Unintelligent design (recurrent laryngeal nerve)

Hi Slavesque I think if you are going to make this sort of claim, you should explicitly state exactly what those functions are and also explain why it is a better design to have those organs as they are.Specifically:The Recurrent Laryngeal Nerve - what is the function of having this nerve deliberately routed from the brain, down the neck and into the chest, and then back up the neck to the larynx? And why is that better than routing it directly to the larynx?The Blind Spot in the Retina - what is the function of having the nerve connections on the front of the retina (where they will interfere with light reaching the retina) and then passing through the blind spot (which..er..gives us a blind spot) in order to get to the brain? And why is that better than having the nerve connections at the back of the retina where they can connect straight to the brain without giving us a blind spot?

Hi SlevesqueI have read the article in your link.The author summarises by making the point that failing to identify a function is not evidence that there is no function. I completely disagree. Observing no function is strong evidence of no function, but not necessarily proof.I accept that there may be many organs that were cited in the past as being vestigial, but which have since been found to possess some function. However, as far as I am aware, no such function has been found for all organs, including the RLN.Also, the article and your argument miss an important point. Vestigial organs are exactly what you would expect to find under the Theory of Evolution. In fact, you could say Evolution DEMANDS that there should be vestigial organs. It would be evidence against Evolution if there were no apparent vestigial organs. And Evolution does actually provide an explanation of the function of vestigial organs — I.E. that they had a PAST function that is no longer required. That is a simple and complete explanation. It is indisputable that there are some gaps in our biological knowledge, but Evolution fills this gap in perfectly.There is always the opportunity to provide a better explanation than the Theory of Evolution does in this case, but it would have to be a heck of a good one.Fair play to you, though, for having a go at this one without any support!

Slevesque Come on. You can't claim that providing an explanation for something (provided it is entirely logical and reasoned) is "feeding on the gaps". It is good not to be complacent and to examine other possible explanations for vestigial or "badly designed" organs, but Evolution provides a perfectly logical and complete explanation - by far the best explanation - and so you need to come up with an even better explanation as an alternative. Those who attribute vestigial organs to being a consequence of Evolution are not being lazy. The fact that it is very easy to explain this problem by the Theory of Evolution does not make that a poor explanation. It makes it a very good one! When you have a clear, simple, easy answer, one that fits in perfectly with the whole of the Theory of Evolution, why do you have to look for an alternative or more complex one? I accept that it may not be a true vestigial organ (I.E. it is not completely redundant), as it clearly still has a function. But, again, Evolution provides a complete explanation for the circuitous routing. Evolution does not "feed on the gaps" in the way that Creationism feeds on "gaps" in the fossil record. Evolution provides a completely logical explanation for vestigial, inefficient or vulnerable organs. (I thnk "inefficient" and "vulnerable" are better terms than "badly designed" and get away from the dysteological argument). I’m not a biologist (no shit!) but I understand that organisms are very complex and that no individual or species is likely to survive if it is dragging along completely useless organs. So it is extremely unlikely that you will find many, if indeed any, completely useless organs. Just to consider the evolution of the whale. It starts as a four-legged species that lives partly on land and partly in the water. As it evolves to live more and more in the water, it’s limbs will gradually change to become more adapted for use in the water and less well adapted for use on land. The function of the limbs changes, but there is always likely to be a function as long as the limbs are there. If you’ve got something, it’s more of an advantage for it to have a minor function than no function at all! Whales now have very short vestigial rear limbs tucked into the lines of the body. I would be willing to guess that even though there may be no obvious purpose to this limb, as it is it must form an integral part of the whales’ skeletal structure and its buoyancy/balance in the water. I.E. the rest of the body must have adapted gradually to compensate for this remaining limb as it became smaller and smaller, so that it was always incorporated into the whole, otherwise it would be like dragging an anchor. That’s not to say it wouldn’t be to the whales’ advantage finally to rid themselves of this remaining stump, but ONLY if this happens gradually and the rest of the body adapts as necessary to compensate for this.So, back to the RLN, it is possible that while it is routed as it is, the body may have adapted to take advantage of that routing. And it is worthwhile investigating to see if this is the case. (Although, I don’t think you’ve provide any proper examples with evidence that it has, only some vague suggestions!) But that wouldn’t change the fact that it is routed that way primarily as a consequence of evolution and that it is likely it would have been more advantageous if it had been possible to have a shorter route between the brain and the larynx.

Hi Slevesque It's been a while since I heard the full explanation for this, so I hope I get this right! My understanding of the path taken by the RLN is that its route takes it around one or more arteries/organs. In fish, this nerve serves the gills. Fish don't have a neck, so the route around the equivalent arteries/organs is relatively direct. Mammals have a larynx, which I understand is ultimately an adaption of the gills of our ancestors. The RLN that connects the brain to the larynx is an adaptation of the same nerve that connected the brain to the gills of our ancestors. Mammals have evolved a neck, and the arteries/organs that the RLN goes around are in the chest of mammals. As mammals (or our intermediate ancestors) evolved the neck and chest, the selection pressures must have been that either the RLN goes down the neck and around the arteries and back up the neck, or the arteries go up the neck to the throat area, around the RLN and back down to the chest - or the arteries and RLN meet somewhere in between! (There has obviously never been a mutation that allows the RLN to unwind itself from these arteries - I suppose such a mutation is technically very unlikely to happen.) It is clear that natural selection favours taking the RLN on the long route via the chest. This seems intuitively to be the best option, as you obviously don't want arteries to be any longer or more exposed than necessary. I hope I got that more or less right. I'm open to being corrected by any biologists.I find one of the best way to picture these kind of adaptions is to imagine the development/evolution of an old city. Why do new roads and railway lines serving a city centre not always run straight? Because there are old buildings, older roads, natural topography, etc that all get in the way. A city usually develops as a series of compromises. A city that was designed completely from the beginning - AND WAS TO REMAIN FOREVER EXACTLY AS IT WAS DESIGNED - would be very different. I find it impossible to imagine a city that would never adapt in any way, though, and survive.As I say, there are very likely other smaller pressures that may have made small-scale tweaks to the routing of the RLN, but these would still ultimately be to do with the evolution of the body as a whole.The door is always open for other, better explanations. The ball's in your court.

Hi JustNobody & Welcome In this particular case, I'll leave your theories to others to criticse. I'll just say that I think it's important that lay-persons such as you and I express our understanding of these matters in these discussions. That's really what this is all about. It's important for the experts (biologists in this case) to appreciate how much or how little the public understands of their theories, so they can develop their arguments and explanations accordingly. Don't be reluctant to articulate your understanding on these things.

You make a good general point. However, I fear it may back-fire in the case of the reccurent laryngeal nerve, where it might be argued by a creationist that the ciruitous route of the nerve in all mammals is evidence of a particular "feature" being adopted and incorporated across all "models".

I agree. I was just considering the creationists' argument that there may be some as yet unexplained advantage to having the RLN routed as it is. That's a ridiculous argument, of course, because you could say that about anything, and they do!

Sorry, this was a copy of my previous message. Now deleted.Edited by Jumped Up Chimpanzee, : No reason given.