Like other lemurs, they had smaller brains than comparably sized anthropoids. Once again, this suggests lower visual acuity in lemurs than in anthropoids. The primate skull has a large, domed cranium, which is particularly prominent in anthropoids. In the anthropoids lineage, this mutation likely occurred 40 to 25 million years ago. Simians (anthropoids) include monkeys and apes, which in turn includes humans. All anthropoids have a single-chambered uterus; tarsiers have a bicornate uterus like the strepsirrhines. Anthropoids, on the other hand, use allogrooming to manage agonistic interactions.