Contrary to popular belief, SCIENCE still hasn’t a working theory as to why the Sun is somewhat aperiodically oscillatory. There are lots of theories, but they contradict. None of the theories predict well.
There was the still unexplained 200-year long Mayan Famine and Drought which killed over 1 million people. This corresponded to yet another period of anomalous solar activity, we really ought to have better models of solar activity and the mitigating actions humanity can take to deal with such periods.
It not just the Big Ice Ages but smaller fluctuations
The Little Ice Age was 1450-1880. It was a large temperature excursion in the Northern Hemisphere – but slow enough that it largely wasn’t noticed as “an event” due to non-existent record-keeping and the time-constant of the decline. It was long, and it was tough.
350-650 AD was another period of anomalously cold hardship. Doesn’t have a formal name, but the sharp onset (over a period of less than a decade) corresponds fairly well with the Fall of the Holy Roman Empire. Europe’s defenses, robbed of a (then) geopolitically potent military and industrial supporting infrastructure, was overrun by all nature of external invaders. A dark period of history, punctuating the well-named Dark Ages. Yet, we know not how, why, or what manner of contributing forces lead to this. The Sun may well have been contributing.
You will note the Maunder Minimum corresponding rather roughly with the little ice age. With – however – a nice reverse between Sporer Minimum and Maunder.