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There is always a certain amount of background radiation present, for example due to ionizing radiation from the sun and other stars. Also certain materials like granite may emit relatively large amounts of radiation.

Ionizing radiation may cause mutations in the DNA (Gevertz et al, PNAS 1985). Mutations, in turn, may lead to altered phenotypes. Altered phenotypes and survival of the fittest are key to evolution and formation of new species.

What is the (relative) contribution of background radiation on the formation of new species?. In other words, is background radiation a critical component in evolution and would the course of evolution have changed substantially when there would be no such background radiation?

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    $\begingroup$ Welcome to bio.SE! Sorry for the skepticism, but... this question may be too broad. Spontaneous mutations (due to e.g. radiation) may indeed lead to beneficial traits and hence formation of new successful species. However, evolutionary biology is a big discipline and radiation contains many potential candidate particles. Are you talking background radiation, cell phones, UV light, nukes... $\endgroup$
    – AliceD
    Mar 18 '15 at 12:34
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    $\begingroup$ Sorry so unclear. I'm curious about natural radiation ie elements, stars, etc., and if it is essential to biology in the broadest sense? Would the lack of radiation have a negative/positive impact on evolution? $\endgroup$ Mar 18 '15 at 21:50
  • $\begingroup$ Thanks for explaining. I took a bash at re-wording your question and voted to re-open it. Feel free to roll back or change when it does not reflect your initial question. However, it its previous form the question is not suitable for Biology.SE as it needed editing. $\endgroup$
    – AliceD
    Mar 18 '15 at 22:47
  • $\begingroup$ Welcome. I suppose one could come up with estimates of how much "background radiation" influence the mutation rate. The link between mutation rate and speciation is not an easy subject though. I vote to re-open but I think it is good to accept answers to "how much different would the mutation rate be if there were to have no "background radiation"?". $\endgroup$
    – Remi.b
    Mar 19 '15 at 0:50
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    $\begingroup$ This is more on the historical side, but concerns about the effects of radiation were major drivers in the development of evolutionary genetics in the mid-twentieth century, particularly via the work of H. J. Muller. Muller and Theodosius Dobzhansky had very different views of the role of standing genetic variation because they studied very different types of variation: radiation-induced mutation in the former case and chromosomal inversions in the latter. $\endgroup$
    – Corvus
    Mar 19 '15 at 4:59
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Is background radiation a critical component of evolution? No, it most certainly is not.

The DNA replication and DNA repair mechanisms aren't perfect and errors happen without any external cause or catalyst. You could say mutations happen on their own. There are mutagens that also cause DNA damage or mutations, but they're merely affecting the DNA replication in a negative way, causing it to err more often.

So, the effect of background radiation isn't the key here, the key is that the biological processes of DNA replication and repair are not infallible, although radiation does increase the error rate (the rate of mutation) just like many other mutagens do.

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A few points for looking deeper into this question:

  • Radiation is not the only extrinsic source of mutations. One that has to be necessarily mentioned alongside the radiation is the exposure to chemicals - via smoking, drinking and food consumed. These are not necessarily industrial chemicals - e.g., many things found in soil will find their way to water and to the organisms.
  • For multicellular organisms one has to distinguish somatic and germline mutations. The former are relevant for the evolution of cancer tumors (which can be viewed as generations of cells), but this is not what we usually mean by the evolution, since this does not affect the offspring of the organism as a whole. In other words, to affect the evolution the mutations must happen in the egg/sperm cells.
  • Now we are down to the question raised by @DanHorvat: whether the rates of errors during replication are higher than those due to radiation. The former vary wildely among the organisms (e.g., $10^{-4}$ per nucleotide per generation in HIV, but $10^{-8}$ or less for human). The effects of radiation and chemicals may vary depending on the surrounding environment, time period in question, etc.

Thus, I would say that there is no a general answer to this question, although one may certainly compare numbers for a specific organism.

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