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The Planetary Context of Biological Evolution

The Harvard Team is an interactive group of biogeochemists, paleontologists, sedimentary geologists, geochemists, and tectonic geologists assembled with the common goal of understanding the coevolution of life and environments in Earth history. With a multidisciplinary approach, the Team research focuses on three critical intervals of planetary change and major transitions in the evolution of life on Earth:

• The early Paleoproterozoic, when oxygen began to accumulate in the atmosphere and surface ocean (2400-2200 Ma)
• The terminal Proterozoic and Early Cambrian, when animal life radiated (750-525 Ma)
• The Permo-Triassic boundary, when mass extinction removed some 90 percent of Earth’s species diversity, permanently altering the course of evolution (251 Ma)

A primary broad research concept for the Harvard Team is this: The Planetary Context of Biological Evolution. Research endeavors focus on critical intervals of Earth change, as indicated by the first four research areas below, each with associated projects.

• Proterozoic Oxidation of the Earth’s Surface
  • Characterize molybdenum isotopic compositions in black shales, sea sediments, ferromanganese nodules, continental molybdenites, and seawater for insight on environmental redox or fractionation conditions
  • Geochemical study of mid-Proterozoic black shales deposited during maximum flooding in of McArthur Basin, northern Australia
  • Investigate concept that the deep sea was sulfidic, rather than oxic from 1850 Ma until at least 1200-1000 Ma ago, with study of related observations
  • Study ecological patterns, abundance, and diversity of microfossil assemblages in the siliciclastic Roper Group, northern Australia
• Neoproterozoic-Cambrian Environmental Change and Evolution
  • Paleontology, geochronology, tectonics, and environmental changes of this period, looking for models of integrated change in the Earth system
  • Geochronological work on volcanic ashes to constrain ages of fossil embryos in terminal Proterozoic phosphorites from China, determine the age of Chinese glacial deposits, and the tempo of the Cambrian explosion; also work on Newfoundland ash beds associated with Neoproterozoic glacials
  • Investigate trace fossils in India, with current results indicating that Kajrahat limestone is of Paleoproterozoic age; work continues on its bedding features
  • Study Precambrian-Cambrian boundary age in Oman by drilling core ashes to study fossil evidence, glacial deposits, and tempo of changes in carbon and strontium isotopic signatures
  • Test uranium-lead geochronology methods to determine error and confidence levels for geochronolongy time periods
  • Investigate new findings on molecular development, related to understanding early animal evolution
  • Namibia Project: Investigate events preceding low-altitude glaciation in northern Namibia
  • Svalbard Project: Investigate a sequence having lithologic and isotopic signatures of “cap” carbonates (purportedly diagnostic of snowball earth deglaciations)
  • Morocco Project: Study dateable volcanic rocks (from the latest Neoproterozoic (Vendian) continental shelf through Early Cambrian marine facies) to improve Vendian event chronology and investigate its continental-marine environments and biota
  • Mackenzie Mountains (NW Canada) Project: Investigate the timing of banded iron formation sedimentation (relative to the history of glaciation) and examine sections of the cap carbonates in glacial diamictites
  • Field studies in Namibia and Oman for sedimentologic, geochemical, paleontologic, and geochronological investigations of the Precambrian-Cambrian boundary, designed to assess rates of evolution, taxonomic diversity, and metazoan ecology below and above the boundary
  • Develop digital technologies for outcrop mapping, with application of differential GPS to acquire high-resolution maps of geologic features, plus testing laser-based range finders and theodolite total stations
  • Determine distribution of diagnostic mat signatures in ancient siliciclastic rocks (among the diagnostic signatures of life that could be reliably identified in the 2003 Mars rover mission)
  • Explore models of coupled environmental and biological changes at the end of the Proterozoic Eon, plus develop high precision measurements of calcium isotopes to investigate biomineralization in Proterozoic sediments
• Permo-Triassic Mass Extinction Causes and Biological Consequences
  • Consider physical/biogeochemical mechanisms in the end-Permian mass extinction, with development of paleo ocean circulation models, using them to drive biogeochemical models
  • Study timing of the end-Permian mass extinction (considering planetary or extraplanetary processes causing this great extinction) plus biological recovery following the extinction, which set the subsequent course of evolution on Earth
  • Utilize modified standard electron microprobe techniques to make micron-scale elemental maps of silicified plants and provide direct tests of taphonomic hypotheses on silica permineralization (high-resolution, non-destructive microchemical assays critical in Mars sample analysis)
  • Use NMR and soft X-ray techniques to examine lignified tissue distribution in early plants
• Molecular and Isotopic Approaches to Microbial Ecology and Biogeochemistry Isotopic characterization of molecular biosignatures, to understand the functional and systematic relationships of microorganisms in natural ecosystems
  • Isotopic analyses of nucleic acids, using probe-capture techniques for isolation of specific nucleic acids
  • Bacterial fractionations of hydrogen isotopes from methanotrophic bacteria
  • Carbon-isotopic biogeochemical studies, using hydrothermal vent microbial communities
  • Investigate how methane functioned in Earth’s early atmosphere with studies of how methanogenesis occurs in modern sediments and calculating rates of microbial reactions
  • Develop calcium isotope measurements with high precision to investigate biomineralization in Proterozoic sediments

Additional research endeavors for the Harvard Team are these final two areas:

• Geobiology of Neogene Hematitic Sedimentary Rocks

**Study iron-rich sedimentary rocks older than ca. 1850 million years (which preserve microfossils and chemical signatures of ancient life) to investigate biological and physical processes and relate them to paleobiological and geochemical patterns in iron-rich sediments

• Research on Neogene iron deposits (Rio Tinto system, Spain) with petrological, paleontological, and geochemical studies of sedimentary rock samples for insight on Earth’s ancient iron formations and to support planning for NASA’s Mars 2003 lander mission, likely to be in an aqueously deposited hematite area

• Molecular Evolution and Phylogeny
  • Contribute to NAI Evogenomics Focus Group research: identify key metazoans for intensive sequencing efforts, provide data for molecular clocks, and search for key developmental genes
  • Develop a new method to account for the stratigraphic ranges of species not preserved in the fossil record (particularly for primate origins) to understand the relationship between molecular clock and paleontological estimates of evolutionary divergence times
  • De-convolving the biological from geological signals in Phanerozoic marine diversity studies
  • Quantitative analysis of evolutionary patterns in local stratigraphic sections