2003 Annual Science Report
Pennsylvania State University Reporting | JUL 2002 – JUN 2003
A Timescale for the Evolution of Life on Earth - Hedges
0 Field Sites
The following discoveries were made during Year 5:
- An early origin for the rise in complex multicellular life. We found, using molecular clock studies of large numbers of genes (50-200), that plants, animals, and fungi diverged about 1.5 billion years ago, with living groups in each kingdom diverging relatively soon thereafter. This is as much as one billion years earlier than indicated by the fossil record. (Manuscript in preparation).
- Colonization of land by animals (arthropods) in late Precambrian. Using molecular phylogenetic analyses of multiple nuclear and mitochondrial genes, including newly collected data, we found that land was colonized independently by various groups of arthropods, some in latest Precambrian. (Manuscript in preparation).
- A robust method for estimation of the mode. We conducted simulations and used real data to test various methods for estimating the mode of distributions (an important statistic used in molecular clock analysis). We discovered that a bootstrap method lowers the variance of estimates and accordingly devised an improved method for estimation of the mode. (Manuscript submitted.)
- Review papers published. One review paper covered the tree and timescale of life, including recent advances from genomics (Nature Reviews Genetics 3:838-849, 2002). The other paper reviews the latest molecular clock methods for use with genomic data (Trends in Genetics 19:200-206, 2003).
PROJECT INVESTIGATORS:S. Blair Hedges
PROJECT MEMBERS:Davide Pisani
RELATED OBJECTIVES:Objective 1.2
Indirect and direct astronomical observations of extrasolar habitable planets
Origins of cellularity and protobiological systems
Earth's early biosphere
Foundations of complex life
Effects of extraterrestrial events upon the biosphere
Co-evolution of microbial communities
Biochemical adaptation to extreme environments
Biosignatures to be sought in Solar System materials
Biosignatures to be sought in nearby planetary systems