title: Sequence analyses of herpesviral enzymes suggest an ancient origin for human sexual behavior.
abstract: Comparison of the amino acid sequences of the deoxythymidine kinases of herpes simplex (HSV) and of marmoset herpes viruses (MHV) suggests a divergence time of 8 to 10 million years ago for HSV-1 and -2. Like MHV, HSV-1 and -2 cause local infections in their natural hosts, and direct contact between two individuals during the brief period of infectivity is needed for transmission. Because B virus, a nearer relative of HSV, depends on both oral and genital routes of transmission, we postulate that ancestral HSV (aHSV) was similar, and that for HSV-1 and -2 to diverge, genital and oral sites had to become microbiologically somewhat isolated from each other, while oral--oral and genital--genital contact had to be facilitated to maintain both aHSV strains. We propose that acquisition of continual sexual attractiveness by the ancestral human female and the adoption of close face-to-face mating, two hallmarks of human sexual behavior, provided the conditions for the divergence.
mesh_terms: D000818:Animals; D004259:DNA-Directed DNA Polymerase / Q000235:genetics*; D000882:Haplorhini / Q000235:genetics* / Q000382:microbiology; D006564:Herpesviridae / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D010802:Phylogeny; D012264:Ribonucleotide Reductases / Q000235:genetics*; D012725:Sexual Behavior / Q000502:physiology*; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D012264:Ribonucleotide Reductases; D013937:Thymidine Kinase; D004259:DNA-Directed DNA Polymerase