Soup may seem like a fairly uninteresting or pedestrian food to many people, but before there was pottery or domesticated animals, soup was a luxury food for many hunter/gatherers. In order to understand its status as a prehistoric luxury food there are several key bits of information that need to be provided.
First, in temperate, subarctic, arctic, and even in places like the Australian Western Desert where temperatures can go below freezing some nights, staying warm is a major challenge and can be essential for survival. Fires provide limited help in this regard because gathering enough wood to keep an entire family warm all night (and day) demands a lot of time and work as well as someone to watch and stoke the fire periodically. What most people did most of the time is rely on body heat (together with heat retaining clothing) to provide most of the warmth needed, either from vigorous activities or by consuming a lot of calorie rich foods.
Second, the only types of foods that provide people with significant calories are starches (including sugars) and lipids–basically oils, greases, and fats. Unfortunately, for most hunters and gatherers, meat or protein is not what is in short supply in the wild environments, it is starches and lipids. Even the digestion of meat requires lipids to metabolize the proteins in meats. Eating very lean meat without any fat leads to what is sometimes referred to as “rabbit starvation”–rabbit because wild rabbits were so lean. A person could eat pounds of lipid-less meat every day and still starve. Even today, people who want to lose a lot of their body fat go on protein rich-no fat diets so that the metabolizing of meat proteins will burn off the available body fat.
Unfortunately for hunter/gatherers, most wild animals usually have very low amounts of body fat, often 5% or less. Compare this to domesticated animals like the meat bought in stores today where there is typically 25-30% or more fat content. In fact, the first thing that hunters typically do after killing an animal is to cut open the intestinal cavity to see how much fat is in the animal. If there is not enough fat, the animal is often left for other scavengers. The essential need for lipids is why fats and oils are so highly prized in most hunting and gathering societies, and even in many traditional agricultural societies that rely to a significant degree on body heat to maintain adequate and comfortable body temperatures. Think about the desire for fat-tailed sheep. Natural selection has also given people having natural tastes for lipids better survival chances, so that these tastes have become part of our genetic propensities and lead to our overconsumption of “rich” or fried food whenever it is available.
A third bit of information to note is that animal fats and oils are primarily produced inside bones. Most people today don’t often break up bones to see what is inside, so the spongy-looking “cancellous” bone at the ends of the long bones may be a novel thing for many, but that is where most of the fats are produced. The fats are then concentrated as marrow in the central parts of the long bones; and marrow was one of the prized delicacies of hunter/gatherers–rich gobs of fat that are easy to get at. There was also a lot of fat in the cancellous bone material, but the problem was how to get it out. Some Neandertals seem to have smashed up the ends of the long bones into a paste that could be sucked on or eaten–and even today, some people like to chew on the cancellous ends of chicken long bones. An even better strategy for extracting fats from cancellous bone was adopted by anatomically modern people in the Upper Paleolithic who broke up the cancellous bone into small bits and then boiled the bone to release the fats and make soup! A similar technique was later used to extract oils from fish heads and hard-to-get-at nut meats by boiling them up into soups.
A fourth thing that we need to recognize is that boiling anything before there was pottery was not an easy affair. It required leak-proof containers like pitch-sealed bark buckets, carved wood or stone bowls, or very tightly woven baskets. It also required making long tongs for removing hot rocks from fires, procuring wood for fires and finding types of rocks that would not shatter in fires. The fires had to be kept hot enough for long enough to heat up the rocks to glowing which could then be placed in the water-filled containers to make the water boil. And voilà! Soup!–a very rich soup.
Because this process required special containers and materials, it was time and effort-consuming, probably only used for special occasions or when in dire need. Because of the efforts involved and the high value placed on lipids, soups were greatly relished. This is why soups are key features in the story of The Eyes of the Leopard which is set in the Upper Paleolithic, 20,000 years ago. If you have the opportunity to read this story, I would encourage you to take a look at the contexts where soups were consumed. It is also interesting to see how soups continued to be important in later feasting cuisines like the relished soups for the ancestors celebrated in the Shang dynasty poems of China.