Human ancestors may have already spread to North Africa earlier than expected, according to a discovery of a stone tool

East Africa is the cradle of humanity and the place where our hominin ancestors invented for the first time sophisticated stone tools. This technology, which dates back 2.6 million years later, is thought to have spread to Africa and the rest of the Old World.

But new research, published in Science, has discovered an archaeological site in Algeria containing similar tools that can reach 2.44 million years old. The team, led by archaeologist Mohamed Sahnouni, unearthed stone tools at the Ain Boucher site which, according to their estimates, are between 1.92 and 2.44 million years old. This suggests that human ancestors have spread to the region much earlier than previously thought or that stone tool technology was simultaneously invented by earlier living hominins species. outside of East Africa.

The artefacts belong to the "Oldowan" – the oldest known industry of the stone tool. Rounded river pebbles, used as hammer stones, were used to peel other pebbles, turning them into simple cores. The flakes were then transformed into scrapers and various knives by resharpening their edges. It was essentially a tool kit for the treatment of animal tissues, such as bone marrow, bone and brain tissue, but also plant material. However, we do not know for sure which hominin species created the first Oldowan tools – potentially Australopithecus or Homo Habilis.

The stone tools are very similar to those of the early Oldowan sites in East Africa. The bones on the site even have cutting marks, where a stone tool is dug into the bone during the butcher's shop. Cutting marks may mean that these hominins were actively hunting.

But we had never found Oldowan tools at the earliest in the East African Rift Valley, more than 4,000 kilometers away. We have always assumed that it started about 2.6 million years ago. We should not find him so far from his initial place of residence at this age unless he has forgotten something.

Many archaeologists suspect indeed that there is an invisible ghost somewhere in the machine. Findings from ancient hominids sites in southern Chad suggest that some of our oldest ancestors lived well beyond East Africa. Sites similar to the Oldowan were also discovered outside of Africa, in Georgia, 1.8 million years ago – which seems surprisingly early.

Game changer

The new discovery tells us that our focus on East Africa as the birthplace of the first humans is too narrow – we should be doing what Sahnouni and others have always done and watching elsewhere. The same team recently released results for another Oldowan site in Algeria dating back about 1.75 million years, but finding Oldowan's tools earlier half a million years ago changes the game.

It all depends on the reliability of this date of 2.44 million years. Meeting specialists will scrutinize the details with the utmost care. According to the paper, four different techniques were used. Paleomagnetic dating measures the direction and intensity of the Earth's magnetic field in sediments – it is locked in rocks when they form, which helps tell us how old they are.

The team found that the upper level corresponded to a short period of normal polarity between 1.77 and 1.94 years. Sediments at the lower level were in a long period of reverse, between 1.94 and 2.58 years.

For more accurate dates, the team turned to a dating technique called electron spin resonance dating, which measures the radioactive decay in quartz sand grains. However, they used a less common version of the technique that worked near its upper bound of reliability in this age range. The measurement provided an age of 1.92 m, younger than paleomagnetism suggests.

The relevance of this latter method raises some concerns, but the team has been honest about it. They also compared the dates with the extinction times of the animals on the site, which suggested that the date was not impossible.

To get a better idea of ​​the maximum age of the tools, they used a technique to estimate sedimentation rates – essentially the time it took for the different layers of the site to form. However, you must perform sophisticated statistical work and map them to paleomagnetic results. By extrapolating over time, the team calculated that the actual age of the lower level was 2.44 million years old. I suspect that dating specialists will look at this carefully.

Mystery Hominin?

Now to our ghost. The oldest tools ever discovered outside of Africa are those in Georgia dating back to 1.8 million years ago. There is a small Oldowan – like site in Pakistan dating back to about the same time, and sites richer in kernels and flakes in eastern China, 1.66 million years ago. If the Georgian site represents the first departure from Africa, these first African migrants arrived very quickly in Pakistan and China.

In Georgia, the tools may have been created by the first Homo erectus, which dates back about 1.8 million years. As there is Homo erectus specimen from China dating back 1.6 million years, it's easy to assume that Homo erectus These are probably the species that have spread technology tools around the world – and much faster than expected.

But we can not be sure. And if our ghost was a kind of ancient African hominin anterior to Homo erectus – such as Homo Habilis? The Oldowan may have started more than 2.6 million years ago and was already widespread throughout Africa 2.4 million years ago.

Perhaps our mysterious Hominin started emigrating from Africa 1.8 million years ago and she led her glitter industry to the east. This would certainly give him more time to travel these immense distances. Perhaps Homo erectus they only migrated east to leave Africa later, in the footsteps of an old traveler of whom we know nothing.

So that's a lot, but nobody expected Oldowan tools in Georgia when they were discovered. This has caused a lot of controversy, but most archaeologists are now comfortable with this discovery. Georgian archaeologists have returned, worked more and proved their case. I have no doubt that Sahnouni and his team will do the same.