Lecture on Natural History and the Origins of Life

Introduction

• Study of natural history driven by understanding origins.
• Fossils help map the tree of life, but have limitations.
• The story of life predates fossils, starting from the Big Bang.

Origin of Life

• Post-Big Bang universe forms atoms, stars, galaxies, planets, and life.
• Life's order emerged from universal chaos.
• LUCA (Last Universal Common Ancestor) is central to the study of life's origins.

Evolutionary Biology

• Charles Darwin: Theorized a primordial form as life's origin.
• LUCA: Not the first living thing, but the ancestor of all current life.
• Genomics advances allow better tracing of life's lineage through RNA, DNA, and proteins.

Carl Woese's Contribution

• Discovered archaea in 1977; proposed new life domain.
• Divided life into three domains: Archaea, Bacteria, Eukaryotes.
• Suggested LUCA arose from a chaotic environment with progenotes.

The Progenote Model

• Progenotes: Basic genetic fragments with a membrane, incapable of true reproduction.
• Genetic information swapped randomly, key life elements evolved.
• Early life likely existed in an "RNA world."

Modern Perspectives

• Advances in genomics allow reconstruction of LUCA's genome.
• Minimal genome approach: Identifying essential genes common across all life.
• 2003 Study: LUCA had 500-600 genes, simple RNA-based metabolism.
• 2006 Study: Suggested LUCA had 1000-1600 genes, more complex.

Revised Tree of Life

• Genetic evidence suggests two main branches: Bacteria and Archaea/Eukaryotes.
• Archaea may be ancestors of eukaryotes, affecting views on LUCA.
• 2016 Study: Reconstructed LUCA's genome, indicating life in hydrothermal vents.

Hydrothermal Vents Hypothesis

• LUCA may have metabolized hydrogen gas and CO2.
• Genes found in archaea/bacteria linked to such environments.
• Potential loss of these genes over time as life evolved.

Ongoing Research and Conclusions

• Multiple views on LUCA and its environment; research is ongoing.
• LUCA's search reflects the purpose of natural history.
• Future directions: More genomic comparisons and studies.

Further Learning and Engagement

• Encouragement to view companion videos for deeper understanding.
  • PBS Space Time
  • It’s Okay to Be Smart
• Audience engagement in learning about the origins of life.