Evolution does not account for anything. It proposes to account for variations in species.
See the above logic diagram of the Scientific Method.
As I understand Darwin’s theory the question he set out to answer was how biodiversity came about.
His research concentrated on birds of similar appearance and differences in beak structure that facilitated different feed habits.
Darwin’s hypothesis boils down to natural preserve and accumulate minor advantageous genetic mutations.
Unfortunately, Darwin’s theory never makes it any farther than this. His theory can not be tested. No one has to my knowledge ever been able to induce a successful mutation. Most natural mutations are fatal. Those natural mutations that are not fatal are for the most part detrimental. Those that are not fatal or detrimental are simply cosmetic and do not increase the survivability of the mutant.
With no experimental testing possible and no observable natural phenomena supporting the hypothesis the theory remains unproven and unprovable.
In other words, Darwin’s theory is on a par with Intelligent design.