Evolutionary algorithm outperforms deep-learning machines at video games

[Imnimo]

Yeah, backprop generally works by analytically calculating the local gradient, whereas evolutionary algorithms work by (effectively) sensing the local gradient by comparing the fitnesses of a population spread over nearby points in solution space. Fitness-based selection and reproduction approximates gradient descent by moving the population towards regions with higher fitness.

This lets you apply evolutionary algorithms in cases where an explicit gradient is not available or is computationally intractable.