Please tell me, what are the most plentiful life forms on the planet. Are they not single-celled creatures who do not use intercourse for reproduction?
So how is that method of reproduction not successful?
Yup. So how is that method of reproduction not successful?
If you consider biological success as topping out at being a single-cell life form, you've got a point. I'd flip it around as evidence that asexual reproduction works for simple life forms, but higher life forms require something more. The mutation into separate sexes permitted more genetic variation, and so massively accelerated the evolutionary process for those particular life forms. Personally, I'd consider humanity a pretty good biological success.