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CENTRAL LIBRARY · PERMANENT FEATURE

Earth & Humanity: A Long Journey

A planet takes shape. Life persists. People change the world.

Walk through deep time in seven chapters. Follow rocks, fossils, tools and writing—and ask how we know.

Frontispiece: AI-generated artwork inspired by fossils, not a photograph of a real specimen.
  • Seven chapters
  • An exhibit about timescales
  • Sources within every chapter

Begin with any chapter. Each offers a route back and a detour to another part of the library.

OBSERVATION ROOM 01 · CHANGE THE SCALE

Where does human time fit?

Fit Earth’s history into one width, and the markers for humans and writing crowd near the right edge. Change the time window and compare the spacing.

Within each window, distance is proportional to time. The four windows are viewing choices, not four official starting dates. The size of a dot does not represent a duration or an uncertainty range.

Start with Earth’s history in one width.

Earth’s timescale

Time across this width
4.54 billion years
One percent of the width is
45.4 million years
Markers and dates
4.54 billion years ago2.27 billion years agoPresent
  1. Earth’s estimated ageAbout 4.54 billion years ago
  2. Life evidence in the Dresser FormationAbout 3.48 billion years ago
  3. The base of the CambrianAbout 538.8 million years ago (±0.6 million)
  4. The end-Cretaceous mass extinctionAbout 66 million years ago
  5. The timespan of Homo sapiensFrom about 300,000 years ago
  6. Early written records at UrukAround 3200 BCE (roughly 5,200 years ago)
  7. The building of the Old Bess engine1777 (249 years before 2026)

All seven selected markers fit in this window.

Enlarge a more recent part of Earth’s history.

Look across 600 million

Time across this width
600 million years
One percent of the width is
6 million years
Markers and dates
600 million years ago300 million years agoPresent
  1. The base of the CambrianAbout 538.8 million years ago (±0.6 million)
  2. The end-Cretaceous mass extinctionAbout 66 million years ago
  3. The timespan of Homo sapiensFrom about 300,000 years ago
  4. Early written records at UrukAround 3200 BCE (roughly 5,200 years ago)
  5. The building of the Old Bess engine1777 (249 years before 2026)

Markers older than this window 2

Markers outside the window are not moved to an edge. Choose a longer window to see them.

Change the scale as you enter the human chapters.

Look across 300,000

Time across this width
300,000 years
One percent of the width is
3,000 years
Markers and dates
300,000 years ago150,000 years agoPresent
  1. The timespan of Homo sapiensFrom about 300,000 years ago
  2. Early written records at UrukAround 3200 BCE (roughly 5,200 years ago)
  3. The building of the Old Bess engine1777 (249 years before 2026)

Markers older than this window 4

Markers outside the window are not moved to an edge. Choose a longer window to see them.

Look more closely at changes in life and record-keeping.

Look across 12,000

Time across this width
12,000 years
One percent of the width is
120 years
Markers and dates
12,000 years ago6,000 years agoPresent
  1. Early written records at UrukAround 3200 BCE (roughly 5,200 years ago)
  2. The building of the Old Bess engine1777 (249 years before 2026)

Markers older than this window 5

Markers outside the window are not moved to an edge. Choose a longer window to see them.

A date for what, exactly?

An estimated age, preserved evidence, a geological boundary, a regional record: identifying the kind of marker helps show what a timeline can tell us.

Dates, qualifications and sources for all seven markers

Positions use a display model with 2026 as the present. Geological and prehistoric ages are approximate. Around 3200 BCE is rounded to about 5,200 years ago; 1777 is 2026−1777 = 249 years ago. These are not unconverted radiocarbon BP dates, whose reference year is 1950.

  1. 01
    Estimated age

    Earth’s estimated age

    About 4.54 billion years ago

    A representative estimate used to place Earth’s formation. The dot does not mean the planet was completed at one instant.

    U.S. Geological Survey · Powell Expedition—Geologic Time. Then and Now.

  2. 02
    Evidence preserved in rock

    Life evidence in the Dresser Formation

    About 3.48 billion years ago

    Researchers examine layered rock structures as evidence of biological activity. This dates preserved evidence; it does not establish the moment life began.

    Natural History Museum, London · The oldest evidence of life on Earth could help us discover ancient life on Mars

  3. 03
    A geological boundary

    The base of the Cambrian

    About 538.8 million years ago (±0.6 million)

    The numerical age listed by the ICS for a boundary defined in a reference rock section. It is not a date on which all animals appeared.

    International Commission on Stratigraphy · Global Boundary Stratotype Sections and Points — Fortunian

  4. 04
    An event in the geological record

    The end-Cretaceous mass extinction

    About 66 million years ago

    A time when many groups, including non-avian dinosaurs, disappeared. Extinction was not a planned stage on a path toward humans.

    Smithsonian National Museum of Natural History · Extinction Over Time

  5. 05
    A timespan inferred from evidence

    The timespan of Homo sapiens

    From about 300,000 years ago

    The approximate beginning of our species’ timespan in the Smithsonian account. It does not mark one first person or one precisely located birthplace.

    Smithsonian Human Origins Program · Homo sapiens

  6. 06
    An example from one region

    Early written records at Uruk

    Around 3200 BCE (roughly 5,200 years ago)

    A regional example of early writing, rounded to about 5,200 years ago for this display. Writing did not begin everywhere in the same year.

    The Metropolitan Museum of Art · The Origins of Writing

  7. 07
    The year one machine was built

    The building of the Old Bess engine

    1777 (249 years before 2026)

    One concrete example of Boulton and Watt’s steam engines. Its construction year is not a simultaneous worldwide starting date for industrialization.

    Science Museum Group · Climate and the collection

Marker sources checked: November 6, 2026

SEVEN CHAPTERS · BEGIN WITH A QUESTION

Seven doors into a long journey.

Read in sequence to connect the questions across time, or explore whichever chapter interests you now.

  1. 01

    A planet and its oceans

    How did the planet beneath us form?

    Use meteorites, rocks and the Moon to investigate Earth’s age and the story of its water.

    Read this chapter 8 min read
  2. 02

    Life and its environment

    What can preserve evidence of life?

    Tiny cells leave large questions. Separate evidence of past life from the mystery of its origin.

    Read this chapter 9 min read
  3. 03

    Diversification and extinction

    How did the living world change?

    Follow changing bodies, feeding relationships and habitats through fossils, branching lineages and extinctions.

    Read this chapter 9 min read
  4. 04

    Human origins and journeys

    Where did we come from?

    Bring fossils, tools and genetic evidence together to explore human movements and encounters.

    Read this chapter 9 min read
  5. 05

    Food and changing ways of life

    What changes when people grow their food?

    Gathering, hunting, tending and growing: explore different combinations, choices and costs.

    Read this chapter 8 min read
  6. 06

    Cities and writing

    How can many people keep a record?

    Explore cities, writing and states across regions, asking how people organized life and kept records.

    Read this chapter 8 min read
  7. 07

    A connected world

    How do distant events reshape everyday life?

    Follow trade, knowledge and energy, alongside coercion, unequal gains and environmental change.

    Read this chapter 8 min read

OBSERVATION ROOM 02 · FOLLOW THE EVIDENCE

From what survives to the time it reveals.

Different clues reveal different parts of the past. Compare what each can tell us—and what remains uncertain—as you read.

01—03

Rocks and fossils

Ask what survived and in which layer. Read age measurements alongside interpretations of the traces.

Go to the related chapter
04—05

Tools and genetic evidence

Objects, inherited information and places of encounter provide different views of human history.

Go to the related chapter
06—07

Records and traces of everyday life

Ask who recorded something and why. Set written accounts beside evidence from homes and food.

Go to the related chapter

BACK INTO THE LIBRARY · FOLLOW ANOTHER QUESTION

There is another good question beyond this journey.

Return to familiar tools and conventions with a wider view of their history. The rest of the library remains yours to explore.