Before revision: Although the main adaptive function of human sexual activity is reproduction, human sexual activity also includes the adaptive constraint of avoiding close inbreeding, since inbreeding can have deleterious effects on progeny.
After revision: Avoidance of inbreedingAlthough the main adaptive function of human sexual activity is reproduction, human sexual activity also includes the adaptive constraint of avoiding close inbreeding, since inbreeding can have deleterious effects on progeny.