Humans arose during the last two million years, according to available fossil evidence, with so-called “modern humans” – that is, humans leaving behind evidence of culture, art, technology – emerging perhaps as recently as 70,000 years ago, or perhaps 200,000 years ago. Nobody is quite sure and a bitter argument is raging about the exact when and where, though nearly everyone agrees the first such “modern” people arose somewhere in Africa before migrating elsewhere.
This means that humans evolved coincident with the ice ages, that two million year period we call the Pleistocene within which ice has advanced and retreated on a roughly 100,000 year cycle, at least 20 times, with the most recent ice age having its “maximum” about 20,000 years ago before retreating until, maybe 12,000 years ago, the ice was mostly gone (except for some remaining caps in Canada and Eurasia). But, before that 20,000 year ago maximum, there were many rises and falls during the previous 80,000 years. It seems that even during the height of an ice age the summers could be hot, maybe as hot as today, just shorter, and of course the winters were colder. It also seems that the temperature could rise and fall over a very very short period, maybe as little as a year or two, certainly a decade. It seems likely that the way an ice age begins is not that somehow glaciers far in the north grow thicker and thicker and then march inexorably south to cover much of the land north of 40 degrees north; instead, a more likely cause is that the snows fail to melt one summer, then another, then another, until after 10 years the snow compresses to ice and after 100 years a thick glacier in place exists.
The earliest humans, as far as we know, did not farm, or grow crops. This invention, agriculture, started about 10,000 years ago, following the latest ice age, when a roughly 10,000 year period – the interglacial – began, when the weather stabilized for centuries of warmer weather. It may be, in fact I am sure it was, that humans during the ice time worked a form of “primitive” agriculture – using fire to clear underbrush so food plants could thrive, for example. The first human societies, whether modern or not, were hunter-gatherers, seeking game for meat and gathering nuts, fruits, edible plants, as well as foraging along the shore for shellfish and seafood, and of course fishing.
The ice age warm time between ice advances before the warm time we are now in occurred about 120,000 years ago. It was called the Eemian, and lasted 10,000 years. The average temperature during that interglacial was apparently warmer than even today’s warmer days, maybe as much as one or two degrees Celsius warmer, and the sea level back then was as much as 20-50 feet higher than the sea level is today. During the over 20 previous ice advances during the Pleistocene, land bridges appeared as sea levels dropped because of all the fresh water locked in ice. Sea levels dropped as much as 330 feet from sea levels today, and during the entire ice period, as the ice advanced and retreated, so did sea levels vary.
All of this serves to show that there were short periods of generally stable warm climate conditions called interglacials that lasted between 5,000 and 15,000 years (generally) with the warm period before the one we are now in – and approaching the end of according to the glacial record – happening over 100,000 years ago, maybe before the appearance of so called “modern” humans. This means that for most of human history, in fact for all of it, we lived and evolved during periods of great changes in climate, huge changes, some times happening within a year or two, and certainly within one or two lifetimes. These changes in temperature, weather, sea level, storm intensity all surely greatly influenced behavior patterns of prey animals and the location of edible plants. Along the seashore, the tide lines would rise, and fall, some times greatly, and all these changes would alter the locations and behavior of seafood clusters.
Of course, we humans have incredibly short memory spans. Who among us knows, for example, what our grandparents or great grandparents did every day to live? These days many people remember winters when the snow was much deeper, when they were children, though maybe that was because they were half their adult height. When I was a kid in the 1950s I remember vivid stories and memories of the Great Depression, seeing older men and women still carefully saving and pressing flat tin cans for reuse. Most people alive back then knew of times when electricity was scarce, even unavailable. A life without electricity today would seem unimaginable for most people alive in developed economies. Yet, a century ago, 1921, electricity was still not available for over half the U.S. population. The point here is that huge change is happening all the time these days and we forget about the change as time passes, and especially as those who lived in such different times pass on, because then instead of hearing directly from an eyewitness we hear from someone who was told by someone, and this must be the case for almost anything that happened more than 60 or 70 years ago. And, beyond that, say, back to the Civil War, the people alive then are now our great or great-great or even great-great-great grandparents, myths of imagination and memory.
So, even though during most of our history the climate has changed greatly and often, any changes occurring over, say, a century and surely over two or three centuries would not be seen in the immediate life of anyone living, not really, such that then there would be legends of warmer times, or colder times, almost myths, lost in the haze of memory and history. And this means that we humans think that what has been happening in our most recent memory – a year or several years – is what has and will always happen. We are, if nothing else, adaptive, and so we adapt, and as the climate changes, we adapt or die. We need to find new hunting grounds, or new edibles. We need to move the village because the sea now floods our shelter. The great herds upon which we depend have suddenly wandered away over newly exposed land that rose from the sea (though in fact the land emerged from the falling sea).
All of which to say, even though the climate has changed always (but changed much less during the warm times between glacial advances and retreats), within the lifetime of one person, much of the change, maybe all of it, would be impossible to see, and big changes over, say, four generations would soon be considered exaggeration or myth. What is true, though, is that the changes taking place force adaptation, learning, adjustment, flexibility, and this was surely the case everywhere on earth, even those places near the equator far from the advancing ice, because they, too, would be changing as well.
I think it was the ice ages that had much to do with making us human, maybe as much as the control of fire for the ability to build culture and learning with stories. These days many if not most among us think we face a climate crisis. What many if not most of us fail to realize is that the human condition is exactly one of adapting to climate crises, and it has always been so.