I'm going to leak over from my New Book topic and engage in some more shameless self promotion. I think you will find that our book, Slings & Slingstones, The Forgotten Weapons of Oceania and the Americas, just published (finally) by the Kent State University Press, addresses many of the questions posed here. It is currently a featured book at, and can be purchased at, www.kentstateuniversitypress.com , also available thru other online vendors like Amazon and B&N, who are offering it at a lower price.  

I do want to say a couple things. Lovelock Cave was not quite the only site which yielded pre-Columbian slings in N. America. Slings were also recovered from nearby Humboldt Cave, Nevada. These dated younger than the Lovelock sling, to ca. 2000 years ago (YA). Also, it appears that the oldest, surviving, slings in the world, RC dated to more than 4000 YA, were recovered from Peruvian Preceramic sites. The simple reference for this info. is, "see our book". But other than that, a ref. for Humboldt Cave is: The Archaeology of Humboldt Cave, Churchill County, Nevada, 1956, by Robert F. Heizer and Alex D. Krieger. Refs for Peruvian Preceramic slings are: The Preceramic Excavations at Huaca Prieta Chicama Valley, Peru, 1985, by Junius B. Bird and John Hyslop; Chavin and the Origins of Andean Civilization, 1992, by Richard L. Burger; A Preceramic Settlement on the Central Coast of Peru, Asia, Unit 1, 1963, by Frederick Engel.                            

Obviously I think it's "good" and worth the money. But we'll just have to see what unbiased readers think as it gets read and the critics start to weigh in. That said, I wish it had been priced lower, but I'm afraid that decision was out of our (the authors) hands. I don't know how much you've hunted around online, but you might find some lower prices, or wait around a little more and some vendors will probably start discounting a bit -- like Amazon and B & N in the U.S. already have. You might also suggest to local libraries, museums, institutions of higher learning, that they acquire it and then just check it out or read it there.        

I have always had a mental image of a stable native American population, slowly disrupted by the movement of Europeans west, but not rapidly changing otherwise.

However, some recent reading suggests a large indigenous population (in the range of 20 million) particularly in the central Mississippi and plains area.  Contact with the Europeans and the Old World diseases killed 95% of them. 

That must have left a considerable vaccuum for Eastern tribes to expand into, and maybe it confuses the evidence for local use of slings and bows. 

I'm speculating, don't really know anything about this, but it is fascinating.