A variety of things might have caused this ultimately lethal wound, but researchers think the best candidate is a projectile weapon such as the ones crafted by the Homo sapiens of the time.
Churchill and his colleagues examined Shanidar 3, one of nine Neanderthals discovered between 1953 and 1960 in a cave in northeastern Iraq’s Zagros Mountains. The team also ran experiments with a specially calibrated crossbow, which they used to deliver stone-pointed spears with different forces to simulate a thrusting spear and a long-range projectile weapon like a dart. [...]
Then, the researchers compared the wounds created by the different scenarios, finding the thrusting spears did lots of damage, breaking multiple ribs.
“With the projectile weapon, even though it’s traveling faster, it’s a lot lighter and it tends to make distinct cut marks in the bones without injuring surrounding bones. That’s like what we saw in Shanidar 3,” Churchill said.
Neanderthals had spears but only the thrusting varietal, not the throwing ones, so it seems likely that the spear which inflicted the fatal wound was thrown by a modern human.
Modern humans used spear throwers, detachable handles that connected with darts and spears to effectively lengthen a hurler’s arm and give the missiles a power boost.
Shanidar 3 didn’t die immediately. The wound shows evidence of some healing, so he probably died several weeks after from infection.