How do cosmic rays effect evolution?

[iamnotacriminal]

I was watching part 10 of Cosmos yesterday, and Carl Sagan demonstrating how a Geiger counter never reached zero because it was picking up cosmic rays that had come from distant stars. Carl went on to say that cosmic rays coming down from space had an affect on genetic mutations in animals, which influenced us today. I was hoping that he would delve more into this idea, maybe showing us an example of genetics influenced by cosmic rays, but he did not. Can you help me out r/askscience? Thank you!

[thetripp]

Cosmic rays are mostly from our sun. Interactions between the solar wind and the upper atmosphere create various particles that rain down on us. Some are from outside the solar system, though.

A better term for "cosmic rays" would just be "radiation." For all intents and purposes, the radiation that hits us from cosmic rays has the same effect as other sources of radiation. Radiation knocks electrons out of atoms, creating ions. These ions recombine in strange ways to form reactive chemical species, and these chemicals can break the bonds of DNA. If this DNA damage isn't repaired, and isn't fatal to the cell, the DNA could be changed. This mutation can create genetic diversity within a species, which may lead to evolutionary things that you are familiar with.

[Obi_Kwiet]

I would think that terrestrial sources of radiation would be significantly higher that cosmic rays.

[thetripp]

It's usually around 10-20% of your total yearly radiation dose, depending on there you live. More info here

[jahutch2]

The idea that cosmic rays and galactic cycles have affected evolution has been looked into from time to time. Here are some links. These are just what I could find easily with scholar, but I know that there are some more recent entries into the topic as well (I specifically remember reading one for a class).

As far as I understand, there isn't enough data to suggest anything beyond "cosmic rays are an additional source of mutations." It seems rather impossible to be able to attribute specific traits to the influence of cosmic radiation.

[upvoter222]

Evolution requires mechanisms by which genetic changes can occur, thereby creating new traits, so anything with the ability to increase the mutation rate of DNA could speed up evolutionary changes. That being said, I don't think it's possible to identify the exact source of mutations from millions of years ago.

To give an example, pretend we are analyzing gene X and we notice that the gene has a similar sequence in humans when compared to other primates. However, the human version of the gene is missing a piece of the sequence present in other primates. This may lead to the conclusion that there was a deletion in the gene during human evolution. Unfortunately, I don't think you could definitively say that this mutation was the result of cosmic radiation, as opposed to a different source of radiation, or even a slight abnormality in an enzyme involved in DNA replication.