Interesting question. The singing is practically the same for all bands in this genre (called mathcore). Wikipedia lists Post-hardcore, Extreme metal, Crossover-thrash, Progressive metal and Jazz fusion as the stylistic origins, most of which can be traced back further to punk and heavy metal (the two main influences of Napalm death).

The earliest song that is shouted more then sung would probably be "Paranoid" by Black Sabbath (1970):



"If you know your enemies and know yourself, you will not be imperiled in a hundred battles." Sun Tzu