Population expansion in Africa began from 11000 to 12000 years ago,before the appearance of agriculture.  Researchers from China's Fudan University have found that earth’s human population may have begun expanding before the Neolithic period and widespread development of agriculture. The report, which links the introduction of agriculture to a preceding population boom, was published in the web-based open access journal Scientific Reports, an affiliate of Nature Publishing Group on October 18, 2012. Professor Jin Li, Director of the Center for Contemporary Anthropology at Fudan University, explained that according to previous archaeological findings, agriculture is thought to have first developed in the Fertile Crescent—the area between the Tigris and Euphrates Rivers in the present-day Middle East—around 11, 000-12,000 years ago, and then developed independently in other regions over the next few thousand years.  In East Asia, agriculture began in the Dadiwan Culture about 8000 years ago. However, the research group found that population expansions began in East Asia roughly 13,000 years ago, before the birth of agricultural civilization in this region.  The primary author of this study, Doctor Zheng Hongxiang, noted that the methodology is distinguished other studies addressing this question, being among the first to use mitochondrial DNA analysis. To compare global patterns of population growth, the group analyzed over 900 mitochondrial genomes generated by The 1,000 Genomes Project. The samples represented 11 populations in Africa, Europe and the Americas and enabled the group to identify the expansion of DNA lineages and reconstruct historical demographic variations. They found that population expansion in Africa began from 11,000 to 12,000 years ago, 13,000 years ago in Europe about 13,000 years ago, and in America from 8,000 to 12,000 years ago. In every instance, population growth preceded the widespread development of crop growth and domestication of animals. Elaborating on the methodology of the research, Zheng explained that there are a lot of normal mutations in human genome that have been handed down from our ancestors. Because some of them are young whereas some are old, we can build an evolutional history of human beings by studying the sequence of the mutations, which forms a tree structure called lineage. By constructing lineages and studying the mitochondrial genomes which are related to maternal inheritance, investigators can identify the periods when population expansions happened.  It is generally thought that climate and technology are major factors which affect population expansions. This study shows a correspondence between the genetic variation and the climate variation of the earth, indicating specifically major population expansions took place after the Last Glacial Maximum (the peak of the last ice age) but before the Neolithic period. The investigators suggest that the milder climate after the Last Glacial Maximum may have offered a more amiable environment and may have been an important factor in prehistoric human expansions. Reversing the conventional thinking of the cause-effect sequence, the study concludes that the increase in population size was like one of the driving forces that led to the introduction of agriculture, turning it from a supplementary food source to the primary one.  However, further studies will be required to confirm this hypothesis. Jin pointed out the great value of their research and compelling results, noting that this is the first time the 1,000 Genomes Project has been used to analyze the mitochondrial genomes for reconstructing the population variation across different continents. The findings have brought new insights to the origins of agriculture and the history of human civilization on earth, questioning long held assumptions about the relationship between the two.Chinese Social Sciences Today, No.370, Oct.24, 2012. (Translated by Yang Lu)