You seem to be suggesting that anything which is seen to confer survival advantage must have been due to an evolutionary process - presumably driven by unguided events.
Do you see any possible flaw in this line of thought?
Nope - I think you are misunderstand or misrepresenting evolution by natural selection.
Firstly all traits we have as humans are generated by evolution, as they were not present in earlier stages of the evolutionary process, all the way back to the emergence through evolution of the very first life forms.
Secondly the point about evolution is that random and unguided events happen all the time. Some confer survival advantage, some are completely neutral in terms of survival and some are detrimental to survival. If an individual possesses a trait that confers survival advantage then is is ... more likely to survive to a point where it can produce offspring. If that trait is hereditable it will be passed on those offspring and they will have greater chance of survival. Over time the trait becomes becomes more and more common in the population, eventually to the extend that a new variety, strain or even species emerges where this trait is dominant.
Of course if a trait is detrimental it will disappear as it make the individual less likely to survive. Neutral traits, may or may not survive.
Evolution becomes more complication when, firstly, some traits are co-inherited with others and also when a change in environmental conditions occurs. The latter may reveal a trait to be beneficial (or detrimental) when is wasn't so under previous environmental conditions. So if a species of fresh water organism has a trait that confers survival under high salinity conditions it may be neutral in freshwater. But if there is a storm surge or change in sea levels that means its environment becomes contaminated with sea water, only those organisms with the salinity-resistant trait will survive.
That's evolution by natural selection, and, no, there is no flaw in this line of thought, albeit I think there is a major flaw in your thinking in that you seem to think that the random process of variation/mutation etc only produces positive traits - it doesn't - it produces positive, negative and neutral traits. The point is that those positive traits are retained if hereditable.