The archaea and bacteria get by without sex and don't senesce. But when the first eukaryotes, our genetic ancestors, put these organisms to work to produce energy, it was with mixed results. They happily used the energy, which has enabled us to become all that we are, but it put the mechanisms of their eventual demise—death programs, if you will (and Hayflick certainly won't)—right into the heart of their cells. Only through sexual shuffling of genes could the cells mitigate against it.
