# Asexual stick insects keep sex-chromosome dosage systems after a million years

_Friday, August 7, 2026 at 7:00 PM EDT · Science · Latest · Tier 2 — Notable_

![Asexual stick insects keep sex-chromosome dosage systems after a million years — Primary](https://scx2.b-cdn.net/gfx/news/2026/scientists-make-surpri.jpg)

Bangor University-led research on Timema stick insects finds that dosage compensation and related sex-chromosome controls remain fully functional even after more than a million years without sexual reproduction, phys.org reported, citing a PNAS paper.

Some Timema species reproduce by parthenogenesis, developing from unfertilized eggs, so balancing gene expression between XX females and XY males is no longer needed. Scientists expected the unused system to erode, but gene expression work on rare males showed the mechanisms still work, lecturer Darren Parker said.

The authors say the result challenges assumptions about how fast biological systems decay when selection relaxes. The study is Parker et al., Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2531501123.

## Sources

- [phys.org](https://phys.org/news/2026-08-million-years-sex-erase-insects.html)

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