Plant growth, habitat of various microorganisms, sustenance conditions for the fauna and flora, are determined by the quality of soil. However, alteration in the properties of soil leads to various deficiencies/diseases in plants and thereby affects dependent fauna. The alkalinity and acidity of the soil refer to the change in pH value of the soil. In the North East India, most of the soils lack calcium (Ca) and are acidic. Therefore, majority of the fauna and flora have lower availability of Ca due to leaching, caused by the heavy rainfall. The present study hypothesizes that the life originating from areas deficient in Ca, impacts their bone concentration and facial formation. This makes them phenotypically distinct from their counterparts residing in the other regions which have alkaline soils or have the optimum pH value of soil. Strongly acidic soils, might have led to the formation of the major Mongolian Race in humans.
A natural medium for the growth of plants on the immediate surface of the earth, comprising of unconsolidated mineral and organic matter, is referred to as soil. It supports the growth of plants by providing nutrition for photosynthesis through harboring different minerals and nutrients required for the fixation and reduction of atmospheric carbon dioxide [
Among the various chemical properties of soil, (salinity, carbon to nitrogen ratio, cation exchange capacity, organic matter), pH is highly important for the normal growth of fauna and flora. Basically, pH is the measure of the acidity or alkalinity of a soil which is measured as the logarithmic scale which implies that a drop of 1-unit in pH is a 10-fold increase in acidity. Based on the measure of pH, soil is categorized as neutral (pH 7.0), acidic (pH < 7.0) and alkaline (pH > 7.0). This occurs due to H+ exchange processes that involve vegetable soil solutions and soil minerals [
Acidic and alkaline soils are distributed throughout India [
In India, most areas of the North East (NE) states predominantly, have strongly acidic pH value of the soils. These regions, lying between 25.5736˚N, 93.2473˚E, also receive heavy rainfall (annual rainfall 1350 mm) [
Many studies assessing the genetics behind the phenotype of a human being reported many genes to be responsible for governing the morphogenesis of facial structures. However, various studies determining the interactions between human genes and the environment have also established that the expression of genes of individuals are influenced by their surroundings/environment [
The NE Region (NER) of India, spreading over 255,090 km2 (
varies between 21˚C - 31˚C (high) and 12˚C - 20˚C (low) [
The people originating from the states of NE India are phenotypically different from other Indians. Moreover, people with an ancestral background/history associated with these states also possess the similar morphology [
Soil benefits humans through various ways such as by recycling the nutrients, maintaining the optimum cationic and anionic balance, sustaining biodiversity and habitat, conserving water level, ensures food availability and governs the interactions between humans and various chemicals and pathogens [
Alkaline soils are found in Indian states of Uttar Pradesh, West Bengal, Punjab, Bihar, Orissa, Maharashtra, Tamil Nadu, Madhya Pradesh, Andhra Pradesh, Gujarat, Delhi and Rajasthan. Overall, these states cover an area of about 7 million hectares [
It has been observed that the acidic soils have pH value 5.0 or even less than that and receive more than 750 mm annual rainfall. Acidic soil is prominently found in the seven sister states of NE India viz., Assam, Meghalaya, Arunachal Pradesh, Mizoram, Nagaland, Manipur, Tripura and some areas of West Bengal and Bihar in India. All these states are humid and experience heavy rainfalls over the year (annual rainfall 1350 mm) [
Besides heavy rainfall, the other factors leading to the acidity of soil are continuous removal of lime and other base elements by crops and accumulation of acids contained in the manures, application of acid forming fertilizers in the soil, microbial action, formation of soil on the acidic rocks [
Human races represent different groups of people that share certain visible physical characteristics (facial features, skin color, eyes formation, hair texture, etc.). Also referred to as subspecies, these races are differentiated at genetic level and are geographically confined. However, they may coexist at any given time [
Indian population belongs to the Mongoloid race. Although belonging to the same race, certain striking differences are still observed among the populations residing across the Indian states. People with NE Indian origin look distinct from Indians originating from the rest of the Indian states. Ecological, biological, geographical, racial, gender and age factors affect the variations among (inter-) and within (intra-) the population [
People originating from Russia, a part of the Asian continent, and different regions of Europe survive on various soil types. Prominent among those found in Europe are Cambisols, Chernozems, Calcisols, Solonetz and Podzols, where Cambisols and Chernozems cover most of the land area viz., 26.72% and 9.00%, respectively [
Besides the features of the soils found in these countries, Russia receives moderate annual rainfall ranging between 200 - 750 mm [
Both the factors, i.e., no leaching as well as Ca rich soils, lead to adequate amount of available Ca to the plants. Hence, the humans feeding on Ca rich plants get enough Ca to support mineralization of their bones. Therefore, Caucasoids (the human race found in Russia and the European continent) are influenced by the highly available Ca in their diet resulting in usually medium to tall stature with well-defined and sharpened facial features. The face is narrow, long and lacks protrusion of the jaws. The chin is pronounced and nose is sharp with a high nasal bridge [
The nutrient imbalance may be in the form of deficiency as well. The NE soils which are acidic and lacking sufficient Ca cause deficiency of Ca in humans due to the consumption of Ca-deficient plants growing on such soils. Insufficient Ca levels in the soils cause deterioration of cell membranes leading to leakage and thus, loss of cell components. Ca acts as a messenger in the regulation of nutrition uptake processes and other metabolic processes occurring in the plants [
In humans, Ca is the most important mineral that forms the basis of bone mineralization. Its deficiency in the human diet (due to intake of Ca deficient plants) leads to many deficiencies such as low bone composition and dimensions, high incidence of dental caries, rickets, osteomalacia and osteoporosis, and defective non-skeletal processes [
It is believed that the genetics of an individual decide the phenotype. However, various genetic studies provide evidences to support the current hypothesis. Different genes express themselves and are responsible for specific physical appearance of an individual. In different studies by Ahlgren and co-workers (1999), Hu et al (2003) and Brito and co-workers (2006, 2008), genes namely, FEZ (frontal ectodermal zone) and Shh (Sonic hedgehog) govern the morphogenesis of facial structures [
However, various studies on interactions between human genes and the environment have established that the expression of genes of individuals are influenced by their environment [
Overall, the deficiency of Ca in the diet of the NE Indians occurs due to the acidic nature of the NE Indian soil which lacks Ca. An insufficient amount of Ca in the diet leads to reduced bone mineralization in humans which results in their distinct phenotypic appearance, as of the Mongolian race. The other two major human races of the world might also get the explanations in some other soil variables.
The author acknowledges her relatives, friends and Miss Krishna Tokas for their moral support and motivating her to pen down the proposed hypothesis. The author also acknowledges Knowledge Isotopes Pvt. Ltd. for their assistance in writing the review.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
The research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Barthakur, I.K. (2018) Soil pH as a Phenotype Determinant in Humans: Proposing a Scientific Hypothesis. Open Journal of Soil Science, 8, 36-46. https://doi.org/10.4236/ojss.2018.81003