X-chromosomal diversity may reflect climate (when considering human expansion from Africa)

Previous research indicates that a climatic signal is present in mitochondrial diversity, but absent in other genetic diversities (e.g., X-chromosomal) and cranial diversity. Such research has included analysis which adjusted diversity for distance from Africa (i.e., to account for the global expansion), and seeing whether this adjusted diversity is associated with climate. Detection of a relationship between adjusted diversity and climate may be affected by the choice of African location from which distance is measured. To bypass this potential effect of location, some analyses in the present research only featured populations who are located outside of Africa. The present research (Studies 1 and 2) used various diversities which were sourced from previous research. Autosomal, X-chromosomal, and cranial diversities were adjusted for distance from Africa. This adjustment was not used regarding Y-chromosomal diversity; a preprint suggested that Y-chromosomal diversity does not signify expansion from Africa. In Study 1, adjusted X-chromosomal diversity increased with minimum temperature. Other adjusted diversities were not related to minimum temperature. In contrast to previous research, an association was indicated between the ratio of X-to Y-chromosomal diversity and climate in Study 2, which may suggest a relationship between sex-biased migration and climate--this relationship could drive the climatic signal in X-chromosomal diversity. Conscious of replicability, Study 2 examined whether a climatic signal is present in X-chromosomal diversity when an alternative dataset is used; a signal was not detected. Therefore, it seems unclear whether X-chromosomal diversity is associated with climate.