> I don't have a citation, but this seems almost certain

Like I said, you do not understand evolution.

Yes, I know about the short timescale for lactase persistence. You'll note that it's two mutations.

Now you need to demonstrate that "increased desire to reproduce" is something that 1) is directly traceable to genetics, 2) is only a few mutations away, and 3) the intermediate forms lead to better evolutionary advantage. All you have is an unfounded belief.

From a paleobiology perspective, human population was stable for a much longer time than this relatively recent exponential expansion phase. If there were such thing as a genetic imperative pushing humans towards higher fecundity, it would have occurred long ago.

> Buffalo

This is why I said millions, not 500,000. You'll notice that there are no Plains Indians living as they once did.

> Some particular version of experiences are constantly being made unavailable

Yes. And who are you to say that your belief in exponential population growth gets priority over the experiences that others want to have?

> I don't think that genocide was caused by overpopulation so much as the US government's desire for westward expansion

Interesting how you managed to decouple population pressure and western expansion. (Note that I don't say "overpopulation" but "population pressure".) Do you think the following summaries are wrong?

"With the Louisiana Purchase and subsequent land acquisitions, U.S. territory grew exponentially in the first half of the 19th century. Populations huddled on the east coast saw grand opportunities to move into more expansive areas where land was cheap and more arable than it was back east, particularly in New England." - http://www.ask.com/history/were-reasons-westward-expansion-9...

"As the population of the original 13 Colonies grew and the U.S. economy developed, the desire and attempts to expand into new land increased" - http://www.pbs.org/kera/usmexicanwar/prelude/md_introduction...

"In order to grow, the capitalistic economy and republican form of government needed surplus land and abundant natural resources such as wood, fossil fuels, minerals, and water. Many feared that without a surplus the parceling of limited resources to a growing population would eventually lead to class conflict. Not everyone embraced this philosophy." - http://www.encyclopedia.com/doc/1G2-3406401030.html

"The most important forces [in the westward expansion] are population growth and the decrease in transportation costs," Vandenbroucke said. "Population growth is mostly responsible for the investment in productive land - without it less than half of the land accumulated in 1900 would have been accumulated." - http://www.eurekalert.org/pub_releases/2008-02/uosc-wcw02280...

Or this quote regarding Manifest Destiny, from https://en.wikipedia.org/wiki/Manifest_destiny :

> The United States, while intending never to acquire lands from the Indians otherwise than peaceably, and with their free consent, are fully determined, in that manner, progressively, and in proportion as their growing population may require, to reclaim from the state of nature, and to bring into cultivation every portion of the territory contained within their acknowledged boundaries. In thus providing for the support of millions of civilized beings, ...

All of those are explicit statements that the US expansion was strong driven by a growing population.