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2018-08-28 13:10:39   •   ID: 2020

Lithic Projectile Points: A success Story

Figure 1
Figure 2
This is 7 cm long Ounanian Point, found at Erg Tit in Algeria. Tit today is a small village in the commune of Tamanrasset, in Tamanrasset District. Certainly a successful projectile point from the local Epipaleolithic. More about Ounanian Points-see here: 1541 , and here 1544 .

Lithic projectile points crush, slice and generally disrupt a greater volume of tissue than do wood-tipped missiles (Sisk and Shea 2009, 2011), which made them such a successful innovation since their first appearance during the MSA of South Africa, roughly at 80-70 k.a. BP.

The aim of producing projectile points is the effective hurting and killing of animals and other humans. The depth of penetration into the target is mainly influenced by the mass-velocity relationship, the tip cross-sectional perimeter (TCSP), and the tip angle .

The tip cross-sectional area (TCSA) and the tip cross-sectional perimeter (TCSP) are widely used to gather quantified information about projectile points (definition: see external links).

Both TCSA and TCSP show a direct correlation with the width and thickness of the projectile. TCSA and TCSP do not allow to proof, that a tool was used as projectile, but they allow to suggest what kind of launching system (spear, dart, arrow) fits to the presumed projectile. In this post the discussion is limited to spear throwers propelling a dart and to bow and arrow systems.

From the physical point of view, there are two important factors that influence penetration of a projectile: kinetic energy and linear momentum. Both kinetic energy (K) and linear momentum (P) depend on mass (m) and speed (v).

Kinetic energy is the energy associated with the motion. The kinetic energy of an object is directly proportional to the square of its speed (K = (0,5) x mv2).

Linear momentum is a vector quantity describing that the projectile is holding its trajectory or more correctly describes the targeted amount of mass in motion (P = mv).

Therefore, the velocity of a projectile is an important measure of weapon performance because velocity directly affects a projectile’s range, momentum, and kinetic energy, and thus its impact on the target and killing efficiency.

There is no ideal launching system for all situations-the decision of using a spear thrower or a bow–if you have both – depends on the target pray. Some large game hunting societies preferred the use of a dart propelled by a spear thrower.

“Paleoindians who used the weapon to hunt very large animals, with the intent of penetrating the body and killing with hemorrhaging, would have needed heavy darts to reach adequate levels of kinetic energy and momentum to be lethal. Experiments on elephant carcasses support this “(Whittaker et al. 2017)

Maximal width is one way of approaching past projectile weaponry. There is general agreement, that lethality of projectiles is greatly enhanced by arming them with broad, sharp points.

Point symmetry is an important determinant of flight-path stability and ensures uniform distribution of impact forces on the target (Beckhoff 1966).

Tip angles: In general angles of 30–40° are suggested to be the ideal according ballistic theory.

Tanging: An axial tang may theoretically provide the most stable hafting, but specific arrangements may have compensated for the inherent asymmetry of non-axial points, which are even more common during Prehistory. Because hafting devices have usually not survived in the record-the appearance of such arrangements can only experimentally simulated.

Durability: An important point fur the hunter is the durability of his hunting system. Thin lithic points are easily fractured, therefore a thicker-based, more conical, point is better at resisting compressive forces and thus impact fracture.

Bifacial Points vs. Unifacial Points: Bifacial points allow easier hafting, deeper penetration and a multi-purpose use, e.g. as knifes.

Serration: If used as an arrowhead, serrated projectiles are supposed to cause increased hemorrhage of the prey. This seems reasonable, but to my knowledge this assumption has not been experimentally evaluated till now.