Darwin, Wallace and the pentadactyl limb

Charles Darwin and Alfred Russel Wallace both came up with the idea of evolution by natural selection. The pentadactyl limb is one clue that very different animals share a common ancestor.

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Darwin and Wallace

Darwin sailed on HMS Beagle from 1831 to 1836. He studied animals and fossils, including finches and tortoises on the Galápagos Islands, and spent over 20 years developing his theory.
Wallace collected species in South East Asia and reached the same idea. In 1858 he sent his ideas to Darwin, and their work was presented together that year.
Darwin published On the Origin of Species in 1859.

The pentadactyl limb

Mammals, birds, reptiles and amphibians have limbs with the same basic pattern of bones: one upper bone, two lower bones, small wrist bones and five digits (penta = five, dactyl = finger).
The limbs do very different jobs: a human arm grasps, a bat's wing flies, a whale's flipper swims and a horse's leg runs.
The shared pattern suggests these animals evolved from a common ancestor, with natural selection adapting the limb to each way of life.

Impact on modern biology

Evolution explains how all organisms are related, which underpins classification (now based on DNA as well as features).
It explains antibiotic resistance and why we must use antibiotics carefully.
When Darwin published, his ideas were controversial: they challenged religious beliefs that species were created as they are, and he could not explain how characteristics were inherited.
Worked example

A bat's wing and a whale's flipper look very different. Explain why scientists think bats and whales share a common ancestor.

  1. Both limbs contain the same basic pattern of bones: the pentadactyl limb.
  2. Building the same pattern by chance in unrelated animals is very unlikely.
  3. So they probably inherited it from a common ancestor, then natural selection adapted it for flying or swimming.

Answer: Both have a pentadactyl limb with the same bone pattern, so they are likely to have inherited it from a common ancestor.

Key idea

Darwin (HMS Beagle, Galápagos) and Wallace (South East Asia) both proposed natural selection; Darwin published On the Origin of Species in 1859. The pentadactyl limb, with the same bone pattern used for different jobs, is evidence of a common ancestor.

Key words
Evolution
The change in the inherited characteristics of a population over time, through natural selection.
Natural selection
Individuals with alleles that make them better adapted are more likely to survive and reproduce, so those alleles become more common.
DNA
Deoxyribonucleic acid: a double helix of two strands of nucleotides that carries the genetic code. Bases pair A with T and C with G.
Antibiotic
A medicine that kills bacteria or stops them growing. Antibiotics do not work on viruses.

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  1. Who proposed the theory of evolution by natural selection with Wallace in 1858?

    1. Gregor Mendel
    2. Charles Darwin
    3. Louis Pasteur
    4. Carl Linnaeus
    Show the answer

    Answer: Charles Darwin

    Darwin and Wallace presented their papers together.

  2. Darwin was born in 1809 and published On the Origin of Species in 1859. How old was he when it was published?

    Show the answer

    Answer: 50 years

    1859 − 1809 = 50 years.

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Sources and references

Checked by the GCSE-ready editorial team, 16 October 2026. Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.

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