NO one knows why we reproduce by having sex. All the arguments in favour of sex are countered by stronger arguments in favour of self-cloning: asexual reproduction, where an organism produces a copy of itself, is a much more efficient way to pass your genes down to the next generation. The puzzle is, why hasn’t asexual reproduction taken over? Asexual reproduction does exist in patches of the natural world, but sex is everywhere.
To Charles Darwin, the reason for the prevalence of sexual reproduction was “hidden in darkness”. More than a century later, in 1976, Maynard Smith said the problem with sex was so intransigent it made him feel "some essential feature of the system is being overlooked." Three decades later, the problem is still here.
The intriguing thing is, if you look at sex in terms of how it evolved its relationship with death, some interesting things begin to emerge. Could it be that sex is not the prime driver biology has taught us to believe?