An article by Veronique Greenwood covers the discovery of feathers on a North American dinosaur: “Paleontologists Uncover the First Feathered Dinosaur Fossils in the Americas”. Dinosaurs are remote from hominins, but there is one aspect of the story to which I wanted to draw attention:
The finds had implications beyond the obvious. Ornithomimids were first unearthed more than 100 years ago, but paleontologists only learned about the existence of dino feathers 15 or so years ago. And the fact that no one had ever looked for feathered dinosaurs in river sandstone before got the researchers thinking: "What about fossils that were collected 10, 20, 30, 50, 100 years ago?" Therrien says. "If paleontologists had known it was possible to preserve impressions of soft tissue in sandstone, well, maybe these other specimens were covered with feathers, and they were just destroyed during preparation."
Our methods of recovery and preparation of fossils may, in some cases, be destroying evidence of soft tissue or non-bony structures. The preservation of such structures is idiosyncratic and rare, and so not readily predicted in any particular fossil context.
Archaeology has gone through similar revolutions in the past. Archaeologists used to discard sediment after it was sifted; later they began to employ flotation of the material in water, which in some cases allowed organic remains to be separated and identified. Calculus was once scraped off teeth to make them easier to study; now we know that the calculus can preserve phytoliths and starch grains that provide strong evidence of diet.
It’s not obvious how fossil preparation and recovery might be altered, but clearly with the Malapa site, excavation and preparation team is planning with extreme care for exactly this kind of reason. If paleontologists are finding dinosaur feathers in sandstone, any context with articulated hominin bones needs to be considered with extreme care.