We can't know. But we don't have any reason to believe the opposite.

With accurate scientific language we don't say "constants are constant". We say "we had never find any experiment or scenario where the constants are not constant".

It's similar to courts. We say not-guilty instead of innocent. If we suspect a guy killed some other guy but we can't find any clue or evidence that this guy murdered the other we can't accuse him to be the murderer. But we can't say neither that this person is innocent.

I infer the the key of your question is that all the measures and data we have about elementary particles are very indirect, we are not able to picture a elemental particle mentally as we can picture the Moon holistically, where we have lot of measures like light, shape, maps, trajectory, even go here and bring rocks.... and still we know that's the moon as an holistic tangible entity.

The marble model is almost discarded, although can be useful and accurate enough for many applications same as the "nuclear liquid drop model" that models the whole atom's nuclei as a small drop of liquid.

As far as we know elemental particles can be described as waves. Although the more "recent" model and the one that is considered to give more elemental explanation is the Quantum Field Theory and the Quantum Electrodynamics, where particles can be defined as quantums of an underlining field. So the field is the one that exists by its own and the particles are just certain kind of "ripple" in that field. Again that's another model. And it's difficult to visualize so we all rely on abstract math descriptions. By the way the quantum field theories are among the most ever precise theories created so far, the one that makes predictions with a bigger numerically accuracy.

Also as a curiosity I suggest seeing this interesting video, which shows the pilot wave hypothesis, which seems to be having both, the wave properties as waves and at the same time marble alike nature. It helps to visualize or conceptualize certain properties we know of particles https://www.youtube.com/watch?v=nmC0ygr08tE

that's another hypothesis, we can't know much, the problem with evolution is that there are so many things we can't reproduce it on laboratories that we are not able to provide a answer to a why-question.

For example we don't know why we have long beards and long hair and we have to cut it, we are the only kind of animals whose have certain parts of our body with hair length that is not self regulated

In addition, there is a side effect of that which is called the ant mill. Ants loose the track and start to follow the other ants if the path gets in a curl and start to walk in circles till exhaustion.