Evidence for evolution and classification — Edexcel GCSE Combined Science
Fossil and stone tool evidence for human evolution, and how genetic analysis led to the three-domain system of classification.
Revision notes
3 short notes, in the order of the specification. Each one in short:
Fossils of early human ancestors show how they changed over time. Ardi, from 4.4 million years ago, could walk upright but could still climb trees. Lucy, from 3.2 million years ago, walked upright on two legs but had a small brain. Fossils from 1.6 million years ago show a larger brain and longer legs.
Stone tools give evidence of how early humans lived, because stone survives for a very long time. The oldest tools are simple stones with a few chips knocked off, while later tools are more complex and specialised, suggesting greater skill and intelligence. Tools are dated from the age of the rock or sediment layer they are found in.
Organisms were traditionally classified into five kingdoms: animals, plants, fungi, protists and prokaryotes. Improved genetic analysis showed that the prokaryotes are not all closely related, so a system of three domains was introduced above the kingdoms. The three domains are Archaea, Bacteria and Eukarya, which includes all organisms with a nucleus.
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Quick check questions
Which is older, Ardi or Lucy?
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Ardi (4.4 million years ago; Lucy is 3.2 million years ago).
How are stone tools dated from their environment?
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By finding the age of the rock layer, or materials found with them, in which they were buried.
Name the five kingdoms.
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Animals, plants, fungi, protists and prokaryotes.
What are the three domains?
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Archaea, Bacteria and Eukarya.
Frequently asked questions
What fossil evidence is there for human evolution?
Fossils show a gradual change from ape-like ancestors to modern humans. Ardi, from 4.4 million years ago, walked upright but could climb trees. Lucy, from 3.2 million years ago, walked upright with more human-like feet. Fossils from 1.6 million years ago show a larger brain and longer legs. Upright walking came first.
Why was the three-domain system introduced?
The three-domain system was introduced because improved genetic analysis showed that the prokaryotes are not all closely related. Comparing genetic material revealed differences that observing structure could not. So the prokaryotes were split into two domains, Archaea and Bacteria, with all organisms that have a nucleus in a third domain, Eukarya.
What do stone tools tell us about human evolution?
Stone tools show that early humans became more skilful over time. The oldest tools are very simple, with a few chips knocked off to make a sharp edge, while later tools are more carefully shaped and specialised for different jobs. This suggests greater skill and intelligence, which fits with fossil evidence of larger brains.
Why is the fossil record incomplete?
The fossil record is incomplete because most dead organisms decay before they can fossilise, so fossils are rare, and many of the fossils that are found are incomplete. This is why scientists sometimes disagree about human evolution, and why new fossil discoveries can change ideas about how early human ancestors changed.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026