How long before evolutionary traits revert or change?

Question

I've been dreaming up what I would consider to be an "ideal" sentient being and there have been a variety of fantastic responses to some of my other questions that got me re-examining my design.

First, let me give you a very brief description:

Reptilian/avian in basic external and internal biological structure.
About the size of an armadillo, stands upright with a tail for support and balance, opposable thumbs, three other fingers. And, much like an armadillo it would have an exterior shell, however more like a segmented turtle shell that it can escape into.
Cuttlefish-like eyes that allow for seeing polarized light.
Densely packed neural clusters in the brain like parrots, so in an animal the size as described above, about the same intelligence as a human.. just much older.
Naturally occurring anti-freeze agent in the blood stream, much like the leopard frog, and the ability to slow down their metabolism like a painted turtle to a point of using almost no oxygen for long periods of time (months, potentially longer).

Anyway, all of these things could potentially come about naturally in the right kind of environment (long periods of darkness/cold followed by long periods of light/heat, unsophisticated predators, etc,).

My problem is, at what point of an intelligent species evolution do the rigors of the terrestrial living no longer apply and begin to revert?

Take humans for example. We are relatively hairless, have very poor teeth for killing prey, etc. We have hands to catch food with, and can build shelters so we are by and large weak compared to other animals that still rely on their speed/camo/shells/eyesight/etc. to survive.

Could my invented species exists in the form described, or is it more likely that due to the time and evolution of their species after mastering the use of their hands they would begin to devolve?

Answer 1

There is no "devolving" in science. Everything just drifts in the general direction of being better fit for the environment. And the environment changes all the time. You can imagine this as eternal dance.

So, after what time intelligence would start to be hindrance instead of a bonus? We only know one species that for sure is intelligent - us. That's horribly small sample. There also were Homo neanderthalensis, and other Homo species, but wasn't here long enough.

For us, with our tools and our intelligence, we transform our environment. Pressures that made us smart are long gone. But we seem to keep our intelligence, gain more of it, even. Why? Because we create our own evolutionary pressures. Humans have to be successful, tricky or something to find a mate and have children. And to make children's life good enough for them to survive.

There is no reason for other intelligent species not to be able to change their environment and create evolutionary pressure for intelligence. It is safe to assume that they will be quite similar in that aspect.

Answer 2

Unless there is a vast DISADVANTAGE to the shells or any of the other characteristics, they will still have them. OR if they interfere in any way with a ADVANTAGEOUS trait.

For example, the jaw bite strength of the great apes is better than ours. You would not think that that is connected to brain capacity, but it is.

I can see the anti-freeze blood, system shut down being one of the things to go, because I can't see higher brain function being preserved in the low-oxygen state. (I'd give them a lesser form of it. Human beings still have jaw strength, it just doesn't compare to their cousins'.)

Look at their characteristics and ask yourself how any of those could be a DISADVANTAGE and how any of them might get in the way of the ADVANTAGE of higher intelligence and a different environment.

Therefore, they might not be able to get their heads in the shells anymore, at least not well--if they evolved to have a higher brain capacity than their less evolved counterparts (even if they have special neurons and what not. space is space.)

Also, tails. Once an animal is largely walking upright, the tail goes. If they are on all fours more often, then they keep it. You can see this with the apes (our closest relative which has a more upright posture than monkeys). The upright posture and the skeletal structure means that a tail actually doesn't help with balance once they stand up.

Human eyesight, by the way, is actually very good in the animal kingdom. It's geared for daylight, mainly, but we actually see more colors than most predators, which served us well for the berry picking, determining ripeness and if something was poison. You might say cats have better vision--and they do, when it comes to movement and night vision. But during the day, we see better than they do, and in colors that they can't see. By that measure, we have the better vision.

The eyes of your armadillos will likely remain the same or pretty close, if we are using humans as the model.

Dichromats may be better at "breaking the camouflage of predators and prey," but trichromacy is advantageous for gathering. (There's actually a difference between human men and women--more men are colorblind than women, more women can tell the subtle difference between colors. Females, by and large are better equipped to gather, and men to hunt).

Answer 3

So, as someone said, there's no such thing as devolving, just a better fit for the environment. The idea that something is "more highly evolved" is a bugbear of biologists. Just ask one of them and they'll rant at you. Lots. Bacteria, for example, have more generations, so they've probably gone through more evolution than we ever will. We are more complex, but not more highly evolved than bacteria.

Environments can be full of changes that encourage complexity or not, and plenty of animals have gone "backwards" in complexity terms. Yet, sometimes, not all is lost. For example, fish versus aquatic mammals like dolphins and whales, in which mammals keep a lot of their complexity on the inside, while on the outside being pretty identical (functionally) to fish. Sometimes going backwards rom a more complex place can help you solve problems better.

This also leads into the phase space adjacent. So, the path through the space of all possible types of creatures (the phase space, in science), matters a lot to where you end up. Evolution can't really jump, it can only move towards phase spaces adjacent, so as long as you can trace an evolutionary path that makes sense (i.e. your species doesn't suffer from having something, but a while ago, it was vitally important), you'll never see a loss of that complexity. This point was made by things we have that are pointless but never got rid of, like our appendixes.

Also, sometimes useless or niche things turn into suddenly useful things. So, there's the belief that birds came to be because feathers were used for display and maybe insulation, while some dinosaurs learned to glide between trees. These bridged the gap between not flying and flying.

So, for your species, you probably want to have a bunch of things that have happened or are happening that would cause them to develop like you wish. For some traits that are historical (e.g. fish have vertical tails, aquatic mammals have flat tails), these will persist for a long time, since it really doesn't matter and the evolutionary difference is small, but other traits need constant selection. So, it's worth identifying any that are one or the other and, for those, making sure that the environment provides the constant stimulation they need.

I think with yours, most of the traits would be prone to constant change, with maybe an exception of polarisation and shells. Anyway, here's some stuff I thought might work as an example:

Anti-freeze and hibernation - any environment with extremes of temperature or water would give rise to this, so you're probably looking at a planet with some really weird variable stuff going on (high eccentricity, maybe, high inclination), to keep this level of complexity in the gene-pool for everything. It would be unlikely to have your species evolve from one of the more extreme environments, but if all animals are similarly disadvantaged, it's not a problem. (Also, the book Three Body Problem comes to mind, there's a planetary environment that's extreme enough to cause issues that force all life to hibernate)

Polarised light - As long as there's a situation where they developed the polarised light as a defense mechanism or hunting mechanism, this would also stay in the gene pool. So, polarised light is meant to be good at glare, so that might be a helpful mechanism in dealing with a planet with extremes of sunlight. Alternately, there may be something (e.g. dust, water vapour) which polarisation helps to cut out, or it was super-useful to their immediate ancestors.

Shells- if you have an extreme environment, these might still be quite useful. If there are intense radiation flares or sudden extreme rains due to temperature variations (e.g. sudden hail) then most animals would have shells for a very long time.

Size - if the extremes can also favour small animals and put a ceiling on size, you'd likely prevent human-scale.

Answer 4

I think you are thinking about evolution in the wrong way. Evolution is the passing on of traits and the mutation of genes. The reason it seems to be adapting is that beneficial traits allow things to out compete those that get negative traits. And when you get out competed in the wild, you usually don't pass on your lower quality genetics.

So if the trait is attractive to other members of the species, it should get passed on. It actually doesn't matter how useful/not useful the traits are, if they are surviving to a breeding age(and actually breeding), the trait will be passed on.