I've been reading 13 Things That Don't Make Sense: The Most Intriguing Scientific Mysteries of Our Time (2010) and Chapter 10 concentrates on the subject of Sex. The author argues that we do not know why humans, or animals, have evolved to reproduce sexually rather than asexually.
Asexual reproduction is far more efficient according to the author, who backs his claims up by citing Richard Dawkins amongst others.
He hasn’t done it yet. In his 2004 book The Ancestor’s Tale, he again admits defeat over the origin of sex. “To do justice to all the theories would take a book—it has already taken several . . . Yet no definitive verdict has emerged.” In the end, he settles for discussing a consequence of sexual reproduction, rather than explaining its origin. The question of what is so good about sex is one that “betters scientists than I have spent book after book failing to answer,” Dawkins admits.
He suggests we have Ptolemaic view of sexual reproduction, which has been shaped over the centuries (quote needed)
Has any progress been made to explain why animals reproduce sexually? Or is it an incorrect assertion in the first place, and we've known for a while?