This suggests we have to look deeper. The alternative explanation that they are all 0.5 solar-mass primordial black holes is no better. On the one hand we have no evidence that primordial black holes exist at all in general, much less as the dominant component of dark matter halos in galaxies. The microlensing experiments are still in their infancy, and are improving steadily with time. Ideas and observations, both pro and con, are being developed along a number of lines.
Some ideas get considerable attention, only to fall apart on small details of interpretation.
This question still commands a lot of attention in the press. It will be very interesting to watch how this question plays out over the next few years. Copyright 1998 Richard W. Pogge, All Rights Reserved.