Hi Fernando
,
these are definately arrow heads. Many African arrows are made in 4 parts, the fletchings, the main shaft to which a thinner shaft is attached, it is this thinner shaft that the arrow head is fixed. When an animal or human is struck with an arrow, the 'instinct' is to remove it quickly, 4 legged animals will try to dislodge the arrow by rubbing against trees or rocks often the thin shaft breaks leaving the arrow head still embedded in the wound.(this is the reason for the thinner, weaker section.)
Nearly all African arrow heads are dipped or wiped in poison. Unlike most other 'hunting' arrows which are much larger and are used to kill the animal by hitting main arteries or vunerable areas. African's rely on the animal being poisoned, larger animals may take some time to die,(the amount of toxin to 'body weight' ratio) and the tribesman can spend a whole day tracking the 'wounded' animal until it finally dies or is too weak to escape.
African bows tend not to have a high 'draw weight' (the amount of force required to draw the bow) this means they are unable to propel heavy broadheaded arrows with any real speed or penetrative 'power'.
Whether this is due to the qualities of the wood available (in Africa) to make bows or due to the terrain etc that mean't that poison arrows were preferred....I do not know.
Regards David