Rather, modern humans are the result of millions of years if mosaic evolution. Mosaic evolution: this evolution is ongoing meaning that our species continue to be subject to natural selection. The evolution at different rates of various related or unrelated features or unrelated features within a lineage or clade: bipedalism: habitual upright locomotion on two feet. Dental & cranial morphologies: robust: physically strong, durable, gracile: slight, slender. Why did humans evolve bigger brains: ecological- early hominins evolved larger brains to improve their ability to hunt or forage for unpredictable food sources. In this theory male provisioning was a necessary outcome of the monogamous, bipedal hominins enjoyed increase fitness because they could invest more care and protection into a few offspring. Africa, which has intense solar radiation and heat, particularly in open environments. A vertical body posture increases convective heat loss and evaporative cooling.