Nature and Nuclear Reactions

I've blogged about toilets evolving in nature, but apparently nature also created self-sustaining nuclear reactions:

Perrin and the other French scientists concluded that the only other uranium samples with similar levels of the isotopes found at Oklo could be found in the used nuclear fuel produced by modern reactors. They found that the percentages of many isotopes at Oklo strongly resembled those in the spent fuel generated by nuclear power plants, and, therefore, reasoned that a similar natural process had occurred.
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Scientists think these natural reactors could have functioned intermittently for a million years or more. Natural chain reactions stopped when the uranium isotopes became too sparse to keep the reactions going.

It is amazing to me that the random motion of matter can create a self-sustaining nuclear reaction with an average power output in the 100 kW range. This interesting anecdote of a complex system arising from random processes is evidence that long time periods and random processes can create surprising, complex systems. Maybe even life?