Figure 1.
Location and stratigraphy of the Gademotta Fm.
(A) A map showing the Gademotta ridge and major archaeological localities: the Gademotta type-site and the Kulkuletti area. Inset map shows the relative location of key later Middle Pleistocene sites in the Ethiopian rift, namely (1) Herto, (2) Gademotta, and (3) Omo Kibish. (B) A revised composite stratigraphic section of the Gademotta Fm. and the placement of major archaeological sites.
Figure 2.
A sample of Gademotta pointed artifacts exhibiting micro- and macrofracture features indicative of projectile weaponry.
(A, B) fracture wings on transverse fractures; (C, D) fracture wings on burin-like fractures; (E) impact fractures on two fracture fronts on the distal portion.
Figure 3.
Box-and-Whisker plots of instantaneous fracture velocities for various impact types.
Comparison established by experimental work using obsidian raw material with a distortional wave velocity (C2) of 3865 m/s [11]. Boxes represent inter-quartile ranges; the horizontal lines inside the boxes represent the median values; the tails represent the non-outlier range.
Table 1.
GDM points with fracture velocity values beyond the range experimentally documented for thrusting spears [11] as well as macrofracture patterns considered DIFs [21]–[23].
Figure 4.
Box-and-Whisker plots of TCSA and TCSP comparisons.
TCSA and TCSP plots of pointed pieces from experimental spear tips [25] (Exprm); Klasies River main site MSA I [32] (KRM); Gademotta (GDM). Solid dots represent outlier values.