There is such truth in Nature.

Start with a cage containing five monkeys.
Inside the cage, hang a banana on a string and place a
set of stairs under it. Before long, a monkey will go
to the stairs and start to climb towards the banana.
As soon as he touches the stairs, spray all of the
monkeys with cold water.

After a while, another monkey makes an attempt with
the same result - all the monkeys are sprayed with
cold water. Pretty soon, when another monkey tries to
climb the stairs, the other monkeys will try to
prevent it.

Now, turn off the cold water. Remove one monkey from
the cage and replace it with a new one. The new monkey
sees the banana and wants to climb the stairs. To his
surprise and horror, all of the other monkeys attack
him. After another attempt and attack, he knows that
if he tries to climb the stairs, he will be assaulted.

Next, remove another of the original five monkeys and
replace it with a new one. The newcomer goes to the
stairs and is attacked. The previous newcomer takes
part in the punishment with enthusiasm.

Again, replace a third original monkey with a new one.
The new one takes to the stairs and is attacked as
well. Two of the four monkeys that beat him have no
idea why they were not permitted to climb the stairs,
or why they are participating in the beating of the
newest monkey.

After replacing the fourth and fifth original monkeys,
all the monkeys that have been sprayed with cold water
have been replaced. Nevertheless, no monkey ever again
approaches the stairs. Why not? Because as far as they
know that's the way it's always been around here.

And that's how Marine Corps policy begins...