The Aridity Hypothesis argues that the expansion of drove early hominin evolution and diversification

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.

Answerair masses develop near the equator are warm; tropical air mass