Recurrent laryngeal nerve
by Jonathan Sarfati
Photo Wikipedia.org
Published: 5 August 2010(GMT+10)
Quite a number of atheopaths have recently been using the mammalian “recurrent
laryngeal nerve” as an argument against design. So not surprisingly, many
readers have asked for a response. But since the Apostle of Atheopathy himself,
Richard Dawkins, is one of the keenest proponents of this arguments, our
new book The Greatest
Hoax on Earth? Refuting Dawkins on evolution already has a response,
which we reprint for this article.
Dawkins complains about the recurrent laryngeal nerve:
“It is a branch of one of the cranial nerves, those nerves that lead directly
from the brain rather than from the spinal cord. One of the cranial nerves, the
vagus (the name means ‘wandering’ and is apt), has various branches,
two of which go to the heart, and two on each side to the larynx (voice box in mammals).
On each side of the neck, one of the branches of the laryngeal nerve goes straight
to the larynx, following a direct route such as a designer might have chosen. The
other one goes to the larynx via an astonishing detour. It dives right down into
the chest, loops around one of the main arteries leaving the heart (a different
artery on the left and right sides, but the principle is the same), and then heads
back up the neck to its destination.
“If you think of it as the product of design, the recurrent laryngeal nerve
is a disgrace. Helmholz would have had even more cause to send it back than the
eye. But, like the eye, it makes perfect sense the moment you forget design and
think history instead.” (p. 356)
Dawkins then argues that it makes better sense if we evolved from fish, and touching
on something akin to Haeckel’s discredited embryonic recapitulation theory,1 concludes:
“All that we need to know, to understand the history of our recurrent laryngeal
nerve, is that in the fish the vagus nerve has branches that supply the last three
of the six gills, and it is natural for them, therefore, to pass behind the appropriate
gill arteries. There is nothing recurrent about these branches: they seek out their
end organs, the gills, by the most direct and logical route.
“During the evolution of the mammals, however, the neck stretched (fish don’t
have necks) and the gills disappeared, some of them turning into useful things such
as the thyroid and parathyroid glands, and the various other bits and pieces that
combine to form the larynx. Those other useful things, including parts of the larynx,
received their blood supply and their nerve connections from the evolutionary descendants
of the blood vessels and nerves that, once upon a time, served the gills in orderly
sequence. As the ancestors of mammals evolved further and further away from their
fish ancestors, nerves and blood vessels found themselves pulled and stretched in
puzzling directions, which distorted their spatial relations one to another. The
vertebrate chest and neck became a mess, unlike the tidily symmetrical, serial repetitiveness
of fish gills. And the recurrent laryngeal nerves became more than ordinarily exaggerated
casualties of this distortion.” (pp. 359–360)
Richard Owen and opponents of Darwin
Dawkins goes on to describe how the RLN’s detour could be 15 feet long in
a large giraffe. He relates witnessing the dissection of such a nerve in a young
giraffe that had died in a zoo. He expressed admiration of the skill of the team
of anatomists performing the dissection, which increased his respect for the creationist
opponent of Darwin, Richard Owen, who had achieved this feat in 1837. Yet, says
Dawkins, Owen failed to reject the idea of a designer.
This should tell us something. It’s notable that much of the opposition to
Darwin came from scientists2
like Owen, as well as Professor Johann H. Blasius, director of the Ducal3 Natural History Museum of Braunschweig (Brunswick),
Germany, who stated in a review of Darwin’s Origin:4
“I have also seldom read a scientific book which makes such wide-ranging conclusions
with so few facts supporting them. … Darwin wants to show that Arten
[types, kinds, species] come from other Arten. I regard this as somewhat
of a highhanded hypothesis, because he argues using unproven possibilities, without
even naming a single example of the origin of a particular species.”5
Design features of the recurrent laryngeal nerve
As for good reasons Owen did not draw evolutionary conclusions, there are several.
The well-known textbook Gray’s Anatomy states:
“As the recurrent nerve hooks around the subclavian artery or aorta, it gives
off several cardiac filaments to the deep part of the cardiac plexus. As it ascends
in the neck it gives off branches, more numerous on the left than on the right side,
to the mucous membrane and muscular coat of the esophagus; branches to the mucous
membrane and muscular fibers of the trachea; and some pharyngeal filaments to the
Constrictor pharyngis inferior.”6
Dawkins considers only its main destination, the larynx. In reality, the nerve also
has a role in supplying parts of the heart, windpipe muscles and mucous membranes,
and the esophagus, which could explain its route.
That is, Dawkins considers only its main destination, the larynx. In reality, the
nerve also has a role in supplying parts of the heart, windpipe muscles and mucous
membranes, and the esophagus, which could explain its route.
Even apart from this function, there are features that are the result of embryonic
development—not because of evolution, but because the embryo develops from
a single cell in a certain order. For example, the embryo needs a functioning simple
heart early on; this later descends to its position in the chest, dragging the nerve
bundle with it.
Also, would a circuitous route necessarily be bad design? There could be reasons
for this (and in the case of the RLN we have a good idea, as per Gray’s).
Biologist and geologist John Woodmorappe’s review of Jerry Coyne’s book
Why Evolution is True (which Dawkins recommends for its section on the
RLN (note, p. 356) points out:
“Human-designed machines and structures are full of such things as circuitous
wiring and plumbing, but that hardly means that they are not the products of intelligent
design.
“Now let us consider situations in which a circuitous route is actually harmful
to its bearer. The automobile with its engine in front requires a long, tortuous
exhaust system perched underneath the car. This clearly makes it more vulnerable
to injury from obstructions than the short exhaust system of engine-in-back cars
(I speak from personal experience). Following Coyne’s logic, should we suppose
that engine-in-front cars are not the products of intelligent design? No. We realize
that there is an engineering trade-off between the advantages of the car with its
front-situated engine and the concomitant disadvantage of its more easily-damaged
long, circuitous exhaust system.”7
Related articles
Further reading
References
- Grigg, R.,
Ernst Haeckel: Evangelist for evolution and apostle of deceit, Creation
18(2):33–36, 1996; creation.com/haeckel. Return to
text.
- Foard, J., Holy war?
Who really opposed Darwin? Popular belief has it back to front …
, Creation 21(4):26–27, 1999; creation.com/holy-war
Return to text.
- German herzoglich, presumably established under the auspices
of the local duke (Herzog). Return to text.
- Wieland, C.,
Blast from the past, creation.com/blasius, 16 June 2006. Return
to text.
- Director Blasius interview: “Evolution is only a Hypothesis”,
1859, cited in Braunschweiger Zeitung, 29 March 2004. Return to text.
- Available online at www.theodora.com/anatomy/the_vagus_nerve.html/.
Return to text.
- Woodmorappe, J., Why evolution need not be true, J. Creation
24(1):24–29, 2010. Return to text.
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