The numerical argument that the age of the galaxy gives sufficient time that it should be well-covered with probes seems reasonable. However, extending that ar

The numerical argument that the age of the galaxy gives sufficient time that it should be well-covered with probes seems reasonable. However, extending that argument to "...and the various probes will have then competed in a Darwinian struggle leaving only a few voracious survivors causing a galactic-scale grey-goo scenario." does not seem especially well supported.