Ancient human ancestors known as Homo erectus may have been both intellectually and physically lazy, scientists say — a pair of failings that may have contributed to their extinction about 500,000 years ago.
In a study in the journal PLOS ONE, Ceri Shipton of the Australian National University School of Culture, History and Language was part of a team that excavated a site in central Saudi Arabia, where a number of H.erectus artefacts have been found.
At the time, perhaps a million years ago, the Arabian Peninsula was a vastly different landscape than it is today, with rivers the size of the Tigris and Euphrates flowing eastward toward the Persian Gulf. Shipton’s site lay near the headwaters of one of these rivers, in a region known Saffaqah — now barren desert. “You hardly see any vegetation at all,” he says.
It’s also a fairly flat landscape, he adds, interspersed with long, rocky ridges that rise steeply to heights of about 60 metres. “If you climb to the top, you can see for miles,” he notes. “It’s starkly beautiful.”
But the H.erectus community that lived along the river at the base of one of these ridges didn’t seem interested in climbing them — either for the view or to get the best rocks for making stone tools.
Instead, they appear to have used whatever they could find lying around their camps, even if they were of lower quality.
“At the site we looked at, there was a big, rocky outcrop of quality stone just a short distance away up a small hill,” says Shipton.
“But rather than walk up the hill, they would just use whatever bits had rolled down and were lying at the bottom. When we looked at the outcrop, there were no signs of activity — no artefacts, and no quarrying. They knew it was there, but they seem to have thought, ‘why bother?’”
Not that they were truly lazy. In that wetter era, there were elephants in the Middle East, and these people hunted them. “They found evidence in Israel that they were ganging up on them in coordinated attacks,” Shipton says. And he notes, “the tools they made were particularly well-suited to butchering large animals.”
Then, a few hundred thousand years ago, the climate dried and not only the elephants, but H.erectus, disappeared. “We think climate change is the explanation,” notes Shipton.
But he also thinks that an unadventurous spirit, which he describes as expressing itself as “localised,” “short-term” and “least effort” planning, may have contributed.
The H.erectus communities were culturally very conservative. Five layers of excavation showed no changes in their tools. “The sediment samples showed the environment around them was changing,” says Shipton, “but they were doing the exact same things with their tools.”
Ran Barkai, chair of the Department of Archaeology and Near Eastern Cultures at Tel-Aviv University, Israel, disagrees with the characterisation of H.erectus as lazy.
“Homo erectus is probably our direct ancestor, and should be treated with respect,” he says.
“If Homo erectus were lazy, we, their descendants, would most probably not be here now. Being lazy was not an option in the Stone Age. There was no welfare, no Social Security, and no Wal-Mart.”
In a 2018 paper in the journal Proceedings of the Prehistoric Society, he also noted that evolutionary conservatism isn’t necessarily bad.
“[M]easuring evolutionary success in the survival time of species,” he and colleague Meir Finkel wrote, “the most successful species are the conservative ‘living fossils’ such as the horseshoe crab or Cycas plant, which have not changed morphologically for over 100 million years.”
In this context, he says, H.erectus, which survived and spread across much of Africa, Asia, and Europe for over a million years, was “very, very successful in evolutionary terms”.
Their ultimate disappearance, he suggests, was probably a side effect of their success. “Overhunting of big mammals forced them to hunt smaller animals and thus change biologically and culturally,” he says.
And who did they change into? “Us,” he says.