Endogenous retroviruses (ERVs) are viruses that at some point in the past inserted themselves into the nuclear genome of a host's germ cell. Once integrated in a germ cell the virus would be passed on from one generation to the next and the endogenous retroviral genome would therefore be inherited to new species that evolve from the original host. 'ERV sequences and fragments make up about eight per cent of the human genome,' explains Professor Jens Mayer from the Department of Human Genetics at Saarland University. Endogenous retroviruses are found not only in humans, but also in other mammals such as horses, cattle, apes, koalas and, as has now been shown, in polar bears and giant pandas.
Click "source" to read more.