we will have to repeat what we have already written in order to complete the picture of the reality of the biology of living things. what is present is a repetitive experiment of varying designs, some of which fail, dissipate and rapidly become extinct. others succeed and last for long periods, but in the end the fate of the various species become extinct purely for natural reasons such as change in the environment or failure to compete with new types of organisms or similar. as for the story of human evolution, the lecturer said, the records and g e o l o g i c a l evidence indicates that about 7 million years ago, a climate change in the world led to a signifi cant decline in the forests of east africa and as a result, large swathes of long savannah plants opened up. so our ancestors had the opportunity to leave the forests and move to the savannah and adapt to that nature. here we come to the topic of walking on two legs, which is a rare phenomenon among other animals, when our ancestors had adapted to climbing trees and walking on the four limbs, but the extreme nature of the savannah forced them to stand to know the dangers surrounding them. in this environment, the percentage of calorie consumption from animal sources increased which required organized collective labor. this led to the emergence of the second factor: the growth of the brain, the evolution of its size and its role. what are the consequences of walking on two legs and increase in the size of the brain? walking on two legs has had a tremendous impact on the development of modern man because this behavior freed his upper limbs from the function of walking, allowing arms to make tools, making use of the arm to fi ght and throw spears with precision which other living creatures cannot. but because the human skeleton was originally designed to walk on the four limbs, some negative results from the column, pelvis, hip and knee occurred as a result of the process of modifi cation to members who could walk on two legs instead of four. in order for a woman to walk and run in balance, her birth canal had to narrow while this limitation does not apply to objects that walk on their four limbs. the size of the brain, is considered the second property. the human brain began to grow signifi cantly more than 3 million years ago. of course, the size of the brain determines the size of the head, and as a result it increases the size of the head in the newborn and needs a bigger delivery channel, but we noticed that the birth canal has been reduced by walking on the legs. here we face the random natural selection that causes changes in the human body have adverse effects to each other irrationally or even completely insane. it is clear here that there is a struggle for the forces of nature, where some traits are more successful than others, regardless of whether this is contrary to other qualities. we mentioned some of the supposed causes that led to the emergence of walking on the legs but what led to the enlargement of the human brain that we see today? the views here look contradictory, but there is a widespread and convincing assumption that the main catalyst for the massive growth of the human brain is the increase in the number of people in the savannah community and the complexity of the relations between the members of these groups… of cumulative culture. the third part of the article will appear in tomorrow’s edition of the newspaper.

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