CrowdScience: Why do we have males and females?

CrowdScience goes right back to the dawn of human evolution to answer this tricky question, and charts how sexual reproduction began. Marnie Chesterton gets to enjoy the faintly bizarre experience of admiring her own sex chromosomes under a microscope, and there’s much scientific discussion of what determines sex in nature and how the sex of human offspring is decided, as well as how reproduction manifests in lots of species, including in animals that seem to have the ability to change their sex.