Genes compete with variants of themselves to dominate specific locations in the genome of their species. An organism’s overall physical structure, its “body”, provides a local environment to promote the successive replication of the gene variants that code for the attributes of that very structure. The variants that outcompete their rivals do so precisely because they code for attributes of their host structures that promote the replication of those very variants better than the attributes that other variants code for promote the replication of those other variants.