The tools, whose makers may or may not have been some sort of human ancestor, push the known date of such tools back by 700,000 years; they also may challenge the notion that our own most direct ancestors were the first to bang two rocks together to create a new technology.
The discovery is the first evidence that an even earlier group of proto-humans may have had the thinking abilities needed to figure out how to make sharp-edged tools.
Jenkins said he was also initially skeptical of the find, commenting "it would have been a hard sell" from many other researchers.
Jenkins, who three years ago reported discovery of 14,000-year-old evidence of human DNA in a cave in Oregon, said he was concerned that settling or rodents had mixed up the specimens in Texas.
The find is unprecedented for archaeological studies in India, said archaeologist Michael Petraglia of the University of Oxford, England, who was not part of the research team.
Lepre said a layer of volcanic ash below the tool site set a “floor” on the site’s age: It matched ash elsewhere that had been dated to about 3.3 million years ago, based on the ratio of argon isotopes in the material.
Researchers discovered more than 3,500 quartzite tools of the distinct Acheulian design used by the earliest humans in Africa starting more than 1.5 million years ago.
They dated the tools to at least 1.07 million years old and some possibly 1.51 million years old.
The tools ”shed light on an unexpected and previously unknown period of hominin behavior and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone,” said lead author Sonia Harmand, of the Turkana Basin Institute at Stony Brook University and the UniversiteÌ Paris Ouest Nanterre.
Hominins are a group of species that includes modern humans, – were the first to craft such stone tools.“We essentially have a magnetic tape recorder that records the magnetic field … By tracing the variations in the polarity of the samples, they dated the site to 3.33 million to 3.11 million years.