I Contain Multitudes: The Microbes Within Us and a Grander View of Life Audiobook by Ed Yong

The Origin of Eukaryotic Life

• 💡 Eukaryotes evolved from a merger of a bacterium and an archaean, a pivotal event in life's history.
• 🔑 This union, occurring approximately 2 billion years ago, created a third, more complex domain of life from two simpler ones.

The Role of Symbiosis

• 🔬 The archaean provided the chassis for the eukaryotic cell, while the bacterium transformed into mitochondria.
• ⚡ Mitochondria supplied an extra source of energy, enabling eukaryotic cells to become larger, more complex, and accumulate more genes.

A Unique Evolutionary Event

• 🧠 This merger represents what biochemist Nick Lane calls the "black hole at the heart of biology," explaining the vast complexity gap between eukaryotes and simpler cells.
• ⚠️ The event was breathtakingly improbable and has only occurred successfully once in 4 billion years, never to be duplicated.

Impact on Multicellular Life

• 🌱 This single, improbable union enabled the existence of all plants, animals, and anything visible to the naked eye.
• 🌍 After eukaryotic cells evolved, they began cooperating and clustering, leading to multicellular organisms that host vast microbial communities.

Rethinking Microbial Abundance

• 📊 The widely cited 10:1 ratio of microbial to human cells is an inaccurate estimate, based on a wild guess that became enshrined as fact.
• 🔍 Current estimates suggest a roughly even split, with approximately 30 trillion human cells and 39 trillion microbial cells.
• 🤏 Despite their immense numbers, these microbes collectively weigh only a few pounds and are microscopic, with millions fitting on the head of a pin.