  In 1997, an extension of general relativity was proposed that predicts the
dark energy density \Lambda\ to vary linearly with the total number of
macroscopic black holes in the universe. We explore this prediction and find
that \Lambda\ must be roughly constant after the bulk of the stellar mass black
holes are in place, so for a redshift z smaller than unity. Conversely, the
highest black hole formation rate corresponds to the peak in the cosmic star
formation history, earlier than z=1. This yields a fast declining \Lambda, by a
factor of about 5, from redshift 1 to 3. At even earlier times, before many
stars were formed, the value of \Lambda\ should be much smaller than its
current value. These predicted effects are all consistent with current data,
and near future observations can definitively confirm or disproof the link
between the dark energy density and the total number of black holes in the
universe.
