David and Orion: While the galaxy is very very big it is also very very old. The paradox isn't about us not being visited in the last hundred years, it's about why the Earth wasn't colonized at some point during the last billion years.

There are also regional differences within the United States in this regard. In states like New York, Americans of colonial descent have been outnumbered by the descendents of post-1790 immigrants for generations. In many other areas (especially in the south), colonial stock Americans continue to form a large majority of the population. 
 
This is slightly off-topic, but this may account in part for the greater acceptance of the "birther" movement in the south (the idea that Obama was not really born in the U.S.). In addition to racism, this may be due partially to the fact that in areas inhabited largely by colonial stock Americans, the immigrant narrative is not something that people identify or are even much familiar with. Thus, the idea that someone whose father was a native of Kenya is not a natural-born U.S. citizen might be a completely natural assumption.

One factor that probably explains part of the higher rate of obesity in the South is the level of religious participation. Purdue University sociologist Kenneth Ferraro published a study in 1998 showing that religious people had higher rates of obesity that others, and that this differed by denomination, with Baptists being the most likely to be obese. 
 
This might also help to explain part of the east-west divide in the Appalachian region. Western Virginia, for example, is not as heavily dominated (no pun intended) by Baptists as the areas to the west. 
 
One reason that has been suggested to explain this tendency is that it is related to the evangelical Protestant tendency to forbid the use of alcoholic beverages. Because they abstain, many Baptists and other evangelicals might tend to overeat where others might turn to alcohol.

The natural growth rate of the American population from the early colonial period until the Civil War was probably the highest rate of sustained population growth in the history of the world. Throughout this period, the U.S. population was doubling roughly every 25 years, with most of the growth being due to natural increase rather than to immigration. It was observing the growth rate of the Anglo-American population, in fact, that inspired Thomas Malthus to write his famous essay on population growth.

According to the Wikipedia entry linked to in this post, it is estimated that 53% of the U.S. white population is descended from colonial ancestors. Since 85% of the colonial white population was British in origin, this would mean that 45% of the U.S. white population is descended from colonial British stock. Considering that Great Britain was one of the primary sources of immigrants throughout most of American history (even during the Ellis Island period), it is not unlikely that a majority of U.S. whites, even today, are British in origin. This is definitely true if one is referring to descent from the British Isles as a whole (including Ireland). 
 
One problem with using Census Bureau data regarding ancestry is that it is based on self reported answers to the question "What is your ancestry or ethnic origin?" In my experience working for the Census Bureau, a large number of the people that we interviewed had only a vague idea where their ancestors came from. One of the more common answers that we got to this question was simply "I don't know" and many of the answers that we did get seemed to be educated guesses or referred only to the branches of their families that had immigrated here recently. 
 
Since most of those in the U.S. who are British in origin have been here for generations and have no memory of their ancestors immigrating, it is likely that the Census data underestimates the percentage of the population that is of British descent.

Hasn't religion always appealed more to the old than the young? I am not aware of any specific studies from the past, but my impression from reading works from the 19th century forward has been that in the U.S. and Europe religious belief and church involvement have traditionally increased with age, and that the elderly have always been the most religious age group of all. 
 
In churches of various denominations, a common tendency is for young people to drift away when they grow up and leave their pasrents' influence, and then to drift back to church as they grow older.

Why do they have eyes?

"let's look at the percentage of high schoolers who have had 4 or more sexual partners. Here are the data from the representative National Youth Risk Behavior Survey. From 1991 to 2007, this percentage has decreased. This is the strongest argument against the declinist hypothesis." 
 
I am a declinist, and I consider this to be the strongest argument in support of my position. The reason kids today don't fuck around as much as previous generations has entirely to do with the fact that teenage boys don't pursue sex as vigorously as the boys in previous generations did. (Not sure why this is, but it probably has something to do with internet porn; the boys have just masturbated themselves into indifference.) But the girls today are more eager for sex than ever. I know this because I'm in my late 30's, and I have never had an easier time sleeping with college girls than I do today. This has nothing to do with money (don't spend a dime on 'em), and everything to do with the craving young women have for sexual adventure with men who really want to fuck them. And, in this respect, the boys their age are conspicuously lacking.  
 
For whatever reason, teenage boys today are squeamish, scattered, and conspicuously lacking in exuberant vitality. But the girls... well, girls are the new boys. So, even for a declinist like me, I guess there is something to love about Gen Y.  
 
Keep on sucking, boys. More for me.

What's wrong with these women majoring in Literature? It doesn't mean they're not smart. Even if they had some affirmative action of some kind, they still need to be smart to get into Harvard or Yale. There is a Verbal SAT too, you know. Maybe that was their forte. Almost all students at a place like Harvard or Yale are pretty damn smart, although they aren't necessarily genius level, as the 25 Percentile at Harvard or Princeton is about the same as the 75 Percentile at UTexas or U. of North Carolina. Anyway, as a man, I believe I have a MUCH higher probability of finding a hot, classy girl majoring in Literature than in Math or Engineering. And Danica McKellar gets blown out of the water by any of those girls.

Not only legacies, but also recruited athletes have to be taken into account. They get admissions help and are majority white. I'm sure very few recruited athletes are Asian. This may account for the difference. You can't replace the offensive line with more computer geeks, or alumni will complain.

I support your theory that people should not waste there time defending you. 
 
Having been around the world does it make me a racist for having preferences.