Tribal spears : Taiwan/Philippines/Asia

[yuanzhumin]

Hello,
I have a question about Asian tribal spears.
I have noticed that nearly ALL the spears made by the Taiwanese aboriginal tribes have an iron nail-shaped point socketed at the bottom end of the shaft, opposite to the head :

-Is this a very distinctive element of the Formosan spears or is this something that we can also widely see in the Philippines indigenous spears or among any other asian indigenous tribes spears ?

I have checked around among the other Asian ethnic groups, but most of the time only the heads are pictured or drawn. When the whole shaft is, I didn't notice any nail-shaped point socketed at the bottom end.

I know about the Taiwanese weapons, but not that much about the other ethnic groups in the Asia-Pacific area. What's your opinion ?

You can see on my website two examples of Taiwanese Rukai spears with this iron nail-shaped extremity (www.formosatribal.com - click on Catalogue in the headlines, then go to Rukai).
Thanks
Nicolas