Why does evolution tend to result in systems that tend to act rationally? Explain.

Question

anonymous · Answer

Natural selection.  Wackos don't have as much of a chance to perpetuate their genes.

anonymous · Answer

Evolution as a whole occurs through natural selection in order to improve efficiency, lifespan, and survival of said living objects (cells, species, etc).

If you are looking at a specific timeframe you can see irrational behavior but as a whole over time, in order to survive, living things tend to act rationally. 

Essentially we learn from our mistakes which is usually caused by irrational or specific behavior.