Oddly enough, humans found it easier to survive during the last ice age than in times of milder climate; in the future we may face similar challenges too.
Survival can be difficult in extreme environments and today we assume that subpolar or polar regions fit perfectly into that definition. However, the Inuit people, the Lapps or Laplanders of Scandinavia, the different tribes that abound in the permafrost of Siberia and the bands or tribes of hunters of the last ice age, which ended about 12.000 years ago, provide us with a very different picture.
At the end of the last ice age humans found themselves in a very precarious situation because many of the species that they relied on were getting extinct one after one: there were even hairy rhinos living in snow-covered regions, and such animals constituted not only the main dish for those people, but the basis for almost everything they had or produced for themselves, like footwear, clothing and so on. Take out the hairy animals that live in the tundra, and if you also live there you will be facing starvation.
A fairly modern example of he same interaction is the case of the Indians of the United States and their dependence on buffalo herds to live and prosper; once the buffalos were decimated by white hunters, those tribes went into oblivion because adaptation to newer environmental conditions is not always easy.
Those primitive humans could survive fairly well within the environment that they knew after hundreds of generations of nomadic activities; for hundreds of thousands of years species like Homo sapiens neanderthalensis existed and thrived, and with each succesive generation they imporved not only the intelligence that was slowly giving shape to modern humankind, but also their instincts and abilities as survivors.
Curiously enough, there are many skills and techniques used today in survival courses and training that indeed appeared sometime during prehistory. How to start a fire is one example; the use of natural medicines is another. The ways of prehistory are not completely gone, but they remain the stuff of survivalists, archaeologists and other enthusiasts.
Since the end of the last ice age humans developed agriculture, cities, armies and other items that constitute the paradigm in which we find ourselves today: civilization. Accadians, Hurrites, Kollas, Khmers and modern-day Taiwanese share a few common things despite the ostensible differences between all those nations: they had or have armies, political regimes, law, some sort of alphabet and so on.
What is happening with our environment will likely cause yet another series of significant changes. It is not that cities will vanish into the night but we might be facing in the coming decades and centuries some difficult choices like those that turned those early nomadic hunters into agricultors: we know that it was not easy at all. The development of agriculture was a very traumatic thing for humans, a remedy of last resort in order to survive.
The paradigm of civilization seems to be now overstretched: religious wars at a global scale, climatic change, scarcity of resources and a lot of other serious troubles. There are two possible paths to follow: either fe start finding real solutions to these problems, or we may end in the future like our ancestors, watching as our sources for everything we have, enjoy or suffer vanish before our own eyes, and then, who knows?