Welmer

A reader sent me an article pointing out that sex-chromosome chimerism has been found to be quite common in sheep. The estimated rate of sex-chromosome chimerism in sheep is over 4%, but I suspect it would be found to be somewhat higher with more extensive tissue testing.

This is relevant to the Chimera Hypothesis due to evidence for homosexuality – particularly male homosexuality – in sheep. The chimerism studied here is purely sex-chromosome chimerism, which only measures chimerism from opposite sex cell lines, almost certainly from opposite sex siblings. The opposite sex cells were found to have the ability to migrate to tissues other than blood and become transcriptionally active. In rams, they were found in white blood cells, which have been observed transforming into nerve cells in the presence of nerve growth factor. This suggests that chimerism in brain tissue could result from chimeric macrophage transformation into transcriptionally active nerve cells.