Evolution of body structure

Seregon - Split this from Population Dynamics Thread as it was getting rather off-topic and deserved it's own thread.

gdt1320 wrote:

Determining cost/benefits of evolutionary adaptions

So i think evolutionary adaptations can be sorted into two categories, mechanistic and behavioral. Mechanistic would cover the species interactions with compounds. I.E. what it can eat, what it is toxic too, what it is resistant against, etc. behavioral would be how it interacts with members of its own species, and other species.

Mechanistic adaptations can be divided into two subgroups, direct and indirect.

Direct adaptations would be altering enzymes, and proteins to be more resistance at something (possibly through changes in amino acid sequences, or glycosylation steps), at the cost of efficiency.

Indirect adaptations would be the development of new compounds within the system to balance out some negative effect. I.E. developing an antidote that neutralizes a toxin or parasite. These would come at the cost of requiring more compounds, or energy. (Developing new limbs, or body parts could probably fit under this description as well)

I'm still looking into behavioral, because I don't know much about AI. But maybe parameters such as aggressiveness, awareness, socialization, would be a good key few.

You seem to be forgetting the keystone of our simulated evolution, which is macroscopic structure. It will most likely be the hardest to quantify.

~sciocont wrote:

You seem to be forgetting the keystone of our simulated evolution, which is macroscopic structure. It will most likely be the hardest to quantify.

I've actually put quite a bit of thought into this, but I'm still fleshing it out. The train of thought I'm following now is that each macroscopic structure will have some influence on the species's parameters.

For an example, lets say a species is developing sight. If they already had vision, it probably won't change much. But if they are developing eyes (or any other sight organ) for the first time, it will make them more aware, better able to find food/prey, but also increase the risk of a fatal or critical injury to that species, and may also take more resources/energy to develop this new organ.

EDIT: To clarify, by developing specialized organs to function better, they increase risk of injuring those organs and becoming critically disabled by loss of function, leading to an increase in statistical fatalities.

Also, depending on how "fast" the evolution will be taking place, there may need to be a series of steps that developing new organs takes place in. I'd like to get the programmer's input on this because there are many different ways of doing this.

1. No steps (goes from no organ, to fully functional organ [0 to 1])

2. Predetermined steps (gores from no organ, to a slightly functioning organ, to a better functioning organ, to a fully functioning organ) in a set number of steps [0 to 0.25 to 0.5 to 0.75 to 1].

3. Variable (program would be limited in how far it could push the evolution and settle on an optimum value, that would probably be some very random number i.e 0.572479 or something. There would need to be a way of selecting what the parts look like if they aren't pre-set. This may be outside our scope for now, and I was not going to follow this path unless the programmers/artists decide they want to.

About the steps on developing an organ, in my opinion they are all possible. From the programming side, i dont think there is any problem having a semi-formed organ, which in turn only works partially. Even more, I through we were going to havedegrees on how good an organ is, so fully formed doesent even fit completely.

On the artistic side (representing the organ), if we design an animation that shows the organ going from noting to fully formed, we could choose the exact part where we are in evolution and choose that.

To wrap up, we can do it, but the question is how we should do it.

For developing an organ (or organelle, limb, enzyme, toxin, or any other 'discrete' addition to a creature), what I had in mind was similair to your option 3. I got the idea from a random post somewhere else on the forum, but I can't remember where:

- When mutating, the species has a very small random chance of adding the 'seed' of a new feature, which is 0% developed in your terminology.
- In further mutations, it's possible that developing this seed is advantagous, in which case it will do so. The possible adaptations could be numerous, depending on the seed (using the femur example, it could grow longer, stronger, lighter, or the leg could have increased muscle mass, stronger tendons etc.).
- If a seed does not get developed further, there is a small random chance of it being lost at each mutation.

The idea here is to mirror as closely as possible actual evolution. Innovative mutations (which produce something completely new) are very rare, and cannot be selected for, but once they appear they often lead to rapid evolution of that feature (if it is benificial). Also, some seeds may only be possible if a precursor feature has been sufficiently developed (e.g.: light sensitive cells -> eye spots -> eyes).

Also keep in mind that many of these features (like organs) will be invisible to the player.

I love your idea, seregon.I dont know how it will work with bones and muscles, as there must be a lot of them, but with individual organs it can eotk be great.

I think it would work ok for bones, given a basic starting skeleton. If we limit skeletons to being bilaterally symetrical (like almost all 'life as we know it', as similair to spores system), we can start with an organism with a spine of a certain length/number of vertebrae, and then add limbs as seeds. Further vertebrae, or additional bones in limbs, may also be added as seeds, then grown. It's something we'll need to test to see if it works ok, but I think it can be done.

I'd also suggest that we have a fairly limited number of possible bone segment types, and these be reused as much as possible. For example, your upper arm and upper leg work almost exactly the same way, with 2 muscles used to flex or extend a fixed joint (elbow, knee) below, and being themselves moved by a ball & socket joint (shoulder, hip) above. The joints of the finger work in a similair way (although the muscle for that is actually in your forearm, I'm not sure we can deal with that in the engine). Somewhere on the forum scio has a list of joint types (4 I think), so we should only really need one bone segment type for each of those, with each bone segment controlling the joint below it (further away from the spine).

Note that we can also handle creatures without a spine, by using either a notochord, carapace segments (insects, crustaceans), or hydrostatic skeleton (most other invertebrates).

edit - found scio's joint concept.

I've been looking about animals, and here it is what i came up with. Please note i'm not a biologist so probably some of the information could be wrong.

Animal kingdom divides into two subkingdoms, parazoa and eumetazoa. Parazoa is pretty much only consists of sponges, so it's not interenting*. Eumetazoa, in its part, divides into two groups, radiata and bilateria. Radiata are defined by having radial simmetry, and are composed by jellyfish and jellyfish-like animals. Bilateria are defined by being simmetrical by one plane (left and right are simmetrical).

To this point, we can alredy say that most animals (all of them except sponges) aresimmetrical in the way spore is.

If we get down the Bilateria side, things get a bit tricky. Acording to one clasification, bilateria are classified into 6 groups. Orthonecitida, Rhombozoa, Acoelomorpha and Chaetognatha are groups with very few cells, and are not really meaningfull. Protostomia** has subdivisions, of which the meaningfull ones are arthropods (mostly insects), moluscs (soft body with an optional shell), and annelids (worms which structure is divided in very similar rings).

Up to here, we have 3 model of bodies. Arthropods, whose body is divided into 3 segments whose limbs have joints and having an exoskelleton. Annelids, who (usually) have 3 segments, the middle one being repeated many times. They also have some kind of exoskeleton. I dont really know how to describe moluscs, as it covers from snails, to squids, to clams.

The remaining group from the Bilateria are the Deuterosome. They include Echinodermata (sea stars), Chordata and two other non meaningfull groups. The Chordata is the really interesting group from here. The main Chordata subgroup are vertebrates, which have a spinal column.

So up to now, the basic structure we have is a creature with something to suport its structure (whether it is through bones, exoskeleton, or both***), probably with limbs**** (the only exception i saw was snakes), and optionally divided into 3 parts*****, with the possibility of the middle one being repeated many times. The remaining structure I dont have comprissed here is the one from moluscs. Also, some other structures could fit in here, I just looked at the ones we know are possible.

Notes:

Spoiler:

Sorry for doublepost, but my post up there is alredy long enough.

In order to detect whether the structure can hold the creature up, we could look at the creature's skin hardness (wich also helps with defense), and radiate from the skin inwards with the depth defined by how hard is the skin. Then, add bones as another option to hold the structure up, which radiate its support outwards from them. If any part of the creature is not suported by anything, then the creature is not possible and changes should be done.

Edit: I see someone moved part of the thread to a new thread. I was thinking about suggesting into doing that, but i dont think it is necessary any more. I didnt know this could be done.

This was getting way off-topic for the population dynamics thread, so I've split it into a new thread.

...Now, where did I leave me invertebrate biology textbook... Belgium, can't find it, so this is from memory.

Most of what you posted looks right, though theres a little more detail there than I'm familiar with. I'm really not sure how the echinodermata end up in bilateria, as they definately have radial symmetry. It's possble that bilateral symmetry evolved twice, I'm not sure. I can't find a diagram which matches the detail of what I can remember from my book, so it's hard to say. The best I could find was this, which more or less confirms what you said, though I'm sure there are a few other interesting groups in the deuterosomes.

For now then, we have the following skeleton types:
Cartilage/bone skeleton
Anything from the hagfish and lamprey up, though we could include the hermichordates here too, as the skeleton and body structure are very similair. Everything I discussed above applies to this group (I think?).

Exoskeleton
Insects, crustaceans, and to some extent arachnids (though they don't have a chitinous exoskeleton they function in a similair way). Movement of the limbs is a mixture of hydrostatic pressure (as below), and I do believe they have some skeletal muscle too, will need to check that. Most arthropods have (as you say) a head, thorax, and tail, though the thorax and tail may be composed of multiple sections.

Hydrostatic skeleton
The skeleton is basically composed of segments of liquid encased in smooth muscle. The muscle is divided into circular and longitudanal groups. Longitudanal muscle runs along the length of the segment, and can be used to shorten, or even bend the segment, circular muscle is antagonistic to this, and can lengthen the segment and keep up the required pressure for bending. Annelids, cnidaria, echonidermata, and molusca all use some variation of this system, though they have wildly different methods of actually moving around using it.

Hydrostatic skeletons are used in both bilateraly and radially symetrical animals, though theres no reason we can't allow radial animals with the other skeletal structures in thrive:
Bilateral symetry skeleton
Usually distinguished by having a distinct front and back, with the left and right being mirror images. Having a front allows the animal to concentrate both its sensory organs, and it's neural system, there, forming a head.

Radial symetry skeleton
Most radial animals don't have a head (octopii aren't radial), and therefore have undeveloped sensory and nervous systems. While most can move, they do so based on very basic stimuli, such as moving towards or away from light.

...that's all I've got for now. Each skeletal system can be neatly divided into units (bones, exo-segments, and hydrostatic cells), so the 'seed' system should atleast be possible, though it may or may not work well. I'm a little uncomfortable with how we should deal with radial creatures, and I see no real way of them becoming sentient or even developing a significant sensory system.

edit (no. 3...) - all molluscs use the same system, they just have very different ways of using it. Slugs and snails use a foot to move, but use a hydrostatic (I believe) skeleton to twist and turn their body. The tentacles of the octopii, as well as the eye stalks of snails, are also hydrostatic. Bivalves have muscles for closing their shells, and ussually get around (if at all) using a water jet, as do cuttlefish.

...and edit number 4. I appear to be grouping two types of muscle together where I shouldn't. Many of the examples of hydrostatic skeletons I gave aren't, and are in fact muscular hydrostats. These work slightly differently, in that instead of a fluid filled cavity surrounded by muscle, they are simply a single muscle using the fluid pressure in it's own cells to function. For our purposes though, I don't see any need to distinguish between these two options?

And finally, the last two pages of this worksheet contain the sorts of diagram I'm looking for. If anyone wants to do some more research, this is called a cladogram, and divides species by phylogenetic developments.

edit - I found scio's joint concept, here.

edit:

Daniferrito wrote:

Fun fact about the differentiation between Protosomia (invertebrates) and Deuterosome (Vertebrates). When creating a new creature, still in early embrionary stage, the few cells form an empty sphere with an opening. If that opening becomes the mouth, it belongs to Deuterosome. If the opening ecomes the anus, it belongs to Protosomia. The other hole is opened shortly aferwards.

I'll see you fun fact, correct you slightly, and raise you a slightly disgusting one: In the deuterosomes (which includes us!) the opening actually starts at the anus. A second opening doesn't actually form, rather the first one is extended through the embryo, forming it's gut, before comming out at the mouth.

I dont think a radial skeleton would be possible, in my opinion it would qualify more as an exoskeleton. Anyway, as you stated, radial symerty wouldn't allow to reach awake stage, so i dont think we should worry to much about it.

I didn't know about the hydrostatic skeleton, but it actually makes a lot of sense. compress it a bit to make it rigid, or leave it not compressed to be more flexible. I dont think it would be viable outside water, what do you think? Also, could it be used as circulatory system at the same time? The varying pressure (i believe) could destroy small capilars. So now we have three kinds of structure that can hold the corpse together, and as they exist on earth we know they are possible. More types could be added as long as they are logical.

I've been thinking, and the only need for segments we have would be for worm-like creatures with repeated parts. Still, repetition means simplicity in design, and that doesen't allow geting to the awake stage. Maybe as a latter adition.

I just looked back at the place where i saw the difference between Protostomes and Deuterostomes, and i can't believe i readed that backwards. I didn't know about the second opening going from the inside out. At least we are not the case of moluscs (and probably many other types), were only one opening is ever created, being used as both things.

Actually, many other kinds of structure could be possible, i just listed the ones that nature proved us as possible and good ones. I also left out the ones that are sessile, as plant-like gameplay and structure deserves its own thread.

Daniferrito wrote:

I didn't know about the hydrostatic skeleton, but it actually makes a lot of sense. compress it a bit to make it rigid, or leave it not compressed to be more flexible. I dont think it would be viable outside water, what do you think? Also, could it be used as circulatory system at the same time? The varying pressure (i believe) could destroy small capilars. So now we have three kinds of structure that can hold the corpse together, and as they exist on earth we know they are possible. More types could be added as long as they are logical.

I've been thinking, and the only need for segments we have would be for worm-like creatures with repeated parts. Still, repetition means simplicity in design, and that doesen't allow geting to the awake stage. Maybe as a latter adition.

Probably the best example of a terrestrial hydrostatic skeleton is the earthworm, though there are probably many more. Muscular hydrostats also have their uses (for example, the tongue, an elephant's trunk). The main limitation to them is that they are relatively slow to move, though I don't think strength is an issue. Most earth examples of hydrostatic skeletons are also fairly primitive (with the exception of the octopus).

Most primitive creatures do not even have capillaries, and have whats called an 'open' circulatory system, where the blood flows freely through the tissue. It's far less efficient, and only works for relatively small creatures with low metabolic rates.

Finally, hydrostatic skeletons work best when segmented, it gives them more control, atleast as far as I'm aware. That might need some more research though.

I agree with everything else you said, we can look into radial skeletons when we get that far, though I doubt it's realistic, or necessary. I hope there aren't too many more skeletal options, three is already going to make our lives complicated, but we'll see what else people come up with.

I know some creatures have open circulatory systems, they are suposed to be the precursors to the closed ones. Anyway, i was only wondering if hydrostatic skeletons could be used as circulatory systems at the same time, not if it actually happens. Now that i think of it, it would need all the hydrostatic skeleton to be merget together, so a separated circulatory system would be needed.

Sorry, I guess I didn't quite answer the question. As far as I'm aware, hydrostatic skeletons only work if they are sealed. Having said that, it is feasible that some blood vessels would have similair muscles in order to push blood along, and some certainly do have the ability to constrict to restrict blood flow, they just wouldn't work as skeletons because they are not closed.

If it works on pressure (think a half inflated baloon, as is it is flexible, but if you press one part, the baloon gets rigid). Another example there is (this one is from wikipedia) is mammal's pennis, which is considered as a similar structure to hydrostatic skeletons. So I believe some kind of sharing (to some extent) can be done between circulatory and hydrostatic systems. By the way, i was refering at all time to closed systems, as open ones are barely any more than filters.

Should we discuss about other systems like circulatory (as i alredy started), digestive/excreting, breathing, senses (vision, smell, sound),... here or should we make a diferent thread for that kind of organs?

I'm a bit late to this, but i think a lot of this can be settled with parts already enumerated in the OE CC. Parts there should cover all manner of skeletons. Also, note that evolution never creates new organs from scratch- organs develop from other repurposed organs. This is why we have an organ design thread. I was going to collect organs and map them all out in a tree saying what could evolve into what and how large the change would be. The idea was to have a big flowchart for every level of every organ, and changing the level or type of an organ would be a possible mutation.

Not to advertise here, but if you are in need of software for creating such an organ flowchart, I highly recommend you check out this program. It is free, and Seregon showed it to me, its awesome! I am currently using it for the Research Web.

Even though organs dont appear from nowhere, we need to create the at some point. All early multicelular creatures start without any differenciation between the cells (as parazoa), and they eventually generate specialized tissues (Eumetazoa), and that tissues further organize into organs.

Skeletons in the OE CC dont cover hydrostatic skeletons, and we also need to define when a skeleton structure is enough to keep the creature in one piece. I personally dont think a spine cord is mandatory, as a less centralized nervous system is possible (that of invertebrates).

Daniferrito wrote:

Even though organs dont appear from nowhere, we need to create the at some point. All early multicelular creatures start without any differenciation between the cells (as parazoa), and they eventually generate specialized tissues (Eumetazoa), and that tissues further organize into organs.

Skeletons in the OE CC dont cover hydrostatic skeletons, and we also need to define when a skeleton structure is enough to keep the creature in one piece. I personally dont think a spine cord is mandatory, as a less centralized nervous system is possible (that of invertebrates).

Skeletal system should contain the "wormacle" part which is sued to define hydrostacically supported structures such as tentacles and annelid bodies. You're absolutely right about organs, I just wanted to point out that later in evolution, we'll be modifying existing organs instead of creating new ones from nowhere.

Yes, for most 'standard' organs, you can't really add a new one, and adding anything new should be a very rare event. However I do see the 'seed' idea as the only real way of adding new limbs, it does need some more though though.

Also, what is a wormacle? I've never heard it before, and a google search throws up our own OE concept as the 6th result.

Seregon wrote:

Yes, for most 'standard' organs, you can't really add a new one, and adding anything new should be a very rare event. However I do see the 'seed' idea as the only real way of adding new limbs, it does need some more though though.

Also, what is a wormacle? I've never heard it before, and a google search throws up our own OE concept as the 6th result.

That was my name for the structure part in the skeletal tab that creates tentacles or wormlike bodies. (Good news, we're #6 on google for something)

A food for thought about Gravity and its effects on evolution / effects on already developed species

Looked around, and couldn't find anything on it so imma take the ban risk and bring this up. Evolution also will not just dictate on environmental adaptation, the ecosystem is a major part yes, but also gravity has a big impact as well i would assume, the more gravity pull a planet has, the more muscular and thicker boned a creature will have to be. Lets take Elcor from Mass Effect(and this is the only example) for example, they are built for their planet, they are big, muscular, and thick boned, because they have to be, this also means they are slow and sluggish.

Now another thing on this, if your space faring species colonizes another planet that has a different gravitational set, you will either have to develop and somehow land artificial gravity generators for them to survive fully, because how a body works, the organs, joints, bones, vessels, capillaries and the like are setup for our world, if we went to another place and decided to just live there, you can bet we will not live long, because our bodies would not be able to adjust fast enough to the new force, or heck, you walk out of your lander, and next thing you know, you cant even stand up because the force pulled you down and pinned you. Just some food for thought and a little theory.

Then again on the other end of the spectrum we got elephants (I am excluding the humpback whale because this would induce a long discussion that i would rather avoid) But lets say there is another planet out there that has a species the exact same size as a elephant and we switch them out, If the new species is from a heavier planet, it won't be affected, however it will likely starve due to i may not be able to feed on anything here, whereas our elephant will begin to have massive health issues on the planet with more gravity, even if i can eat whatever it wants there, soon because of how it carries itself, its insides would be pulled down causing an array of issues, this would probably make digesting hard to do, blood flow would be limited as the heart was not made for such force. And even if a small species was formed on the planet with more gravity, it would most likely have developed skeletal reinforcement and more tendons, that or it is a very very lightweight species that has very well made joints and strong tendons for reacting to force when running or jumping, hearts would also have to be strong enough to pump blood correctly.

So i would assume that evolution of body structure will depend on a massive amount of different things, gravitational force being an important factor on development.

So now the fun question, will this be a factor in the game? :cat: 

I hate to be this laconic, but yes.

That was anticlimactic.

It was a question that could have been a lot more concise.