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 included analysis which adjusted diversity for distance from Africa (i.e., to account for global expansion), and saw whether adjusted diversity is associated with climate. The indication of a climatic signal 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 which are located outside of Africa. The present research (Studies 1 and 2) used various diversities which were sourced from previous research. Autosomal, X-chromosomal, mitochondrial, 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. 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. Other adjusted diversities, including (surprisingly) mitochondrial, were not found to be associated with minimum temperature. Data from one dataset, but not another, was supportive of a relationship between sex-biased migration and climate—it seems unclear if this relationship would underlie a climatic signal in X-chromosomal diversity. Therefore, it is uncertain i) if X-chromosomal diversity is associated with climate, and, ii) why there might be an association. Further replication research on this topic is called for.