  Recent data indicate one or more moderately nearby supernovae in the early
Pleistocene, with additional events likely in the Miocene. This has motivated
more detailed computations, using new information about the nature of
supernovae and the distances of these events to describe in more detail the
sorts of effects that are indicated at the Earth. This short
communication/review is designed to describe some of these effects so that they
may possibly be related to changes in the biota around these times.
