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Our results reveal complex population - specific histories , with female - biased admixture from Khoisan - speaking groups associated with the incorporation of click sounds in one Bantu - speaking population , while concomitant levels of potential Khoisan admixture did not result in sound change in another .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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