12,000 years ago, the natural cycling of the Earth’s axis ended the Ice Age. That’s non-anthropogenic climate change. Over the next few thousand years of climate volatility, Earth became overall warmer and wetter than it had been for the previous 120,000 years. All humans at the time were hunter-gatherers, which I’ll call HGs.

HGs in subtropical latitudes were affected, but not badly. With about 125 species of plants to eat, each with different water needs, habitats, and seasons, there was always some food available. Climate changes brought stress to animal populations, making hunting easier as the herds clustered around food or water sources or simply become weaker. These humans populations probably got a little hungry during some seasons, and surely grumpy if a fave nosh disappeared, but nature remained provident, and mass death unknown.

In the northern hemisphere, the ecosystem changed completely. Familiar plant species disappeared. Cold-adapted mammals, keystone species, declined and ultimately became extinct. HGs had to work hard. They learned to hunt large animals in teams. They processed unfamiliar plants–grains, pulses, and legumes were hugely successful in the warming climate–to make them palatable. Pasta? They started preserving and storing food. They no longer viewed nature as provident.

Eventually they learned how to culture some plants and domesticate some animals, leading to the birth of farming, aka the Neolithic Revolution. I’ll call human farmworkers FWs. FWs work much longer hours than HGs, work often related to the future–preparing the fields, maintaining tools, harvesting and storing food. Their entire crop can be wiped out quickly, and they share infectious diseases with farm animals. They less diverse diets than HGs, making them less healthy, and a less diverse genome, due to mass death.

On the other hand, when conditions produced a plentiful harvest, FWs thrived, and overall their numbers grew. Quickly, they–we!–took over the world. That’s why we now have HG physiology and FW culture and values. To Be Continued…