One of the best solutions I heard was that the forest slowly changed to a bush, so more time had to be spend on the ground instead of in the trees.
When the trees get further and further apart, the legs get more important than the arms. Fossilised human ancestors remains and weather graphs should be able to confirm/disprove this.
Lucy
Bible
Search Results
"Death & Dead" were found 827 times in 751 verses.
Thats a Whole Lotta Suffering