I ended up spending a day researching early predecessors to the modern mohawk we know and love. That first guy (Clonycavan Man) is based on a mummified corpse found in a peat bog in Ireland. The bog preserved him so well that scientists were able to analyze and deduce all kinds of bizarre stuff about this guy. For instance, based on what was in his stomach, he was murdered (yes, murdered!) during the warm season. He was tortured, possibly as a sacrificial offering to whatever crazy god(s) that were worshipped at the time. Based on his clothes and the fact that he had 'hair gel' IMPORTED FROM FRANCE OR SPAIN, he was most likely a young (twenty something) one-percenter bon vivant. He was fairly short, so he probably styled his hair this way to appear taller.
Oh, and did I mention that his nipples were sliced off??! Yeah, apparently sucking a king's nipples showed subservience back in the good ol' days. He was perhaps a contender to be king, and his killers cut his nipples after sacrificing him in order to prevent him from becoming a king. Also, his skull was cracked open. Seems like overkill to me.
Since the photo available is pretty inhuman looking, I loosely based his look on that of a recreation. Nobody knows what he really looked like, so I didn't stress too much over it.
Supposedly Syrian warriors also wore mohawks (based on some ancient artwork), but for the life of me I could not find any images to support this theory. Therefore, I apologize to my Syrian friends for their exclusion.
The Cossacks had a pretty sweet look going on, but they were also pretty hard to find images of. I based my drawing on a modern Cossack reenacting street musician.
The Mohawk indian tribe that falls under the umbrella of Iroquois is a mohawk sporter we are all familiar with, so I won't get into it. I based my drawing on a painting by Robert Griffing. It's worth noting that the Indian version of the mohawk is actually a square of hair on the back of the head (usually braided, adorned, etc.) rather than a stripe of hair running front to back.
The 101st airborne division of U.S. paratroopers sported mohawks (and face paint) during World War II. It is rumored that they did it because Germans called them 'savages', but it may well have just been a way to appear more intimidating or even just to separate themselves from infantry on the ground. You may remember that Robert De Niro's character, the iconic mohawk wearing Travis Bickle, was a Vietnam veteran. Mohawks made a resurgence among the military in the Vietnam war as well.
I have to thank my old high-school pal (and former mohawk wearer) Chad Wiener for cluing me into MohawksRock.com. This was a fantastic source of inspiration/photo reference for the "mall punk" after poor results from searching Google with keywords like Good Charlotte, Hot Topic, Green Day, AFI, Blink 182, etc. If you want to waste a few hours peeking into the lives of some kids trying way too hard, I strongly recommend MohawksRock.com.