Hominin Fossils

Correct in one sense. A. afarensis had an ape-sized brain, a projecting face, and long arms, and no one describes it as human.

The claim being tested is not whether Lucy was human but whether she was bipedal, since that is the trait that separates the hominin line.

The skeletal evidence is specific. The pelvis is short and bowl-shaped rather than tall and flat; the femurs angle inward so the knees sit under the body's centre of mass, which is what allows walking without swaying; and the knee joint has the valgus angle characteristic of habitual bipeds. Chimpanzees have none of these.

The Laetoli footprints independently record a bipedal gait with an arched foot at 3.66 million years.

The cases are real. Piltdown was a deliberate forgery accepted from 1912 to 1953. Nebraska Man was named from a single tooth in 1922 that proved to be a peccary's.

Their history is the relevant part. Piltdown was suspect for decades precisely because it fitted the accumulating evidence badly — it had a large braincase with an ape jaw, and the record was showing the opposite order. It was exposed by fluorine dating applied by scientists.

Nebraska Man was retracted by its own describer, Henry Fairfield Osborn, in 1927, five years after the announcement. It never appeared in a textbook as established, though it did appear in a newspaper illustration.

Java Man was not a fraud. Homo erectus is now represented by hundreds of specimens across Africa and Asia.

The first part is close to correct, and the position has moved toward it. Neanderthals buried their dead, used pigment, made tools and adhesives, and interbred with modern humans — their DNA is present in living people. See Ancient DNA.

The rickets explanation, proposed by Rudolf Virchow in the nineteenth century, does not survive the sample. Rickets is a childhood vitamin D deficiency producing bone deformation, and it does not produce a consistent skull shape, occipital bun, or brow ridge across hundreds of individuals in different regions over 300,000 years.

Genomes settle it. Neanderthals differ consistently from modern humans in ways diet cannot produce, and their lineage separates from ours around 600,000 years ago.

The species boundaries are the artefact here. Palaeontologists divide a continuous record into named species for practical reasons, which creates the appearance of discrete forms.

The disagreement over classification is the evidence against the objection. Homo habilis has been argued into and out of Homo repeatedly; A. sediba and H. naledi both carry mixtures of traits that resist assignment. Specimens that are difficult to classify are what an intermediate looks like.

The trait-by-trait sequence is also clear: bipedalism at about 4 million years, stone tools at 3.3 million, brain expansion beginning around 2 million, modern body proportions at 1.6 million.

Fair for some specimens. Sahelanthropus is known mainly from one distorted cranium, and early reconstructions of several species were revised.

Not all are fragmentary. Turkana Boy is a nearly complete skeleton, Lucy is about 40%, and H. naledi is represented by over 1,500 elements from multiple individuals.

The published record also includes the raw material. Casts are distributed to institutions, CT scans are archived, and reconstructions have been publicly revised when new material contradicted them — which is how the disagreements above became visible.