What is the field that deals with observing an individual's fitness within a system called?

Question

Foreword: Perhaps this question is better suited for statistics.stackexchange.com, but I'm deeply interested in studying about both the living thing and the statistics side of things.

Everything in this universe that has surviving and procreation as some of its goals, given finite resources, operates within a competitive system. As such, one is rewarded for doing well, as well as punished for doing badly. Ane extreme proof of this system is the savanah, where faster(?) gazelles can outrun lions so that they can continue existing & procreating and the slower ones get eaten.

My question is, then, is there any literature that studies the fitness of individuals inside systems?

Assume we built a model StocksTraderFitness and based on only assumptions at the very start, we tell the model about 4 qualities it should look at and their importance:

level-headed => 1.3
does well under stress => 1.7
is good with maths = 1
loves risk = 1.3

We then create 1000 StockTraders and we let them out inside the system, based on a FitnessFunction, we keep calculating how they are doing and once we reach an observable good spot, we try to see whether or not our model was good and if these weights of importance don't match these of the winners', we re-adjust our model, or even better yet, we observe new qualities we hadn't even thought about through pattern recognition.

Is there literature or a field that studies this in the context of living things?

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Side note, perhaps it helps with an answer.

My original, actual intent with reading on this is that I believe fitness is akin to what we popularly call intelligence: you do well in the systems you believe are meaningful to you, therefore you are intelligent and the study of discrepancies between humans' personal care about these systems. I had an argument with my grandmother when I was 12 and it made me realize that she's wrong in my system (in a way that I can also test & prove), but she's right inside her's (that she can also test & prove), simply because we are humans, it doesn't mean we submit or attribute importance to every system put in front of us and as such, biases are formed, which leads me to think that the current world-view, perhaps hindered by popular media of the bias is that it's evil, when in fact, it's a core building block of ours.

Answer 1

The study of physiological fitness is simply evolutionary biology. The study of animal behavior and how it evolved is ethology. John Maynard Smith was one of the first to apply mathematical modeling, especially game theory, to the evolution of species. It is now a well-established field (see for example the wikipedia page for evolutionary game theory). But other mathematical frameworks, such as dynamical systems, have been applied to the question. https://en.wikipedia.org/wiki/Evolutionary_game_theory

The precise algorithm you describe is called an evolutionary algorithm and is a well-known, well-studied subclass of optimization algorithms that are loosely inspired by biological systems (e.g. genetic algorithm, particle swarm algorithm...). These algorithms are useful when trying to optimize a high-dimensional and/or highly non-linear function. https://en.wikipedia.org/wiki/Evolutionary_algorithm

As for your side note I think you didn't think this through very carefully. Firstly you are now talking about behavior, not physiology. It is far less clear how behaviors are shaped by evolution. Then you describe how an observer would attribute value to an environment, while fitness is precisely the opposite. Finally there is no notion of "value" in evolution. You might be fit in one environment, but not in another. It doesn't make you any better or worse.