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In a broad
sense, Geobiology is the use of information preserved in and by
the biosphere to attack problems of importance for understanding
the geological evolution of the Earth. The interaction of life
with the earth works in two directions: life has had an enormous
impact on the chemical and physical evolution of this planet,
and in turn, global changes in the surface environment of the
earth have left their imprint on the genetic and molecular systems
which are part of every living thing. In the past, the thrust
of geobiological work at Caltech (and elsewhere) has focused primarily
on the first of these domains, the effect of life on earth; this
work includes many of the isotopic, biogeochemical, and biomineral
studies of Patterson, Epstein, Lowenstam & their students. Today,
researchers in our division continue to study the geochemical
signatures of life (examples include the discovery of magnetofossils,
and the discovery that bacterial arsenate respiration can precipitate
arsenic sulfides), but the approach taken to explore these problems
has now expanded to include molecular genetics.
Why should
geological and planetary scientists be interested in molecular
geobiology, and genetics in particular? One answer is simply that
genes are fossils. In many cases, genes are extraordinarily ancient
in origin and contain information about past events and environments
on this planet. There are many examples of this, from the "Snowball
Earth" episodes in the Proterozoic triggering evolution
of the Superoxide dismutase, to bursts of True
Polar Wander during the Cambrian Evolutionary Explosion.
A second answer is that understanding how extant organisms function
at the molecular genetic level will better enable us to interpret
past, present and even extraterrestrial biogeochemical signatures.
Though exploring
the molecular evolution of organisms and their organic and inorganic
products, research in the Geobiology program at Caltech will interrogate
the history of life on earth as well as the role the biota continue
to play in shaping modern environments.
