Love-hungry teenagers and archaeologists agree: dating is hard.
But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.
“Eventually a crystal becomes saturated with trapped charge – all the defects are filled – but this technique is usually capable of going back more than 100,000 years,” Spooner says.
This fits with the 49,000-year-old radiocarbon date, given that it takes a few hundred years before amassed sand is firmly trampled into the floor and no longer exposed to sunlight.
Previous multi-grain OSL dating at a number of ancient sites have suggested humans arrived in Australia well over 50,000 years ago, but Spooner is sceptical of many of these dates.
So along with radiocarbon dating, they use a technique known as optically stimulated luminescence (OSL) dating.
It finds the age of the sediment surrounding artefacts – sediment which may have once been outside sand trampled into caves tens of thousands of years ago – by measuring when it was last exposed to the sun.