ausjulius
I really can't explain why since you have put holes in my hot and humid theory
. Most of the swords I have from that region of Africa are under 24 inches long the symetrical ones are made more for stabbing rather than hacking. Maybe they preferred spears to swords as their main battle weapon they are easier to produce and do not need to hard be tempered? It could be just a cultural thing or maybe they did not have access to large amonts of good quality Iron ore? All I know is that their weapons were very effective for what they were designed to do. I think if you studied how these tribes fought, battle tactics and such it may shed some light on the subject. From what I can remember Zulus for years fought by having there warriors take turns throwing light weight spears at each other from a distance until Shaka came up with the larger heavier bladed stabbing spears and close quarter combat tactics similar to what the Romans used with their gladius and shields.
Lew