I don't know what you mean by "coincidence", but it certainly wasn't planned or designed into our species. Organic organisms die due, at the very least, to cell degeneration. Simple as that.
Death is a natural phenomenon but it doesn't mean that it was shaped by nature,
the death is a must otherwise no one could survive due to the lack of resources,
nature won't understand what is good and what is bad for the future of earth, death
is planned from the beginning and it's a good plan rather than thinking of it as "just happened to be so",
see for example how dogs die in very early ages, and still it's natural for dogs, whereas humans can
live to around 100 years and it's natural for humans, whereas turtles never get old and they die
by a disease or by an accident and that's still nature.