Biology · Year 11 · Module 3 · Lesson 8
HSC Exam Practice
Human Evolution
Short answer
1.Short answer
Explain the difference between saying “humans evolved from chimpanzees” and saying “humans and chimpanzees share a common ancestor.”
Describe three anatomical features that indicate bipedalism in a hominid fossil and explain what each suggests about posture.
Explain the significance of Australopithecus afarensis (Lucy) as evidence against the idea that large brains evolved before bipedalism.
Explain why ancient DNA is a powerful source of evidence about human evolution and identify one limitation of this evidence type.
Account for why Homo naledi is described as having “mosaic traits” and explain why this makes simple linear models of human evolution inadequate.
Data response
2.Data response — hominid cranial capacity and bipedalism timeline
The table below summarises approximate cranial capacity and bipedalism status for key hominid species. Use the data to answer the questions that follow.
| Species | Approx. date | Approx. cranial capacity (cc) | Bipedal? |
|---|---|---|---|
| Australopithecus afarensis | ~3.2 MYA | ~450 | Yes |
| Homo habilis | ~2.4–1.4 MYA | ~600–800 | Yes |
| Homo erectus | ~1.9 MYA–117,000 ya | ~900–1100 | Yes |
| Homo naledi | ~335,000–236,000 ya | ~465–610 | Yes |
| Homo sapiens | ~300,000 ya – present | ~1200–1450 | Yes |
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Describe the general trend in cranial capacity from A. afarensis to H. sapiens, referring to at least two specific values.
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Using the data, explain how Homo naledi disrupts a simple linear model of brain-size increase in human evolution.
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Identify one conclusion about bipedalism that can be drawn from these data, and explain what A. afarensis specifically reveals about the order in which bipedalism and large brains evolved.
Extended response
3.Extended response
Evaluate the claim that the hominid fossil record and ancient DNA evidence together support a branching model of human evolution rather than a simple linear chain. In your response, refer to at least two named hominid species, two types of evidence, and provide a clear evaluative conclusion.
Biology · Year 11 · Module 3 · Lesson 8
Answer Key & Marking Guidelines
Section 1 · Short answer · 2 marks · Band 3
Sample response. “Humans evolved from chimpanzees” incorrectly implies that modern chimpanzees are direct ancestors of humans [1]. “Humans and chimpanzees share a common ancestor” is accurate: both lineages descended from an ancient shared ancestor approximately 6–7 million years ago, and neither evolved from the other. Modern chimpanzees are our closest living relatives, not our ancestors [1].
Section 1 · Short answer · 3 marks · Band 3
Any three of the following, each with explanation: Foramen magnum — a central position indicates the skull balanced over an upright spine [1]; Broader pelvis — needed to support body weight and internal organs during upright locomotion [1]; Inward-angled femur (valgus knee) — allows weight to pass through the knee while walking upright on two legs [1]; Arched foot — provides a rigid lever for forward propulsion in bipedal walking [1].
Section 1 · Short answer · 3 marks · Band 3
Lucy was clearly bipedal (central foramen magnum, broad pelvis, angled femur) [1] but had a cranial capacity of approximately 450 cc — far smaller than the ~1350 cc of modern humans [1]. This directly shows that bipedalism evolved before large brains, contradicting the idea that brain enlargement was the first or primary trend in human evolution [1].
Section 1 · Short answer · 3 marks · Band 4
Ancient DNA is powerful because it can test relatedness directly and reveal interbreeding events between lineages that cannot be inferred from physical appearance alone — for example, it showed that modern non-African populations carry ~1–4% Neanderthal DNA [1+1 for power + example]. One limitation: ancient DNA only survives in some environmental conditions and cannot be extracted from many fossils, especially older or tropically preserved specimens, so it cannot be applied universally across the hominid record [1].
Section 1 · Short answer · 2 marks · Band 4
Homo naledi has a mosaic of features because it combines primitive characteristics (small brain ~465–610 cc, curved fingers typical of earlier hominins) with more modern features (teeth and foot structure), all in a species that lived relatively recently (~335,000–236,000 years ago) [1]. A simple linear model predicts that more recent hominids should be uniformly more modern in all traits, but H. naledi contradicts this, showing that different traits evolved at different rates in different lineages — consistent with a branching, not a linear, model [1].
Section 2 · Data response · 7 marks · Band 4–5
(i) 2 marks. The general trend is an increase in cranial capacity from approximately 450 cc in A. afarensis to 1200–1450 cc in H. sapiens [1], representing a roughly threefold increase across the hominid record, with intermediate species showing intermediate values (e.g. H. habilis at ~600–800 cc, H. erectus at ~900–1100 cc) [1].
(ii) 3 marks. Homo naledi lived approximately 335,000–236,000 years ago but had a cranial capacity of only ~465–610 cc — comparable to A. afarensis (~450 cc) from over 3 million years earlier [1]. This disrupts a simple linear model because that model predicts each later species should have a larger brain than all earlier species [1]. H. naledi shows that a small-brained species coexisted with larger-brained hominids in relatively recent times, indicating that the hominid record is branching rather than a single progressive sequence [1].
(iii) 2 marks. Conclusion: all five species listed were bipedal, indicating that bipedalism evolved early in the hominid lineage and was retained across all major groups [1]. Specifically, A. afarensis (~3.2 MYA) was bipedal while having a cranial capacity of only ~450 cc, showing that bipedalism appeared long before the major increases in brain size seen in later Homo species [1].
Section 3 · Extended response · 7 marks · Band 5–6
Marking criteria (1 mark each):
- Names at least two hominid species and uses them as evidence for branching (e.g. coexistence of H. naledi with larger-brained contemporaries).
- Refers to fossil evidence and what it shows (anatomy, bipedalism, morphological trends).
- Refers to ancient DNA evidence and what it shows (interbreeding, e.g. Neanderthal ancestry).
- Explains why neither evidence type alone is sufficient (fossils cannot show interbreeding; DNA is not available for every fossil).
- Explains the branching model: multiple lineages coexisting, different trait combinations, not a single ladder of progress.
- Reaches an explicit evaluative conclusion that the branching model is better supported than the linear chain model.
- Quality mark: response is coherent, uses precise terminology from the lesson throughout, and the conclusion follows logically from the evidence cited.