HAD to Be Sharp

""God made Arrakis to train the Faithful.""

- The Wisdom of Muad'Dib, Dune

If your means are limited, you have to show resourcefulness. This is especially true if the environment one works and lives within is unforgiving and dangerous. Simply surviving in places like a Death World can make people stronger and tougher, and those who live in such places can be expected to be more than a match for those who don't have to spend every day simply fighting to stay alive. If the world is dangerous enough and generations of people have survived in such a place, natural selection ensures that the toughest and most resourceful will live through, and over time those who live in this environment will change to adapt.

Enter this trope, which deals with people, whether individuals, societies, or entire species, that are meaner, tougher, stronger, and/or smarter than others because their home is the kind of place that breeds out those not fit to survive. Often the cause for a proud warrior race/species. If this is applied to humanity it might imply that Humans Are Warriors. When this is created artificially it is The Spartan Way.

People Who Have To Be Sharp:
 * Barbarian Tribe
 * Disaster Scavengers
 * Father Neptune
 * Intrepid Merchant
 * Mother Russia Makes You Strong
 * Old Soldier
 * Proud Warrior Race
 * Humans Are Warriors
 * Space Cossacks

Reasons Why You Have To Be Sharp:
 * Crapsack World
 * Death World
 * Earth Is a Battlefield
 * Everything Is Trying to Kill You
 * War Is Hell
 * World of Badass

Things To Do When You Are Sharp:
 * Blood Knight
 * Did You Just Punch Out Cthulhu?
 * Glory Seeker
 * Knight Errant
 * Plunder
 * The Quest
 * Take Over the World
 * The Conqueror

Comic Books

 * Scrooge McDuck is made of this trope.

Literature

 * Benefactors by Rudyard Kipling.
 * In the CoDominium universe the second most feared troops in the galaxy (after the Super Soldiers of Sauron) are from Frystaat. A high gravity world with intense heat, blinding sunlight, and lethal wildlife.
 * In Discworld, this trope is used to justify Instant Messenger Pigeon - Ankh Morpork rooftops are full of gargoiles, so the local pigeons have to be smarter than average
 * Dune: Everyone is scared into obedience by the Emperor's Sardaukar, recruited on a prison planet and trained into elite troops. Then they are thrown against Fremen, natives of Arrakis who had just enough industry to stay alive. The results are highly demoralizing. Fremen, upon being informed whom they faced, comment along the line of "ah, we wondered why these were challenging..."
 * The War Against the Chtorr. Chtorran fauna and flora is naturally more aggressive and adaptive than its human equivalent; scientists speculate that Chtorr is a Death World where all life has to be either aggressive or lunch.
 * Aiel in The Wheel of Time are a desert-dwelling Proud Warrior Race known and feared everywhere for being extreme badasses: in the years prior to the start of the books, a coalition of all the western countries was needed to stop them, and actually failed (the Aiel returned to the desert only when they did what they had set out to). It is also implied that this was their destiny, and that they had been sent to live in the desert, 3000 years before, precisely so that they would become a reliable and powerful army for the Dragon Reborn when the time came.

Music

 * One of series from Russian bard Alkor has both the original song and responce (she had a good tradition to accept responces as "part N") giving different variants of this - [Military] Technology ("If not weaponry improvement, we won't leave the caves at all") and Agricultural Technology ("If the mammoths were fatter, we won't leave the caves at all").

Oral Tradition

 * Proverbs. "Necessity is the mother of invention". Or an old Russian variant, "the need will force you to eat pies" (instead of plain rye bread, that is).

Tabletop Games

 * Every time you see a Death World in Dungeons and Dragons you can bet there's someone really tough and probably really smart.
 * Spelljammer got Scro. Orcs and other goblinoids in the First Unhuman War were cornered and pushed back by elves. Some settled in a nasty jungle world when no one thought to look for them. When they finally emerged... uh oh. Scro are very dedicated, disciplined, tough and even creative. They see common orcs as backward louts for a reason. For that matter, their best auxiliaries were descendants of those who have surrendered and ended up in a frozen Death World (elves are jerks like this).
 * Dark Sun. All of it. Even cities.
 * Underdark inhabitants in Forgotten Realms. The world below the world is full of creatures incredibly tough just because the Death World requires this... which in turn frequently contributes to the Death World's nastiness. While the Drow technically still are fragile elves and often prefer cheapskate solutions, they are packed with magic to the eartips and are highly lethal whether they fight with blades or brains (their cities are only slightly less dangerous than the wild caverns around). And the Swirfneblin are barely comparable with surface gnomes (except tinkers, who are just that crazy).
 * Hill's Edge is a modest crossroad town. The crossroad in question being right between the Zhentarim of Darkhold, the Free Traders of Westgate, Lords' Alliance and Harpers' headquarters. The trade routes are important enough that an open war would be counterproductive, but things never get boring. The climate is harsh and monster-hunting is a common local sport. The net result as expressed in game mechanics: an average guy walking down the street is at least 4-th or 5-th level fighter; compare to Dark Sun where "commoners" had to be tough enough that adventurers start at 3-rd level.
 * Regional Feats introduced in Forgotten Realms 3 ed. reflect this. Those who live in the jungles learn to survive in the wild, people raised in The Magocracy tend to know how to talk their way around problems and have an eye for magic stuff, and so on.
 * The Drow in Eberron are possibly the toughest humanoid inhabitants of the setting, since they live in the jungles of Xen'Drik and have to tangle with giants for resources regularly.
 * This trope is the reason why, in Warhammer 40,000, one of the acceptable tariffs the Imperium of Mankind imposes on entire planetary governments is... Manpower. Living in a Death World tends to create the sort of humans perfect for cannon fodder in a galaxy where there is only war.
 * Fenris is an ice planet whose ecosystem seems to have been designed by a Norse Mythology buff, inhabited by continually warring pseudo-Vikings. And if that weren't enough the Space Wolves only recruit young warriors who fall in glorious battle.
 * Catachan is a jungle where Everything Is Trying To Kill You.
 * Atilla is pretty much a planet-sized Mongol steppe, as is Chogris, the home of the White Scars.
 * Cadia is a nice, earth-like planet. Oh, and has the Eye of Terror for a neighbor, just a spit away.
 * The majority of Imperial Guard regiments actually come from Hive Worlds. Most often underhive gangs are simply rounded up, given a flak jacket and lasrifle, than dropped onto the front lines with no additional training. In many cases, they don't need it.

Video Games
"For decades they said about Kovir that its only riches are sand and seawater. This joke was still remembered when Kovir de-facto monopolized the world market of glass and salt."
 * This is the background of the Barbarian class in Diablo. Though they specifically reject technology and magic because they think it will make them weaker in the long run.
 * Mass Effect: This is krogan evolution in a nutshell; their planet was so dangerous that for centuries, the most common cause of death was 'eaten by predator'. This explains why they have secondary and even tertiary organs, and why they are Explosive Breeders.
 * The Witcher:

Web Comics
"Dimo: Haff all dose guys vit de baron gone soft over de years -- or haff ve become... sharper because ve leave de group und haff to tink better?"
 * Girl Genius Jägers. They are super soldiers who like to kick ass, laugh loudly and drink, not necessarily in this order - no one expects a Jägerkin to notice everything and get non-obvious conclusions. But they can live for centuries, so any survivor is very much an Old Soldier. And then there are those who wandered for many years on their own both in lands where the people remembers them as ex-conquerors and in wastelands where they are not nearly the toughest creatures...

"Dimo: Most of us Jägers... Vell, ve didn't join up for de thinkink, hyu know? So somebody gots to be de schmot guy. Hangink around vit Maxim and Oggie... Vell, hy used to be de schmot guy."
 * Of course, there's also further specialization.

Real Life

 * Friedrich Nietzsche with his "What doesn't kill you only makes you stronger." Which is subverted in both real life and fiction as often as not.
 * Actually, what Nietzsche meant was that you can learn from what does not kill you, making you stronger. Which is not subverted as much as people seem to think it is.
 * And also that loss, in itself, can also serve as a source of strength. A person who loses a leg won't be winning any footraces, but according to Nietzsche will acquire a greater firmness of character and spirit as a result of the loss.
 * Eighteenth and nineteenth century regimes much preferred mercenaries from extremely nasty wilderness areas. A large part of this was based on this theory.
 * Greek philosophers bragged that Greeks were this because of having to tend farms on their own. Persians were stereotyped as soft and wussy.
 * Venetians and Dutchmen spent generations not only living from the ocean and fighting off all competitors but actually living on the ocean (by way of building "fortifications" against flooding). The result was that Venice managed to take over the Mediterranean for a time. And Dutchmen for a short time managed to Take Over the World.
 * It is sometimes said that carnivores are more intelligent among mammals because they have to catch their food, and sometimes, fight over it with each other. While grass eaters just bow their head and eat.
 * It's animals that have to use their brains (memory/lateral thinking/both) to get their sustenance (food/water/both), not just their senses (hunting requires sight, tracking scent).
 * By the above theory, the ideal place for intellect to grow is in the middle of the food chain, where creatures both have to hunt for their food and have to avoid other predators. Add to that that these creatures are often not that much stronger than their prey (think wolf vs. wild buffalo), and so have to resort to teamwork and tactics to get their meal. Now guess where early humans stood.
 * Mongols. Remember those guys who beat the Chinese and chased the Kumans into the Adriatic Sea? And on the way there beaten up several Russian principalties, Hungary and most of Muslim Middle East as allying with their enemies and/or not sharing their idea of diplomatic immunity? This mostly was reorganized tribal militia without benefits of any non-conventional training methods. Their success stems indeed largely from learning the lessons of the steppes: endurance of great hardship made them tough as nails and good at cooperation, nomadic life made everyone a good rider, hunting and warring in open field gave obvious incentives to develop the best long-range weapons around, territorial clashes of tribes and later a civil war gave them plenty of experience.
 * The one major change Ghenghis Khan did was a total replacement of the former social hierarchy with the united militarized Mongolian nation - his side's creed was that justice means law should be the first priority, merit second, everything else after that. The Yassa itself was mostly formalized and elaborated traditional law with military cohesion emphasized. So their men no longer paid much attention to clan affiliation and seniority, only achievements and command structure. Subodai, his greatest general, an example of having been a 'commoner' who rose to the top. Between the hero cult on par with Greeks and a chance to beat traditional enemies, they tried to be great warriors pretty hard.
 * Finns, living in the Arctic in some of the most beautiful and most rigorous terrain in the world. For example: the Winter War happened after Soviet Union built up its military industry and Red Army had some successes butting in on Spanish Civil War (the defeat there was political rather than military) and won the one against the Japanese on the Manchurian border, both times promoting succesful commanders and demoting or eliminating failures, working out kinks in logistics, strategy, and so on. But then all this rolls into Finland and quickly grinds to halt - the war machine was frantically reinforced, re-equipped (with novelties specifically designed to do this job like the siege tank - KV-2), reformed... nothing was good enough.
 * The flowering of physics in late XIX - early XX centuries. Ernest Rutherford said "We don't have the money, so we have to think." The beginnings of new areas involved a lot of creativity funnelled into making tools and experimental devices in a barn - sometimes literally. The early scientists used to improvise in experiments simply because there were no established methods in their area.
 * Even Lord Rayleigh made his own equipment out of near-junk, despite being a lord in his land - and many, many others. On the way they made a lot of great inventions. Robert Williams Wood was not only the Patron Saint of Education Through Pyrotechnics but, as one of the pioneers of physical optics, made state-of-the-art spectroscopes using materials like sewer pipes or a tombstone, and cleaned one of these by shoving a cat into the pipe and closing it so that the cat had to exit from the other end. Oh, and among other things he was a co-inventor of film animation and cartoon as we know these (you might call him the grandfather of Mickey Mouse), color photography and ultrasonic echolocation.