which is a truly magnificent piece of work (and tackles many of the creationist misrepresentations).

But wait —- I said that we do retain a gill slit as adults. The first embryonic gill cleft in forms the spiracle in many fish today (mainly cartilaginous fish such as rays, that use it to inhale water while they rest on the bottom of the sea — most bony fish lose the structure as adults). In us (and all other tetrapods) it forms the Eustachian tube and the middle ear cavity. So, if you puncture your eardrum, there you have a fully-functional gill slit leading from the outside into the back of your throat.

So — Haeckel’s drawings called fraudulent, and now there’s no evidence for profound similarities between vertebrate embryos? I don’t think so, although those drawings were indeed a little iffy and it’s a good thing that they have now been replaced. He was, after all, basically correct about vertebrate embryos sharing a similarities, even if wrong about the notion of recapitulation.

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Chuck, if you ACTUALLY care about a sense of humility, you would decry the constant hubris of anti-evolution creationists spewing nonsense while claiming that they know more about science than the entire science academy of PhD scientists who have devoted lifetimes to their fields of specialization. As a born-again evangelical Christ-follower who spent my share of years as a Young Earth Creationist speaker/debater back in the Gish-Morris-Whitcomb era, your lame and ancient script is truly groan-worthy. Worse yet, the antics of anti-evolution YEC loons is producing far more atheists than Richard Dawkins ever will.

I would urge you to adopt the appropriate (and Biblical) humility of one who badly needs to learn the basics of the science before presuming to correct the real scientists who have graciously taken the time to tutor you. Proverbs 14:6-8 well describes your foolish behavior on this thread.

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