Rosa Rubicondior: Refuting Creationism - An Evolutionary Arms Race In Space

In this illustration, a phage — a type of virus that infects bacteria — rests on the surface of a host cell. Researchers at UW–Madison designed an experiment for the International Space Station to study how phage-bacteria interactions affect the health of the gut microbiome.

Microbes mutated in space hint at biomedical benefits to humans on Earth – UW–Madison News

In a striking demonstration of the theory of evolution in practice — and something that will have creationists once again insisting on redefining evolution as a theory about one creature turning into an entirely unrelated taxon — an experiment aboard the International Space Station has shown how subtle changes in the environment can dramatically alter an evolutionary trajectory. It also illustrates another major embarrassment for Intelligent Design creationists: evolutionary arms races. Arms races are, of course, utterly incompatible with the idea of an intelligent designer, since running to stand still in a race with yourself is a neat definition of insanity.

Unlike the creationist parody of evolution — carefully engineered to be unprovable because it does not describe what actually happens and what no biologist has ever claimed — the real scientific definition of evolution is simply a change in the frequency of different alleles in a population over time. A definition that creationists know to be irrefutable, hence their persistent attempts to redefine it so that they have something to attack.

The experiment, which had a parallel control on Earth, was designed to observe how bacteriophage viruses that parasitise bacteria and their hosts co-evolved in the microgravity environment of space.

The results have just been published in PLOS Biology. They show that both the T7 phage virus and the E. coli bacteria developed marked genomic differences compared with the Earth-bound populations. The space-station phages gradually accumulated specific mutations that enhanced infectivity or improved their ability to bind receptors on bacterial cells. Meanwhile, the space-station E. coli accumulated mutations that improved resistance to phages and enhanced survival in near-weightless conditions. In other words, what was observed was a genuine evolutionary arms race — and because the environments differed between the space-station populations and the Earth-bound populations, the divergence can be attributed directly to differences in gravity.

The results highlighted another intriguing angle: the mutations that phages and bacteria acquire in space don’t just reveal fundamental evolutionary dynamics, they can also have practical applications for human health on Earth. After 25 days aboard the ISS, both organisms returned with novel mutations not commonly seen under terrestrial gravity, including changes to bacterial surface proteins and corresponding phage adaptations to bind those altered surfaces.

Researchers then engineered phages carrying these space-derived mutations and tested them against bacterial pathogens responsible for urinary tract infections — many of which are now resistant to antibiotics — finding the space-influenced phages were notably effective at killing these otherwise resistant strains. This suggests that the unique selection pressures of microgravity may reveal evolutionary pathways that could be harnessed to design improved therapies for antibiotic-resistant infections back on Earth.

Phage–Bacteria Co-evolution^ An Evolutionary Arms Race. Bacteriophages (or simply phages) are viruses that infect bacteria and are the most abundant biological entities on Earth, outnumbering bacteria themselves by at least an order of magnitude. Wherever bacteria exist — in soil, oceans, freshwater, extreme environments and within the human body — phages follow.

Their relationship is one of continuous antagonistic co-evolution, often described as a classic evolutionary arms race.

When a phage infects a bacterium, it hijacks the host’s cellular machinery to replicate, usually killing the cell in the process. This imposes intense selection pressure on bacterial populations, which rapidly evolve defensive strategies. These include:

Altering or masking surface receptors so phages can no longer attach
Producing restriction enzymes that cut invading viral DNA
Using CRISPR-Cas systems to recognise and destroy phage genomes
Modifying cell walls and membrane proteins to block entry

Phages, in turn, evolve counter-adaptations just as rapidly:

Mutations in tail fibres and binding proteins to recognise altered receptors
Anti-CRISPR proteins that disable bacterial immune systems
Changes in genome structure to evade host restriction enzymes

This reciprocal adaptation can occur over remarkably short timescales — sometimes within days or weeks — making phage–bacteria systems one of the best-studied real-time examples of evolution in action.

Two broad patterns are commonly observed:

Arms-race dynamics – escalating cycles of defence and counter-defence, leading to ever-greater resistance and infectivity.
Red Queen dynamics – continual turnover of genotypes, where neither side gains permanent advantage and both must keep evolving simply to survive.

These interactions strongly shape microbial ecosystems, regulate bacterial population sizes, influence nutrient cycling in oceans, and drive much of the genetic diversity seen in microbes.

Phage–bacteria co-evolution also has practical importance. It underlies the renewed interest in *phage therapy* as a treatment for antibiotic-resistant infections, and provides one of the clearest, experimentally demonstrable examples of natural selection operating through measurable genetic change.

Why “Improbable” Mutations Are Inevitable in Large Populations

Bacterial populations are enormous and reproduce extremely rapidly. In a population of just one billion bacteria, a mutation with a probability of one in a million will arise, on average, about 1,000 times in every generation. Far from being rare events, such mutations are routine.

If one of those mutations confers even a modest advantage — say a 1% increase in fitness — natural selection acts immediately. The probability that such a beneficial mutation will eventually become fixed in the population is approximately:
\[ P_{\text{fix}} \approx 2s\tag{1} \] where \( s \) is the selective advantage. For a 1% advantage \(( s = 0.01 )\), the fixation probability is therefore about 2% for each copy.

With hundreds or thousands of such mutants arising every generation, fixation becomes not a matter of chance but of near inevitability. The expected time to fixation in bacteria can be estimated by:
\[ t_{\text{fix}} \approx \frac{2}{s} \ln(2N)\tag{2} \] where \( N \) is the population size. For microbial populations, this often corresponds to tens or hundreds of generations — sometimes only days or weeks.

In other words, mutations that creationists like to describe as “astronomically improbable” are not only expected, they are relentlessly amplified by selection in large, fast-reproducing populations. This is precisely why evolutionary change in microbes is both rapid and experimentally observable.

The experiment and its relevance for both the Theory of Evolution and human health are detailed in a press release from the University of Wisconsin-Madison by Renata Solan

Microbes mutated in space hint at biomedical benefits to humans on Earth
Researchers are interested in studying effects on the gut microbiome and antibiotic-resistant infections.
In September 2020, UW–Madison biochemists launched a small box containing viruses and bacteria into space to investigate the ways microbes such as those residing in our guts respond to space conditions. Now, the bacteria and phages (viruses that infect bacteria) have returned to Madison with hints about how space travel may impact the gut microbiome and clues about how to treat antibiotic-resistant bacterial infections on Earth.

Our experiment was about more than learning what happens when bacteria and phages travel in outer space. We are asking questions about how mutations acquired in space might be relevant on Earth.

Professor Srivatsan Raman, co-lead author
Department of Biochemistry
University of Wisconsin-Madison
Madison, Wisconsin, USA.

The researchers’ findings are reported in the journal PLOS Biology.

Bacteria-phage relationships are essential to maintaining a healthy balance in the human gut microbiome: Gut bacteria evolve to evade infection, and in response, phages mutate to find new ways to infect bacteria. Raman’s lab is harnessing this relationship to design phages that can compete with and combat bacterial infections.

Space is such a unique environment. It has the potential to reveal possibilities for how phages can evolve that are hidden on Earth.

Dr Philip Huss, co-lead author
Department of Biochemistry
University of Wisconsin-Madison
Madison, Wisconsin, USA.

With scientists and astronauts spending extended periods of time in space — and the onset of recreational space travel — it’s become important to understand how environments with reduced gravity (microgravity) impact the evolutionary dance between bacteria and phages. Sustained microgravity is difficult to establish on Earth. But on the International Space Station, a space-based national laboratory, it’s possible to do research in the near-weightless conditions that are ideal for the Raman Lab’s study.

On Earth, we know that phages move around their environment and find a bacterial host to infect. Then they enter and kill the bacteria. But in outer space, do these rules of engagement still apply? If there is no gravity, then the way that phages move around their environment will just be different. The ways they attack bacteria will be different.

Professor Srivatsan Raman.

The UW–Madison scientists engineered phages to exhibit thousands of different mutations and sent them to space. For 25 days, ISS scientists incubated different combinations of the phages and bacteria together and in isolation. Back in Madison, the same experiments were replicated under Earth’s gravity.

Huss and Chutikarn Chitboonthavisuk (a former graduate student in the Raman Lab) found key differences when they compared the phages and bacteria grown in space with those grown on Earth. In space, the phages and bacteria acquired novel mutations: Proteins on the surfaces of bacteria changed and in turn, phages mutated to bind to these altered surfaces. As a result, the mutations that allowed phages to infect bacteria in space differed from those on Earth.

The Raman Lab then engineered phages with a variety of mutations that were successful in space to test their effectiveness against bacterial pathogens on Earth, putting the novel phages to work against bacteria responsible for urinary tract infections. Currently, more than 90% of the bacteria that cause UTIs are resistant to at least one antibiotic.

Designing an experiment for space

Designing a space-bound experiment required that the researchers stick to a prescribed set of materials that can fit in a confined space. To ensure that their study was feasible and met the safety standards of ISS research, the team partnered with Rhodium Scientific, a biotechnology company that works with researchers to facilitate scientific exploration in space.

We found that the novel combinations of phage mutations were really effective at killing UTI pathogens on Earth. And that’s pretty surprising. Why would an experiment in space inform how to design phage therapies on Earth? We don’t exactly know, but one of our hypotheses is that the environmental factors stressing UTI bacteria somehow mimic the stress bacteria experience in microgravity, making their surface proteins similar.

Professor Srivatsan Raman.

With the experience gained through their first experiment’s voyage, the researchers are now working on answering bigger questions — with experiments that must still fit in the same, small box — for a future space launch.
First, we asked basic microbiology questions, just in space, now, we’re ready to study systems of multiple phages and bacteria that more closely represent the complexity of the human microbiome. What novel interactions occur in space, and what can we learn from them here on Earth?

Dr Philip Huss.

Publication:
Huss P, Chitboonthavisuk C, Meger A, Nishikawa K, Oates RP, Mills H, et al. (2026)
Microgravity reshapes bacteriophage–host coevolution aboard the International Space Station. PLoS Biol 24(1): e3003568. https://doi.org/10.1371/journal.pbio.3003568

Abstract
Bacteriophage–host interactions play a fundamental role in shaping microbial ecosystems. While extensively studied on Earth, their behavior in microgravity remains largely unexplored. Here, we report the dynamics between T7 bacteriophage and Escherichia coli in microgravity aboard the International Space Station (ISS). Phage activity was initially delayed in microgravity but ultimately successful. We identified de novo mutations in both phage and bacteria that enhanced fitness in microgravity. Deep mutational scanning of the phage receptor binding domain revealed striking differences in the number, position, and mutational preferences between terrestrial and microgravity conditions, reflecting underlying differences in bacterial adaptation. Combinatorial libraries informed by microgravity selections yielded T7 variants capable of productively infecting uropathogenic E. coli resistant to wild-type T7 under terrestrial conditions. These findings help lay the foundation for future research on the impact of microgravity on phage–host interactions and microbial communities and the terrestrial benefits of this research.

Fig 1. Experimental design to evaluate microgravity interactions on the ISS.

Samples were prepared on Earth, with quality checks to ensure cryovial integrity and prevent leakage during freeze–thaw cycles. Identical sets were frozen, then thawed and incubated either in microgravity on the ISS (left) or terrestrially (right) for defined intervals. All samples were re-frozen and later analyzed on Earth for phage and bacterial titers, whole-genome sequencing, and deep mutational scanning of the T7 receptor binding protein tip domain.

Huss P, Chitboonthavisuk C, Meger A, Nishikawa K, Oates RP, Mills H, et al. (2026)
Microgravity reshapes bacteriophage–host coevolution aboard the International Space Station. PLoS Biol 24(1): e3003568. https://doi.org/10.1371/journal.pbio.3003568

Copyright: © 2026 The authors.
Published by PLoS. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What makes this experiment particularly awkward for creationism is not merely that evolution occurred — which they routinely deny — but that it did so in real time, under controlled conditions, and in a manner that fits the theory precisely. Small genetic changes accumulated, selection acted on those changes, and populations diverged in predictable ways. No creature turned into another “kind”, no miracles were required, and no guiding hand was visible. Just mutation, selection and differential survival, operating exactly as evolutionary theory says they should, and populations diverging under different environmental pressures just as the theory predicts.

Even more damaging is the unavoidable presence of an evolutionary arms race. Bacteria evolved defences; phages evolved counter-measures; bacteria responded again. This reciprocal escalation has no coherent interpretation within Intelligent Design. A designer forced to redesign its own creations in response to the failures of its earlier designs is not demonstrating intelligence but incompetence. Arms races are a hallmark of blind natural selection, not foresight.

The experiment also neatly exposes another persistent creationist misunderstanding: that evolution requires rare, fantastically improbable events. In microbial populations numbering billions, mutations are not rare, selection is relentless, and adaptation is rapid. Change is not speculative or hypothetical; it is routine, measurable, and now even observable beyond Earth’s gravity.

Once again, creationism is left with only its familiar escape routes: denial, redefinition, or dismissal. But the evidence here is unusually clean. Identical starting populations, identical timescales, different environments — and different evolutionary outcomes. If this is not evolution in action, then the word has no meaning at all.

In the end, the lesson from the International Space Station is the same as the one learned in every laboratory, every clinic, and every genome: life adapts because it must, not because it was designed to. And the more closely we watch it, the harder it becomes to pretend otherwise.

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