Humans are Earth's dominant species. They are a race of bipedal beings. Very few humans have dragon companions. The majority of humans that appear in How to Train Your Dragon are Vikings, though not all. Some other groups include the Northern Wanderers, the Inuit, and the Sami.
According to Viking legend, a Viking known as Great Hairybottom lost his boot in the bogs of the Barbaric Archipelago and declared that as long his bog remains there, there will always be Vikings in the Archipelago. 
Later (it is unknown how much later) the human race was at war dragonkind, who were being lead by a great Seadragonus Giganticus Maximus known as Merciless. The war was ended by Hiccup Horrendous Haddock I, who became the first King of the Wilderwest. Hiccup the First was told the secret of the Dragon Jewel in exchange for putting a mark upon his forehead. The Kingdom of the Wilderwest was place of equality between human and dragon even though each new king treated dragons worse than the last. This culminated in the reign of Grimbeard the Ghastly who enslaved both humans and dragons to build the city on Tomorrow.   
Around 300 years prior to the events of How to Train Your Dragon, a tribe arrived on the Isle of Berk. The Vikings were almost immediately bedeviled by dragons. The Vikings decided to fight back, and a full out war started, that lasted for generations. 
- ↑ How to Twist a Dragon's Tale (Book 5), Cressida Cowell. 2007.
- ↑ How to Break a Dragon's Heart (Book 8), Cressida Cowell. 2009.
- ↑ How to Steal a Dragon's Sword (Book 9), Cressida Cowell. 2011.
- ↑ How to Betray a Dragon's Hero (Book 11), Cressida Cowell. 2013.
- ↑ How to Train Your Dragon: Behind the Scenes