Match these items. 1 . adam common species 2 . eve physical appearance 3 . common kind image 4 . homozygous the mother of all living 5 . fieldwork male and female 6 . phenotype different alleles 7 . ethnocentrism seeing a group as inferior 8 . sin and death studying people where they live 9 . shadow act in pairs 10 . heterozygous adam's heritage 11 . alleles studies all aspects of culture 12 . language identical alleles 13 . holistic forms a barrier

 swamps, deserts and ice fields are among the clearest examples of natural barriers. Rivers are a more ambiguous example, as they may obstruct large-scale movement across them (especially by armies) but may facilitate smaller-scale movement along them in boats, once some of the people in the region have developed the relevant technologies. Seas have likewise been an obstacle at first, then a convenient medium for transport along coastlines, and finally a medium for intercontinental transpor