I came across an issue relating to species appearances and disappearances.
However, it was hard for me, with a biochemistry/metabolic nutrition
background to understand a broad species issue. Basically, the issue goes
like this. Species have gone extinct throughout the fossil record into today.
Supposedly, not all of the recent extinctions can be blamed on humans
wrecking the ecology. On the other hand, there is a point in the fossil
record where new species appearances seem to cease (unless species is
defined rather broadly). My question is: how do we explain this change in the
balance between extinction and appearance?