Bipedal Locomotion???

Question

1. What parts of our anatomy reflect changes for bipedal locomotion? What are these changes?

2. How did the development of bipedal locomotion affect human culture and social behavior?

Answer 1

metal gear? it cant be.

Answer 2

You asked this same question a little while ago, so I'm giving the same reply.

The foramen magnum (where the spine and skull join) has been relocated from the back of the skull to the base of the skull, since the skull must be perpendicular to the spinal column. The upper and lower spine of bipedal creatures must be curved to absorb the shock of the bipedal gate. In contrast, the spine of apes is nearly straight. In addition, the rib cage of bipeds is barrel shaped, in contrast to the inverted V-shape of the apes. The muscles that attach to these bones must be restructured to accommodate the skeletal changes.

Longer legs and smaller toes, arched foot and a different transmission of weight when in motion (now heel to ball, instead of along the outside and to toes as in primates).

Modern human hip joints are larger than quadrupedal ancestral species to better support the greater amount of body weight passing through them, as well as a shorter, broader shape. This alteration in shape brought the vertebral column closer to the hip joint, providing a stable base for support of the trunk while walking upright. Also, because bipedal walking requires humans to balance on a relatively unstable ball and socket joint the placement of the vertebral column closer to the hip joint allows humans to invest less muscular effort to balance.The shape change of the hip may have led to the decrease in the degree of hip extension, an energy efficient adaptation.

The vertebral column of humans takes a forward bend in the lumbar (lower) region and a backward bend in the thoracic (upper) region. Without the lumbar curve, the vertebral column would always lean forward, a position that requires much more muscular effort for bipedal animals. With a forward bend, humans use less muscular effort to stand and walk upright. Together, the lumbar and thoracic curves bring the body's center of gravity directly over the feet. Also, the degree of body erection (the angle of body incline to a vertical line in a walking cycle) is significantly smaller to conserve energy.

Enlarged knee joints to support the weight.

The first answerer is correct about the b*****s changing into a sexual signal as a result of bipedalism, in primates they are usually long and dangly. The human face has also converted lips into a secondary sexual signal that mimics the 'lower lips'. If you get a good look at female chimps they have swollen red vulvas, but that's not part of the human anatomy you see when upright, so the focus has shifted to the lips you can see when upright.

It's not seen often in modern humans, but steatopygous buttocks are also a bipedal adaptation. You really only see it in Bushmen and the Negrito peoples now. It's the hugely fat buttocks that you see on ancient Venus figurines, it allows toddlers to ride on their mothers backs more safely when the mothers are moving.

http://olimu.com/Notes/Steatopygia.jpg

Standing upright allowed the hands to develop opposable thumbs, and that allowed advanced tool use, and opened out other food sources. Once we could run fast over long distance, humans began stamina hunting (running down over long distances) and started eating a lot more meat, improving the fat and protein in our diet and allowing for more brain growth. All our complex cultural behaviours are related to this increase in brain size.Things like writing, farming, construction, etc.

Socially, well we aren't really that much different to other primates. It means we've adapted to use our faces as the primary means of visual communication, instead of things like raising hairs on our backs, or flashing our buttocks like baboons (although you'll still see this throwback behaviour after alcohol). Our focus is on what is at eye level, the face.

You'll also notice that most forms of ornamentation center around the upper half of the body, the part most often seen up close. It also makes vertical height visually more significant than outright body mass.

5 days ago