Evolution Timeline Table
From the Origin of Life to the Modern Age. A journey through deep time.
Precambrian Era
Hadean/Archean/Proterozoic Period
The longest span of time (~88% of Earth's history). Origin of single-celled life (prokaryotes), then eukaryotes, and finally multicellular soft-bodied organisms.
Paleozoic Era
Cambrian Period
Rapid diversification of life. Most major animal body plans appeared.
Ordovician Period
Diversification of marine invertebrates. Ended with a mass extinction due to glaciation.
Silurian Period
Life begins to colonize land more extensively. First jawed fish appear.
Devonian Period
Fish diversify (Sharks, Placoderms). Transformations lead to first tetrapods walking on land.
Carboniferous Period
Giant insects and vast swamp forests dominant land. Reptiles evolve amniotic eggs.
Permian Period
Ended with the largest mass extinction in history (96% of marine species lost).
Mesozoic Era
Triassic Period
Life recovers. First dinosaurs and first true mammals appear. Pangaea starts breaking.
Jurassic Period
Dinosaurs dominate land. First birds (Avian dinosaurs) evolve from theropods.
Cretaceous Period
Flowering plants (Angiosperms) appear. Ended by K-Pg Extinction event (Asteroid).
Cenozoic Era
Paleogene Period
Mammals fill ecological niches left by dinosaurs. Whales return to the sea.
Neogene Period
Grasses spread globally. Early human ancestors (Hominins) diverge from apes.
Quaternary Period
Cycles of glaciation. Evolution and dispersal of Homo sapiens.
The Story of Life on Earth
Evolution is the change in the characteristics of biological populations over successive generations. This timeline maps the major milestones that shaped the biodiversity we see today.
How Evolution Works: Natural Selection
Variation
Individuals in a population have different traits (mutations).
Competition
More offspring are produced than can survive. Resources are limited.
Survival
Individuals with advantageous traits survive better ("Fit").
Reproduction
Survivors pass on their "good" traits to the next generation.
Evidence for Evolution
Fossil Record
Fossils show a progression from simple to complex life forms over strata layers.
Genetics (DNA)
All life shares the same genetic code. Humans share ~98% of DNA with chimps.
Biogeography
Distribution of species (like marsupials in Australia) supports tectonic plate movement.
Frequently Asked Questions
What is the Cambrian Explosion?
The Cambrian Explosion (approx. 541 million years ago) was a relatively short evolutionary event during which most major animal body plans appeared, leading to a rapid diversification of life.
How many mass extinctions have occurred?
There have been five major mass extinctions in Earth's history. The largest was the Permian-Triassic extinction ("The Great Dying"), and the most famous is the K-Pg extinction that wiped out the non-avian dinosaurs.
Are birds related to dinosaurs?
Yes. Birds are living dinosaurs. They are descendants of theropod dinosaurs (the same group that includes T-Rex) and are the only dinosaur lineage to survive the K-Pg extinction.
What is the "Age of Mammals"?
The Cenozoic Era (66 MYA to Present) is often called the Age of Mammals because, after the dinosaurs went extinct, mammals radiated to fill the empty ecological niches.
When did humans evolve?
Anatomically modern humans (Homo sapiens) evolved in Africa approximately 200,000 to 300,000 years ago during the Quaternary Period of the Cenozoic Era.
What is the difference between an Era and a Period?
Geological time is divided hierarchically. An Era (e.g., Paleozoic) is a very long division of time that contains smaller subdivisions called Periods (e.g., Cambrian, Ordovician).
What was the "Great Oxidation Event"?
Occurring in the Precambrian Era (Proterozoic), this was when Cyanobacteria produced massive amounts of Oxygen through photosynthesis, permanently changing Earth's atmosphere and allowing for aerobic life.
What is Natural Selection?
Natural Selection is the process where organisms better adapted to their environment tend to survive and produce more offspring. It is the key mechanism of evolution proposed by Charles Darwin.
What is a fossil?
A fossil is the preserved remains or traces of ancient organisms. They provide crucial evidence for how life has changed over millions of years.
Did humans and dinosaurs coexist?
No. Non-avian dinosaurs went extinct 66 million years ago, while early human ancestors didn't appear until millions of years later. We are separated by a vast gap in time.