The microbes wonthe most abundant life on Earth

For roughly the first 3 billion years of life on Earth, there were almost only microbes, and bacterial biofilms really do coordinate their colonies with waves of potassium ions. The game's ending “The microbes won” asks: what if life hid in the deep when oxygen arrived, and never grew any animals? A planet-scale microbial mind is fiction.

This page first explains how to unlock the ending, then covers the real history of microbes: the common ancestor, the three domains, the rise of oxygen and endosymbiosis. It then covers the real research behind the novel Solaris.

How to unlock it

• Hint: What if life hid in the deep when oxygen arrived, and never grew any animals...
• Condition: At “Great Oxidation Event”, choose “Hide in the deep”, do not unlock Collagen or Animals, and reach Human origins.
• Note: If “Memory echo” skips straight past these eras, you can turn it down in “Upgrades”.
• Reward: In the next universe, the planet's surface carries a glowing microbial mat.

The ending belongs to the Life category.

The real history of microbes

For roughly the first 3 billion years, life on Earth was almost only microbes. This is the core fact of this ending. During that long time, the following things happened.

• Home of the common ancestor: Working backward from modern genes, the last common ancestor of all life may have lived near deep-sea hydrothermal vents that were hot, oxygen-free and rich in hydrogen (Weiss et al., Nature Microbiology, 2016).
• Vent ecosystems: Ecosystems that do not depend on sunlight exist around deep-sea hydrothermal vents, giving the origin of life a new candidate site (Corliss et al., Science, 1979).
• Stromatolites: Rocks in Greenland may preserve microbial structures 3.7 billion years old, though this interpretation is still disputed (Nutman et al., Nature, 2016).
• A third kind of life: Comparing ribosomal RNA showed that "bacteria" are really two very different kinds of life, and archaea became a separate branch (Woese and Fox, PNAS, 1977).
• The three-domain system: The tree of life was redrawn into three great domains: Bacteria, Archaea and Eukarya (Woese, Kandler and Wheelis, PNAS, 1990).
• Asgard archaea: Lokiarchaeota found in deep-sea sediment carry many genes that were thought to exist only in eukaryotes (Spang et al., Nature, 2015).

When oxygen arrived

Oxygen in the atmosphere did not arrive all at once. It rose over a long and repeated process (Lyons, Reinhard and Planavsky, Nature, 2014). One of the choices at “Great Oxidation Event” in the game is “Hide in the deep”.

Endosymbiosis and more complex cells

Mitochondria and chloroplasts were once independent bacteria that were swallowed and became part of the cell. This theory was rejected by more than a dozen journals at the time (Margulis, published as Sagan, Journal of Theoretical Biology, 1967). Fossils of an ancient red alga show that sexual reproduction and multicellular life are at least 1 billion years old (Butterfield, Paleobiology, 2000). About 700 million years ago, Earth may have been almost completely covered in ice (Hoffman et al., Science, 1998). As for genetic material, DNA is a double helix, and its base pairing suggests how genetic information can be copied (Watson and Crick, Nature, 1953).

These are all related real studies for this ending. They describe the history of microbes. They cannot prove that microbes could rule an Earth without animals.

A related novel

Stanisław Lem's Solaris (1961) is about scientists studying a planet covered by an ocean. The ocean may be one giant mind. It does not respond to any language, but it turns each person's deepest memories into physical beings. Its scientific background is this: the Gaia hypothesis and the ionic signals of biofilms are real research, while an ocean covering a whole planet being one mind is fiction.

Game lore, not real

A planet-scale microbial mind is fiction. Real biofilms do coordinate their colonies with waves of potassium ions, but that is coordination inside a colony, not consciousness.

Want to read the originals? Search these titles

• Weiss et al. (2016): "The physiology and habitat of the last universal common ancestor"
• Corliss et al. (1979): "Submarine thermal springs on the Galápagos Rift"
• Woese and Fox (1977): "Phylogenetic structure of the prokaryotic domain: The primary kingdoms"
• Woese et al. (1990): "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya"
• Lyons et al. (2014): "The rise of oxygen in Earth's early ocean and atmosphere"
• Sagan (1967): "On the origin of mitosing cells"
• Hoffman et al. (1998): "A Neoproterozoic snowball Earth"