by Jamie Henzy — Among retro­viruses, the deltaretro­virus genus is some­thing of a shady bunch, its mem­bers lurk­ing in the shad­ows, caus­ing trou­ble in the form of per­sis­tent in­fec­tions that re­sult in lym­phomas and leukemias. At this time, we know of no en­doge­nous se­quences that might be their ancestors—the lone retro­vi­ral genus…