Benveniste R E, Todaro G J
Proc Natl Acad Sci U S A. 1975 Oct;72(10):4090-4. doi: 10.1073/pnas.72.10.4090.
Domestic pigs (Sus scrofa) and other members of the family Suidae have multiple copies of type C viral gene sequences in the cellular DNA of all their tissues. Partially homologous viral gene sequences are also found in cellular DNA of rodents, particularly Muridae. The results lead to the conclusion that type C viral genes were introduced into the Suidae lineage as a result of trans-species infection by an ancestral xenotropic murine virus. The rate of evolution of the virogene sequences in the pig appears to be much slower than that of genes that have remained in the rodent lineage; this may be a consequence of transfer from a shorter-lived animal (the rodent) to a longer-lived one (the pig). We estimate the time of gene transmission as 5-10 million years ago and conclude that the present-day porcine type C virogenes most closely approximate the viral genes as they were several million years ago in the rodent lineage.
家猪（Sus scrofa）和猪科的其他成员在其所有组织的细胞DNA中都有多个C型病毒基因序列拷贝。在啮齿动物，特别是鼠科动物的细胞DNA中也发现了部分同源的病毒基因序列。这些结果得出结论，C型病毒基因是由于一种祖先嗜异性鼠病毒的跨物种感染而引入猪科谱系的。猪中病毒基因序列的进化速度似乎比留在啮齿动物谱系中的基因要慢得多；这可能是由于从寿命较短的动物（啮齿动物）转移到寿命较长的动物（猪）的结果。我们估计基因传播的时间为500万至1000万年前，并得出结论，当今猪的C型病毒基因与几百万年前在啮齿动物谱系中的病毒基因最为接近。
