Killing and eating people, with a bit of trade on the side

Goblins, giants, and humans have lived alongside each other for tens of thousands of years.  Dealing with each other isn't just something they talk about; it's part of their deep culture, the stories and practices passed on for generations without anyone knowing why.  Whole civilizations have evolved and fallen in this multi-species environment.  These species have learned how to truly coexist: not to live in peace, but to simply survive in the face of such competition.

Humans and Goblins

Humans and goblins are direct competitors.  They both hunt for the same game and live in similar environments.  If they're living near each other, someone's getting hurt.

(New Zealand's All Blacks rugby team)

It starts with threats: humans shout and bare their teeth, the goblins whistle and imitate human voices, both sides continuing until one backs down.  Usually someone does, moving their families to better grounds, away from the threat.  Humans are good at looking scary, so goblins are usually the first to leave.

But if both sides are desperate or angry enough, it escalates.  Goblins steal and eat the humans' dogs, the humans set fire to the forest where the goblins live, the goblins murder some humans, the humans murder some goblins, and eventually only one side is left in the area, chewing on the remains of the other.

(World Rainforest Movement)

Natural boundaries help stabilize the relationship; good rivers make good neighbors.  With hissing goblins on one side and shouting humans on the other, neither side will risk a crossing.

Some areas are only suited well for one or the other.  Humans don't usually live in the deepest forest where goblins like to dwell high in the trees.  Goblins don't often cross expanses of water (since they don't swim well and don't build boats) so islands off shore are usually occupied by humans.

(Steve Rawlings)

Thousands of years of learning have led to some natural aversion.  Goblins don't like dogs.  Even if they don't know why, it still keeps them from danger.  Humans have learned to be wary of noises in the woods.  The sound of a baby crying or someone calling for help is probably a trick, made by creatures that can imitate sounds to lure in prey.

Goblins and Giants

Goblins and giants aren't in quite as direct of competition.  Goblins hunt for fresh meat; giants like theirs a bit old.  Goblins ambush prey in woods where they can hide; giants set their traps in open lanes where animals travel.

Being nomadic, giants tend to have a wider range of people they trade with, making them natural merchants.  Goblins want things they can't make themselves, like ropes, bags, and ornaments, and they can offer dead animals in return.  Trade is common between these two species.

Giantish traps, however, have caused something of an evolutionary arms race.  After all these millenia, goblins have learned two things:

1. Traps are dangerous.
2. Traps may contain food.

Goblins that can steal meat from traps without getting caught themselves are more likely to survive in lean times, so their trap-defeating knowledge is likely to spread.  But giants who construct traps that goblins can't steal from will be more likely to have food for themselves, so their trap-constructing knowledge is likely to spread.

Giants and Humans

Long ago (or so they say) humans used to hunt giants, skinning and eating them.  The giants swore they would get their revenge, but the humans forgot the threats and kept hunting.  Then one day, the surviving giants came down from the hills and wiped out whole tribes of humans, killing until no humans would dare hunt them again.  Now the two peoples live in peace.

Whether the story is true or not, it illustrates an important point: peace is a safe strategy between humans and giants.  If a giant kills a human, the humans could hunt down the giant, but then the giant's descendants might come back decades later to avenge their ancestor.  Humans are good at making strong, temporary teams.  Giants are good at remembering and holding a grudge.

Where are all the men?  (The Godfather)

The safest way is peace with a bit of forgiveness.  Giants and humans both have a healthy respect for each other, tinged with fear.  Humans tell their children stories about the fearsome yet wise people who dwell in the highlands.  Giants tell of the fearsome yet brave people down in the valley.  Both come together to trade.

There's another solution to these interactions: wars of extermination.  In some parts of the North, humans and giants fell into a cycle of vendettas that could only be broken with overwhelming force.  There are isolated pockets of humans in the wilderness who have learned to kill any giants who come near and have done so for generations.  Likewise, there are giants out there who have learned to kill humans who drift into their land.

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Overall, everyone has learned to be a little wary when dealing with people of other species.  After so many long generations side by side, everyone has learned to tread softly but carry a big stick.

Then about a hundred years ago, the elves showed up, with no experience dealing with other intelligent species.