1491
If you had a standard American education more than a few decades ago, your view of Native American societies before the arrival of European colonists is likely inaccurate. There were many more Native Americans, in more dense settlements, than you were taught. They consciously transformed the landscapes in which they lived on a vast scale, contrary to the still popular romantic image of bands of meek people dwelling lightly upon the earth. And they did so over a very long period of time, with human settlement beginning perhaps as long as forty to fifty thousand years ago.
These are the revisionist theses collected by journalist Charles C. Mann in 1491 (2005) after many interviews and field trips with a variety of experts including archaeologists, geneticists, botanists. It's clear enough that Mann's sympathies are with the revisionist positions, but he takes pains to give equal time to skeptics. The intended effect is clearly to persuade the reader that in the fullness of time, the revisionist views will be vindicated.
I was surprised, as I think most laypeople would be, about how little consensus there is among academics about these pre-Columbian societies, even on such fundamental questions as population size and migration chronology.
Specialists in Native American demography can be divided into old guard "low counters" and insurgent "high counters". The low counters reckon that fewer that the population of the whole hemisphere did not exceed ten million (page 107).
In stark contrast, Henry F. Dobyns, a path-breaking High Counter, arrived at a population range of 90 to 112 million by multiplying Native population counts well after European contact by the reciprocal of the presumed rate of fatality due to pandemic illness (principally smallpox). That methodology implies pandemic deaths of eighty to one hundred million. The world population in the fifteen hundreds was only around five hundred million, so if these high count figures are correct, fully one fifth of the world population died in this period
The arrival of a second wave of a second wave of humans in the Americas was clearly catastrophic for the descendants of the first. But when did this first wave arrive?
The consensus narrative for much of the twentieth century went something like this: around twelve thousand years ago, lower sea levels meant that Siberia and Alaska were connected. But Western Canada was under the vast massive Laurentide ice sheet, blocking notional Alaskans' access to the rest of the continent. Then, around twelve thousand years ago, this ice sheet retreated, opening an ice-free corridor. The earliest artifacts in the Americas, like those found in Clovis, New Mexico, had been dated to a few centuries after the ice-free corridor opened. Open and shut case, right? The creators of the Clovis artifacts must have been among the early descendants of the initial group of migrants across the Bering strait and into North America.
The challenge to this narratives comes from genetic research. Mitochondrial DNA in some Native populations it thought to have changed about 0.2 to 0.3% every ten thousand years. By analyzing the acccumulated genetic divergence of Native American subpopulations, geneticists Neel and Wallace concluded that the ancestral population from which they all descend must have migrated between twenty two and twenty nine thousand years ago. Dental and linguistic evidence also suggests an earlier arrival time (page 189).
Perhaps the most interesting part of the book was Mann's discussion of the ecological impacts of pre-Columbian societies. To take just one startling idea: it may be the landscape that European colonists encountered had, unbeknownst to them, been shaped by generations of Native American use of wildfire to keep elk, deer, and bear available for consumption without domesticating them (page 286).
I grew up in Maryland, where the interactions between Native Americans and European colonists are perhaps a little better remembered - through historical markers and school curricula - than in some other parts of the country. But before picking up 1492 I had read more about the precolonial history of India or China than I had read about the precolonial history of the region I grew up in. If you're in a similar position, I recommend reading a few chapters of 1491.
If you want a brief sample of Mann's writing on one of the topics covered in the book, check out his 2002 article in The Atlantic about Native Americans in the Amazon.