← All books

What Is Life?
by Lynn Margulis and Dorion Sagan, Niles Eldredge


Lynn Margulis' "What Is Life?" is not just a book about the definition of life, but a celebration of its diversity and interconnectedness. Through engaging prose and stunning visuals, she guides the reader on a journey through the history of life on Earth, highlighting the often overlooked role of symbiosis in evolution.

Here's a breakdown of the book's key arguments and themes:

1. Challenging the Status Quo:

  • Margulis critiques the prevailing Darwinian view of evolution as solely driven by random mutation and competition.
  • She argues that symbiosis, the mutually beneficial merging of different organisms, has been equally crucial in shaping life's complexity.

2. The Endosymbiotic Theory:

  • The book champions Margulis' groundbreaking endosymbiotic theory, which explains the origin of complex, eukaryotic cells.
  • This theory posits that mitochondria (responsible for energy production) and chloroplasts (responsible for photosynthesis) were once free-living bacteria that merged with other cells, forming a mutually beneficial relationship.
  • This revolutionary concept, initially met with resistance, is now widely accepted in the scientific community.

3. Life as a Web, Not a Tree:

  • Margulis argues against the traditional "tree of life" model, suggesting instead a more interconnected web-like representation.
  • She emphasizes that horizontal gene transfer (the exchange of genetic material between different organisms) has been a major force in evolution, blurring the lines between individual species.

4. Microbial Domination:

  • The book celebrates the often-invisible world of microorganisms, emphasizing their vital role in shaping the planet and sustaining all life forms.
  • Margulis argues that humans are not the pinnacle of evolution, but rather one branch among many in the vast and interconnected web of life.

5. Gaia Hypothesis:

  • Margulis discusses the Gaia hypothesis, which proposes that Earth's living organisms and their environment are interconnected and regulate each other to maintain conditions suitable for life.
  • While acknowledging the controversy surrounding this theory, she encourages readers to consider the interconnected nature of life and our planet.

Overall, "What Is Life?" is a thought-provoking exploration of life's origins, diversity, and interconnectedness. Margulis challenges readers to move beyond traditional evolutionary paradigms and appreciate the profound role of symbiosis in shaping the living world. Her passionate prose and compelling evidence make this book an engaging read for anyone interested in the wonders of biology and the evolution of life on Earth.