The Savannah Ape hands would retain the simian single crease pattern for some considerable
time but there would be constant selective pressure for increased dexterity and motor
control in holding crude implements and throwing stones or wooden clubs at small
The characteristic oblique three crease palm of modern humans probably evolved through
selection of savannah apes using hand axes. Those apes who could make better hand
axes would have a higher rate of survival, and thus a proportionately greater number
of offspring. Flint is a common rock found in many parts of Africa. Obsidian (a naturally
occurring glass) is associated with areas of volcanism in that area too. These materials
were probably selected by savannah apes for making crude weapons. Both materials
can splinter into shards - leaving sharp edges. The first weapons will have been
naturally occurring pieces of these materials - of a suitable size to hold in the
hand. Only one part of the stone or glass needed a sharp edge and the rest of it
needed to be smooth enough for a reasonably comfortable hold.
To hold a hand axe properly, you need to cup your hand. The more modern hand is more
capable of cupping than the primate hand, which is more effective at folding around
cylindrically shaped objects such as branches.
Primarily these hand axes would be used for hacking carcases into pieces which would
be easier to carry back to the nest area.
Eventually they would discover that hitting one flint against another would knap
off a piece leaving a new sharp edge. Better still - a series of delicate blows to
the edge of the flint would create an extended sharp area around the lower edges.
These crude implements would be capable of sharpening the ends of their digging
sticks - to make a spear which could be thrown at, say, a herd of gazelle at a water
hole. A small herd would present a broad target for such a weapon - even if it were
thrown without much expertise.
The ability to successfully surprise animals at water holes and spear them to death
would be the beginning of a new era of the savannah ape and the beginning of their
domination over all other species.