TL; DR: Evolution, or at least survival, tends to favor safe strategies over high-risk strategies.
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You can edit the link by starting it wth the second phys.org and it will work.
The paper in Evolutionary Human Sciences is just popularizing the population genetics theory done since 1962 (by JBS Haldane, SD Jayakar, John Gillespie and others) with economic risk management calculations. If people want to see a simple, and hopefully clear, explanation of the population genetics theory part, see section II.11 (Temporal variation in fitness) in my free downloadable textbook Theoretical Evolutionary Genetics.
Fixed it, Thanks!