3 ms·

> Seems obvious that a structure present in pretty much ALL humans has some evolved purpose. Contrast with the length of the recurrent laryngeal nerve: https:

by msla 5y ago

> Seems obvious that a structure present in pretty much ALL humans has some evolved purpose. Contrast with the length of the recurrent laryngeal nerve: https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve > The extreme detour of the recurrent laryngeal nerves, about 4.6 metres (15 ft) in the case of giraffes,[27]: 74–75 is cited as evidence of evolution, as opposed to Intelligent Design. The nerve's route would have been direct in the fish-like ancestors of modern tetrapods, traveling from the brain, past the heart, to the gills (as it does in modern fish). Over the course of evolution, as the neck extended and the heart became lower in the body, the laryngeal nerve was caught on the wrong side of the heart. Natural selection gradually lengthened the nerve by tiny increments to accommodate, resulting in the circuitous route now observed.[28]: 360–362 Imagine how long the nerve must have been in long-necked sauropods: https://bioone.org/journals/acta-palaeontologica-polonica/volume-57/issue-2/app.2011.0019/A-Monument-of-Inefficiency--The-Presumed-Course-of-the/10.4202/app.2011.0019.full https://bioone.org/journals/acta-palaeontologica-polonica/vo... > The course of the recurrent laryngeal nerve appears to be an unchanging aspect of tetrapod embryology, being as developmentally fixed as the presence of a heart and paired vessels to the head. The existence of 28 m neurons in the RLN of Supersaurus may seem fantastic, but they appear unavoidable given what we know of tetrapod embryology and evolution. Other neurons in the bodies of sauropods were even longer, spanning the entire distance from the brainstem to the tip of the tail, and may have been the longest cells in the history of life. These incredible cells represent the interplay of evolutionary innovation and developmental constraint: the acquisition of giant, long-necked and long-tailed bodies built on a deeply conserved tetrapod bauplan.

klipt 5y ago
Hmm yes but a suboptimal nerve is still not the same as a useless nerve - I'm sure you wouldn't want a surgeon pulling yours out because "I don't see the use of this!" ;-)
voldacar 5y ago
>Contrast with the length of the recurrent laryngeal nerve Yes but that is noteworthy precisely because it is the exception to the general rule. It is almost always (99%+) correct that a strange structure has some kind of meaningful purpose.
PeterisP 5y ago
However, your own answer clearly lists the evolved purpose of that nerve - it was the simple and straight line from brain past the heart to the gills; and there is an obvious reason why it can't be changed - there's no direct mutation possible to route it to the other side. On the other hand, there generally are possible direct mutations that would significantly reduce any tissue/structure, so if they aren't "chosen", then that does indicate that the tissue still has some purpose (which might have no relation to the purpose it had when it first appeared).

by msla 5y ago

klipt 5y ago

Hmm yes but a suboptimal nerve is still not the same as a useless nerve - I'm sure you wouldn't want a surgeon pulling yours out because "I don't see the use of this!" ;-)

voldacar 5y ago

>Contrast with the length of the recurrent laryngeal nerve Yes but that is noteworthy precisely because it is the exception to the general rule. It is almost always (99%+) correct that a strange structure has some kind of meaningful purpose.

PeterisP 5y ago

However, your own answer clearly lists the evolved purpose of that nerve - it was the simple and straight line from brain past the heart to the gills; and there is an obvious reason why it can't be changed - there's no direct mutation possible to route it to the other side. On the other hand, there generally are possible direct mutations that would significantly reduce any tissue/structure, so if they aren't "chosen", then that does indicate that the tissue still has some purpose (which might have no relation to the purpose it had when it first appeared).