In a Creepy Twist, One of The Oldest Tombs in Sweden Is Missing All of Its Skulls

<img width="128" height="52" src="https://www.sciencealert.com/images/2024/02/BuriedSkull.jpg" alt="Buried skull"/>
What happened here?

https://www.sciencealert.com/in-a-creepy-twist-one-of-the-oldest-tombs-in-sweden-is-missing-all-of-its-skulls