If you want to know how our ancestors survived on this blue planet, it’s important to know what they ate at each meal. There is always some organic matter in the cultural relics (such as pottery) used for cooking, but we can’t judge whether these materials are left by the last cooking or represent the accumulation of food residues during multiple cooking processes. The study was published in scientific reports on August 27. A group of scholars from New Zealand, Britain and the United States found seven unglazed earthenware pots and carefully set up seven sets of initial and final recipes composed of corn, wheat and deer meat. The next process was sloppy: each of the seven scientists picked a pot and cooked a “meal” each week based on a set of recipes and ingredients. We don’t know if the cooked food has been eaten well, but after each meal, they don’t use detergent and brush to clean the pot thoroughly – after simply flushing it with water, the pot will be used again for cooking a week later, until it has been used 50 times. At this time, the residue samples in the pottery pot will be carefully collected, and then taken to cook 1-4 times different from the previous ingredients, and sampling again. < p > < p > after the end of the whole year’s ancient human cooking simulation experiment, seven pottery pots with the abbreviation of “Chef” as the number and cooked more than 50 times left burnt food residues, thin-layer residues adhered to the inner wall of the pot, and lipids absorbed by the wall of the pot. These materials will help archaeologists solve a puzzle that has puzzled archaeologists for many years: can we rely on the remains of the last cooking in the pot to infer what other ingredients were in the pot before the meal? The reason why these scholars tried so hard to understand the recipes of their ancestors is that there was a wealth of information behind the choice of food by the ancients. On the one hand, the composition of food represents the resources that can be collected locally or the commodity trading network established; on the other hand, it also reflects the values of consumers. Therefore, understanding their food composition can help us reconstruct the natural and social environment in which human ancestors lived. Since 1970, studies have confirmed that organic residues in ancient cooking utensils retain their original chemical composition, which can help us understand the ancient cooking process. If the carbon and nitrogen stable isotope method is used to analyze carbonized residues in cooking utensils and compare them with the components in uncooked food, the proportions of C3 plants (such as wheat) and C4 plants (such as corn) in the residues can be roughly obtained, as well as the proportion of terrestrial and aquatic biological components. In addition, the content and ratio of plant sterols, alkyl resorcinol, free and esterified sitosterol, which are biomarkers of ancient Cereals, can be detected to distinguish which kind of food material the fat absorbed by the inner wall of cooking utensils comes from. < / P > < p > in this study, scientists analyzed the carbon and nitrogen stable isotopes of the charred food residue, and found that the burnt food residue represents the food composition of the last cooking in the pottery pot, rather than the accumulation of food cooked in the whole process of using the pottery pot or in recent use. However, the thin layer of residue adhered to the inner wall of the pot not only represents the last cooking food, but also retains the traces of food cooked several times before. With the change of food composition in the pot, the composition of this layer of residue is constantly “rewritten”, and is most affected by the last cooking. Therefore, this layer of residue represents mainly, but not just, the “last meal.”. The lipid absorbed by the wall of ceramic pot represents the gradually absorbed lipids in previous cooking. Moreover, although it can be seen that the lipid composition changes with the change of the recipe, even after several times of cooking with the new recipe, the lipid composition can not completely correspond to the lipid composition in the new recipe. This means that with the increase of cooking times, the fat absorbed by the wall of pottery pot is slowly replaced, but it still represents the mixing of all cooking food in the process of using the pottery pot. As to whether the new pot wall can be used for cooking, it remains to be studied whether or not the new pot wall can be used as a substitute for cooking. As a result, with the change of food composition in the pot, the change rate of the residue in the pottery pot from fast to slow is: burnt food residue & gt; thin layer residue adhered to the inner wall & gt; lipid absorbed by the pot wall. The components of the three residues reflect the cooking contents at different time scales: the lipid absorbed by the wall of the pottery pot reflects its use history; the thin-layer residue adhered to the inner wall of the pottery pot reflects the recent cooking situation; and the burnt food residue reflects the cooking situation in the last time. < / P > < p > the different time scales represented by different residues can help archaeologists to study the changes of food sources during the use of cooking utensils, and also help them understand the local ecological environment closely related to food collection and production in ancient times, as well as the utilization of resources by the ancients. This group of scientists’ unremitting “no brush pot” experiment provides us with a new method to infer the dietary composition of the ancients: the charred food residue obtained from ancient cooking utensils and the carbohydrate and protein in the thin-layer residue adhered to the inner wall, together with the lipid absorbed by the pot wall, constitute the different nutritional dietary composition of ancient humans. In addition, the service life of ceramic cookware can be estimated by quantitative and qualitative recipe composition provided by surface residue, qualitative recipe composition provided by absorbed residue, and radiocarbon dating of specific compounds. < / P > < p > it should be noted that diet includes preparation, cooking and storage. This study only tested the residues left after cooking food for a year in a ceramic cooker by boiling and “accidentally” scorching. In the paper, the researchers pointed out that if certain conditions were changed in the process, such as using other materials of cooking utensils, using other cooking methods, or for a longer time, it may no longer meet the conclusions of this study. SpaceX beat blue origin and Northrop Grumman to win a $316 million air force contract