Scholars are unclear and in dispute as to possible causes for variations in human sex ratios at birth.[16][17] Countries which have sex ratios of 108 and above are usually presumed of engaging in sex selection. However, deviations in sex ratios at birth can occur for natural causes too. Nevertheless, the practice of bias against girls, through sex selective abortion, female infanticide, female abandonment, as well as favoring sons with regard to allocating of family resources [18] is well documented in parts of South Asia, East Asia, and the Caucasus.