Humanoid Evolution: Dragon-Like Adaptability & Development

[caters]

Currently my humanoids have powers in their genetics but they all appear similar for a given gender, age, and height.

My humanoids are 4 times as tall as a human and live on an earth-like planet that is 4 times bigger than earth(the size of neptune), and has 4 times as thick of an atmosphere for all layers. This planet has 4 moons and orbits a double binary star(a type of quadruple star that is made up of 2 binary stars) The planet is called Kepler Bb(like B flat in music).

But they can evolve into reptilian species, bird-men, bear-men, and other species of humanoid.

Now I know that there can be multiple paths that lead to the same result but let's say that a humanoid evolves into a reptilian species. Each reptilian species has different degrees of adaptation with snake-like species having the highest ability to adapt and crocodilian-like species having the least ability to adapt. Dragon-like humanoids are 1 exception to this in that they can adapt to any environment even though they are most closely related to lizard-like humanoids which don't have as much ability to adapt.

Ability to adapt from greatest to least:

Dragon-like -> Snake-like -> Lizard-like -> Turtle-like -> Tortoise-like -> Crocodilian-like

Let's say that the humanoid is dragon-like.

Now how would it likely evolve that way?

Like this?

Common ancestor -> Cold-blooded -> Scales -> 2 extra limbs halfway between the 2 existing sets of limbs -> Wings -> Scales get thicker -> Ability to metabolize any living thing dead or alive

Or some other way?

And how would it develop?

Like this?

Big egg -> Hatch -> Walks on 4 legs -> The back legs grow longer than the front legs -> Wings start growing -> Dragon-specific abilities like fire breath develop -> Can't fly anymore if it is a huge species but can still fly if it is a smaller species

or some other way?

And how can I apply these ideas to the other species like bird-men and bear-men and how they would evolve and develop?

 

[DaveC426913]

My humanoids are 4 times as tall as a human and live on an earth-like planet that is 4 times bigger than earth(the size of neptune)

Surface gravity increases linearly with radius, so Kepler Bb will have Earth 4Gs at the surface.
Your humans, if their bodies are scaled up proportionally, will mass 64 times an Earth human (4x4x4).
This means your humans' legs are supporting 256 times the weight (per unit surface area of bones) of an Earth human.

This is a major problem. Your Keplerians are, even naked, holding up a similar weight to an Earth human having to support a 15 ton weight.

This is known as Galileo's Square-Cube Law:
https://en.wikipedia.org/wiki/Square-cube_law#Biomechanics

 

[caters]

I consider gravity in categorising a planet as Earth-like as well as liquid water, atmosphere, and other things. Also this is fiction so the gravity can be 1G in my story even if it would be 4G in real life.

 

[DaveC426913]

Also this is fiction so the gravity can be 1G in my story even if it would be 4G in real life.

Calling it fiction isn't license to break natural laws. But calling it fantasy is. It can still be space-based, but you're free from the requirement to stick to plausible behavior.

OK, Kepler Bb is a 1G, your Keplerians are only supporting 64 times as much weight on their legs as humans do. Keplerians will need to be built with legs like an elephant's to support the weight.

Unless, as before, you waive any semblance to science. Gulliver's Travels was a very entertaining story that did not burden itself with the problems of a 80 foot tall human.

 

[Loren]

I consider gravity in categorising a planet as Earth-like as well as liquid water, atmosphere, and other things. Also this is fiction so the gravity can be 1G in my story even if it would be 4G in real life.

More like fantasy. However, you are free to do what you like. You will just be alienating a significant segment of science fiction readers if your worlds are not even remotely realistic.

So to answer your original question, almost assuredly they can't. What you propose is much too far out of the ballpark of reality.