The Left Recurrent Laryngeal Nerve

Discussion of a classic biological "design flaw" that provides solid evidence for common descent.

Diagrams are from Jerry Coyne's "Why Evolution is True" and the 3rd edition of the textbook "Evolution" by Mark Ridley. The giraffe image was downloaded from www.giraffes.org

All images are legally used under "Fair Use" for non-profit educational purposes.

Category:

Education

Tags:

• Evolution
• Creationism
• Intelligent
• Design
• ID
• bad
• design
• unintelligent
• flaw
• left
• recurrent
• laryngeal
• nerve
• common
• descent

[finemoves]

@EvoBiologist Just wondering if there are any species descended from fish that don't have this nerve looping around the heart?

[EvoBiologist]

@finemoves Sorry about the delay in getting back to you. As far as I'm aware, the LRLN loops under the aorta in all tetrapods. The looping results from the extension of the neck and the posterior migration of the heart that occurred in the early tetrapods. The longer the neck (and lower the heart), the more dramatic the back-track.

[EvoBiologist]

@fidlfadn Agreed. When beliefs affect other people, they cease to simply be personal in nature.

[fidlfadn]

@fidlfadn And we have people like the woman who commented gleefully at Rapture Ready that she didn't have any qualms about pouring weed killer down the drain any more, because Jesus is coming soon anyway. At that point, this kind of nonsense is no longer amusing.

[fidlfadn]

@EvoBiologist Yep, it's rather depressing, isn't it? Actually, it wouldn't bother me at all- everyone's entitled to believe whatever they want, and who cares whatever bizarre worldviews people have?- but unfortunately, bizarre worldviews have a way of impinging on the lives of all of us: we have a former US president who was convinced that waging war in Iraq was the Biblical prophecy of Gog and Magog come true, for instance.

[EvoBiologist]

@fidlfadn It reminds me of a documented phenomenon among devout followers of religions. Sometimes, when presented with a clear refutation of their beliefs, they will cling even stronger to those beliefs and actually come out the other end even more devout. This has been studied in groups like the Jehovah's witnesses, who had unfulfilled doomsday prophecies years ago.

[fidlfadn]

@EvoBiologist - yep, well done. I've heard about the gulop before, and it is, as you point out, another good argument for common ancestry. But it is still subject to the remarkable talent creationists have of refusing to see the only sensible story here, or rather of going into contortions to explain why an omnipotent and omniscient God would design things in this bizarre, piecemeal, and highly misleading (to evilutionists) way.

[EvoBiologist]

@fidlfadn Thanks! You're right - the more you know (higher IQ, higher education, etc.), the more likely you are to accept evolution. I have yet to see a good explanation for any of these genetic patterns. If you haven't already, check out my GULOP video for the best case I've seen.

[fidlfadn]

There is no "proof" that all this wasn't intelligently designed, of course, but the more you know about it, the more it fits the evolutionary scenario, warts and all, then any sort of Creation scenario. But most creationists are not willing to put in the work to get even a glimpse of this big picture, and those that do, tend to become skeptics.

[fidlfadn]

Nice work, Evo. I've also enjoyed reading your discussion with mejc 2. I've come across his viewpoint often, that the perceived history of common descent that can be read from the genes is claimed to simply be the result of common design. I'm afraid the only cure for this attitude is to familiarize yourself with the big picture- not only the LRLN, but also the ERV's, the disabled globin genes, the trees generated by just cytochrome c, etc.