Species of the genus ‘Homo’ are all extinct except humans, which are thought to have evolved from australopithecine ancestors originating in East Africa.
[2] The development of the modern human has taken place over some 300,000 years and unique adaptations have resulted from ecological pressures that Homo Sapiens has faced.
Due prominently to ecological and behavioral factors, the modern human muscular system differs greatly from that of our early primate ancestors.
Since muscles and the accompanying ligaments and tendons are present all throughout the body aiding in many functions, it is apparent that our behavior and decisions are based upon what we are and how we can operate.
At this time our ancestors had not yet switched to full-time bipedalism and so searching for food on the ground did not make sense because there was too much energy and risk involved.
They were not very formidable opponents to more dominant mammals such as large ancient cats (lions, leopards) but their ability to be better hunters and gatherers along with their corresponding brain development, gave them the advantage to add high-calorie nutrient supplies such as meat to their diet.
[6] Humans became taller as the years passed after becoming bipedal which lengthened back muscles at the base of the tail bone and hips which in effect made them weigh more, further hampering their abilities in the trees.
It is well known that the Homo sapiens line of primates developed the opposable thumb which opened the door to many muscle functions not yet possible in the hand and other upper body regions.
By having to center the force of gravity on two feet, the human thigh bone developed an inward slope down to the knee which may have allowed their gluteal abductors to adapt to the stress and build the necessary muscle.
[11] Compared to our closest living relatives, chimpanzees and bonobos, Homo sapiens' skeletal muscle is on average about 1.35 to 1.5 times weaker when normalized for size.