Goals

How Does Life Begin and Develop?

Goal 1
How Life Arose on Earth

Goal 2
Organization of Matter into Living Systems

Goal 3
How Life Evolves

Goal 4
Coevolution of the Biosphere and the Earth

Does Life Exist Elsewhere in the Universe?

Goal 5
Limits for Life

Goal 6
Habitable Planets

Goal 7
Signature of Life on Other Worlds

Goal 8
Life on Mars and Europa

What is Life's Future on Earth and Beyond?

Goal 9
Environmental Change on Earth

Goal 10
Terrestrial Life in Space

Question: How Does Life Begin and Develop?
Goal 4: Determine How the Terrestrial Biosphere has
Co-Evolved with the Earth

Trace the coupled evolution of life and the planet by integrating evidence acquired from molecular biology, studies of present and historical environments, and research in ecology and organismal biology.

Just as life evolves in response to changing environments, changing ecosystems alter the environment of Earth. Scientists can trace the co-evolution of life and the planet by integrating evidence acquired from studies of current and historical molecular biology (genomics) with studies of present and historical environments and organismal biology. We seek to understand the diversity and distribution of our ancient ancestors by developing increasingly sensitive technology to read the record of life as captured in biomolecules and in rocks (fossils), to identify specific chemical interactions between the living components of the Earth (its biosphere) and other planetary subsystems, and to trace the history of Earth's changing environment in response to external driving forces and to biological modifications.

Background

We need to use the geologic record to attach dates and environmental context to evolutionary events, leading to a robust history of the biosphere, based on biomolecular, paleoenvironmental, and paleobiological evidence. Further, by examining the history of life in an environmental context and by studying the evolution of biochemical pathways that yield preservable records (biominerals, accumulations of trace elements, organic molecules, characteristic fractionations of stable isotopes, etc.), we can begin to reconstruct the mechanisms that link environmental and biological changes. Research on these biochemical pathways will also create an inventory of bio-indicators that may be sought in ancient rocks on Earth and on other planets. Specific chemical interactions between the biosphere and its host planet, and their role as evolutionary drivers, will be illuminated by studies of biogeochemical cycles and significant biological byproducts, such as molecular oxygen. The development of Earth's atmosphere will thus be understood in much greater detail, with a new and more fundamental view of factors controlling its levels of oxygen and carbon dioxide. Another outcome will be a better understanding of the evolution of Earth's biosphere. Paleontological evidence for the first appearances of novel kinds of organisms will be integrated with molecular phylogenies using quantitative approaches to the fossil record and precise geochronology. Understanding the full diversity of our evolving biosphere requires that the fossil records of extreme environments be explored and documented, an exercise that also has relevance for the search for life on other worlds. All of this research requires a deeper understanding of evolutionary mechanisms at the levels of molecules, organisms and ecosystems, as discussed under Goal 3. The results contribute directly to the identification of biomarkers (Goal 7).