It'd kill us. There are vital parts of our genome that come from such viruses. The placenta, for example, forms its host-compatible interface layer with the mot

It'd kill us. There are vital parts of our genome that come from such viruses. The placenta, for example, forms its host-compatible interface layer with the mother's uterus using a virus-derived protein. So it is believed that all live-birth mammals derive from an animal that accidentally incorporated viral DNA into its genome.