This past year, my reading has alternated between classic science fiction and non-fiction archaeology or anthropology — two very different literary forms that encapsulate opposite ends of our shared and potential experience. Along the way, I’ve discovered three books that truly span the breadth of human history, from past, present, to future. No three books alone could represent millions of years completely, of course, but these books do provide a concise overview, and though written by three different authors, they complement each other to form an overarching story of human existence.

I’ll be posting separate discussions of each book, with a wrap-up of the three after I’m done with them individually. Let’s begin with The Humans Who Went Extinct: Why Neanderthals Died Out and We Survived by evolutionary ecologist Clive Finlayson.

In The Humans Who Went Extinct, Finlayson supplements his direct experience excavating the last stronghold of the Neanderthals at Gorham’s Cave in Gibraltar with multi-disciplinary research for the causes of human extinction. But humans aren’t extinct, right? Wrong.

Some of our close human cousins didn’t quite make it. Homo erectus flourished in Asia for hundreds of thousands of years while Homo neanderthalensis did the same in Europe, long before our own ancestors ever stepped foot outside Africa. Both species made tools similar to our direct ancestors, and DNA evidence indicates that Neanderthals were most likely capable of speech. The received wisdom of contemporary paleoanthropology and archaeology takes the stance that anatomically and behaviorally modern humans (Finlayson conveniently shortens this to the straightforward “Ancestors”) displaced our cousins when we left Africa and spread throughout the Eurasian continent.

Finlayson examines both the material culture of the Neanderthals and the ecological conditions across the past 125,000 years to argue that their environment degraded repeatedly — from dense forests that supported the ambush hunting style of the Neanderthals (as evidenced by their weapons) to steppe-savanna landscapes where herds or individual prey animals were few and far between and which required a fundamentally different set of technologies and behaviors to succeed.

Neanderthals were not able to adapt to the challenges and opportunities presented by the new, more open landscape. (And with one rare but crucial exception in Central Asia, neither were Ancestors.) The range of humans expanded and contracted with the ebb and flow of forests for thousands of years, placing populations under pressure to the point of local extinctions. Finlayson argues that Neanderthals (and Homo erectus) were pushed to the brink of extinction by the contraction of their traditional environments until the small pockets of survivors were no longer viable populations, cut off from each other and susceptible to one bad winter or outbreak of disease. The last Homo erectus lived on Java until as recently as 50,000 years ago, while Homo neanderthalensis held out at Gibraltar until 24,000 years ago.

Meanwhile, Finlayson suggests that Ancestors on the fringes of our traditional comfort zones were being forced to adapt or die. Most died. He traces the origin of the Gravettian culture to an adaptation by a founder population in Central Asia before about 30,000 years ago. The specific adaptations that enabled these people to survive were the centralized villages that served as home base — and most importantly information exchanges and surplus stockpiles — for the hunters, along with new technologies such as lighter, more portable stone tools that could be adapted to new projectile weapons necessary on the open plains. These people spread west to Europe and northeast across the Bering land bridge to the Americas.

Throughout The Humans Who Went Extinct, Finlayson illustrates how the tension between innovation by fringe populations and conservatism among otherwise stable core populations leads to only two possible results when their environments change. In most cases, environmental challenges have been too great and the vast majority of human diversity has not survived. But when the right opportunities happen to be present, the innovators who take advantage of challenges presented by their environment survive while conservatives who fail to do so die.

The impact of ecology on human success or failure is a theme that will appear again in the next two books we examine.