Paleoecotoxicology: the impact of chemical and physical stress in the evolutionary process

Abstract

Present-day biodiversity, estimated to comprise more than 100 millionspecies, has developed in around 4,000 million years on the basisof the ability of life forms to adapt and multiply at a rate that surpassedextinctions. Species, including humans, depend on the ecosystemsthat have operated with no or minimal human intervention upto recent years. Recent extinction rates are 100–1,000 times their prehumanlevels in taxonomically diverse groups from widely differentenvironments. Moreover, it is accepted that if all species currentlyendangered become extinct, then future extinction rates will be 10times recent rates (1). Although chemicals are the basic units for thedevelopment of life, it seems meaningful to take into accountParacelsus’ statement that “all things are poison and nothing is withoutpoison.” From this perspective it seems obvious that chemical andphysical features have been considered driving forces of evolutionaryprocesses from the beginning of recorded history. Estimates suggestthat the current world production of chemicals is 400 million metrictons. Almost 11 million naturally occurring or man-made chemicalshave been identified in the CAS Registry File, although only a smallportion of them is commercially available. I would like to present thehypothesis of a direct link between chemical stress and a major massextinction process, the Cretaceous-Tertiary (C-T) event, with the aimof providing a more holistic view on the potential of chemical stresson the evolutionary process.