Human Evolution

Q1 — Sample Band 6 response (7 marks), annotated

Fossil evidence reveals physical anatomy directly. It can show skull shape and cranial capacity (brain size), pelvis structure, femur angle, foramen magnum position, jaw shape and tooth proportions, and the presence or absence of features such as prognathism. Together these allow scientists to infer bipedalism, diet, and to compare morphological change across species over time. [1 — two or more specific features named and explained]

However, fossil evidence is incomplete: not every individual fossilises, preservation is biased towards hard parts, and geological processes can destroy or distort remains. Gaps in the record are therefore expected and do not invalidate conclusions drawn from preserved specimens. [1 — limitation of fossil evidence]

Ancient DNA tests genetic relatedness directly and can reveal interbreeding between lineages. For example, comparison of Neanderthal ancient DNA with modern human genomes showed that modern non-African populations carry approximately 1–4% Neanderthal DNA, demonstrating that interbreeding occurred after early Homo sapiens left Africa. [1 — ancient DNA role + specific example]

Ancient DNA also has limitations: it only survives in some environmental conditions and cannot be extracted from all fossils, particularly older ones or those from warm, humid environments. [1 — limitation of ancient DNA]

Combining both sources produces a stronger reconstruction because they address different questions. Fossils show what organisms looked like and how their anatomy changed over time; ancient DNA shows genetic relationships and gene flow events. When multiple independent lines of evidence — fossils, tools, ancient DNA — point toward the same conclusions, confidence increases significantly. [1 — why combining is stronger]

Overall, neither evidence type alone is sufficient. Fossil evidence without genetic data cannot reveal interbreeding; ancient DNA without fossils cannot show anatomical transitions. The most reliable accounts of human evolution synthesise both. [1 — evaluative judgement]

[1 quality mark — coherent argument with precise lesson terminology]

Q2 — Sample Band 6 response (8 marks), annotated

The “march of progress” display is an oversimplification. The first problem is the assumption that brain enlargement and bipedalism progressed together in lockstep. In fact, Australopithecus afarensis (Lucy) was clearly bipedal — shown by a central foramen magnum, broad pelvis and angled femur — but had a cranial capacity of approximately 450 cc, far smaller than modern humans. Bipedalism appeared first; brain enlargement followed later. This directly contradicts the idea that the entire package of “human” features evolved together. [1 — Lucy / bipedalism before brain enlargement]

Homo naledi further undermines the model. Despite living recently (approximately 335,000–236,000 years ago), it retained a small brain and curved fingers typical of earlier hominins, alongside more modern teeth and foot structure. If evolution were a simple ladder where each later species is uniformly more “advanced”, Homo naledi should not exist in this form. Its mosaic anatomy shows that different traits evolved at different rates in different lineages. [1 — H. naledi mosaic traits explained]

The display also implies each species evolved directly into the next. But multiple Homo species coexisted at various times — different lineages were present simultaneously rather than sequentially replacing each other in a single chain. A branching model captures this: it shows multiple lineages diverging from common ancestors, some going extinct, others persisting, and some interbreeding. [1 — coexistence and branching model]

Representing the species as overlapping branches would be more accurate because it would show that some lineages coexisted rather than appearing one after another, that different lineages can diverge in different directions, and that no single line of ancestry links every species in a simple chain. [1 — branching more accurate + reason]

The “march of progress” is a poor model overall. While it captures the broad fact that bipedalism and brain size increased over evolutionary time, it misrepresents the pace, order and complexity of change. It implies a teleological progression toward modern humans as the “goal”, which is not supported by the evidence. A branching tree with overlapping branches, labelled with specific trait changes, would be more scientifically accurate. [1 — justified conclusion]

[1 quality mark — coherent, well-structured, uses lesson terminology precisely]

Q3 — Sample Band 6 response (6 marks)

The claim is partly defensible but largely flawed. [1 — overall judgement]

What is defensible: It is true that the fossil record is incomplete and that ancient DNA is not available from every fossil. These are genuine limitations: fossilisation is rare, preservation is biased toward hard parts, and DNA degrades over time. Acknowledging these limitations is scientifically appropriate. [1 — concedes defensible element]

What is flawed — “impossible to draw reliable conclusions”: An incomplete record can still be highly informative. The preserved fossils that do exist show consistent patterns — bipedalism appearing before brain enlargement, a general increase in cranial capacity, and the mosaic traits of Homo naledi — all of which fit the predictions of evolutionary theory. Multiple independent lines of evidence (fossils, stone tools, ancient DNA) converge on the same conclusions, strengthening the reconstruction. [1 — refutes “impossible to conclude”]

Flawed — overlooking convergence of evidence: The claim treats completeness as necessary for reliability. It ignores that incomplete evidence is still valid when multiple independent lines agree. Ancient DNA, even if unavailable for all fossils, provides powerful confirmation where it is available; its absence from some specimens does not eliminate the value of the evidence from those where it is present. [1 — convergence of evidence refutes the claim]

Flawed — all or nothing thinking: Science does not require a complete record to draw conclusions; it requires that conclusions are proportionate to the evidence and acknowledged to have uncertainty. The hominid fossil record, while incomplete, is extensive enough to support well-evidenced and carefully qualified conclusions about human evolutionary history. [1 — science works with incomplete evidence]

Defensible reformulation: “The fossil record of human evolution is incomplete and ancient DNA is not available for every fossil, making full certainty impossible. However, the preserved evidence — including transitional morphologies, the chronological pattern of traits in the fossil record, stone tools, and ancient DNA where available — is consistent with a branching pattern of human evolution and supports well-evidenced conclusions about key hominid species and trends. Conclusions should be qualified by the limitations of the evidence, but the overall reconstruction is reliable.” [1 — defensible reformulation]