Rosa Rubicondior: Refuting Creationism - Observed Rapid Evolution

White-flowering Arabidopsis growing in sand at a beach near the Baltic sea. The plant, a member of the mustard family, grows in a broad range of climates, from alpine to desert, and is commonly used in genetic experiments in the lab.

Moisés Expósito-Alonso/UC Berkeley

One-of-a-kind experiment tracked plant evolution in response to climate change at 30 sites worldwide - Berkeley News

You won’t need to spend long on a creationist social media site before someone demands evidence of “observed evolution”, only to shift the goalposts the moment you provide exactly that: measurable changes in allele frequencies within a population in response to environmental change. At that point, they usually abandon the scientific definition of evolution and retreat instead to one of their childish caricatures of it — one species suddenly turning into an unrelated taxon, new structures appearing overnight, or, most absurdly of all, unable to let go of the arrogant assumption that the entire universe has a single purpose - to produce them - a bacterium somehow “becoming human”, as though evolution had a preordained anthropocentric goal.

So we can predict with some confidence how creationists will react to news that science has now published precisely the sort of evidence they keep demanding. In a paper published on 26 March 2026 in the journal Science, a team led by Assistant Professor Moisés Expósito-Alonso of the University of California, Berkeley, reported the results of a remarkable outdoor evolution experiment designed to measure how quickly plants can adapt to changing climates. The researchers planted genetically diverse populations of the common laboratory plant Arabidopsis thaliana across 30 climate zones in Western Europe, the Mediterranean, the Middle East and North America, ranging from the snowy Alps to the heat of the Negev Desert, and tracked the evolutionary changes over five years.

Of course, the purpose of the experiment was not to “test” the Theory of Evolution. Evolutionary theory was the framework on which the entire study was built and by which the results were interpreted. The aim was to observe evolution in real time and discover how quickly plant populations can adapt to climate change — and where the limits of that adaptive capacity may lie.

An early analysis of the first three years of genomic data — covering 12 plots at each of the 30 sites, 360 experiments in total — showed that most populations evolved rapidly in response to their new environments. In many locations, similar genetic changes appeared repeatedly, exactly as one would expect when natural selection favours variants suited to local conditions. In the hottest environments, however, the pattern was different: although some populations showed genetic change, it appeared chaotic rather than predictably adaptive, and these populations subsequently went extinct.

If this pattern proves typical of other plant species, it is deeply concerning, because rising global temperatures are precisely the conditions to which many plants will now need to adapt if they are to avoid climate-driven extinction. The study suggests that rapid adaptation is possible, but also that there may be a tipping point beyond which extreme heat pushes populations past an evolutionary breaking point.

Observed Evolution in Real Time — and Why Scientists Use Arabidopsis thaliana. Creationists often demand evidence of “observed evolution”, but what they usually mean is not evolution as biologists define it. In science, evolution is simply a change in the frequency of heritable variants — alleles — in a population over successive generations. It does not mean one organism suddenly turning into a completely different kind overnight, as in the childish caricatures creationists so often rely on. When environmental conditions favour some inherited variants over others, those variants become more common in later generations. That is evolution by natural selection, and it is precisely what this study measured. [1]

This is why the experiment is so important. Rather than inferring evolution indirectly from fossils or comparing living species, the researchers watched it happen in real time. By planting genetically diverse populations in different climates and following them over several years, they were able to track which genetic variants increased in frequency, which populations adapted successfully, and which failed and went extinct. In other words, this was not merely evidence that evolution must have happened in the past; it was direct observation of evolutionary change happening in the present. [1]

The plant chosen for the experiment, Arabidopsis thaliana — thale cress — is one of the most important model organisms in modern plant biology. It is small, easy to grow, produces large numbers of seeds, and has a short life cycle, which allows scientists to observe multiple generations in a relatively short period. Its genome is also small and was the first plant genome to be fully sequenced, making it especially useful for linking visible changes in survival and reproduction to underlying genetic changes. [2]

Because Arabidopsis is so well understood genetically, it allows researchers to do something much more powerful than simply noting that some plants did better than others. They can identify the actual genetic variants associated with adaptation to cold, drought, or heat, and see whether similar changes arise repeatedly in different places facing similar conditions. That makes this study especially valuable, because it shows not only that evolution occurs, but that it can be predictable — at least up to a point. [1]

So, when creationists claim there is no such thing as “observed evolution”, what they really mean is that they are unwilling to accept the scientific definition of evolution. Studies like this one leave them with no such excuse. Scientists have observed populations changing genetically in response to environmental pressures, exactly as evolutionary theory predicts. The only thing missing is the creationist caricature — and that is missing because it was never what the Theory of Evolution said in the first place. [1]

The experiment and its significance are explained for a lay audience in a UC Berkeley News item by Robert Sanders.

One-of-a-kind experiment tracked plant evolution in response to climate change at 30 sites worldwide
Simultaneous experiments pinpointed genetic variants associated with successful adaptation to climate change — and the tipping point beyond which plants can’t adapt.
For decades, ever since biologists recognized the potential environmental harms from climate change, they have worried that plants will not be able to evolve fast enough to adapt to a rapidly warming planet. But the pace of research to understand how species respond has been slow, typically based on single, stand-alone experiments by isolated research groups around the world.

Moisés (Moi) Expósito-Alonso grew frustrated with that approach. Instead, he and his colleagues created a network of fellow scientists to plant simultaneous experiments in 30 different climate zones around Western Europe, the Mediterranean, the Middle East and North America and allow them to evolve for five years, untended except for weeding. The goal of this unique experiment was to tease out how fast these plants — a genetically diverse mix of the common lab plant Arabidopsis thaliana, an annual within the mustard family — would evolve under different climate stresses, ranging from the snowy Alps to the heat of the Negev Desert.

Information about the speed of evolution, along with the genetic shifts that accompany it, are key to creating models that will help to identify the plants and animals at risk as their environments change around them, said Expósito-Alonso, a UC Berkeley assistant professor of integrative biology.

White-flowering Arabidopsis growing in sand at a beach near the Baltic sea. The plant, a member of the mustard family, grows in a broad range of climates, from alpine to desert, and is commonly used in genetic experiments in the lab.

Moisés Expósito-Alonso/UC Berkeley

All of those species that are under protection, for example in natural parks, will still suffer from changing local climates, and we will need to devise some sort of strategy to understand their chances of novel climate adaptation by themselves, or perhaps even aid them. My hope was to generate this quantitative data as a resource so that we can better understand rapid adaptation and make predictions, anticipate where are the risks, where might be the tipping points, where we have to pay attention. I think that without this fundamental understanding, we won’t be able to save them.

Assistant Professor Moisés Expósito-Alonso, lead author.
Department of Integrative Biology
University of California Berkeley
Berkeley, CA, USA.

An analysis of the first three years of genomic data from the experiments — involving three generations of plants in 12 separate plots at 30 locations, or 360 distinct experiments — shows that in most cases, these plants evolved genetically to adapt to the new environments. However, some experimental populations, especially those in the most extreme warm climates, did not show signs of early evolution at all. Instead, they displayed seemingly random trajectories that preceded their extinction.

Our big questions were, ‘At what speed does evolution go?’ and ‘When will it not go?’ What we could show is that this tempo, if given enough genetic diversity, can be three, four, five years. We can directly see for the first time how certain DNA variants — adaptive variants — take over in certain populations as evolution happens.

Assistant Professor Moisés Expósito-Alonso.

Plots of Arabidopsis thaliana partially covered by snow in Brixen im Thale, a town in the Kitzbühel Alps of western Austria. This was one of 30 research sites around Europe, the Middle East and the U.S. in which biologists planted 12 separate plots to study genetic evolution under the influence of climate change.

Genomics of rapid Evolution to Novel Environment (GrENE) network consortium

But the researchers also found that not all populations adapted efficiently enough to survive, particularly in the hottest environments.

In the warmest environments — perhaps most representative of future climates under global warming — populations with predictable evolutionary changes survived, while those with chaotic genetic changes went extinct. This reveals that, while rapid adaptation to climate change is possible, extreme heat limits populations to small sizes, which can push populations past an evolutionary breaking point toward extinction.

Assistant Professor Moisés Expósito-Alonso.

The paper, led by Expósito-Alonso and the Genomics of rapid Evolution to Novel Environment (GrENE) network consortium, was published today (March 26) in the journal Science. The experiment, which was coordinated in collaboration with J. F. Scheepens of Goethe University Frankfurt in Germany and François Vasseur of the University of Montpelier in France, ran from the fall of 2017 through spring 2022, though the paper’s genomic analyses involved up to the first years through the spring of 2020.

Adapt or perish

Expósito-Alonso’s goal was not only to measure the speed of evolutionary adaptation, but to identify the gene variants or genetic mutations in a population that allow adaptation to a changing environment. He made sure that each plot contained a genetically diverse population of several hundred plants, sourced from populations throughout Arabidopsis’s mostly temperate range. The expectation was that this diversity would ensure that at least some plants in each plot contained the rare genes that a resilient population needs to adapt to new conditions.

Some plots were planted in cities, such as this group of 12 near apartment buildings in Cologne, Germany.

GrENE network consortium

If those rare gene variants, or alleles, are present, adaptation to the new environment should involve changes in genetic composition, such as an increase or decrease in the frequency of some alleles, the emergence of new mutations and changes in their frequency, or the recombining of multiple mutations.

To capture these changes, he and a large consortium of about 75 colleagues took flower clippings every year in the spring and sequenced the plants’ whole genomes. Based on sequences of over 70,000 survivors in over 2,500 pooled spatio-temporal population samples, they pinpointed millions of alterations in expressed genes that signified the plant population’s efforts to adapt and survive in a new environment. These gene alterations were different in different climates, though similar across similar climates, demonstrating the repeatability of these adaptations.

What we’re most likely seeing is adaptation through pre-existing genetic variation that gets re-used in different ways. If a variant is adaptive in one environment, its frequency goes up.

Dr. Xing Wu, first author
Department of Integrative Biology
University of California Berkeley
Berkeley, CA, USA.

The tip-off that this was adaptation by natural selection — the survival of individual plants that are best adapted to the new environment — was that several of the 12 plots at each location showed similar changes in gene frequency. Another indication was that several of 12 plots in each of two locations of a similar environment — for example, Spanish and Greek dry shrublands — showed similar changes. This was observed in 24 of the 30 locations. Among the genes most affected were those that sense heat stress and those controlling when plants flower.

Healthy, flowering plots of Arabidopsis growing in Würzburg, Germany.

GrENE network consortium.

While some genetic changes were theoretically expected in an experiment like this with abundant diversity and severe climate exposure, Expósito-Alonso said that he was very surprised to find that the speed of allele frequency changes was higher than most biologists would have predicted.

In addition, not all plots showed evolutionary adaptation — some ended in extinction.

There were some climates where either there were no shifts, so the frequency of those genetic variants was the same, or there were shifts, but they were not repeatable in the different independent replicates. So there was evolution from genetic drift, just stochastic changes, but not evolution driven by natural selection, natural climate pressures.

Tatiana Bellagio, co-first author
Department of Integrative Biology
University of California Berkeley
Berkeley, CA, USA.

Because the team sampled each of the 360 plots annually for several years, they were able to document that those plots showing random or no genetic shifts in the first years of the experiment eventually died out.
For a population to survive in the long term while experiencing climate change, most likely it has to undergo natural selection, especially when we’ve challenged them with these new climates. I think this is very exciting because it’s telling you, unless there is an evolutionary rescue — unless there are some genotypes that have an increased fitness, are propagated more and shift allele frequencies — the population will not be able to sustain its size after five years, at least in warm environments.

Assistant Professor Moisés Expósito-Alonso.

Making educated guesses

With the knowledge of our Arabidopsis, we can make some educated guesses of who is going to survive in which location, [though each species may need its own long-term experiment to understand its genetic vulnerabilities.] With this type of modeling, calibrated in a model species, and a deep understanding of the tempo of evolution and the strength of climate mismatch and adaptation, we could potentially aid hundreds or thousands of species.

Assistant Professor Moisés Expósito-Alonso.

Expósito-Alonso and the team continue to analyze the last generations of plants and are planting seeds collected each year from the plots to continue the evolutionary experiments. He has also begun plot experiments at Berkeley, some involving plants other than Arabidopsis

One of his long-term ambitions is to catch rapid evolution in natural populations, directly observing year-to-year genetic variation in wild plants that are naturally experiencing climate oscillations as well as ongoing global warming. This would capture for the first time the steady drumbeat of evolution that’s hidden within healthy and apparently stable ecosystems. He might even be able to capture the sudden genetic changes triggered by drought or wildfire.

Nature has that appearance of stability in the eyes of human observers. For example, California grasslands and forests, season after season, look pretty much the same,” he said. “But genotypes are changing all the time. So being able to see that is kind of my dream.

Assistant Professor Moisés Expósito-Alonso.

Co-first authors of the paper are Xing Wu, Tatiana Bellagio and Meixi Lin, who have joint appointments with UC Berkeley and Stanford, and Yunru Peng and Lucas Czech, previously at the Carnegie Institution of Stanford. Consortium members included scientists from nine U.S. states as well as Spain, Norway, Germany, Switzerland, Canada, Greece, Estonia, Poland, the Netherlands, France and Israel.

Publication:
Xing Wu et al.
Rapid adaptation and extinction in synchronized outdoor evolution experiments of Arabidopsis
Science 391, eadz0777 (2026). DOI:10.1126/science.adz0777

Structured Abstract

INTRODUCTION
Contemporary evolution in natural environments is being documented in many plant and animal species. However, an integrative understanding of the dynamics of rapid adaptation to different climates—the tempo, genetic architecture, predictability, and population feedbacks—remains unclear for most species. The gold standard to experimentally study the dynamics of evolution has been represented by microbial long-term laboratory experiments combined with genome resequencing, but such experiments remain challenging in multicellular macroorganisms, especially in ecologically realistic environments.

RATIONALE
We studied the evolutionary and population dynamics of rapid adaptation in different climates with an internationally synchronized outdoor evolution experiment using the annual plant Arabidopsis thaliana. After coordinated planting of an equal mixture of 231 A. thaliana accessions, 12 replicates were established at 30 sites across Western Europe, the Mediterranean and Levant, and the United States for up to 5 years. Experimental sites spanned contrasting climates—from urban European environments to the likely edge of the species’ niche, the Negev desert. Combining high-coverage sequencing of 231 founder accessions with pooled whole-genome sequencing of more than 2500 samples of surviving adults comprising more than 70,000 tissue samples in the first 3 years, we characterized the dynamics of evolution in real time across climates.

RESULTS
Standing genetic variants changed in frequency rapidly across experiments, with repeatable trends among populations within similar climates but diverging trends across contrasting climates. Allele frequency shifts significantly exceeded neutral expectations. We reason that much of such shifts may be attributed to environmental natural selection, as we observed significantly synchronized (both increasing and decreasing) trends in allele frequency shifts across independent population replicates, both within one garden and in different gardens with similar climates. Such repeatability was observed in 24 of 30 gardens. Accessions from climatically matching origins increased in frequency, following patterns of past local adaptation with the strongest signals for annual mean temperature. Yet for accessions from warm regions, where we found strong local adaptation signals, we detected evidence for a recent adaptation lag; that is, they had the highest fitness when transplanted to gardens ~1.5°C colder than their home sites.

Experimental evolution genome-environment associations (eGEA) identified genomic regions that overly diverge across climates, including both known adaptive loci, such as a florigen-encoding gene, as well as genes potentially involved in thermal response, such as CAM5. This gene, found in a region with low linkage disequilibrium, represented one of the most pronounced allele frequency shifts, which is best explained by selection coefficients reaching –46 to +60% from cold to warm gardens, respectively. The overall genetic architecture was highly polygenic, but allele trajectories were partially predictable using genomic offset models.

CONCLUSION
Despite evidence for rapid evolution across several climates, evolutionary trends were unpredictable in a fraction of gardens and experimental replicates. In the warmest environments, which are expected to become more prevalent with global climate change, we found that early-generation evolutionary repeatability separated persisting experimental populations from those that suffered extinction, suggesting eco-evolutionary tipping points where extreme selection overwhelms adaptive potential. Although rapid climate adaptation is possible through standing genetic variation, understanding which environmental, genetic, or species-specific conditions dictate evolutionary limits will be critical for predicting biodiversity responses to climate change.

Rapid evolutionary adaptation across climates in A. thaliana.
(Top left) A coordinated distributed evolution experiment establishing outdoor gardens with a mix of A. thaliana natural populations. (Top right) Populations were seeded outdoors with an equal genotype mixture, exposed to natural local climatic conditions, and whole-genome sequenced over years. (Middle center) Example allele with divergent trend along an annual temperature gradient. (Bottom left) Genome scan pointing to an example allele. (Bottom center) Estimated environment niche of the original source population either carrying or not carrying an adaptive allele. (Bottom right) Survival of replicated experimental populations after years, explained by early repeatable evolutionary trends in warm locations.

Abstract
Climate change forces species to adapt rapidly to avoid extinction. To directly observe rapid adaptation and extinction, we conducted synchronized evolution experiments with Arabidopsis thaliana in 30 locations across Western Europe, the Mediterranean, the Levant, and North America. Whole-genome pooled sequencing of ~70,000 surviving plants revealed repeatable allele frequency shifts in similar climates but divergent shifts across contrasting ones, indicating evolutionary adaptation. We identified genetic variants linked to climate adaptation, including genes involved in processes ranging from thermal-stress sensing to spring-flowering timing. Evolutionary trends were often predictable, but variable, across environments. In warmer climates, evolutionary predictability correlated with population survival over 5 years, whereas erratic changes preceded extinction. These results show that rapid climate adaptation is possible, but understanding its limits will be crucial for biodiversity forecasting.

Xing Wu et al.
Rapid adaptation and extinction in synchronized outdoor evolution experiments of Arabidopsis
Science 391, eadz0777 (2026). DOI:10.1126/science.adz0777

Copyright: © 2026 The authors.
Published by American Association for the Advancement of Science. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What makes this study so awkward for creationists is that it hands them exactly what they claim to want, then leaves them with nowhere honest to go. This was not a computer model, not an inference from fossils, and not a historical reconstruction from deep time. It was a five-year, synchronised outdoor experiment across more than 30 sites, following genetically diverse populations of Arabidopsis thaliana as they changed under different climatic conditions, with whole-genome sequencing of roughly 70,000 surviving plants. In other words, it was observed evolution in the plain scientific sense: heritable genetic change in populations over generations.

And that is the problem. For years, creationists have demanded “evidence of observed evolution”, but when science provides precisely that, many immediately retreat into a parody of evolution that no biologist has ever proposed: a bacterium turning into a human, one “kind” abruptly becoming another, or novel organs appearing overnight. But those absurdities are not the Theory of Evolution; they are childish caricatures of it. What this experiment observed was exactly what evolutionary biology predicts and exactly what the scientific definition requires — populations adapting genetically to local environmental pressures, sometimes repeatedly and predictably, and sometimes failing when conditions became too extreme.

So the goalpost-moving is itself a tacit admission of defeat. If “observed evolution” does not count when it is directly measured in real populations, under real environmental conditions, over multiple generations, then the phrase no longer means anything except “evidence I have already decided not to accept”. The demand was never for evidence at all, but for a contrived impossibility based on a deliberate misrepresentation of the science. Studies like this expose that game very clearly.

What this research really shows is that scientists are not losing confidence in evolutionary theory, as creationists have been confidently predicting for decades. On the contrary, they are using it so successfully that they can design experiments around it, predict the kinds of genetic change they expect to see, and then watch those changes unfold in the field. Once again, reality conforms to evolutionary theory, while creationist dogma survives only by redefining success as failure the moment the evidence arrives.

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