Irrigation of crops led to salinization of the soil, Sumer was located on a flat plain that provided no natural barriers to invasion, and the land became too swampy to grow adequate crops.
3<span>Ecoregions; 4 Flora and fauna; 5 History</span>
While historically, <u>pseudoscientific </u>theories of race were preferred, modern explanations of race mostly focus on <u>cultural elements</u>.
A race is a division of people into social or physical groupings that are typically seen as separate within a particular civilization. The 1500s saw the phrase become widely used to describe a variety of social groupings, particularly those distinguished by deep familial ties.
The phrase first applied to bodily (phenotypical) characteristics in the 17th century, and then to national loyalties. According to contemporary research, race is a social construct, an identity that is determined by socially constructed standards. Race does not have a physical or biological significance that is intrinsic, while being partially based on physical similarities between groups.
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