Human Evolution
ICSE Class 10 · Biology · Chapter 14
What this chapter covers
- What evolution means
- Humans as primates
- Lamarck's theory of inheritance of acquired characteristics
- Use of organs: the neck and forelimbs of the giraffe
- Disuse of organs: vestigial organs in humans
- Why Lamarck's theory was rejected
- Darwin's theory of natural selection
- Adaptation of the peppered moth
- Lamarck and Darwin compared
- Human ancestors
- Trends in human evolution
Key points
- Evolution is the gradual change in the inherited characteristics of populations over many generations, which can lead to new species.
- Human beings are primates; humans and modern apes share an extinct common ancestor.
- Lamarck (1809) proposed the use and disuse of organs and the inheritance of acquired characteristics, using the giraffe's neck and forelimbs as his example.
- Vestigial organs in humans include the wisdom teeth, the vermiform appendix and the muscles of the pinnae.
- Lamarck's theory was rejected because acquired characteristics do not alter the genes of reproductive cells; Weismann's mouse-tail experiment showed this.
- Darwin's theory (1859): overproduction, struggle for existence, variation, survival of the fittest, inheritance of useful variations and origin of new species.
- The peppered moth shows natural selection in action: soot-darkened trees favoured the dark form (industrial melanism), and clean air later favoured the light form again.
- The human ancestors in order: Australopithecus, Homo habilis, Homo erectus, Neanderthals, Cro-Magnon man and Homo sapiens sapiens.
- Through the series, bipedalism became perfected, cranial capacity rose from about 450 cc to about 1400 cc, canines became smaller, the forehead became vertical, brow ridges reduced, a chin developed, body hair reduced, and height and erect posture increased.
Questions answered
Define organic evolution.
Organic evolution is the process by which complex and varied forms of life have developed from earlier, simpler forms through gradual changes over a very long period of time.
What is an acquired characteristic? Give two examples.
An acquired characteristic is a feature developed during an organism's own lifetime through use of organs, habits or surroundings, not inherited from its parents. Examples: a wrestler's strong muscles; a scar from an injury.
State the two main ideas of Lamarck's theory.
(i) Use and disuse of organs: organs used more grow stronger and larger, organs not used shrink and may disappear. (ii) Inheritance of acquired characteristics: changes acquired during life are passed to the offspring.
Name three vestigial organs in human beings and state one reason why each is regarded as vestigial.
Wisdom teeth (often have no room in the shorter jaw and do no useful grinding); vermiform appendix (plays no part in digestion in humans, though large and useful in plant-eaters such as the rabbit); muscles of the pinna (too weak to move the ear, unlike in the dog or cow).
Why was Lamarck's theory rejected? Give one experiment in support of your answer.
Acquired characteristics are not inherited, because they do not change the genes in the reproductive cells. Weismann cut the tails of mice for over twenty generations, but every new generation was born with normal tails.
List the main points of Darwin's theory of natural selection in the correct order.
Overproduction; struggle for existence; variation; survival of the fittest (natural selection); inheritance of useful variations; origin of new species.
Why does the term "fittest" in survival of the fittest not mean "strongest"?
The fittest is the individual best suited to its particular environment and most successful at leaving offspring. A small, well-camouflaged moth can be fitter than a large, conspicuous one.
Explain industrial melanism with reference to the peppered moth.
Before industrialisation, light moths were camouflaged on pale, lichen-covered trunks and dark moths were eaten by birds. Soot blackened the trunks, so dark moths became camouflaged and light moths were eaten. Dark moths survived and bred more, and their proportion rose above 90 per cent. Colour was inherited; the environment selected the better-hidden form.
Past board exam questions
ICSE 2027 sample paper · 1 mark
Who proposed the theory of ‘Natural Selection’?
Show answer
Charles Darwin
ICSE 2027 sample paper · 2 marks
Mention two characteristic features of Australopithecus.
Show answer
Any two: walked erect on two legs (bipedal); small brain (cranial capacity about 500 cc); lack of chin; body covered with hair; ape-like face with projecting jaws.
ICSE 2026 sample paper · 1 mark
Industrial melanism is the phenomenon by which the peppered moth:
- die due to industrial growth.
- in polluted areas, became darker in colour for better camouflage.
- became lighter in colour due to natural selection.
- became resistant to industrial pollution.
Show answer
in polluted areas, became darker in colour for better camouflage.
ICSE 2026 board paper · 1 mark
What is the scientific name of modern man?
Show answer
Homo sapiens sapiens (Homo sapiens).
ICSE 2026 board paper · 2 marks
(a) Who proposed the theory of Natural Selection? (b) Name the organism which was used as an example to explain Industrial Melanism.
Show answer
(a) Charles Darwin (with Alfred Russel Wallace).
(b) The peppered moth (Biston betularia).
ICSE 2026 sample paper · 2 marks
Mention two body features of Australopithecus.
Show answer
Any two:
1. Walked erect on two legs (bipedal); height about 1.2–1.4 m.
2. Small brain, cranial capacity about 500 cc.
3. Prognathous (projecting) face with no chin.
4. Projecting eyebrow ridges.
ICSE 2025 sample paper · 1 mark
While studying the stages in the evolution of man, a well-developed chin is observed in
- Homo habilis
- Homo erectus
- Homo sapiens
- Australopithecus
Show answer
Homo sapiens
ICSE 2025 board paper · 1 mark
A scientist wanted to conduct a genetic experiment on mice. He cut the tails of all the mice and made them reproduce. What will be the phenotype of the offsprings?
- All the offsprings will be tailless.
- There will be a mix of tailed and tailless offsprings.
- All the offsprings will have tails.
- Tail of the offsprings cannot be predicted.
Show answer
All the offsprings will have tails.