I wouldn't expect the ability to evolve in Eukaryotes if a GRB happened near Earth, but I see no reason why frequent GRBs in a distant galaxy would put a ceiling on complexity. Here's how I see it going down:
1. Life evolves. Not radiation resistant except for a group of bacteria that like to hang out in uranium-rich soil (or something).
2. GRB. Radiation-resistant bacteria repopulate the planet.
3. Radiation-resistant mechanism breaks in 99% of bacteria, but vestiges remain.
4. Mechanisms to handle bigger genomes evolve (Let's call them "eukaryotes" for the sake of the argument).
5. Single-celled "eukaryotes" invade the uranium-rich soil ecosystem by fixing the vestigial radiation resistant genes.
6. GRB. Radiation-resistant prokaryotes and radiation-resistant "eukaryotes" repopulate the planet.
7. Rinse, repeat.
8. Eventually there will be big multi-cellular radiation-resistant "eukaryotes" walking aroud.
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> life on earth is very sensitive to climate change
We are very sensitive to climate change, as are a bunch of higher organisms we care greatly about. Life on Earth? Not a chance. We couldn't come close to sterilizing the planet if we wanted to.
1. Life evolves. Not radiation resistant except for a group of bacteria that like to hang out in uranium-rich soil (or something).
2. GRB. Radiation-resistant bacteria repopulate the planet.
3. Radiation-resistant mechanism breaks in 99% of bacteria, but vestiges remain.
4. Mechanisms to handle bigger genomes evolve (Let's call them "eukaryotes" for the sake of the argument).
5. Single-celled "eukaryotes" invade the uranium-rich soil ecosystem by fixing the vestigial radiation resistant genes.
6. GRB. Radiation-resistant prokaryotes and radiation-resistant "eukaryotes" repopulate the planet.
7. Rinse, repeat.
8. Eventually there will be big multi-cellular radiation-resistant "eukaryotes" walking aroud.
----
> life on earth is very sensitive to climate change
We are very sensitive to climate change, as are a bunch of higher organisms we care greatly about. Life on Earth? Not a chance. We couldn't come close to sterilizing the planet if we wanted to.