'Cheshire Cat' Escape Strategy

The study of one of the most abundant unicellular eukaryotes seems to show that sex was invented to escape viral infections. In their normal haploid form-

Emiliania huxleyi produce mineral scales and form gigantic populations that are visible from space. But when attacked by marine viruses, they transform into haploid cells which only contain a single chromosome (N). These new, non-calcifying, highly motile cells are totally invisible to viruses (and undetectable on satellite photos) so that the species can live in peace to await safer times.

Primitive single-celled predecessors to the Earth's flora and fauna changed their form by separating their 2 chromosomes to become motile and to eliminate binding points used by invading viruses. When the viral onslaught abated they recombined into their normal two-chromosome form. The fact that the process accelerated genetic variations and precipitated evolution to more complex forms was just an unavoidable by-product.