||June 14, 2001 GSA Release No. 01-18 Scientists Share
Multidisciplinary Discoveries at "Earth System Processes" (II)
Session Highlights - SESSION 23: Tuesday, June 26. ARCHEAN EARTH
AND CONTEMPORARY LIFE: THE TRANSITION FROM AN ANAEROBIC TO AN
AEROBIC MARINE ECOSYSTEM Session 30 Abstracts ] - Can you
imagine our world being devoid of oxygen for almost half of its
history? And suddenly there's an abrupt rise at ~2 ga? This
amazing picture of our Earth is finding increasing support from
rock record geologic data. - "But what intrigues physical and
biological scientists alike is 'why the rise and why at ~2 ga'?"
remarked Janet Siefert, co-chair for this session. Siefert is a
molecular evolutionist at Rice University in Houston, Texas. -
"We know with increasing certainty from geologic biomarkers,
fossils, and molecular phylogenies that the organisms most
likely responsible for this rise, the ubiquitous cyanobacteria
or their ancestors, were surely present at least half a million
years prior to the rise. So why