World's Oldest Stone Tools Predate Humans

The oldest handmade stone tools discovered yet predate any known humans and may have been wielded by an as-yetunknown species.
The 3.3-million-year-old stone artifacts are the first direct evidence that early human ancestors may have possessed the mental abilities needed to figure out how to make razor-sharp stone tools. This has led to a re-think on the kind of environmental and evolutionary pressures that drove the emergence of toolmaking.
Chimpanzees and monkeys are known to use stones as tools, picking up rocks to hammer open nuts and solve other problems. However, until now, only members of the human lineage — the genus Homo, which includes the modern human species Homo sapiens and extinct humans such as Homo erectus — were thought capable of making stone tools.
Ancient stone artifacts from East Africa were first uncovered at Olduvai Gorge in Tanzania in the mid-20th century. Those stone tools were later associated with fossils of the ancient human species Homo habilis, discovered in the 1960s.
It was thought that the earliest stone tools were made by the first members of Homo. The success of this species was thought to be because they were smart enough to build tools to make their lives easier. The tools could be used for hunting, or stones could be struck against one another to make fire. Whatever the application, it was considered that such tool-making was special to Homo.
However, there were hints of primitive tool use before Homo habilis. In 2009, researchers at Dikika, Ethiopia, dug up animal bones nearly 3.4 million years old that had slashes and other cut marks, evidence that someone used stones to trim flesh from bone and perhaps crush bones to get at the marrow inside. This is the earliest evidence of meat and marrow consumption by hominins — all the species leading to and including the human lineage after the split from the ancestors of chimpanzees. No tools were found at that site, so it was unclear whether the marks were made with handmade tools or just naturally sharp rocks.
Now, scientists report stone artifacts that date back long before any known human fossils. Until now, the earliest known tools were about 2.8 million years old. The artifacts recently discovered are 3.3 million years old and are by far the oldest handmade stone tools yet discovered — the previous record-holders, known as Oldowan stone tools, were about 2.6 million years old.
It remains unknown what species made these stone tools. They could have been created by an as-yet-unknown extinct human species, or by Australopithecus, which is currently the leading contender for the ancestor of the human lineage, or by Kenyanthropus, a 3.3-million-year-old skull of which was discovered in 1999 about a kilometer from the newfound tools. It remains uncertain exactly how Kenyanthropus relates to either Homo or Australopithecus.
The stone tools were discovered in the desert badlands of northwestern Kenya, where the arid, rocky terrain resembles a New Mexican landscape.  The artifacts were found next to Lake Turkana in 2011 almost by accident. Excavations at the site, named Lomekwi 3, have uncovered 149 "Lomekwian" stone artifacts linked with toolmaking.
The researchers tried using stones to knock off and shape so-called flakes or blades — a process known as knapping — to better understand how these Lomekwian stone artifacts might have been made. They concluded the techniques used may represent a stage between the pounding used by earlier hominins and the knapping of later toolmakers.
Analysis of carbon isotopes in the soil and animal fossils at the site allowed the scientists to reconstruct what the vegetation there used to be like. This led to another surprise — back then, the area was a partially wooded, shrubby environment. Earlier, scientists thought that sophisticated toolmaking came in response to a change in climate that led to shrinking forests and the spread of savannah grasslands. Stone blades likely helped ancient humans get food by helping them cut meat off the carcasses of animals, given how there was then less food such as fruit to be found in the forest. However, these findings suggest that Lomekwian stone tools may have been used for breaking open nuts or tubers, bashing open dead logs to get at insects inside, or maybe something not yet thought of.
The Lomekwi 3 evidence suggests that important evolutionary changes that would later be really important for Homo to survive on the savannah were actually evolving beforehand, in a still-wooded environment.
"The capabilities of our ancestors and the environmental forces leading to early stone technology are a great scientific mystery," Richard Potts, director of the Human Origins Program at the Smithsonian's National Museum of Natural History, who was not involved in the research, said in a statement.
This discovery also has implications for understanding the evolution of the human brain, researchers say. Toolmaking required a level of dexterity and grip that suggests that changes in the brain and spinal tract needed for such activity could have evolved before 3.3 million years ago.
The scientists are now looking at the surfaces and edges of the tools under microscopes and with laser scans to try to reconstruct how they were used, "and also
studying the sediment in which they were found to search for trace elements or residues of any possible plant or animal tissues that could be left on them after
use.
Adapted from the article by Charles Q. Choi in Live Science