Tools, paints and other artifacts excavated from an ancient rock-shelter in northern Australia are giving new glimpses into early life Down Under. The first humans may have arrived on the continent 65,000 years ago — 5,000 years earlier than previously thought — and they were sophisticated craftspeople, researchers report July 19 in Nature.
Archaeologists unearthed three distinct layers of artifacts at Madjedbebe, Australia’s oldest known site of human habitation, during digs in 2012 and 2015. The oldest, deepest layer contained more than 10,000 relics of human handiwork. This cache included the world’s oldest polished ax heads, Australia’s oldest seed-grinding and pigment-processing tools, stone points that may have been spearheads, as well as hearths and other remnants of human activity.
“When people think about our ancient ancestors, they either tend to have a view that our ancestors must have been primitive, less culturally diverse, or they take the view that our ancestors were probably extraordinarily culturally impressive,” says Peter Hiscock, an archaeologist at the University of Sydney who was not involved in the study. “This indicates the latter view. The moment people get to Australia, they’re doing all this really smart stuff.” They were probably building fires to light nighttime activities, grinding seeds for food and using ochre paints to decorate cave walls or their own bodies, Hiscock says.
Previous estimates of the earliest human habitation of Australia — between 47,000 and 60,000 years ago — came from artifacts found at Madjedbebe in 1989. But archaeologists doubted those results because there were no detailed descriptions of the artifacts and it was unclear whether the artifacts were the same age as the surrounding sediment, says study coauthor Zenobia Jacobs, an archaeologist at the University of Wollongong in Australia.
Jacobs and colleagues estimated the ages of the newly uncovered artifacts by more precisely locating the artifacts underground and applying a method called optically stimulated luminescence dating, which reveals the last time a mineral grain was exposed to sunlight, to the sediment where the artifacts were found. Along with radiocarbon dating on charcoal remains from human-made fires, these analyses yielded a much more precise estimate for the age of sediments surrounding artifacts at various depths. The tests indicated that the deepest layer of artifacts — between about 2.15 and 2.6 meters below the surface — ranged in age from about 53,000 to 65,000 years.
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To say that humans first set foot in Australia exactly 65,000 years ago may be “a somewhat optimistic interpretation of the data,” Hiscock says. That’s because items buried in sand are liable to shift around a little. He suggests a more conservative estimate of human arrival between 55,000 and 60,000 years ago. Still, Hiscock says, that narrowed range is a major improvement over the wide, uncertain time span that archaeologists were working with before.
These new dates may provide insight into when humans migrated out of Africa (SN: 12/24/16, p. 25). That in turn could help determine when humans interbred with archaic hominids on other continents — such as Neandertals in Europe and Denisovans in Asia — whose genes linger in the DNA of some modern people (SN: 6/13/15, p. 11).