The oldest tools in chipped stone testify to the repeated invention of stone tools

A new archaeological site discovered by an international and local team of scientists working in Ethiopia shows that the production of stone tools has its origins more than 2.58 million years ago. Previously, the oldest evidence of systematic production and use of stone tools was 2.58 to 2.55 million years ago.

Analysis by researchers of early Stone Age sites, published this week in the Proceedings of the National Academy of Sciencessuggests that stone tools may have been invented many times in many ways before becoming an essential part of the human lineage.

The excavation site, known as Bokol Dora 1 or BD 1, is close to the discovery in 2013 of the oldest fossil attributed to our genus Homo, discovered in Ledi-Geraru in the Afar region of north-east of Ethiopia. The fossil, a jawbone, is about 2.78 million years old, about 200 000 years before the oldest crumbled stone tools. The Ledi-Geraru team has been working for five years to determine if there is a link between the origins of our genus and the origins of the systematic manufacture of stone tools.

Significant progress in this research was discovered when geologist Christopher Campisano of Arizona State University saw sharp-edged stone tools emerging from sediments on a steep, eroded slope.

"At first we found several artefacts on the surface, but we did not know what sediments they came from," says Campisano. "But when I peeked over the edge of a small cliff, I saw rocks coming out of the mudstone face." I climbed up the bottom with my hammer and I found two beautiful stone tools that were starting to degrade. "

It took several years to manually search for meters of sediment before uncovering an archaeological layer of animal bones and hundreds of small pieces of chipped stone representing the earliest evidence of our direct ancestors who made and used knives in stone. The site records a wealth of information on how and when humans started using stone tools.

The preservation of artifacts comes from the fact that they were buried near a water source.

"By examining the sediments under the microscope, we found that the site was exposed for only a very short time.These tools were dropped by the first humans at the edge of a water source, and then quickly buried. This is how Vera Aldeias, renowned geoarchaeologist, of the Interdisciplinary Center for Archeology and Behavioral Change at the University of Algarve, Portugal, stayed.

Kaye Reed, who studies the ecology of the site, is leading the Ledi-Geraru research project and is associated with the Institute of Research on the Human Origins of the University of L & # 39; 39, Arizona State, alongside Campisano, and notes that the animals discovered with these tools were similar to those found a few years ago. kilometers further along with the oldest Homo fossils.

"The first humans who made these stone tools lived in a habitat totally different from that of" Lucy, "said Reed. "Lucy" is the nickname of an ancient species of hominin known as Australopithecus afarensis, which was discovered at the Hadar site in Ethiopia, about 45 km southwest. from the new BD 1 site. "The habitat, which was formerly comprised of shrubs and riparian forests, has been transformed into open meadows with few trees.Even fossil giraffes were eating trees. ;grass!"

In addition to dating the volcanic ash several meters below the site, project geologists analyzed the magnetic signature of the site sediments. During the Earth's history, its magnetic polarity is inverted at identifiable intervals. Other previous archaeological sites, close to the age of BD 1, are found in "inverted" polarity sediments. The BD 1 site is in sediments of "normal" polarity. The reversal from "normal" to "reversed" occurred about 2.58 million years ago, geologists knew that BD 1 was older than all known sites so far .

The recent discovery in Kenya of ancient percussion or percussion tools by means of stone tools dating back 3.3 million years, termed "Lomekwian", and bones dismembered in Ethiopia bears witness to the deep history of our ancestors who made and used tools. However, recent discoveries of tools made by chimpanzees and monkeys have put into question the ideas of "technological monkey" of human origin.

Archaeologists working on the BD 1 site were wondering how their new discovery of stone tools fit into this increasingly complex picture. They discovered that not only were these new tools the oldest artifacts ever attributed to "Oldowan", a technology that takes its name from the discoveries of the Olduvai Gorge in Tanzania, but that was also distinguished from the tools made by the chimpanzees, monkeys or even by older human ancestors. .

"We expected to see an indication of a Lomekwian evolution to these early Oldowan tools.However, when we looked closely at the models, there was very little connection with what the Lomekwian was doing. We know of older archaeological sites or with tools made by modern primates, "said Will Archer of the Max Planck Institute of Evolutionary Anthropology in Leipzig and University of Cape Town.

The main differences seem to be the possibility for our ancestors to systematically shred the smaller sharp-edged tools of the larger stone nodules. Chimpanzees and monkeys typically use tools for percussion activities to hammer and break foods such as nuts and seafood, which seems to have been the case with Lomekwian's 3.3 million-dollar tools. # 39; years.

Something changed 2.6 million years ago and our ancestors became more precise and more adept at hitting the edge of the stones to make tools. BD 1 artifacts capture this change.

It seems that this change in tool making occurred around the same time that the teeth of our ancestors began to change. This can be seen in Ledi-Geraru's Homo jaw. When our ancestors began to process food before eating using stone tools, we began to notice a reduction in the size of their teeth. Our technology and our biology were intimately linked, even 2.6 million years ago.

The lack of clear links with the earlier technology of stone tools suggests that the use of tools has been invented many times in the past.

David Braun, an archaeologist at George Washington University and lead author of the paper, said: "Since primate species around the world regularly use stone hammers to search for new resources, it seems very likely that many ancestors humans have found new ways to use stone artifacts to extract resources from their environment If our hypothesis is correct, we expect to find a form of continuity in the form of artifacts after 2.6 million. years, but not before this period. "

There are 2.6 million years ago, there seems to be a long term investment in the use of tools as part of the human condition.

The continuation of the field investigations in the Ledi-Geraru project area already provides a better understanding of the behavior patterns of our oldest ancestors. New sites have already been found and the Ledi-Geraru team will begin excavations this year.

###

This research was funded by the National Science Foundation of the United States and the John Templeton Foundation.

This research, "The oldest known Oldowan artifacts at> 2.58 Ma in Ledi-Geraru, Ethiopia, highlights the initial technological diversity", is published in the Proceedings of the National Academy of Sciences.