Y Chromosome Fades, Yet Males Persist: Amami Spiny Rat Reveals a New Route to Maleness
New research shows the Y chromosome is decaying in mammals, but the Amami spiny rat demonstrates that maleness can be controlled by an autosomal SOX9 enhancer—driven by a 17,000-base-pair duplication on chromosome 3—allowing male development without the SRY gene. This turnover indicates that the Y’s loss does not doom a species and suggests other mammals may use alternative genetic switches, though the exact mechanisms vary and require further study.