The multiproxy reconstruction of the late quaternary site at Deeping St. James, Lincolnshire is to be carried using the laws of stratigraphy and checking for biogenic materials. In contrast to the view of the early geologists stratigraphic data is more dependable. They held the opinion that catastrophic events were the principal culprits of environmental change. The law of superposition states categorically that the stratum on top is younger than the below it. The single layer (stratum) is deposited through water, ice or air. The sedimentation allows a geologist to establish the relative age and make inferences pertaining to the strength of the tectonic forces. The climatic influences can also be deduced from the obtained information. Quaternary organisms survive as fossils. Lone fossils have less impact than fossil assemblages.
The Quaternary period is considered by many experts as having begun 2.6 million years ago. The assemblage of coleopteran fossils in the sediments is a useful indicator of the Quaternary terrestrial thermal environment. The advantage of using the sediments is due to the abundance of the coleoptera (beetles) in the reduced condition since deposition in the sediments. Coleoptera are critical organisms in the indication of the palaeo-environmental periods. According to the late professor Evans, J.G molluscan analysis is another vital tool in the reconstruction of archaeological environments. He studied the factors that influence and fundamentally control distribution of land snails. These factors have a strong correlation to the environmental conditions. The Molluscs are thus an integral part in determining the period within which certain climatic events occurred.
Climatic significance of coleoptera
The exoskeleton of the coleoptera is principally important in the survival of the organisms. The loss of the exoskeleton would lead to the exposure of the organisms' organ systems. The exposure of the organ system will then lead to the irradiation of the vital organs. The exoskeleton is made up of a material known as chitin. Sclerotin has been found in some species of coleoptera and it serves the same the function as chitin. The exoskeleton prevents desiccation of the organism and entry of any disease causing organism (pathogenic organism). In the harsh environment, the exoskeleton prevents coleoptera from decomposition. The preservation of the fossils allow archaeologists, palaeontogists and other researchers determine the accurate period within which the organisms thrived. It consequently allows the determination of the age of the sediments by approximation.
One of the biggest challenges faced by paleontologists is the limited knowledge that is available on stratigraphy. The inadequate knowledge serves as a monumental barrier to unlocking the mysteries of climatic changes that occurred through history. There is a common belief among experts that attributes the occurrence of coleopteran fossils to significant historical events such as the pre-glacial, glacial and post-glacial periods. The other contradictory school of thought is the belief that all the quaternary insect fossils were remnants of the animals that had become extinct and thus the assumptions made were deviated from the truth. Those who believe that the remnants were extinct also demand that new names be given to these new organisms.
The land snails which are edible have been associated with the transition between the mesothilic and Neolithic period. The land snails have been found to be abundant in the late Pleistocene period, a time in which they were considered a delicacy. The land snails are still considered a delicacy among most communities in the world. Their presence is believed to have been in the period prior to the emergence of the agriculture in the post-glacial period.
According to Cameron, R.A.D the classification of Molluscs found in a given region helps to date the age of the region. The land Molluscs found in the British Isles includes snails and slugs. The snails have a shell covering their body. The slugs on the other hand lack an external shell or are too small in relation to the body size.
The families of slugs are easily identified by presence or absence the keel. The keel is the midline ridge extending to the tail region. The relative length of the keel is also a factor used in distinguishing the families. The other factors used include the position and structure of the mantle and pneumostome. The region posterior to the mantle is known as the body. The pneumostome is the bulging of the lung outward and is located on the right in most families.
The identification of species is made on the basis of presence or absence of bands on bands on body and mantle. The size of the lateral pigmented bands on the body plus the position is an important criterion in identifying the species. The consistency of the mucus produced by the snails and slugs has been used to distinguish the different species of Molluscs.
The slugs depend principally on moisture for their survival. The slugs are usually active at night and shelter themselves from the sun in daylight. They are also highly active in the rainy weather and hide themselves during the dry spells. The best time to look for the slugs is on damp and warm nights when they are most active. The time which is an inconvenience to the scientist is during daylight in a dry weather condition. The slugs usually go to hide under stones, around the base of plants and in the litter.
The factors that control the distribution of land Molluscs are multiple. The fresh water chemistry is a crucial factor that determines the viability of Molluscs. The chemical composition of the water: oxygen levels, carbon dioxide levels and the ionic concentration significantly influence their localization in certain regions. The soil provides most of the calcium required by the snail to build the hard shell.
Temperature levels also influence the distribution of snails and slugs. At temperatures of between 50and 250 C the snails can still mate and reproduce. The optimum temperature range for reproduction is between 200 and 250C. Hyper thermic conditions destroy the Molluscs while hypo thermic conditions inhibit their functioning. Humidity is a vital component to the distribution of Molluscs as the moisture content of the air promotes the survival of Molluscs specifically slugs.The land snails living in temperate regions often hibernateduring the winter (the temperatures are too low for the enzymatic reactions to occur in the snail's body) and during this time gametogenesis (the production of sexually mature male and female gametes) reduces or goes down to a level it is almost completely off. The high sexual activity would normally resumeprior to the end of the hibernation cycle. The longerthe hibernation period of the snails which is usually up to one and a half years when evaluated,the sooner the mating behaviour will occur to compensate for the long dry spell.
The availability of food is a key factor determining the regions where snails and slugs are found. Snails and slugs feed on a variety of plants. The plants fed on by the slugs and snails are at times poisonous to humans but harmless to the snail or slug. This is one of the principal reasons why snails are starved before being killed and cooked for human consumption.
Mechanism used to reconstruct St. James Deeping to the late Pleistocene period
The collection of the samples was done in a highly hygienic manner. The snails were collected from underneath logs, between crevices in the walls of damp buildings and in the litter bins. The pre-determined sample size was 15 snails and slugs but only 11 were captured in the St. James Deeping area. The ambiguous snails and slugs were discarded and excluded from the process of identification. The exclusion criteria wereambiguity of the species and pathogenicity. Some rare snails (mainly found in Africa and Asia) which are involved in disease causation such as Biomphalariaspecies which is a vector for the parasite Schistosoma mansoni, Bulinus species which is the vector for Schistosoma haematobiumand Oncomelania species which is a vector for Schistosoma japonicum. The collection exercise was without hitches and the pathogenic snails were not encountered.
The first step was to identify the Jurassic clay soil found in the Peterborough region where the terraces had been dug up. The soil provided the micronutrients required for growth of L. macalatus which is now distinguishable from the species L. flavus. The species are found in the Family Limacidae. The family is characterized by having creamy white colour. The colour of the members of the family is at times grey or brown. The Limax tenellusis a species that is unique in the family Limacidae. It has darker tentacles (the upper tentacles are larger and contain eyespots) than the rest of the members of the family. It has a yellow colour and produces yellow mucous.
The species is thought to have existed before the start of the agricultural revolution in Mesopotamia. The discovery of the species at Deeping St. James dates the area back to the pre-agricultural period. The second species found in the sediments was the Arion intermedius. The Arion intermediusis a fairly common species in the south of England. The retrieval of the species was an expected find and its description was text book fitting.
The yellow foot mucous(Arion intermedius) which is highly indicative of the species was noted even on the sole of the foot. The lateral bands were noted to be faint. The black spotted foot fringe was noted in 7 out of the 11 snails that were collected. Arion distinctus species were collected majorly in the litter bins during the summer period. The species were noted to have a high preponderance for humid conditions. They were collected in plastic paper bags to simulate the humidity they experienced.
The land snails that were found in the late Pleistocene and early Holocene periods were considered as the low-ranking resources of the periods, compared to the large mammals which walked on toes or had modified toessuch as the antelope, horse ( tafoya) or the deer. The archaeologists and geologists argue thatthe mammals would basically have snails as their diet only in response to extremeshortage of all the other resources.
The other species found in the St. James Deeping area were not helpful in the classification. They didn't give information that was significant to classify the area in the late Pleistocene period. The species discovered were however useful in placing the area in the late Pleistocene period.