Clarity. Also note that ayeaye lemurs sleep in "spherical nests".

On Saturday, December 26, 2015 at 3:57:53 PM UTC-5, DD'eDeN aka note/nickname/alas_my_loves wrote:
> Leaping Lemurs are upright bipeds (Pre-Primates of dry forest, Madagascar)
> Swinging Siamangs are upright bipeds (Asian lesser apes of rainforest)
> Striding Hominins are upright bipeds (Tropical rainforest belt)
>
> Monkeys changed from upright bipeds to quadrupeds because they moved from dry forests to wet thick forests where upright leaping/splashing was less efficient than low dog-like locomotion.
>
> Great apes continue as upright bipeds on branches (E. Morgan article) and on the ground while in thickets and in knee-deep water, but on open ground they knuckle-walk because it is faster.
>
> Great apes and lesser apes (siamangs) have large long arms and upper body, their body mass ie center of gravity is above the navel, so they can't run upright carelessly as humans can with their lower center of gravity.
>
> Human ancestors went from lemur to siamang to bonobo-like ape, then 5.2ma a chromosome mutation (inversion/translocation/fusion) produced (in my opinion) a consequential physiological/behavioural inversion where the usual woven tree canopy bowl nest (all great apes) was replaced in the Homo lineage by a woven ground bowl dome hut (akin to a targa, a Celtic wicker round shield), which protected them against airborne biting insects (mosquitoes) all night, thus the subsequent loss of body fur and replacement with a thin layer of skin fat; and a body morphological change from upper-body strength/length to lower body strength/length. They remained within the thick tropical rainforest, where striding upright bipedalism gradually improved, and only occasionally entered the wide open spaces of the savannas and seas, though often foraging along the edges seasonally.
>
> DDeden