By 6500 BC substantial shifts from meat to milk production occurred in western Anatolia which coincided with the discovery of pyrotechnology and the production of ceramics. Chymosin (formerly known as “rennin” and not to be confused with renin, EC 3.4.23.4, an enzyme in the kidney) is commercially important for cheesemaking, a process which dates back to ∼6000–7000 BC when widespread domestication of sheep and goats occurred throughout the Fertile Crescent although initially animals were probably raised for meat and not milk production as adult lactose intolerance was almost universal ( Kindstedt, 2012). The neonatal stomach of most, but not all, species secretes a special gastric aspartyl proteinase, chymosin, to induce coagulation. Fox, in Cheese (Fourth Edition), 2017 ChymosinĪs far as is known, the milk of all species coagulates in the neonatal stomach to increase the efficiency of digestion and to spread the ingestion of milk more evenly. Thus, the chymosins (EC 3.4.23.4) may be characterized as mammalian fetal or neonatal gastric proteinases belonging to the group of aspartic proteases (EC 3.4.23). For many years it was generally assumed that chymosin was restricted to young ruminants, but it has been shown that chymosin-like enzymes are widely distributed among young mammals. Hammarsten, the first to discover a proenzyme, showed that the rennet was secreted and stored as an inactive component, which was activated through the acid of the stomach. Other designations have been historically used ( pexin, chymase). Consequently, Foltmann suggested a return to the original designation in English, chymosin, subsequently adopted by the IUBMB. Lea & Dickinson suggested the name rennin (derived from rennet), which may be confused with renin (EC 3.4.23.15). The first attempts at isolation of the enzyme were made by Jean-Baptiste Deschamps (1804–1866), a pharmacist in Avallon, and its French name was chymosine (from ancient Greek ‘χυμός’ – khymos, ‘juice’). Cave paintings in the Libyan Sahara (5500–2000 BC) and Sumerian relief and stamp seals (3500–2800 BC) show milk processing and remains of cheese has been found in pots from ancient Egypt (3000–2800 BC). Pal Bela Szecsi, Marianne Harboe, in Handbook of Proteolytic Enzymes (Third Edition), 2013 Name and HistoryĬhymosin, in the form of rennet, has been used by humans for millennia for curding milk in cheese making. We also found that the clades, including the two major current urban pests, Cimex lectularius and C. hemipterus, separated 47 mya, rejecting the notion that the evolutionary trajectories of Homo caused their divergence.

This phylogeny places ancestral Cimicidae to 115 mya as hematophagous specialists with lineages that later frequently populated bat and bird lineages. Because quantifying host shift frequencies of hematophagous specialists and generalists may help to predict host associations when vertebrate ranges expand by climate change, livestock, and pet trade in general and because of the previously proposed role of human pre-history in parasite speciation, we constructed a fossil-dated, molecular phylogeny of the Cimicidae. The bedbugs that parasitize humans are host generalists, so their evolution from specialist ancestors is incompatible with the “resource efficiency” hypothesis and only partially consistent with the “oscillation” hypothesis.

Bats are believed to be the ancestral hosts of cimicids, but a cimicid fossil predates the oldest known bat fossil by >30 million years (Ma).

In general, blood sucking (hematophagy) is thought to have evolved in generalist feeders adventitiously taking blood meals, but those cimicid taxa currently considered ancestral are putative host specialists. All 100+ bedbug species (Cimicidae) are obligate blood-sucking parasites.

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