Haeckel's embryos
By Troy
Britain © 2001
From
HB2548: Haeckel’s Embryos; (ii) Proven false in 1874 by Professor
Wilhelm His, Sr. Ernst Haeckel was convicted of fraud for this in 1874. Human
embryos never have gills -- not even rudimentary ones.
Claim #1:
Haeckel’s Embryos; (ii) Proven false in 1874 by Professor Wilhelm His, Sr.
Wilhelm
His and Ernst Haeckel were bitter enemies who frequently publicly attacked each
other with claims of dishonesty or incompetence. British embryologist Michael K. Richardson, the source of much of
the recent discussion about Haeckel's supposed frauds, stated in one of his
articles on the subject that His failed to make a convincing case against
Haeckel:
Haeckel's
past accusers included His (Leipzig University), Rütimeyer (Basel University),
and Brass (leader of the Keplerbund group of Protestant scientists). However these critics did not give
persuasive evidence in support of their arguments. (Richardson et al. 1998, p.
984)
Richardson
went even further in a recent letter to the journal Nature suggesting
that His may have produced inaccurate drawings of embryos as well, stating that
"there is evidence of sleight of hand" on both sides of the feud
between Haeckel and His (though he believes the evidence is better against
Haeckel). (Richardson & Keuck 2001, p. 144)
As for
Haeckel himself, he responded to some of these accusations in the preface to
the third edition of his book The Evolution of Man:
Many
naturalists have especially blamed the diagrammatic figures given in the
Anthropogeny [The Evolution of Man]. Certain technical
embryologists have brought most severe accusations against me on this account,
and have advised me to substitute a larger number of the elaborated figures, as
accurate as possible. I, however,
consider that diagrams are much more instructive than such figures, especially
in popular scientific works. For each
simple diagrammatic figure gives only those essential form-features which it is
intended to explain, and omits all those unessential details which in finished,
exact figures, generally rather disturbed and confuse than instruct and
explain. The more complex are the form-features, the more do simple diagrams
help to make them intelligible. For
this reason, the few diagrammatic figures, simple and rough as they were, with
which Baer half a century ago accompanied his well-known-known "History of
the Evolution of Animals," have been more serviceable in rendering the
matter intelligible than all the numerous and very careful figures, elaborated
with the aid of camera lucida, which now adorn the splendid and costly atlases
of His, Goette, and others. If it is
said it that my diagrammatic figures are "Inaccurate," and a charge
of "falsifying science" is brought against me, this is equally true
of all the very numerous diagrams which are daily used in teaching. All diagrammatic figures are “inaccurate.”
(Haeckel 1876)
Though
Haeckel defended the relative accuracy of his figures he nevertheless modified
them in later editions of his book to make them more technically accurate, a
fact even noted by Haeckel's modern critic Michael Richardson. (Richardson
1998, p.1289) While it might be true that in hindsight both Haeckel and His's
figures were not always entirely accurate, none of the minor errors they may
contain once corrected change the status of the evidence they illustrate for
evolution.
Claim #2:
Ernst Haeckel was convicted of fraud for this in 1874.
This is a
common creationist claim against Haeckel for which there seems to be no
historical evidence. Unfortunately this
apparent myth has taken such a hold on discussions of Haeckel that even some
mainstream scholars have been taken in by it.
For example Michael Richardson repeated this claim in one of his articles
(Richardson 1997, p.30) (Anon. Ed. 1997, p.23) after reading it in a newspaper
in the U.K. (Hamblin & Moore 1997, p.18) This story, and Richardson's use
of it, was called into question by two German biologists in a letter to the
journal Science:
To some of
them [anti-Darwinists] every sort of vilifying argument [against Haeckel] was
welcome. This seems to still be true
today, as is evidence from recent claims in the British press that Haeckel had
been convicted by his university of alleged fraud. On being asked to disclose their sources, one of the respective
authors kindly referred us to a book agitating against the origin of man from
other primates (which in turn gave no relevant reference), while the other did
not answer our queries. Because, to our
knowledge, no respectable historical source mentions this conviction of
Haeckel, we conclude that the claim for it must be based on hearsay, not fact.
(Sander & Bender 1998, p.349)
Michael
Richardson recognized his error in repeating this undocumented story and wrote
a retraction shortly thereafter:
I am
concerned to find that I may have helped perpetuate a Creationist myth… The
claim that Ernst Haeckel was convicted of fraud was made in The Times. I relied on that statement in a subsequent
publication without seeking a primary source -- clearly a mistake on my part.
(Richardson 1998a, p.1289)
There appears to be no evidence that Haeckel was ever tried
for fraud in the Jena university court, much less that he was convicted of it.
This appears to be a persistent creationist myth, like Darwin's supposed
deathbed conversion. If the
anti-evolutionists want to use this claim, it is incumbent upon them to produce
references to primary material that would substantiate it. None to our knowledge have ever done so.
Claim #3:
Human embryos never have gills -- not even rudimentary ones.
This
is a half-truth. While it is
technically correct that humans don't ever have gills (since they never
function as respiratory organs), humans and other terrestrial vertebrates do
have at one point in their embryological development the same structures that
in fish and the larva of amphibians become gills.
For
example mammals (including humans) and the other terrestrial vertebrates (reptiles,
birds) develop pharyngeal (sometimes called branchial, or visceral) clefts and
pouches (clefts on the outside, pouches on the inside) in the neck and throat.
The only thing keeping them from being true slits is a thin membrane of skin
(which in the first pair of "slits" becomes the ear-drums). While these "slits" do not
normally open in mammals, they do open, and then close up in amphibians,
reptiles and birds. The common
creationist claim that the exterior clefts are merely "flexion folds"
is totally false. They are the outsides
of the "slits" which have corresponding pouches in the throat.
Aortic
arches (blood vessels), which travel in between each of the cleft/pouches, also
develop in humans and other terrestrial vertebrates. However unlike fish and amphibian larva, terrestrial vertebrates
do not develop the finer capillaries (that grow off the aortic arches) that are
used by fish to absorb dissolved oxygen from the water in which they live. So we develop the larger "gill"
blood vessels but not the smaller ones.
In
addition to having the cleft/pouches and aortic arches, the embryos of
terrestrial vertebrates also have pharyngeal arches (cartilaginous supports)
and nerves which also run in between the cleft/pouches just as they do in the gills
of fish. These facts can be found in just about any medical (human) embryology
or comparative vertebrate anatomy textbook, and they have been known since
before the scientific community accepted evolution.
See
the following for examples:
http://www.biology.ualberta.ca/courses.hp/zoo.225/aortic-t.html
http://www.uoguelph.ca/zoology/devobio/210labs/arch1.html
http://www.uoguelph.ca/zoology/devobio/72hrchck/72ck10.htm
http://www.bartleby.com/107/13.html
So while it is technically true that humans never have gills
(a derived structure with the specific function of respiration), they do have
embryonic structures that in fish develop into gills. The developmental fate of these embryonic structures that in
terrestrial vertebrates develop into various derived features (the hyoid
apparatus, tympanum of the ear, etc.) is in fact supportive of evolutionary
biology.
Some
modern creationists like to claim that calling these structures
"gill-slits" is somehow reading evolution into the evidence. However the fact is that many pre-Darwin
creationist scientists recognized the significant of these embryonic features
and tried to understand why God chose to give the embryos of "higher
vertebrates" structures like those of fish. For example there was Louis Agassiz, a creationist and fierce
opponent of Darwin's theory who said the following:
The higher Vertebrates, including man himself, breathe through
gill-like organs in the early part of their life. These gills disappear and give place to lungs only in a later
phase of their existence. (Agassiz 1874)
While
Agassiz was wrong about "higher vertebrates" breathing through their
"gills", he clearly recognized the existence of these gill-like
structures (to the point of calling them gills) even though he wasn't an
evolutionist. This illustrates the
fact that the recognition of the similarities of embryonic structures
across taxa was independent of the acceptance of evolutionary biology. Just as the concept of the geologic column
came to be part of the supporting evidence for evolution (even though its
originators were creationists), so too did the recognized and established facts
of embryology in the early 19th century.
Finally, the embryological evidence in support of evolutionary
biology is in no way dependent upon the diagrams of Ernst Haeckel (despite
their continued use in textbooks).
Creationist attacks on Haeckel and his figures are a straw-man argument
in which they falsely equate all the evidence from comparative
embryology to Haeckel's supposed fraud.
Whether or not Haeckel committed deliberate fraud, the actual state of
the evidence is unchanged and supportive of evolution.
To
recapitulate:
1) Wilhelm
His is not necessarily a reliable source of information regarding the
scientific status of Haeckel's work. He
and Haeckel were openly hostile to each other his opinion could hardly be
considered unbiased. And some have
questioned the accuracy of His's drawings as well.
2) There
is no historical documentation for Haeckel having ever been tried much less
convicted of fraud. This story appears
to be a myth.
3) While
it is technically correct that humans and other terrestrial vertebrates do not
posses "gills" as embryos, they do posses structures that appear to
be homologous in great detail to the structures of fish embryos that develop
into gills. The recognition of this fact is not dependant on the acceptance of
evolution. However the retention of these gill-like structures in the
embryological development of terrestrial vertebrates is best explained by
descent with modification from a fish-like ancestor.
4) The
evidence from embryology (such as the existence of pharyngeal pouches) is not
in any way dependant on Ernst Haeckel or his drawings, fraudulent or not. Or as Michael Richardson put it:
On a fundamental level, Haeckel was correct: All
vertebrates develop a similar body plan (consisting of notochord, body
segments, pharyngeal pouches, and so forth).
This shared developmental program reflects shared evolutionary
history... Haeckel's inaccuracies damage his credibility, but they do not
invalidate the mass of published evidence for Darwinian evolution. (Richardson
et al. 1998, p. 983-984)
References
Agassiz,
Louis (1874) Evolution and Permanence of Type, reprinted in Darwin and His
Critics (1973) by David L. Hull, p. 440
Anon. Ed.
(1997) Embryonic fraud lives on, New Scientist Sept. 6, p. 23
Haeckel,
Ernst (1876) The Evolution of Man V. I (3rd English edition) H. L. Fowle, NY, p. xxxiv-xxxv (preface)
Hamblin,
T. J. and Moore, R. E. M. (1997) The Times Aug. 18, p.18
Richardson,
M. K. (1997) The Forgotten Fraud, The Physiological Society Magazine,
No. 29, p.30
Richardson,
M. K. (1998) Haeckel's Embryos, Continued, Science 281:1289
Richardson,
M. K. et al. (1998) Haeckel, Embryos, and Evolution, Science 280:983-985
Richardson,
M. K. & Keuck, G. (2001) A question of intent: when is a 'schematic'
illustration a fraud?, Nature 410:144
Sander,
Klaus & Bender, Roland (1998) Science 281:349