3.3-million-year-old stone tools overturn archaeological record, predate early humans
Our human ancestors may not have been the first to spearhead new technologies millions of years ago. It would seem other hominins were crafting tools 700,000 years before previously thought. A paper published this week in the journal Nature announces that the oldest stone tools found to date were crafted by proto-humans, marking “a new beginning to the known archaeological record.”
Lead study author Sonia Harmand of the Turkana Basin Institute at Stony Brook University says that 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,” according to science news site Phys.org.
Sammy Lokorodi, a fossil and artifact hunter in Kenya's northwestern desert, led the way to the discovery of 3.3 million-year-old tools. Credit: West Turkana Archaeological Project
Fieldwork in fossil-rich West Turkana, Kenya has revealed primitive stone tools dating to 3.3 million years ago. The stones have clear signs of being intentionally manipulated for crushing or breaking open food, or cutting meat of animal carcasses.
The study article challenges the long-supposed theory that the earliest stone tools were crafted by the genus Homo. Based on dating of the soil layer in which the tools were located, the timeline of hominins using such technology needs to be pushed back by 700,000 years. The Homo genus, modern humanity’s ancestors, only emerged around 2.5 million years ago, and the stone tools date back to 3.3 million years, making the finds very significant.
The Hidden Treasures of Ethiopa’ exhibit at Houston Museum of Natural Science featuring a model of “Lucy”, Australopithecus Afarensis. Some researchers believe it’s possible the Turkana stone tools were made by Australopithecus or a contemporary proto-human species. Jason Kuffer/ Flickr
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The stone tools have clear indications of purposeful rudimentary engineering. Knapping a stone piece by banging two rocks together produces smaller flakes with sharp edges. These sharp objects were useful for cutting meat off bones or working with plants. The rock pieces possess characteristic marks, indicating they’ve been used in crafting, hunting, some sort of processing, or other uses scientist haven’t discovered yet.
The stone tools were precisely dated by analyzing soil layers around the finds. Chris Lepre of Columbia University's Lamont-Doherty Earth Observatory (back to camera). Credit: West Turkana Archaeological Project
Dating the ancient stone tools is done through various soil tests and by comparing it with other finds in situ.
Phys.org reports that “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. To more sharply define the time period of the tools, [Chris Lepre, co-author of the paper and geologist at Lamont-Doherty Earth Observatory and Rutgers University] and Lamont-Doherty colleague Dennis Kent examined magnetic minerals beneath, around and above the spots where the tools were found.
“The Earth's magnetic field periodically reverses itself, and the chronology of those changes is well documented going back millions of years. […] By tracing the variations in the polarity of the samples, they dated the site to 3.33 million to 3.11 million years.”
In addition, human evolutionary scholars have previously thought that the advent of stone tools was linked to, or triggered by, a climate change involving a spread of savannah grasslands, and the subsequent “evolution of large groups of animals that could serve as a source of food for human ancestors,” writes Phys.org. However, animal fossils and carbon isotopes in the soil reveal the area vegetation at the time was already a shrubby, partially forested environment.
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The unique Lake Turkana in Kenya is the world’s largest alkaline lake, as well as the world’s largest permanent desert lake. This archaeologically significant area has offered up fossils of major importance in the study of human origins and evolution.
The landscape of fossil-rich Lake Turkana, Kenya. Wikimedia Commons
Pushing the dating back of these ancient stone tools raises questions about who made the first cognitive leap into intentional engineering and tool making. It also has implications for our understanding of the evolution of the human brain. When and how did the shift come about which synchronized brain changes and hand motor skills required for such behavior? Additional finds may challenge our conventions.
Lepre tells The Guardian , “It just rewrites the book on a lot of things that we thought were true.”
Featured Image: Illustration of the species Homo habilis (genus Homo between 2.1 and 1.5 million years ago) shaping a stone tool by “knapping”. Representational image. Credit: Vassar.edu
By Liz Leafloor