Genomic predisposition is associated with the direction of sex chromosome evolution
- Yang Zhou
- Jiazheng Jin
- Chuan Jiang
- Olga Dudchenko
- Brendan J. Pinto
- Zane Colaric
- Ruqayya Khan
- Arina D. Omer
- Xuemei Li
- Zhenzhen Song
- Li Han
- Wanyi Chen
- Lichun Jiang
- Zhangyue Song
- David Weisz
- Yun Xia
- Yin Qi
- Zhengqing Cao
- Yudian Peng
- Zexian Zhu
- Qi Zhou
- Yan Liu
- Xiaosong Gu
- Stuart V. Nielsen
- Aaron H. Griffing
- Tariq Ezaz
- Arthur Georges
- Ian Brennan
- Erez Lieberman Aiden
- Tony Gamble
- Peng Shi
- Guojie Zhang
2026-08-27
Sex chromosome evolution is among the most dynamic genomic innovations in vertebrates, yet why some lineages evolve XY while others evolve ZW remains unclear. Using chromosome-level genomes from 19 geckos, we found that gecko sex chromosomes originated independently from 16 ancestral chromosomes. Their origins are nonrandom in both time and direction. Five of 11 datable origins coincide near the Middle Miocene Climatic Transition (~10 million years ago). Ancestral gene content is associated with the direction of evolution, with testis-enriched regions tending to evolve into ZW and testis-depleted regions into XY, a pattern observed across multiple amniote sex chromosome origins. Geckos with genetic sex determination repeatedly evolve partial dosage balance through up-regulation in the heterogametic sex. Sex chromosome evolution thus follows constraints from ancestral genomic predisposition and environmental context.