Piran et al., "Cosmic explosions, life in the Universe and the Cosmological Constant," http://arxiv.org/abs/1508.01034 I thought this was interesting. If I'm understanding correctly, the idea is that satellite galaxies such as the Magellanic Clouds have low metallicity, which causes them to host a lot of gamma-ray bursts. These GRBs are deadly to life in the main galaxy. Having a larger cosmological constant reduces the number of satellite galaxies that form, and therefore puts an anthropic lower limit on the cosmological principle. Of course this is all very speculative.