Could the Sun’s Orbit Shape Evolution?

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IIt’s easy to see how the price of a chocolate bar can correlate to weather conditions in Africa. Most cocoa is grown in Africa, so if bad weather were to cause a change in the volume of the cocoa harvest there, it would affect global supply. Downstream, the price could change.

You may be even more surprised to learn that the specific path the blazing sun takes across the galaxy may have a direct influence on fluctuations in microplankton diversity in Earth’s oceans. These are the conclusions of a new preprint led by Peter Ozsvart of the Hungarian Academy of Sciences in Budapest. That’s because the flux of cosmic rays hitting Earth varies, which influences the mutation rate of microplankton, Ozsvart and his colleagues found.

Microplankton form the foundation of the marine food web and support all higher marine life, such as fish and whales. The results therefore suggest that tiny changes in the dynamics of our vast solar system could have had a profound impact on the evolution of life on Earth.

The sun is located about 26,000 light years from the center of our galaxy, aka the Milky Way, and its orbit is almost circular, taking about 230 million years to complete a loop. Orbiting the center of the galaxy, the Sun oscillates vertically with an amplitude of about 200 light years.

Tiny changes in the dynamics of our vast solar system could have had a profound impact on the evolution of life on Earth.

And these oscillations influence the flow of cosmic rays entering the solar system. Cosmic rays are energetic particles – mainly protons and other ions – accelerated to very high speeds, either by the sun itself or by more distant galactic and extragalactic sources. When these cosmic rays collide with molecules in our atmosphere, they create cascades of other particles that cascade onto Earth and its vast oceans. Such particle “showers” ​​tend to lose their vapor once they pass through about 30 feet of water, which happens to be the domain of marine plankton.

Marine plankton are a huge and diverse group of tiny organisms that include phytoplankton, which belongs to the plant kingdom, and zooplankton, which belongs to the animal kingdom. Ozsvart and his colleagues focused on four groups of microplankton whose evolutionary history we already know a lot about, including how the number of species and genera has changed over geologic time.

The four groups of organisms – radiolarians, nannoplankton, dinoflagellates and planktonic foraminifera – each have skeletons measuring between 2 and 300 microns, about the size of very finely ground coffee beans, and are found in a wide range of latitudes and water temperatures. Scientists have data on the radiolarians going back 500 million years and the other three going back 250 million years.

High-energy radiation damages genetic information, most commonly by breaking DNA strands. Cells are designed to repair their own DNA, but the repair process is imperfect. This leads to mutations. The rate of mutations depends on the amount of repair needed, which is in turn affected by the flow of cosmic rays.

Ozsvart and his colleagues calculated the number of new genera of species for each of the groups throughout geologic time and compared it to data on cosmic ray flux on Earth. Their hypothesis was that the distribution of new microplankton genera should be higher at periods of higher cosmic ray flux, and the data appeared to confirm this in a statistically significant way.

Plankton are the largest source of oxygen in our atmosphere and play a key role in nutrient cycling and maintaining the health of marine ecosystems. What would be the “downstream” consequences of an increase in microplankton biodiversity? Much like the weather in Africa affecting the price of chocolate, it is possible – although difficult to predict – that such variations could spread from local ecosystems to the oceans and have a profound effect on the evolution of life as we know it.

Do small, seemingly distant variations in our cosmic environment play a central role in the evolution of life on Earth? Previous studies had proposed that galactic oscillations might correlate with mass extinction events, but these claims have been refuted. Still, the new findings suggest that when searching for the massive forces and impacts that may have shaped evolution, it’s important to look beyond dinosaur-killing asteroids and megavolcanoes to an even more powerful force in our galaxy: the sun.

Main image: Rich Carey / Shutterstock

• Sean Raymond

  Published on October 14, 2025

  Sean Raymond is an American astrophysicist working at the Bordeaux Astrophysics Laboratory in France. He also writes a blog at the interface of science and fiction (planetplanet.net) and has published a book of poems on astronomy.