Researchers at Trinity College Dublin have discovered a universal thermal performance curve that governs how every living organism responds to temperature changes. This pattern, applicable from bacteria to fish, shows performance peaks at an optimal temperature before sharply declining, highlighting limits to adaptation in a warming world. The findings, published in PNAS, suggest evolution cannot escape this fundamental rule.
In a study published in the Proceedings of the National Academy of Sciences in 2025, scientists from Trinity College Dublin analyzed over 2,500 thermal performance curves across thousands of species, revealing a consistent pattern they term the universal thermal performance curve (UTPC). This curve describes how biological performance—whether lizards sprinting, sharks swimming, or bacteria dividing—increases gradually with rising temperature until an optimum point, then drops sharply, potentially leading to physiological breakdown or death at higher heats.
The UTPC applies uniformly to all major groups of life, including bacteria, plants, reptiles, fish, and insects, despite billions of years of evolutionary divergence. As Andrew Jackson, Professor of Zoology at Trinity's School of Natural Sciences and co-author, explained: "Across thousands of species and almost all groups of life including bacteria, plants, reptiles, fish and insects, the shape of the curve that describes how performance changes with temperature is very similar. However, different species have very different optimal temperatures, ranging from 5°C to 100°C, and their performance can vary a lot depending on the measure of performance being observed and the species in question."
Jackson added: "What we have shown here is that all the different curves are in fact the same exact curve, just stretched and shifted over different temperatures. And what's more, we have shown that the optimal temperature and the critical maximum temperature at which death occurs are inextricably linked. Whatever the species, it simply must have a smaller temperature range at which life is viable once temperatures shift above the optimum."
Senior author Dr. Nicholas Payne emphasized the implications: "These results have sprung forward from an in-depth analysis of over 2,500 different thermal performance curves, which comprise a tremendous variety of different performance measures for a similarly tremendous variety of different species—from bacteria to plants, and from lizards to insects. This means the pattern holds for species in all major groups that have diverged massively as the tree of life has grown throughout billions of years of evolution. Despite this rich diversity of life, our study shows basically all life forms remain remarkably constrained by this 'rule' on how temperature influences their ability to function. The best evolution has managed is to move this curve around—life hasn't found a way to deviate from this one very specific thermal performance shape."
The researchers plan to use the UTPC as a benchmark to identify any species that might subtly deviate from this pattern, particularly amid ongoing climate warming.