BiologyICSE Class 10 · Chapter 14

Human Evolution ICSE Class 10: Lamarck, Darwin and Our Ancestors

Updated 14 October 2026 · Fact-checked

Evolution is the gradual change of living things over many generations. Lamarck proposed that characters acquired by use and disuse are inherited; Darwin explained evolution by natural selection, survival of the fittest, as in the peppered moth. Human ancestors from Australopithecus to modern man show increasing brain size, upright posture and smaller canines.

What Human Evolution is about

Living things today are descended, with change, from earlier forms. Evolution explains how. Two classic theories try to explain the mechanism: Lamarck's inheritance of acquired characters and Darwin's natural selection. Humans, too, evolved through a series of ancestors.

The CISCE 2027 syllabus covers: Lamarck's theory of inheritance of acquired characteristics, with reference to use of organs (neck and forelimbs of the giraffe) and disuse of organs (vestigial organs in humans: wisdom teeth, vermiform appendix, pinnae); Darwin's theory of natural selection, survival of the fittest, with the example of the peppered moth; and a brief idea of human ancestors: Australopithecus, Homo habilis, Homo erectus, Neanderthals, Cro-Magnon and Homo sapiens sapiens (modern man), compared for bipedalism, cranial capacity, size of canine teeth, forehead and brow ridges, chin, body hair, and height and posture.

Weightage: CISCE publishes no chapter or unit weightage for ICSE Biology. Human Evolution is in the 5. Human Evolution part of the 2027 syllabus and can be asked in both Section A and Section B of the 80-mark paper.Source: CISCE ICSE Biology (Science Paper 3) syllabus, examination year 2027

Key concepts

Lamarck's theory: use and disuse

Lamarck's theory of inheritance of acquired characters has two ideas:

1. Use and disuse: organs that are used often become larger and stronger; organs not used become smaller and may disappear.
2. Inheritance of acquired characters: such changes, gained during an organism's life, are passed on to the offspring.

Use (giraffe): ancestral giraffes are imagined to have had short necks. Stretching to reach leaves high on trees lengthened their necks and forelimbs a little; this was inherited, and over generations the neck became very long.

Disuse (vestigial organs): organs no longer used shrank over generations.

Criticism: experiments show that acquired characters are not inherited. For example, when the tails of mice were cut off generation after generation, the young were still born with tails. Changes to body cells do not alter the genes in the gametes.

Worked example

Explain the long neck of the giraffe according to Lamarck.

Try it first, then show the solutionSolution

Ancestral giraffes stretched their necks and forelimbs to reach high leaves (use).
The slightly longer neck acquired in life was passed on to offspring.
Repeated over many generations, the neck became long.

Answer: Use of the neck plus inheritance of the acquired change.

Vestigial organs

Vestigial organs are organs that are reduced and non-functional (or nearly so) in an organism, but were well developed and functional in its ancestors or are functional in related animals.

In humans:

Wisdom teeth (third molars): in the mouth; often do not erupt properly, as human jaws became smaller with a softer diet.
Vermiform appendix: a small tube at the start of the large intestine; functional in plant-eating mammals for digesting cellulose.
Muscles of the pinna: most humans cannot move their ears, unlike many mammals.

Vestigial organs are evidence that humans evolved from ancestors in which these organs were useful. They are not simply 'useless parts'.

Worked example

What are vestigial organs? Give one example from the human mouth.

Try it first, then show the solutionSolution

Reduced, non-functional organs that were functional in ancestors.
In the mouth: wisdom teeth.

Answer: As above; wisdom teeth.

Darwin's theory of natural selection

Darwin's theory rests on these observations and conclusions:

1. Over-production: organisms produce far more offspring than can survive.
2. Struggle for existence: offspring compete for food, space and mates, and face predators and disease.
3. Variation: no two individuals are exactly alike; many variations are inherited.
4. Survival of the fittest (natural selection): individuals with useful variations survive and reproduce more; those less suited die out.
5. Inheritance: useful variations are passed on and accumulate over generations.
6. Origin of species: over a very long time, accumulated variations give rise to new species.

For the giraffe, Darwin would say: giraffes varied in neck length; those with longer necks reached more food in times of shortage, survived and bred, passing on long necks.

Worked example

Explain the long neck of the giraffe according to Darwin.

Try it first, then show the solutionSolution

Giraffes naturally varied in neck length.
When food was scarce, those with longer necks reached more leaves and survived.
They passed on the inherited variation; over generations long necks became common.

Answer: Natural selection of an existing, inherited variation.

Peppered moth: natural selection in action

The peppered moth (Biston betularia) in England exists in a light (speckled) form and a dark (melanic) form.

Before industrialisation, tree trunks were pale, covered with lichens. Light moths were camouflaged; dark moths were easily seen and eaten by birds. Light moths were common.
After industrialisation, soot killed the lichens and darkened the trunks. Now dark moths were camouflaged and light ones were eaten. The dark form became common: this change is called industrial melanism.
When pollution was later reduced and trunks became lighter again, the light form increased once more.

The environment (birds as predators) selected whichever colour was better camouflaged: survival of the fittest.

Worked example

In which organism was industrial melanism observed, and what selected the dark form?

Try it first, then show the solutionSolution

The peppered moth, Biston betularia.
Birds ate the moths that stood out against the soot-darkened trunks, so dark moths survived and bred.

Answer: Peppered moth; predation by birds (natural selection).

Human ancestors compared

Order (oldest first): Australopithecus → Homo habilis → Homo erectus → Neanderthals → Cro-Magnon → Homo sapiens sapiens. (Cranial capacities are approximate.)

Ancestor	Bipedalism / posture	Cranial capacity	Canines	Forehead, brow ridges	Chin	Body hair	Height
Australopithecus	bipedal, but posture not fully erect	about 450-500 cc	fairly large	low forehead; heavy brow ridges	absent	abundant	short (about 1-1.4 m)
Homo habilis ('handy man'; made stone tools)	bipedal	about 650-800 cc	smaller	low forehead; brow ridges	absent	abundant	short
Homo erectus (upright man; used fire)	fully erect	about 900-1100 cc	reduced	low, sloping forehead; heavy brow ridges	absent	less	taller (about 1.5-1.8 m)
Neanderthals	erect, stocky build	about 1450 cc	small	sloping forehead; heavy brow ridges	weak, receding	less	short and sturdy
Cro-Magnon (cave paintings)	fully erect	about 1600-1650 cc	small	high, vertical forehead; small brow ridges	prominent chin	little	tall (about 1.8 m)
Homo sapiens sapiens (modern man)	fully erect	about 1350 cc	small	high forehead; brow ridges reduced	prominent chin	very little	tall

Overall trends: fully upright bipedal walking; increase in cranial capacity (brain size); smaller canines (cooked, softer food); higher forehead and smaller brow ridges; development of a chin; loss of body hair; increase in height and an erect posture.

Worked example

Give two characteristic features of Cro-Magnon man.

Try it first, then show the solutionSolution

Prominent chin and high, vertical forehead with small brow ridges.
Large cranial capacity (about 1600-1650 cc), tall and fully erect (also made cave paintings).

Answer: Prominent chin; large cranial capacity (or tall, erect, high forehead).

Human Evolution in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Lamarck tested

Suppose a bodybuilder with very large muscles from years of training hopes his newborn son will inherit his strong arms.

Would Lamarck agree? What does modern understanding say?

Try it first, then show the solutionSolution

Lamarck: muscles enlarged by use are acquired characters and would be inherited.
But acquired changes in body cells do not change the genes in sperms.
So the son will not inherit the trained muscles; he inherits only his father's genes.

Answer: Lamarck would agree, but acquired characters are not inherited.

Memory hook: Gym muscles stay in the gym, not in the genes.

Natural selection today

Suppose a farmer sprays the same pesticide every season, and after some years the insects are hardly affected by it.

Explain this using Darwin's theory.

Try it first, then show the solutionSolution

Insects vary; a few happened to be resistant to the pesticide.
Spraying killed the non-resistant ones; resistant insects survived and reproduced.
Over generations, the resistant variation became common.

Answer: Natural selection of resistant variants.

Memory hook: The spray selects the survivors.

Peppered moth

Suppose a nature club studies moths on dark, soot-covered trees near an old factory and on pale, lichen-covered trees in a distant forest.

Predict which colour of peppered moth would be more common in each place and explain.

Try it first, then show the solutionSolution

Near the factory, dark moths are camouflaged on dark trunks; birds eat the visible light moths.
In the forest, light moths are camouflaged on pale lichens; birds eat dark moths.
So dark moths are common near the factory, light ones in the forest.

Answer: Dark near the factory; light in the clean forest.

Memory hook: The moth that matches the bark survives.

Topics in this chapter

Human Evolution: key facts

Sequence of human ancestors: $Australopithecus \to H. habilis \to H. erectus \to Neanderthal \to Cro-Magnon \to H. sapiens sapiens$; Oldest first.
Darwin's chain: $over-production \to struggle \to variation \to survival of the fittest \to new species$; Natural selection.
Lamarck's chain: $use/disuse \to acquired change \to inherited (claimed)$; Not supported by experiments.
Trends in human evolution: $brain ↑, canines ↓, brow ridges ↓, chin ↑, body hair ↓, posture erect$; Seven features in the syllabus.

Human Evolution: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

Peppered moths on tree bark

Picture-based question on natural selection.

Draw

Two tree trunks side by side: one pale with lichens, one dark with soot.
A light and a dark moth on each trunk.
A bird near the conspicuous moth on each trunk.

Label

light (speckled) form
dark (melanic) form
lichen-covered bark
soot-covered bark
predatory bird

Watch out: Show the camouflaged moth hard to see on each trunk.

How the board asks Human Evolution

The question patterns to expect, and the method that works for each.

Question type	How it is asked	Method
Compare ancestors	Differentiate Australopithecus and modern man on body hair, chin or cranial capacity; features of Cro-Magnon.	Give specific features (abundant vs very little body hair; prominent chin), not vague words.
Sequence	Arrange ancestors in order of evolution beginning with an underlined one.	Learn the six in order; Homo erectus comes before Neanderthal and Cro-Magnon.
Lamarck vs Darwin	Explain the giraffe's neck by each theory; the mice tail experiment.	Lamarck: use + acquired inheritance; Darwin: existing variation + selection.
Vestigial organs	Define; give an example from the mouth, ear or intestine.	Reduced, non-functional now, functional in ancestors; answer from the part named.
Peppered moth	MCQ: industrial melanism observed in; explain the change in moth populations.	Background colour + bird predation = selection.

Tricks to remember Human Evolution

Short memory aids. Say each one aloud once, then use it on a question the same day.

A Handy Erect Neighbour Cro-ssed to Sapiens
Australopithecus, Habilis, Erectus, Neanderthal, Cro-Magnon, Sapiens.
Use it when: Order of ancestors.
Lamarck = Lifetime changes
Lamarck thought changes made in a Lifetime are passed on; Darwin said nature Decides which inborn variations survive.
Use it when: Comparing the theories.
W-A-P vestigial
Wisdom teeth, Appendix, Pinna muscles.
Use it when: Vestigial organs in humans.
Cro-Magnon's chin
Cro-Magnon was the first with a Chin to be proud of.
Use it when: Features of Cro-Magnon.

Human Evolution: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Example 1: Industrial melanism · 1 mark · MCQBoard level

In industrial areas of England, the dark form of the peppered moth became common because:
(a) soot darkened the wings of light moths during their lives
(b) birds more easily spotted and ate light moths on soot-darkened bark
(c) dark moths laid more eggs in polluted air
(d) the moths needed dark wings to absorb more heat

Try it first, then show the solutionSolution

(a) is a Lamarckian idea: an acquired change is not inherited. (c) and (d) are not the cause recorded.
Dark moths already existed; on soot-covered trunks they were camouflaged while light ones were eaten by birds, so the dark form was selected (natural selection).

Answer: (b)

Example 2: Mice tails · 1 mark · Assertion-reasonHarder board level

Assertion (A): Mice whose tails are cut for several generations still produce young with tails.
Reason (R): Acquired characters are inherited.
(a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
(c) (A) is true and (R) is false.
(d) (A) is false and (R) is true.

Try it first, then show the solutionSolution

(A) is true; (R) is false. The experiment disproves inheritance of acquired characters.

Answer: (c)

Example 3: Vestigial organs · 2 marks · Short answerBoard level

Define vestigial organs and give two examples in humans.

Try it first, then show the solutionSolution

Reduced, non-functional organs that were functional in ancestors.
Vermiform appendix; wisdom teeth (or pinna muscles).

Answer: As above.

Example 4: Australopithecus vs modern man · 3 marks · Short answerHarder board level

A museum places an Australopithecus model beside a model of modern man. Write one contrasting point for each of: (a) body hair, (b) cranial capacity, (c) chin.

Try it first, then show the solutionSolution

(a) Australopithecus: abundant body hair; modern man: very little.
(b) About 450-500 cc versus about 1350 cc.
(c) No chin versus a prominent chin.

Answer: As above.

Example 5: Darwin's postulates · 3 marks · Short answerBoard level

State the main points of Darwin's theory of natural selection.

Try it first, then show the solutionSolution

Over-production of offspring; struggle for existence.
Variation among individuals, many inherited.
Survival of the fittest; useful variations inherited and accumulate, giving new species.

Answer: As above.

Example 6: Sequence · 1 mark · Very short answerHarder board level

Arrange in order of evolution, beginning with Homo habilis: Cro-Magnon, Homo erectus, Homo sapiens sapiens, Homo habilis, Neanderthal.

Try it first, then show the solutionSolution

Habilis → erectus → Neanderthal → Cro-Magnon → sapiens sapiens.

Answer: Homo habilis → Homo erectus → Neanderthal → Cro-Magnon → Homo sapiens sapiens.

Example 7: Giraffe two ways · 3 marks · Short answerHarder board level

Compare how Lamarck and Darwin explained the long neck of the giraffe.

Try it first, then show the solutionSolution

Lamarck: necks lengthened by stretching (use) during life, and the acquired length was inherited.
Darwin: giraffes already varied in neck length; long-necked ones survived food shortages and bred more.
Difference: Lamarck's change is acquired; Darwin's is an inherited variation selected by nature.

Answer: As above.

Example 8: HOTS: canines and diet · 3 marks · Short answerHOTS / competency

Suggest why canine teeth became smaller during human evolution, linking it to two other changes in the ancestors.

Try it first, then show the solutionSolution

Use of tools (Homo habilis) and fire (Homo erectus) meant food was cut and cooked, so large canines were less needed.
Smaller jaws and teeth accompanied the larger braincase and higher forehead.
This also fits wisdom teeth becoming vestigial in a smaller jaw.

Answer: Tools and cooking reduced the need for large canines; jaws became smaller as the brain enlarged.

Case-study practice (Section B style)

Read the situation, then answer every part. In the board paper this is a 5-mark question split into 2 + 1 + 2 marks.

Skull comparisons

Suppose a museum displays three skull casts: Skull 1 with heavy brow ridges, a sloping forehead, no chin and a cranial capacity of about 1000 cc; Skull 2 with a high forehead, prominent chin and about 1650 cc; Skull 3 with a very low forehead, no chin and about 480 cc.

(i) · 2 marks
Identify each skull from the syllabus list of ancestors.
Answer
Answer: Skull 1: Homo erectus; Skull 2: Cro-Magnon; Skull 3: Australopithecus.
(ii) · 1 mark
Arrange them from oldest to most recent.
Answer
Answer: Skull 3 → Skull 1 → Skull 2.
(iii) · 2 marks
State two trends shown by the skulls.
Answer
Answer: Increasing cranial capacity; reduction of brow ridges with a higher forehead (and development of the chin).

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Wisdom teeth often fail to come out properly. Explain why they are called vestigial organs and how their reduction is linked to a change in diet. (2 marks) (2 marks)

Step	Marks
Vestigial organs are reduced and non-functional now but were well developed and functional in ancestors; wisdom teeth were useful third molars in ancestors	1
With softer, cooked food the jaws became smaller, so these teeth are no longer needed and often lack space to erupt	1

Explain industrial melanism in peppered moths. (3 marks) (3 marks)

Step	Marks
Before industrialisation, light moths camouflaged on lichen-covered trunks; dark moths eaten by birds	1
Soot darkened trunks; dark moths camouflaged and light ones eaten	1
Dark form became common: natural selection (survival of the fittest)	1

Where students lose marks in Human Evolution

The slips examiners see most often, and what to write instead.

Mistake: Wrong organism for industrial melanism
CISCE examiners' comments, 2024: candidates chose house flies or mice instead of the peppered moth; in 2025 some wrote 'moth' or 'paper moth' instead of peppered moth (Biston betularia).
Wrong working
Industrial melanism: house fly.
Right working
Peppered moth, Biston betularia.
Do this: Write the full name.
Usually costs: 1 mark.
Mistake: Vague comparison of body hair
CISCE examiners' comments, 2024: differentiating Australopithecus and modern man on body hair, candidates wrote 'long hair, short hair, facial hair'.
Wrong working
Australopithecus had long hair.
Right working
Australopithecus: abundant body hair; modern man: very little body hair.
Do this: Compare amount of body hair.
Usually costs: 1 mark.
Mistake: Vestigial = useless; wrong example
CISCE examiners' comments, 2025: candidates called vestigial organs 'useless body parts', wrote 'teeth' instead of wisdom teeth, or ignored 'in the mouth' and gave the pinna or appendix.
Wrong working
Vestigial organs are useless parts; example: molar teeth.
Right working
Reduced organs functional in ancestors; in the mouth: wisdom teeth.
Do this: Mention ancestors; answer for the body part asked.
Usually costs: 1-2 marks.
Mistake: Generic Cro-Magnon features
CISCE examiners' comments, 2025: candidates wrote 'used tools' or 'were intelligent' instead of specific features such as a prominent chin.
Wrong working
Cro-Magnon used tools.
Right working
Prominent chin; high forehead; cranial capacity about 1650 cc; tall and erect.
Do this: Use the syllabus features list.
Usually costs: 1 mark each.
Mistake: Swapping the order of ancestors
CISCE examiners' comments, 2024: in a sequence question, candidates swapped Homo erectus and Cro-Magnon.
Wrong working
Cro-Magnon → Homo erectus
Right working
Homo erectus → Neanderthal → Cro-Magnon
Do this: Learn the six-step order.
Usually costs: 1 mark.

Practice questions on Human Evolution

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which of these is a vestigial organ in humans?
(a) Heart
(b) Vermiform appendix
(c) Kidney
(d) Liver
Hint
Reduced, non-functional.
Answer
(b)
Q2 · 1 mark · MCQBoard level
The human ancestor known for making stone tools is:
(a) Australopithecus
(b) Homo habilis
(c) Cro-Magnon
(d) Neanderthal
Hint
Handy man.
Answer
(b)
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Dark peppered moths became common in industrial areas.
Reason (R): Soot made the moths' wings dark during their lifetime.
(a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
(c) (A) is true and (R) is false.
(d) (A) is false and (R) is true.
Hint
Selected, not painted.
Answer
(c): dark moths already existed and were selected because they were camouflaged.
Q4 · 3 marks · Very short answerBoard level
Name the ancestor: (a) with the smallest cranial capacity; (b) that buried its dead and had a stocky build; (c) that is modern man.
Hint
Oldest; Neanderthal.
Answer
(a) Australopithecus (b) Neanderthal (c) Homo sapiens sapiens
Q5 · 2 marks · Short answerHarder board level
Explain how the muscles of the pinna became vestigial, according to Lamarck.
Hint
Disuse.
Answer
Humans stopped using these muscles to move their ears (disuse), so they became smaller, and the reduced condition was inherited over generations.
Q6 · 2 marks · Short answerHarder board level
State two differences between Lamarckism and Darwinism.
Hint
Acquired vs inherited variation.
Answer
Lamarck: changes are acquired during life by use and disuse; Darwin: variations are inborn and inherited. Lamarck: the environment directly causes change; Darwin: nature selects among existing variations (survival of the fittest).
Q7 · 2 marks · Short answerHarder board level
List four trends in the evolution of humans.
Hint
Brain, teeth, face, hair.
Answer
Increase in cranial capacity; reduction of canines; higher forehead with smaller brow ridges and development of a chin; reduction in body hair (also erect posture and greater height).
Q8 · 2 marks · Short answerHarder board level
Why are wisdom teeth called vestigial, and why do they often cause problems?
Hint
Smaller jaw.
Answer
They were useful to ancestors with larger jaws and coarse diets; in modern humans with smaller jaws they are not needed and often lack space to erupt properly.
Q9 · 3 marks · Short answerHOTS / competency
Bacteria exposed to an antibiotic for many generations become resistant. Explain using Darwin's theory and say why Lamarck's view would not fit.
Hint
Pre-existing resistance.
Answer
Some bacteria already varied in being resistant; the antibiotic killed the rest, and resistant ones multiplied (natural selection). Lamarck would say bacteria became resistant by 'trying', but resistance arises from existing inherited variation, not effort.
Q10 · 3 marks · Case-basedHOTS / competency
A fossil skull shows a cranial capacity of about 1450 cc, heavy brow ridges and a receding chin. Which ancestor is it likely to be, and how does it differ from Cro-Magnon?
Hint
Large brain, primitive face.
Answer
Neanderthal. Cro-Magnon had a prominent chin, a high vertical forehead with small brow ridges, and a slightly larger cranial capacity (about 1650 cc), and was taller.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Scientific name of the peppered moth?Show answer
Biston betularia.
2.Who proposed inheritance of acquired characters?Show answer
Lamarck.
3.Another phrase for natural selection?Show answer
Survival of the fittest.
4.Ancestor known as 'handy man'?Show answer
Homo habilis.
5.First ancestor known to use fire?Show answer
Homo erectus.
6.Ancestor with a prominent chin and about 1650 cc brain?Show answer
Cro-Magnon.
7.Approximate cranial capacity of modern man?Show answer
About 1350 cc.
8.Vestigial organ in the intestine?Show answer
Vermiform appendix.

Best order to study it

Learn Lamarck's theory with the giraffe and vestigial organs, and its criticism.
Learn Darwin's six points and the giraffe explanation.
Learn the peppered moth example.
Learn the six ancestors in order with the seven features.
Practise comparison and sequence questions.

Quick revision checklist

The night before the exam: can you do each of these without looking?

Can you explain the giraffe's neck by Lamarck and by Darwin?
Can you define vestigial organs and give three human examples?
Can you explain industrial melanism?
Can you list the six ancestors in order?
Can you compare any two ancestors on chin, brow ridges, canines, body hair and cranial capacity?

Human Evolution: frequently asked questions

Do I need exact cranial capacities for ICSE 2027?

The syllabus asks for a brief idea of the trend of increasing cranial capacity. Approximate values help in comparisons, but the trend and the relative sizes matter most.

Is Lamarck's theory accepted today?

Not in its original form: acquired characters are not inherited through genes, as experiments such as cutting mice tails showed.

Are other evidences of evolution (fossils, homologous organs) in the 2027 syllabus?

The 2027 syllabus lists the two theories, vestigial organs and the human ancestors; focus on those.

Based on: CISCE ICSE 2027 Biology (Science Paper 3) syllabus; CISCE ICSE 2027 Biology (Science Paper 3) specimen question paper and marking scheme; CISCE Analysis of Pupil Performance, ICSE Biology (Science Paper 3), 2025; CISCE Analysis of Pupil Performance, ICSE Biology (Science Paper 3), 2024