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I want to explore the possibilities of an alien species not much unlike that of known to Earth: snakes going through evolution in a way that made them able to reach the intelligence necessary to use tools and form civilizations.

With arms and legs, of course, which implies that this species may have similarities with lizards and other reptiloid races, as well.

This assumption implies a lot of serious changes, e.g. in diet (exclusively omnivore snakes vs exclusively herbivore lizards), but right now, I have a specific question about perception.

I'm not a biologist, so I may be wrong, but I heard a theory that snakes are deaf, or at least they can't hear the way we do. It isn't an option for my species, though: I need them to be able to speak, and that is pointless without hearing.

Is it feasible to assume that during evolution, my snake-like species gained not only proper limbs, but also the ability to hear (and speak)? Would it mean any additional specific biological changes? (e.g. there would be no need to use their tongue the way "original" snakes do)

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    $\begingroup$ Would you be willing to start with a legless lizard instead of a snake? They have ears. (en.wikipedia.org/wiki/Legless_lizard) $\endgroup$ – cobaltduck Mar 23 '17 at 19:05
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    $\begingroup$ phys.org/news/2008-02-snake-mouse-footsteps-jaw.html This might shed some light on the theory you heard. If the jaw thing isn't really what you're looking for, at least this paper states that snakes do have inner ears. It probably wouldn't take too crazy of evolutionary gymnastics to slaps some cartilage on there and get a full-fledged ear. $\endgroup$ – user19838 Mar 23 '17 at 19:07
  • $\begingroup$ @cobaltduck I mean, naming has only formal significance: as long as the origin can be considered snakes, it's possibly fine. $\endgroup$ – Katamori Mar 23 '17 at 20:06
  • $\begingroup$ Snakes can hear. Bone conduction is a thing. They cannot hear frequencies higher than about 1 kHz (about two octaves above middle C), but lower frequencies they can hear just fine. The limbs howver are truely lost. $\endgroup$ – AlexP Mar 23 '17 at 23:09
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    $\begingroup$ If your snake-people have had time to evolve arms and legs, why couldn't they have evolved ears, too? $\endgroup$ – Nuclear Wang Mar 24 '17 at 18:30
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On Earth, snakes evolved from lizards mostly via simplifications. The most famous of those is the loss of legs. But the ears were also affected: when lizards actually hear sound in the range 500-4000 Hz (some up to 10000 Hz), snakes typically only respond to vibrations that they feel through they bellies in the 50-1000 Hz range (see here).

There's Dollo's law: evolutionary losses are unlikely to reemerge. So I see 3 options for your snakes:

  • They are not like Earth snakes at all.
  • They can only "speak" through physical contact.
  • At some point of their evolution, their ancestors got into a very tough situation, where actual hearing was crucial to the survival. Most those ancient snakes died. The few remaining have redeveloped the ears back.
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  • $\begingroup$ Fortunately, both the first and the last points are acceptable for my world - as a matter of fact, the "tough situation" theory is more interesting than most of the things I could come up with! $\endgroup$ – Katamori Mar 23 '17 at 20:36
  • $\begingroup$ Dollo's law seems to not apply here, since the snake-people did re-evolve arms and legs in order to use tools. $\endgroup$ – Nuclear Wang Mar 24 '17 at 18:32
  • $\begingroup$ Dollo's law is a statistical one and has exceptions. But such exceptions are unlikely by themselves, so they have even less probability to stack. And if the snake people have arms and legs and ears, then something very rare has happened along the evolution path, putting a great pressure on them. Or, really, there wasn't an Earth-like evolution at all and no Dollo's law; that's covered by "not like Earth snakes at all", I think. $\endgroup$ – avek Mar 25 '17 at 7:04
  • $\begingroup$ Side note: if the snake people are not like Earth snakes at all, there should be an evolutionary reason why they look like Earth snakes. $\endgroup$ – avek Mar 25 '17 at 7:13
  • $\begingroup$ @avek that's the least problematic parts, imho. I mean, snakes while possessing some really unique traits, are not that complex on their own. I assume I can easily create an environment that supports the existence of snakes. $\endgroup$ – Katamori Mar 26 '17 at 14:19
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Yes it certainly makes sense. Here is why: Claims that a particular animal is deaf or color blind, or lacking in any similar way, should always be taken as dubious. Very often the real finding is that an animal hears or perceives colors differently than a human. For example dogs are not color blind, they are dichromatic.

Snakes seem to posses something like hearing, in that they can detect vibrations (whether this is purely tactile or whether it uses a part of the brain that we would recognize as the auditory context I don't know. But since you are not talking about literal snakes on Earth you can choose). So in the evolutionary process whereby your primitive snake like beings evolve into human like snake beings you could do something like this:

The snakes were already utilizing "sound" in the form of detecting vibrations through the ground. As they evolved towards bipedalism (assuming that is what you want) the ability to detect vibrations in the ground would lessen (as less of the body is in contact with the ground). This could provide the evolutionary pressure whereby the snake beings with a slight genetic variation allowing vibrations to be detected further from the ground would be more successful. There is still a large gap between this and the development of hearing necessary for auditory communication, but it provides a rational start.

There will always be some chance involved in a process like this, because there is no reason to believe that a trait will come to be just because it would be beneficial. I mention this because many people mistakenly think that a trait will evolve because it is useful, or that the need for a trait magically causes it to arise over time. I just wanted to point out that there is no evidence for that type of evolution.

In regard to additional changes: Human like speech and comprehension are computationally complicated and expensive. I would expect larger brains, larger skulls, and possibly the need to be born premature to prevent the large skull from complicating birth.

You could also postulate that they would have more gracile features (like smaller teeth) if you like the idea that social beings can benefit from the retention of juvenile characteristics.

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  • $\begingroup$ Your assumption of hearing evolved because a bipedal creature has less need to "feel" vibrations on the ground is so great that I think I'll accept this answer if no better one comes. You're also right about that speech is inherently complex, but the language I defined for this race is not brutally complex anyway. $\endgroup$ – Katamori Mar 23 '17 at 20:12
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I think this is a definite possibility still. In a world where humans didn't exist, the probability of snakes becoming fully sentient beings is very high.

Although snakes don't have disposable thumbs, they also don't have hearing. But now, civilization has locked up the majority of snakes. This means 2 things:

1: Snakes are more aware of their environment. Only being in small spaces means they are much more aware of their surroundings. This attention to detail may develop their hearing over time.

2: The few snakes in the wilderness also means they have to be aware of their surroundings, on a sort of "survival mode" as such. This means more attention to all of the predators that they may have. When that happens, the snakes, through natural selection, will begin to develop hearing.

I hope this helps!

PS: Here's a photo of a snake as a reference: enter image description here

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  • $\begingroup$ I really don’t see the need for the photo in your answer. Why not include pictures of humans and thumbs “for reference” since you discuss those, too? $\endgroup$ – JDługosz Mar 25 '17 at 7:18
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Not only are snakes not deaf, they actually have a proper inner ear. What they lack is an exposed tympanic membrane (i.e. eardrum) which most terrestrial vertebrates use to transmit vibrations from the air to the inner ear.

Instead, snakes use their entire body as an "eardrum"; vibrations pass from their belly and especially their jaw, affecting the inner ear and allowing them to hear just like other animals. This is more useful to them - vibrations travel through the ground better than they do through the air (which is why you can hear footsteps from far away by putting your ear to the ground), and if they're going to have their head that close to the ground all the time anyway they might as well capitalize on that fact.

If snakes were to stop crawling on the ground, it is likely that the skin covering their inner ear would thin out and develop back into a regular eardrum so they could hear sounds through the air. The bigger question is where their legs would come from - most snakes have already lost any remnant of their legs (aside from simple spurs in some species), and would be unlikely to gain them back. But that's a different question entirely.

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Honestly with an alien species you could go pretty far with unusual genetics. Their evolution comes entirely from their environment, so the need to hear is definitely something that would cause them to develop some sort of ear like structure. not necessarily ears like we see in most land mammals, but when it comes down to it an ear is just a structure that converts pressure waves into something our brain can understand. With an alien species, if you really wanted to, you could even have them process those vibrations through their skin; or give them antennae like insects who use them as both ears and a nose.

Honestly it isn't that hard to imagine anything being able to hear, really the difference is how much. The basic senses can be found in most organisms to some degree, but all at different levels. Do you want them to have really good hearing like bats or dogs? What about their sight? Some snakes see in infrared, do they see like snakes or humans or something else? It's really up to you how you want them to hear or really process anything as long as the basic function is accomplished.

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Since this is an alien species, the issues of real snakes don't apply. We can say that certain features in a specific species are truely lost by looking at the DNA. More difficult to decide by inspection but observed to be the case is areas where development is locked in and any change would probably not work; thus the fixed number of limbs for tetrapods etc.

The aliens are not our snakes. So why not have them able to evolve limbs and hearing? They still have DNA (equivilent) code in place for limbs that can be switched on, or don’t have the developmental lock on limbs so adding a new body segment with limbs might be a thing that happens on that world.

Your snakes might have a keen sense of hearing, unlike Earth snakes, and use it for hunting, to find prey in the leaf litter and strike exactly. Maybe a cobra-like hood provides parabolic reflectors and it hunts like an owl.

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Would you be willing to consider this difference from our snakes? - Your alien snakes develop via metamorphosis, so they are born looking like lizards and then lose limbs and hearing, turning into adult snakes. Or I should say, the ancestors. So (and somewhat correlated with the evolution of humans), the way they'd retain limbs and hearing would be via neoteny (retention of juvenile traits into the adulthood).

Of course, ideally there needs to be an environmental reason for both the metamorphosis and the neoteny, and the only examples I know of where the body plan from larva to adult becomes simpler is in the sea... There's also Caecilians, but I don't know anything about them. However, they seem like a promising venue of exploration.

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snakes can hear, they still have an internal ear, which is the complex part, they also have an ear bone, they just lack an external opening/connection. That could easily re-evolve the that, it would be far easier than re-evolving forelimbs.

They just have to realign the ear bone to contact the skin instead of the jaw.

enter image description here

enter image description here

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I am not a biologist either but snakes can hear just not the same frequencies we hear. So, i think if your snakes have evoloved enough to speak to each other then it is fine if their hearing is evolved too.

On a second note, i dont know the exact number but if a snake can hear up to frequency X Hz then maybe their voices (i dont know i am just guessing) could only go up to X Hz. Ah, unless they're supposed to be heard by others at some point.

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