The effects of heat stress caused by climate change don’t just affect the animals that experience it, but they are passed down through multiple generations, according to a study published in the journal Molecular Biology and Evolution.
As the planet warms, extreme heat events are becoming more common. Scientists know these events can be harmful to wildlife, but a new study suggests the impact may run far deeper than previously thought. In fact, climate change can affect animals all the way to great-great-grandchildren.
Researchers studied fruit flies in two very different climates: sunny, dry Spain and cold Finland. They exposed the flies to a sudden burst of intense heat and then watched what happened to their offspring over several generations.
The results were striking. The first generation of offspring from both groups struggled They were less likely to survive and took longer to develop. But something interesting happened in the Spanish flies: later offspring actually developed faster than normal, as if the heat stress had triggered a helpful response.
Even more surprising, this faster development was still being passed on four generations later, in what would be the great-great-grandchildren of the original flies. Certain patterns of gene activity were also still showing up generations down the line, particularly in the Spanish population.
The findings suggest that heat stress doesn’t just affect the animals that live through it; it can shape the biology of their descendants too. This could mean that as climate change brings more frequent heatwaves, the effects on wildlife will build up over generations, potentially speeding up the pace of evolution.
“The transgenerational effects in gene expression and development time we observed demonstrate that stress might not only select for better adapted flies, but could facilitate evolution,” said lead author Ewan Harney. “Understanding why some variants can respond transgenerationally better than others could be important in identifying at-risk populations as the Earth’s climate continues to change.”
Ewan Harney, Josefa González, Transgenerational effects of heat shock on gene regulation and fitness-related traits in natural Drosophila populations, Molecular Biology and Evolution, Volume 43, Issue 4, April 2026, https://doi.org/10.1093/molbev/msag069