In this lab, we have discussed the savanna hypothesis and how pre-australopithecines challenge this explanation of the evolution of bipedalism. If the savanna environment was not the factor favoring bipedalism, what was?

1. Describe some of the advantages of bipedalism (be sure to think about what life would have been like for our ancestors millions of years ago when bipedalism evolved, including their risk of predation, food availability, etc.).

2. Are there any disadvantages to bipedalism? If so, what are they?

3. Taking into account the possible advantages and disadvantages, why do you think bipedalism might have evolved?

1-As for predation or hunting, humans were favored since they could move faster and flee more easily if they are in danger or want to hunt more quickly.

As for food, the human standing on its two legs made it measure more in length, which favored food since they could reach certain fruits from certain trees, so their food began to be more fruitful or herbivorous and they did not depend so much on the hunting of rodents (more labor).

On the other hand, the evolution of bipedalism favored the species widely since the solar stages and the radiations were more and more intense over the years and the human being was more exposed to these radiations when positioning himself on 4 legs. The day that humans began to position and maintain themselves in a bipedal manner, their exposure surface against harmful radiation decreased, and only the area of the shell is exposed to radiation, considering that it is the area with the most fur to add even more. protection against these radiation.

2-Yes, the disadvantage of bipedalism is the possible chronic future conditions with which the human suffers because he is more affected by gravity, one of these many conditions is the prolapse of the female genital organs, joint disorders in those who they present a lot of stature, the difficulty of venous return in those people with muscular atrophies or little cardiac capacity, the locomotion is much more cordial and complex which made it difficult for those humans who were born with certain motor maturational delays, affections in the spinal column due to increased weight since these are highly demanded to bear certain extra kilos against the effect of gravity, brain lipotimias for lack of possibility of properly oxygenating the brain.

And another factor that is also considered in the gestational stage is that women used to have more miscarriages or little retention of the embryo and / or fetus.

The gestational stage began to last less with bipedalism, which caused certain fundamental systems of the human to mature extrauterine at greater risk of lung infections, and this is due to the effect of gravity that fosters the position of children in the maternal vaginal delivery

3-Bipedalism evolved because it had a great influence that for the species is more important the cause of the advantages than the disadvantages, since humans began to eat better, to expose themselves less to harmful radiation and to flee when it came to power be preyed upon.

Three fundamental reasons that did not go unnoticed for human evolution, since if it did not evolve, the extinction of the human species continued as the only way out.

Explanation:

Key points that should not go unnoticed:

This is the name given to the faculty of walking on two legs. One of the most important changes in human evolution was the appearance of erect posture and biped gait as mechanisms of displacement. Even the oldest Australopithecus fossils show at least partial bipedalism, that is, it appeared very early in human evolution. The shift to bipedalism involves several adaptations:

Skull: In apes the foramen magnum, which is the hole at the base of the skull and with which the spinal column is articulated, is located at the back of the skull. In Homo sapiens the foramen magnum is located in the center of the skull base and faces downwards. In addition there is an increase in the cranial box and a flattening of the face. There is also the disappearance of the sagittal crest, that is, the bony crest along the dorsal midline of the skull, which is associated with strong chewing muscles attached to it, and the superciliary arches over the eyes.

Vertebral column: in Homo sapiens the disposition of the vertebral column is vertical, almost 90º with respect to the pelvis. It has cervical and lumbar curvatures, which allow it to better support the weight of the head and trunk; and at the same time it has a spring effect. In apes the column is arranged diagonally; it is rectilinear, lacks curvatures and participates in the movement of the body during walking (the hind limbs push the body forward and that thrust is transmitted by the spine to the forelimbs).

Pelvis: in men it has widened and is laterally oriented, it receives the weight of the trunk through the spinal column and transmits it to the femurs and feet. In apes it is oriented towards the back and the weight of the trunk is transmitted to the four extremities.

Forelimbs: Human forelimbs are shorter than legs and no longer involved in locomotion. By being totally freed from the locomotive functions, they have been able to specialize in purely human functions (more easily collecting food, making tools, transporting things, etc.). In apes, the upper limb is as long as the leg and is basically involved in locomotion.

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