Einstein is sometimes quoted as saying, “God does not play dice with the universe” * but Einstein was not a biologist! The fantastic and beautiful diversity of the life forms that we see around us is the product of an evolutionary process that depends on random genetic mutation. Ever since the first life forms arose in the primaeval ooze the lottery has been running, and is still running. Successful lines that find an ecological niche survive while others die out. Whatever happens before or after, this part of the process is a lottery.
The inevitable price that we have to pay for genetic diversity is the mutations that are not useful, nor even benign, but positively harmful. But make no mistake; in the world as created, you cannot have one without the other.
“Jedenfalls bin ich überzeugt, dass der nicht würfelt” (I am convinced that He [God] does not play dice). Albert Einstein. Letter to Max Born, In: Einstein und Born Briefweschel.(1969) p.130.