JAVIER TRUEBA / MSF / SCIENCE PHOTO LIBRARY JAVIER TRUEBA / MSF / SCIENCE PHOTO LIBRARY
Excalibur, a biface stone tool found at the Sierra de Atapuerca archaeological site in Spain. Excalibur is thought to have been created by the human ancestor Homo heidelbergensis at least 350,000 years ago. It is made of red quartzite, and it thought to have been created as a ritual axe for use in funeral rites.
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