![]() It is unclear what precipitated the tremendous population growth associated with this second occupation of the Near East and subsequent dispersal ( 7) possibly, cultural advances accumulated to a “tipping point” that supported extreme demographic growth ( 8), or anatomical changes that are not reflected in the paleoanthropological record occurred in the ancestral population. ![]() Only after this point do anatomically and behaviorally modern human remains become widespread in Eurasia. ![]() It is not until at least 50,000 y ago that evidence of behaviorally modern humans occurs in the archaeological record in the Near East. However, current evidence indicates that this near-modern population did not persist in the Near East and was subsequently replaced by Neanderthals during the following glacial period, with little evidence of temporal overlap ( 5, 6). It is clear that anatomically near-modern humans occupied the Levant ( 4) during a warm interglacial period 130 to 80 kya, when this region was ecologically similar to northeastern Africa ( 5). It is important first to distinguish between the presence of early near-modern humans in the Near East and the very distinct OOA exit associated with the Great Expansion. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern human evolution. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the “serial founder effect.” In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. In general, the content and presentation in the CKHG units for Grades 3-5 are appropriate for young readers from the upper elementary grades through middle school.Genetic and paleoanthropological evidence is in accord that today’s human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth’s habitable regions. In other settings, individual CKHG units may be used as supplemental resources. Each lesson may be divided into shorter segments.ĬKHG Grade Levels: CKHG units are correlated to topics at the grade levels specified in the Core Knowledge Sequence, which allows students in schools following the Sequence to build knowledge grade by grade. Students also consider the late-nineteenth century idea of the “closing of the American frontier.” Some of the content of this unit is tied to the “Pathway to Citizenship,” an array of civics-focused knowledge, questions, and activities. ![]() ![]() Students explore the myths and realities of cowboy life and the “Wild West.” Students learn how the United States purchased Alaska from Russia, which provided the nation with a vast territory teeming with wildlife and rich in natural resources. Students consider how transcontinental railroads accelerated the settlement of the West by providing transportation for people and goods and opening new agricultural markets. Students learn how the prospect of gold or silver lured many adventurers westward, while millions of settlers were drawn by the Homestead Act, which Congress passed to encourage western settlement. Focus: The resources for this unit (Westward Expansion After the Civil War) are part of the individual resources titled Native Americans and Westward Expansion: Cultures and Conflicts.This unit (Unit 12 for schools using the CKHG series in Sequence grade-level order) continues the story begun in Unit 10 (Westward Expansion Before the Civil War), and focuses on the causes and effects of the westward movement of Americans in the later 1800s, which often led to conflict with Native Americans displaced from lands they had long inhabited. ![]()
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