Question

NOVA BECOMING HUMAN

1) In trying to understand how rapid the climatic changes were for Homohabilis, how do scientists estimate the rates of change?

2) What was the African climate during the time when our ancestors’ brain size was “flat-lining” (from Sahelanthrous to Lucy).

3) When hominid brain size begins to increase (beginning with Homo habilis), what was happening to the African climate?

Answer 1

Answer 1) Human evolution was very likely affected strongly by the dramatic climate swings of the Pleistocene (when climates were becoming cooler and drier) . These changes no doubt presented powerful new natural selection pressures. Many animal species were driven to extinction by the advancing ice ages . Humanity survived by becoming more intelligent and adaptable . This allowed us to develop new cultural technology to deal with cold environments and changing food sources , especially during the last 1/4 million years. One of the greatest problems in the cold regions would have been the scarcity of plant foods that humans could eat during winter and in response to this, ancestors became more proficient at hunting animals

During ice ages, those species that were not driven to extinction by the cold commonly evolved larger , more massive bodies as a means of producing and retaining more heat . This was specially true of mammals in the northern hemisphere.

2) and 3 ) The disappearance of lakes were followed by periods of extreme drought. At one extreme , the landscape would have been a true Garden , with beautiful fresh water lakes, forests along the rivers. There would have been open spaces to let humans exist easily. with water and lots of resources.

But this quickly changed into bone dry periods , where it was 45 degree celcius in the middle of the day and no natural water resources. Ecollectivelarly humans and other primate species collectively known as hominids were forced to adapt to the new environment , humans developed larger brains evident with homohabilis and homo erectus