You dumbass. Equatorial climates have no winter and endless rain, which means there is an endless supply of plant based food. All you had to do to survive was lounge around your favorite fruit tree patch and ward off competitors while chasing the occasional gazelle. 

A desert is somewhat similar but has a smaller carrying capacity in terms of the amount of life it can support, so the competition is more vicious. 

Contrast these with ANY environment that has a winter. If you have a winter you need to be able to think using abstractions, specialize labor, identify and anticipate crop and bloom patterns and animal migrations, and maximize the efficient use of resources. All of these require a society containing people far more capable of advanced thought. 

Surprise sur-fucking-prise, Africans are retarded and have no sense of abstract thought, sand niggers are the same but way more vicious (see: the Middle East), and whites and East Asians have more advanced societies that have greater efficiency and specialization of labor, less internal violence, and full of people more able to use abstract tonight and pattern recognition to shape their environment as opposed to simple reacting to it.