I recently watched an old documentary - "Nice Guys Finish First" (l1, l2) by Richard Dawkins. Here's a summary of that -

Cheats, Suckers and Grudger's.

Richard's motive here was to dispel the notion of only one major survival force, that of survival of the fittest (The Selfish Gene). He cites cooperation as second major force leading to survival.

He cites Cooperative Altruistic behavior as one of the key forces of nature for survival. He goes on to prove that altruistic co-operation, by-default, is always the best strategy to be more successful in life.

Dawkins goes on to illustrate - 'The tragedy of the commons' - where one tends to be greedy over the common resource. Thus everyone has to pay the cost of imminent demise of the resource. In commons, one tries to maximize ones share. Since this becomes the dominant strategy, it ruins the the resource beyond repair.

He then resorts to Game Theory with - "The Prisoner's Dilemma" to prove his point. The game is simple with two players. Each player can either co-operate or defect. The points given for the 3 possible cases are

Cooperate Defect
Cooperate 3, 3
0, 5
Lose much-Win much
Defect 5, 0
Lose much-Win much
1, 1

The last one is known as the cooperators i.e. suckers. Defectors are cheaters. In one off encounter defection is almost always the dominant strategy. However in a long haul, there is a third category of grudger's, ones who remember the cheats.

American Political Scientist Robert Axlerod invited experts to play this game. He played them against each other in a computer tournament. He got 14 entrants. For example -

Friedman - Cooperative grudger, but then permanently retaliated
Joss - Cooperative but sneaker in cheating (out of blue defection)
Downing - Clever - Updating statistics of C or D (started pessimistically)
Tit for Tat - Nice - Cooperative start, then copied.
Tit for 2 Tat - Nicer, but failed

Only one of the top 15 (rank 8) programs was exploitative. Niceness dominated. Tit for Tat won the tournament hands down. Crime doesn't pay.

Reasons for success of Tit for Tat -
1. Its nice - never the first to defect
2. Not envious - it cannot beat its immediate opponent. Only as well. But does better overall.
3. Forgiving - forgives as swiftly as it retaliates.
4. Simple - Easy to read, un-complicated.

In short, it won because of -

Sufficient expectancy for meeting other nice strategies. If everything was bad, then they would always lose.

Dawkins stresses on the importance of an initial critical number, a critical mass of nice strategies, that get together so as to take off in evolutionary game.

He goes on to cite several examples in nature of the same principle. Are you following up that grudge, or you are playing Tit for Tat. In search for a game both sides can win. There is value for initial niceness, and subsequent forgiveness.

Dawkin's concluding remarks -

"Our brains may be evolved as advanced social organs designed to police tit-for-tat reciprocity to calculate past favors balance debts, an organ of social calculation, designed to make us feel angry when we feel we have been cheated, and guilty when we know we are a cheat.

The American biologist Garret Hardin, who coined the phrase "The tragedy of the commons" also coined another memorable phrase "Nice guys finish last". He coined this as his understanding of the selfish gene way of life. But now with evidence from the Tit-for-tat, we should re-coin the phrase to "Nice guys finish first.""

Summary: Always start with co-operation, be a grudger and yet forgiveness reigns supreme.

Tit-for-Tat. Nice guys finish first. Q.E.D.

UPDATE: The source chapter for this work from the book- The Selfish Gene by Richard Dawkins can be read here.