Climate Change, Last Glacial Cycle and its Impacts on the Modern Human Cultural Evolution

Modern human has been in constant struggle with climate and nature since its first appearance about 200 kya. Earth climate has been in continuous change since the mentioned time, most importantly the effect of glacial cycles were so severe. Facing with such endless environmental challenge, modern humans adopted several different ways to make themselves more adaptable, using elaborate culture was certainly among such ways. This relentless challenge with ever changing climate has had substantial impact on the Anatomically Modern Humans (AMH or Homo sapiens), which eventually along with some genetic changes forced them to become Behaviorally Modern Human or what we call: Homo sapiens sapiens. AMH had no option but to rely on its big brain and its creativity to come up with diverse solutions to compete with nature. Making more efficient tool kits, shelters, clothing, hunting, etc are among such innovations. This article reviews the human evolution story since the 115 kya (MIS 5e), which corresponds to the beginning of the last glacial cycle, to 11.5 kya, which is equal to the starting of Holocene. Right at the end of the MIS 6, the African central regions turned to the deserts. Such climatic change and loss of biomass forced new born human populations (early AMH) to leave these areas and move to either North or South seeking for new landscapes to survive.Evidences of modern humans in southern Tanzania and South Africa dated to 130 and 90 kya represent such dispersions. During the MIS 5e, which was an interglacial period (135-116 kya), proper climatic conditions reopened the central African regions to the human populations. On the other hand, such ideal environmental situation and abundance of food might have been responsible for the proliferations of the human populations, obliging some of them to leave Africa for the Levant. Presence of archaeological sites of Skhul and Qafzeh dates to 119-85 kya is the indicator of these populations. Throughout the whole MIS 5 glacial cycles numerous contractions and expansions of human population ranges took place in Africa and Eurasia. It seems that dense human populations in the reservoirs such as alongside of the beaches (e.g., South Africa, Levant and North Africa) demanded more complexity in the societies and more diverse ways of acquiring foods. Human response to such forces was mostly based on using different methods that we call them culture. During the last stages of the glacial period (30-11.6 kya) the sea level dropped rapidly. That provided human populations with an immense opportunity to expand to the regions they had never walked in such as America and South East Asia islands. Human cultural evolutionary process had two aspects of conscious and unconscious. Through most of the human evolutionary history, this was the unconscious aspect which played a significant role. At each age humans did only minor changes and small insignificant innovations such as change in the hunting methods, storage, clothing, building shelters, etc. Such small changes through cumulative process led to what we see it today as elaborate complex cultures around the world. While some of these modern cultures appear extremely complicated, we must not forget that the root for all such modern, complicated cultures go back to the time that humans started to face with nature and its protégé such as climatic changes and environmental unrest using their brains rather than their bodies.