Now that our troops are finally leaving Iraq (and will soon, hopefully, be departing from Afghanistan), it's time to reflect on the fact that the 20th (and now the 21st) centuries have been so filled with fighting. Interestingly enough, scientists tell us that humans are not DESIGNED to go to war: When it comes to "fight or flight," we are programmed for "flight." This is what has led to our continuance as a species.
The English king Henry VIII had 6 wives, but no sons. His daughter Elizabeth eventually inherited the throne and ruled very successfully, but he beheaded most of his wives because none of them could produce a son (this was before humans realized that men are the ones who are responsible for the sex of a child). High-testosterone men having only daughters is still called the "Henry the 8th Syndrome." Biologists speculate that this may be a kind of protection for our race, so that these men don't pass on their aggressive tendencies to a son, who would in turn increase the collective desire for battle among his colleagues.
There's a hormonal reason for this too. Stress (in both sexes) produces the horrible hormone Cortisol, which lowers the testosterone (and libido) of males. Researchers conclude that this means that we are not designed for war, but for avoiding it, because when men are under stress, their testosterone (and thus their fighting spirit) drops. The military knows this, which is why they train soldiers to obey orders without question, so that under stress, they will behave automatically.
So many of us remember our high school and college history classes as being taught in terms of the wars that were fought throughout the years, all around the world. But the people who retell history in this way have got it all wrong: We're still around because of the wars we DIDN'T fight.
Let's just hope to heck we can remember that in the future.