Leaky caves help chronicle human evolution
© Ali Majdfar/Getty
Rainwater dripping into caves millions of years ago has helped create the first regional timeline of fossils in the Cradle of Humankind.
Caves in South Africa have produced an abundance of fossils of our ancestors, but the age of these fossils is debated, making it tricky to fit them into human evolutionary history.
A team that included researchers from the University of Cape Town used uranium–lead analysis to date flowstones across eight caves in the ‘cradle’. These layers of calcium carbonate, now sandwiched between fossil-rich sediments, formed from rainwater seeping through the rocks and dripping onto the cave floor. The flowstone ages represent six short — and evidently very soggy — intervals between 3.2 and 1.3 million years ago, and the fossils accumulated during the much drier phases in between.
Although gaps in the fossil record remain, flowstones provide useful insights into local climate variability in prehistoric Africa.
- Nature 565, 226–229 (2019). doi: 10.1038/s41586-018-0711-0