For l_c, which contains the probability of the origin of life from non-living precursors, the authors suggest an LU (orders of magnitude) of ~200, and say "though one could easily argue for much larger LU".<p>Indeed one could argue. For example, the simplest known self-contained organism has ~500,000bp of genome which is roughly equivalent to LU (which is log base 10) of 300,000.<p>Obviously simpler organisms _could_ exist, and could have existed in the distant past. But how much simpler they could actually be is pure speculation.<p>300,000 is much bigger than 200. It is so enormous that it completely dominates all the other LU values.<p>It is so enormous that it is difficult to make any informed estimate about the probability distribution of log f_c.<p>But it tells us not to be surprised that we are completely alone in the observable universe.