hmm… that reminds me…need to go fetch me another pair of them FROG ASS BOOTS…they lasted forever. 
It’s not nonsense. I didn’t say natural selection was a guarantee of anything. I’m saying that when it comes to something as major and important as how well protected the neck is, and if, for the sake of this point, we assume that it is possible for mammals to develop such protection, the idea that it simply would never have cropped up in billions of years is simply not credible. The odds against it are impossibly high. That suggests that either it has cropped up (which is what I’m suggesting), or it can’t crop up (which is your next point).
I know. I just think this is also incredibly unlikely. Why would mammals be incapable of developing extra neck protection? We have ribcages, we have skulls. Just connect the two. I’m no biologist but, look, we’re discussing the absence of a major trait that would have a direct influence on survival: what’s more likely, that natural selection is responsible, or that unnamed, hard-to-conceive genetic impossibilities are responsible? I think Occam’s razor points overwhelmingly in favor of the former. If you don’t, then we simply disagree.
This isn’t true: the fact that very few mammals have evolved with greater neck protection doesn’t “certainly point more towards ‘constraint’ than ‘tried it, didn’t work’”. It’s consistent with either. That’s just your interpretation. It’s an interpretation that I think is, while possible, infinitely less likely than that the forces of natural selection have played their role, as they have done with almost all of the other major traits we have. But if you don’t buy that, then you don’t buy it.
Developmental gene suites, such as homeobox genes, are extremely conservative throughout their evolution. There’s a reason no vertebrate has ever evolved extra digits after they were lost. There’s a reason no vertebrate has ever evolved more than 4 limbs. There’s a reason ontogeny does, to some extent, capitulate phylogeny. Development is finely controlled, and messing with these genes usually results in an unviable embryo. Thus, there is much less variation available from which to select. The limiting factor is variation, not selection.
Sure, it’s consistent with either, but surely if the potential were there, it could be coaxed out during development (we have done numerous developmental studies, after all; chicken can grow teeth and horses can grow extra toes and all that).
There are a few possibilites for what we might call "armor:
- A bony extension between the skull and ribcage. Highly unlikely, probably impossible, for reasons mentioned above. Developmental genes are too conservative to allow variation along these lines.
- Dermal ossicles. Among vertebrates, present in many reptilian lineages, but absent in most mammals and birds. The few exceptions are giant ground sloths (Paramylodon and Mylodon). So, possible, but unlikely. Only arose in a couple species as far as we can tell, so may have been the result of new mutations in those lineages, vs. an ancestral trait that has been lost in all other mammals. This would qualify under “mutation has simply not arisen”.
- Ossified tendons in the neck. Tendons can certainly ossify (many dinosaurs have ossified spinal tendons). Tendons tend to ossify most often when they are frequently subject to compression; this tends to not be the case for most animals in their necks. This could be a case of absent variation or negative selection pressures; since pretty much all vertebrate animals – even those which have evolved ossified tendons elsewhere – do not possess them, I’d chalk this up to either variational or developmental constraints. If it were a matter of selection pressures, surely we could find one species in which they evolved and were adaptive.
- Bony extension of the skull, as seen in ceratopsians. A possibility, certainly as they have arisen in at least one successful clade. However, ceratopisans are rather unique in regards to this feature. Others have evolved “shells” (e.g., turtles, glyptodonts), wherein some measure of protection is afforded by armor extending from the back. Humans lack a protective back shell, so that’s pretty much a non-starter. And there has been no evidence of any such extensions forming either in the fossil record or during development in humans or apes, so I’d chalk this one up to “developmental constraints / simply haven’t arisen”.
- Keratinous scales. We see these in pangolins and their relatives, but not elsewhere. I’d chalk this up to new mutation that arose in that group; possible, but simply hasn’t arisen in other groups.
There could very well be options that I haven’t considered, but in each case, “simply hasn’t arisen” and/or “can’t arise due to developmental/structural constraints” are far more likely options than “arose, but was selected against”.
If you’re going to start actively claiming that you have scientific evidence that it’s not physically possible for humans to develop better neck protection, I think you need to cite that evidence. What studies have indicated this? Which biologists believe this? Personally I find it hard to see why it’s “probably impossible” for humans to develop bones somewhere between the skull and ribcage.
Why does it qualify under that? You seem to be confusing “trait hasn’t arisen in the last few thousand years” with “trait can’t arise”. The absence of neck armor in most mammals is not proof of your point. It’s fully consistent with either of our points. If this is supposed to be an objective conclusion that you want me to assent to, you need to provide evidence for it.
Why? If it gets selected against, it gets selected against. In all of these examples you’re trying to draw firm conclusions based on no evidence at all. If this is just what you believe then that’s OK - I just disagree with it. But if you’re trying to convince me, you need to cite some evidence for it.
As we have already established, I completely disagree. I think it’s overwhelmingly more likely that ‘neck armor’ was selected against rather than simply never cropping up, and this is why I think that is: maintaining a free range of motion and mobility in the neck is crucial for allowing mammals to assess their surroundings quickly or to use their jaws as an effective weapon. Any mutation that would protect the neck would also have to limit that mobility. Natural selection has determined that neck mobility provides a greater survival advantage than strengthened neck protection.
Now if you simply disagree with that because that’s your instinctive reaction, then fine. That means we just disagree on this. On the other hand, if you think your position is objectively more valid, supported by evidence or biologists, you need to cite that evidence.
This works both ways, you know. What evidence do you have that indicates it is possible, in light of the obvious evidence that it has not happened?
One cannot produce studies for a negative; you may not have noticed, but there is no research done for why something didn’t evolve.
No, I’m saying the characteristic only arose in one lineage (that I am aware of), ever, among mammals. It is often cited as a synapomorphy for Xenarthra, meaning it does not exist in the ancestors of that group. And it hasn’t appeared in any other group. If you expect me to believe it could be evolved by anyone, you’ll likewise have to provide some evidence.
Similarly, the keratinous scales of pangolins are oft cited as a synapomorphy for Pholidota. Again, if you have evidence that any mammalian group could have evolved these, tried it and were found wanting by natural selection, feel free to provide it.
I should note that you are doing exactly the same (trying to draw firm conclusions based on no evidence at all). My inferences are based on what I know about evolution, nothing more.
As pangolins and the extinct ground sloths demonstrate, it is certainly possible to have both.
So why have no other groups evolved the characteristic? Your claim is certainly just as applicable to pangolins as it is to humans; however, natural selection has clearly acted contrarily to your claim in those cases.
My inferences are based on my knowledge of evolutionary theory. And really, that’s all that’s available for this sort of discussion. As I mentioned, there is no research being done for lack of traits, so neither of us are going to find support in the literature.
So, bottom line: you (and those who have made similar claims in this thread) have provided one possibility. I have provided a couple others. All of them are based on nothing more than speculation and inferences. The only factual answer is “the OP’s question cannot be answered factually.”
It’s not the same, because I haven’t been drawing the same kind of firm conclusions. I’m stating my belief. I have no solid evidence behind it. If that’s the position you’re in too, then OK, we just disagree on this. But if you’re going to make factual statements like these:
Then you need to back them up. If you’re saying human genes are ‘too conservative’ to allow variation along the lines of developing bones in the neck, you need to support that. If you’re saying there’s been no evidence of any such extensions forming anywhere in the mammalian ancestral fossil record, you need to support that, because that would count in your favor (although it wouldn’t be conclusive). I haven’t been making claims like this. All I’ve said is:
- I think it is very unlikely that we are physically incapable of developing greater neck protection.
- Given that, I think it is very unlikely that no mutation in that direction has ever happened, and been subject to natural selection, in millions of years.
- I think there is a coherent explanation of why greater neck protection would not be a survival advantage and would be selected against (it would inhibit neck mobility and damage mammals’ abilities to assess their environment at high speeds or use their jaws as weapons).
For those 3 reasons, I believe natural selection is the reason we don’t have greater neck protection. That’s a belief. If you don’t share that belief, then OK, we disagree. But if you’re saying any of those beliefs are objectively wrong, then you need to justify that with further objective evidence.
Strictly speaking, human beings did develop neck armor through evolution.
We evolved great big brains, with which we were able to discover the secrets of metal-working … 
I still disagree with 2) above. Do you have a cite from Dawkins more directly addressing that? I don’t recall anyone claiming that every possible variation has existed, or that selection far back in the ancestry applies in this case. Ceratopsians had great neck armor, but maybe their neck mobility was limited (saw some pseud-science on the TV regarding that, but I’m just speculating). But those guys all got killed by the ‘big rock’ (more speculation), so they had no chance to pass on those genes (wouldn’t go to humans anyway, this about the mechanism though).
But 1) and 3) are spot on.
Such conclusions are hardly unique to me. Consider, for example, this paper:
or this one:
Or this one:
Now, none of those pertain to this issue exactly. But, they do illustrate my larger theme regarding the nature of developmental constraints - you can’t make small changes to many developmental processes without drastic results, and those drastic results usually either result in a non-viable embryo, or a completely new body plan (which I noted previously). Therefore, my previous statements along these lines were made by logical inference based on the known nature of developmental constraints in vertebrates. It is self-evident that a head-to-torso connection of bony tissue is a dramatic restructuring; such are largely prevented by developmental controls. Thus, I maintain the unlikelihood of such a structure evolving.
So, what is your basis for your claim that “it is very unlikely that we are physically incapable of developing greater neck protection”?
And I have given my reasons why I believe you are wrong. But, as I have already said, there is no “objective evidence” to be had in support of either position, nor was I making unqualified objective statements. The statements I have made are consistent with the known research in developmental biology and the evolution of mammals. This is not a gut feeling or a speculative belief. It is a logical inference. Granted the logic may well be flawed, but there it is.
However, you have only indicated that you “believe” it to be unlikely that such a trait could not have evolved, but have presented no basis for that belief. Convince me that such a trait is not unlikely after all, and I can then be further convinced as to the nigh-inevitability of it having arisen and been selected against.
What, like that filthy Cardassian scum?
I daresay the ability to quickly turn the head and resposition the sensory organs is more useful.
Those studies prove that development constraints can exist that bias the progress of evolution one way or another. But I’ve accepted that: I just think that’s probably not what happened in this case. And developing greater neck protection may or may not be a dramatic restructuring (depending on how significant the protection is) but either way I don’t think that makes it unlikely to evolve. We’ve evolved from lots of ancestral creatures that were more dramatically different from us than that. People used to use your argument here to suggest that evolution was impossible: because how could the structure of the eyeball develop from nothing?
You conveniently cut off the “I think…” from the start of that sentence. That’s just a belief based on what I understand about evolution and biology. I’m not claiming I have evidence for it beyond that.
The statements I have made are consistent with research into developmental biology and the evolution of mammals as well. You are indeed expressing a speculative belief, as am I. Neither of us have good evidence for our positions; we have a shared understanding understanding of biology and evolution, and we disagree on the interpretations we have drawn from that understanding.
Neither of us have presented a basis for our beliefs beyond our subjective interpretations of what we know about evolution. We have two theorems, both of which are consistent with the evidence we have, but the evidence doesn’t point to either of them. So at this point, unless we enlist the opinions of those with more expertise in the subject, I don’t think there’s much further we can say really. Good talk.
This seems to me the most useful supposition here. I’m not sure any of us are armed to draw conclusions about the genetic mechanism. But the most important functions of the animal bodies rely on nerves, blood, air, and food passing through the neck. Despite that, mammals don’t show tremendous variation in neck construction, a good argument for ‘form following function’.
BTW, many mammals use loose skin as a neck defense. But I can’t think of one having loose skin only at the neck at the moment.
Someone upthread noted that the bushy beards natural to some men may have acted as a form of defense - in that anything seeking to bite the neck may get a mouthful of beard.
Doesn’t sound extremely effective, but it may be good camouflage, resembling loose skin to the predator, or just hiding the neck. But women (usually) don’t have beards. Evolution would seem to favor the survival of females, so I’m not sure beards are that important. However Lions are a similar case, sexual dimorphism making the male the protector of the females. That could be why Lions have manes, and us guys have beards (in my case, I have a beard because I’m too lazy to shave).
Whoa, only one other person has mentioned beards? If I let my beard grow for a year, you’d have a hell of a time getting through all that thick curly hair to… bite my windpipe in half or whatever people are imagining.
The only other purpose (intentional or incidental) of beards is ornamental. Letting females know that yes, we are in fact males. This factor shouldn’t be underestimated though. Humans have probably only retained pubic hair to act as crude arrows pointing to our good stuff.
Disagree. The vertebrae are, as has been mentioned, neck armor of a sort. So is the incredibly thick muscle of our neck and the rings around our trachea. It certainly wouldn’t be impossible to develop a different vertebral configuration that is fused (happens naturally), that protects more than just the spinal cord, or that grows larger than normal and forms spines or a ridge, or non skeletal features such as on a stegosaurus or iguana.
Given many species’ (including our own) evolution of neck protection ranging from camo to thick fur crests to spines to scales etc, etc, etc, it seems to me to be far more likely that some sort of more obvious or heavy duty protection as described by the OP is more likely to have been selected against at some point in our evolutionary history than that it has never popped up or is impossible to develop.
That other species evolved neck protection is no evidence whatsoever that humans could, or did, evolve neck armor (above and beyond the basic vertebral skeleton that we share with pretty much all terrestrial vertebrates), or any potential precursors, and that such were subsequently selected against.
And I ask the same thing that I asked TGP: what makes you think that? You have precisely zero fossil evidence to work from to support such a conclusion, and zero embryological evidence that the genes exist that would permit such features to arise in the first place. So why do you think it more likely to have happened and been selected against than to simply have not happened at all?
Why, if it is so likely to have occurred do we not see evidence in many other species? I gave examples of two mammal groups which have evolved neck armor of different types, and those are so unique that the possession of said armor is a synapomorphy for the mammal group in question. Certainly there are those who would benefit more from having neck armor than from having a mobile neck (e.g., any mammal which is preyed upon by any of the big cats, which specifically kill by using a stanglehold on the neck).
Do you believe that every single possible mutation has arisen at some point in the past, and has already been selected for or against? If not, then surely you accept that some potential mutations have simply not come to pass as yet. And if you accept that, then I’m not sure why you are disagreeing with me, since that’s exactly what I have maintained all along: the particular suite of mutations that would result in greater neck armor among humans probably simply haven’t come to pass, and the reasons for that are either luck or internal constraint. And that is a far simpler explanation than your alternative. Occam’s Razor, indeed…
I’m guessing that it could indeed be a case of sexual dimorphism - men being the first defense of the family or clan group against predators, that sort of thing.
Get a bushy enough beard, it may be pretty effective.
If that is the case, the question is solved - we do have neck armor. 
Apparently everyone decided to post about beards at the exact same time as me. This depends on the guy, lots of men can’t really grow beards at all. However my beard is definitely thick and bushy enough that if I grew it long, you’d have a tough time biting my neck or even throttling me. I don’t think it’d offer much protection against say, a spear, but i don’t think it would be useless in a hand to hand fight. Since men have been using weapons since before we evolved into this species, that’s probably why most men don’t grow very thick beards anymore.
No amount of armor that a person could reasonably grow is likely to have much effect on hand weapons.
Our first weapon was probably some sort of club, used for bashing heads. We have significantly thick skulls, but no match for clubs. apparently, human bones (including skulls) have evolved to be thinner than our ancestors’ since the development of weapons - it may be, because having thick bones and skulls simply wasn’t as much of a positive factor - it didn’t convey an advantage. Just speculation on my part, really.
I guess what I’m musing is that, if beards were a sort of armor, they would be of most use against predators that bite throats. The survival of beards among some human populations may be related to sexual selection and even the effect of climate - hot places providing pressure for hairlessness.