Timema stick insects have survived a million years without sex


A female-only species

Stick insects have lived for one million years without sex, genetic research has revealed.

Scientists in Canada investigated the DNA of Timema stick insects, which live in shrubland around the west coast of the US. They traced the ancient lineages of two species to reveal the insects’ lengthy history of asexual reproduction. The discovery could help researchers understand how life without sex is possible

Certain species of Timema stick insects were known to reproduce asexually, with females producing young in “virgin births” without the need for egg fertilisation by males. The insects instead produce genetic clones of themselves.

Dr Tanja Schwander and her team set out to test how old these species were, and therefore to find out how long they had reproduced in this way. By analysing the DNA of the insects, scientists were able to trace back their lineages to identify when they became a distinct species. The team discovered that five of the asexual stick insects were “ancient”, dating back more than 500,000 years. Two of them were even older.

“All the evidence points to Timema tahoe and Timema genevievae having persisted for over one million years without sex,” Dr Schwander told BBC Nature. “Our research adds to the growing amount of evidence that asexuality does not always result in the rapid extinction of a lineage,” she said…

Asexuality does bring certain benefits, including rapid population growth. But the repeated cloning of genes through generations is thought to have significant negative consequences too. This replication means that species are less able to adapt to new environments through “shuffling and tweaking” of genes.

Dr Schwander said: “Why Timema asexuals have been able to persist for so long despite all the predicted negative consequences of asexuality is the focus of ongoing studies.”

On the other hand, I know couples where it just feels like a million years since they had sex.

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