Describe the evidence for human evolution, based on fossils, including: a…

The idea

Fossils give direct physical evidence about how human ancestors changed over millions of years. Ardi (Ardipithecus ramidus), dated to about 4.4 million years ago, shows a mix of ape-like and human-like features: a small brain, long arms and grasping big toe suited to climbing, but a pelvis and leg structure indicating upright walking. Lucy (Australopithecus afarensis), about 3.2 million years ago, had a larger brain than Ardi, fully upright posture and arched feet, showing committed bipedalism. Richard Leakey's discoveries of fossils around 1.6 million years ago (Homo erectus/ergaster) show a much larger brain, longer legs and more modern body proportions, with evidence of tool use. Comparing these fossils in age order reveals trends: increasing brain size, decreasing jaw and tooth size, and increasingly efficient upright walking.

What earns the marks

• Ardi is dated to about 4.4 million years ago and shows a mosaic of climbing features (long arms, grasping toe) and upright-walking features (pelvis shape).
• Lucy is dated to about 3.2 million years ago and shows more committed bipedalism with arched feet and a slightly larger brain than Ardi.
• Richard Leakey's fossils from about 1.6 million years ago show a larger brain, longer legs and more modern body proportions than earlier hominins.
• Comparing fossils in age order reveals trends of increasing brain size, reduced jaw and tooth size, and more efficient upright walking.
• Fossils are dated by the rock strata in which they are found, giving a relative and (with radiometric methods) absolute age.
• The fossil evidence supports the idea that humans evolved from earlier ape-like ancestors over millions of years.

Common mistakes and how to put them right

• Thinking Ardi is fully modern human.

  Put it right: Ardi shows a mix of ape-like climbing features and some upright-walking features.

• Confusing the dates: correction — Ardi is about 4.4 million years ago, Lucy about 3.2 million, and Leakey's fossils about 1.6 million years ago.

• Assuming a bigger brain came first.

  Put it right: The trend is increasing brain size over time, with the earliest fossils having the smallest brains.

• Treating the fossils as unrelated.

  Put it right: They are compared as a sequence showing gradual change.

Exam tips

• Learn the three dates and match each to its key features.
• When asked for trends, state the direction of change (brain size increases, jaw size decreases).
• Link each fossil to the evidence it provides for upright walking or brain size rather than just naming it.