It is "the law" if you think nature as an agent at work and that requires some law to work on. On the other hand it is the consequence if you view it with the concept of "natural process". The difference is subtle: do you conceive it as a work done by an agent or a continuous process?
Whatever it is, one thing is sure that Darwinian theory of natural selection is true for agents in the play ground. Be it living beings, or robots.
The understanding of nature and appreciation to it becomes rather huge once you have the capacity to build and mimic "natural behavior".
Scientists have been working on adaptive and evolutionary robots with capabilities to learn and hence are able to realize the Darwinian selection rule in such robotic agents as the consequence of such learning and adaptive behavior.
See some video...
Evolution of Adaptive Behaviour in Robots by Means of Darwinian Selection
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