Whiptail lizards are an all-female species. Various fish, crustaceans, insects, and worms can reproduce without the male sex. Some microscopic animals, such as bdelloid rotifers, appear to have gone without sex for at least 40 million years. Many common plants such as dandelions are wholly asexual. These species stand as living proof that sex is unnecessary.
Asexual reproduction means holding on to all the equity.
Companies that give away 50 percent of their equity every few years have to grow twice as fast as companies that do not, or the market will bury them. This biological paradox is so puzzling that some biologists have been tempted to chalk up sex to an accident of history. It's useless, but species like ours can't get rid of it. If sex were truly useless, though, a species that did manage to get rid of it ought to say good riddance and return to the happy state of the rotifer. It simply would not do so if sex did not carry some evolutionary advantage.