Ed Yong in The Atlantic:
Last Thursday, the world said hello to Homo naledi, a new species of ancient human discovered in South Africa’s Rising Star cave. As I reported at the time, scientists extracted 1,550 fossil fragments from the cave, which were then assembled into at least 15 individual skeletons—one of the richest hauls of hominid fossils ever uncovered.
But one significant problem clouded the excitement over the discovery: The team doesn’t know how old the fossils are. And without that age, it’s hard to know howHomo naledi fits into the story of human evolution, or how to interpret its apparent habit of deliberately burying its own kind. Everyone from professional paleontologists to interested members of the public raised the same question: Why hadn’t the team dated the fossils yet?
The simple answer is: Because dating fossils is really difficult. Scientific papers and news reports about new fossils so regularly come with estimates of age that it’s easy forget how hard-won such data can be. I asked John Hawks, a biologist at the University of Wisconsin and one of the heads of the Rising Star expedition, to talk me through the various available methods—and why they have been difficult to apply to the latest finds.