Cosmic Radiation and Evolution

Space, Cave, Sky, hole, night

Elements

Extending deep into the earth a cavernous lair exists. Within this hole, no sound can be heard as in the corners of space. Within this hole, one is shielded from the millions of cosmic particles that bombard the planet every day including the human body. This geoasylum exists in the side of a mountain somewhere in America and it was made by man himself.

I learned of this man-made hole from an episode of Radiolab’s podcast titled Elements. The program stated that every day our bodies are bombarded with an unbelievable amount of particles every day.  Inside this hole, though, a few particles may penetrate on the scale of one every couple of months. This led me to wonder how these particles affect our bodies. How do our bodies respond upon encountering these particles? Have our bodies adapted evolutionarily to this constant assault? How would living in a place such as this man-made hole affect us in the short term and long term?

Is it possible that if we live in an environment shielded from random particles that we would have fewer random mutations? This may lead to fewer diseases, but it will also lead to a slower rate of evolution. Maybe most of these particles have no effect on us at all, but pass right through us.

Theory

There is an idea that cosmic radiation does in fact cause mutations in our DNA and affect the rate of evolution. In 1912 Austrian physicist, Victor Francis Hess first discovered that cosmic radiation reaches Earth. Since then, starting with geneticist H.J. Muller, we have learned that radiation such as X-rays can cause mutations in DNA. It has been thus proposed that spurts in biodiversity and human evolution in history can be attributed to influxes of cosmic radiation. Spikes in beryllium have been detected from 780,000, 105,000, 90,000, 60,000, 34,000, and 14,000 years ago; recently in 1987 a supernova occurred that may have a similar effect.

Andrew Collins has been a proponent of this idea. We know that these extreme influxes of cosmic radiation occurred because of the geological record of Earth. In the ice of the Antartic and other places which have remained relatively stable over centuries, there is a record of the isotope beryllium, which is a byproduct of cosmic radiation encountering the earth’s atmosphere. These geological records have been correlated with the increased biodiversity found in the fossil records.

Since 1988 Richard Lenski and his group has grown E. Coli over several generations and recorded the number of new genetic mutations that have occurred in each generation. They have found that the rate of mutations occurred at approximately 1 per second. Recently, a scientist by the name of Augusto Gonzalez has performed some calculations to find a correlation between the rate of new mutations in E. Coli and the rate of neutron radiation that would enter into the E.Coli’s environment. Gonzalez has concluded that the rate of de novo mutations in E. Coli is consistent with the rate in which neutron radiation would ecounter the E.Coli’s environment. This work does not definitively determine if neutron radiation actually causes mutations though, only that the two are correlated.

Together these are still interesting findings. How do errors in DNA transcription factor into this hypothesis? Would transcriptional errors be independent of neutron interference or caused by it?

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