How deep can we look into deep-time?

[Thomas Schlemmermeyer]

Some days ago, I was very pleased to have a discussion with Dr. Keith Brown from
Campinas, via telephone.

The problem is the following: Evolutionary biologists, cladists, systematists
and so on like to look far back - many millions of years.

To derive multiple factor scenarios concerning paleoecology, paleoclimate,
paleovegetation etc. is however notso easy.

Thus Dr. Brown suggested that it is difficult enough to look back to the
Quaternary. Cladists and so on consider in their scenarios events as far back
as the Cretaceous and may not berobust in their predictions (or should one say
postdictions?)

  ANy comments?