Viruses are obligate intracellular parasites. Despite their dependence on host cells, viruses are evolutionarily autonomous, with their own genomes and evolutionary trajectories locked in arms races with the hosts. Here, we discuss a simple functional logic to explain virus macroevolution that appears to define the course of virus evolution. A small core of virus hallmark genes that are responsible for genome replication apparently descended from primordial replicators, whereas most virus genes, starting with those encoding capsid proteins, were subsequently acquired from hosts. The oldest of these acquisitions antedate the last universal cellular ancestor (LUCA). Host gene capture followed two major routes: convergent recruitment of genes with functions that directly benefit virus reproduction and exaptation when host proteins are repurposed for unique virus functions. These forms of host protein recruitment by viruses result in different levels of similarity between virus and host homologs, with the exapted ones often changing beyond easy recognition.

病毒是专性的细胞内寄生虫。尽管病毒依赖于宿主细胞，但它们在进化上是自主的，它们自己的基因组和进化轨迹被锁定在与宿主的军备竞赛中。在这里，我们讨论一个简单的功能逻辑来解释病毒宏观进化，它似乎定义了病毒进化的过程。负责基因组复制的一小部分病毒标志基因显然来自原始复制子，而大多数病毒基因，从编码衣壳蛋白的基因开始，随后是从宿主获得的。这些收购中最古老的收购要早于最后的通用细胞祖先（LUCA）。宿主基因捕获遵循两条主要途径：当宿主蛋白被重新用于独特的病毒功能时，具有直接有益于病毒繁殖和扩展的功能的基因会聚募集。病毒募集宿主蛋白的这些形式导致病毒和宿主同源物之间存在不同程度的相似性，其中延伸的同源物经常发生变化，难以识别。