There's evidence that our savannah ape ancestors experienced unpredictable climate conditions, so it's not that humans are adapted to savannah life, but rather

There's evidence that our savannah ape ancestors experienced unpredictable climate conditions, so it's not that humans are adapted to savannah life, but rather constantly changing conditions that require an adaptable brain: http://humanorigins.si.edu/research/climate-research/effects http://humanorigins.si.edu/research/climate-research/effects