In the biological context the complexity is shifted away from the actual selection algorithm and onto the "scoring function." Although the filter of reproduction is relatively simple [1], the reason why the organism was fit and could ultimately reproduce is very complex. The brain's "topology" is the result of selection pressure favoring adaptations that improve fitness by dynamically adapting to relevant patterns found in the environment. The brain attempts to accurately model important aspects of the complex environment it's challenged with to increase fitness.
[1] Nothing in biology is ever actually simple, even though individuals undergo fitness based scoring, the actual notion of individual is arbitrary. In the case of bees most of the individual bees in the colony are sterile, which is obviously bad for fitness of the "individual." However a few individuals reproduce, so all the sterile worker's fitness is shifted onto the queen/drones through the concept of inclusive fitness. This indirect selection also applies to humans, who undergo inclusive fitness through their siblings. This can even be generalized to your individual cells/organs which function as a colony supporting the gonads which actually undergo direct selective pressure.