MarieM, the ice age didn't just end 12,000 yrs ago. It reached a peak about 60,000 yrs ago and gradually the climate got warmer until the last glaciers left the British Isles about 12,000 yrs ago.
The climate has slowly and steadily warmed since then with one or two relapses such as the "mini Ice Age" in the 17th,18th and early 19th centuries.
We are actually in a warm phase between Ice Ages, and this is the only reason why mankind has been able to flourish so well.
During the last ice age, the very small human population was concentrated in a narrow band around the world roughly between the tropics of Cancer and Capricorn.
Only since the retreat of the glaciers has mankind been able to expand north and south to what we have now.
Contrary to what the global warmists tell us, it will be the return of the ice sheets that seals the fate of mankind as we know it.
However, it won't happen like a disaster movie, in a few weeks or months, it will be over many tens of thousands of years.