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Interrelationships between Evolution, Diet, and Genes
Interrelationships exist between evolution, diet, and genomes. The way that genes are expressed has shown to be relative to their organism's diet choices during their lifetime. Diet choices affect gene expressions, they have an important relationship with genetic environmental factors, epigenetics, and are involved in human evolution. The relationships may apply to animal models, similar to human models, which can be used to identify the genetics of subsequent generations. Proceeding generations from a lineage can inherit epigenetic edits that were induced by diets of the progenitor generation. Epigenetic factors can also leave tags on our DNA that roll into becoming genetic variations incoming generations. Dietary shifts have taken place in the process of human evolution beginning from the hominids. Through the course of evolution, genetic patterns of individuals that have gone through dietary shifts have shown to be indicators of natural selection. Human genome evolution is influenced by nutrition in that some certain changes and additions occur to human metabolism and genomes that affect behavior. There are examples of how evolution has affected environmental factors which inadvertently affect the genes we express and explains dietary choices.

The link between Diet, Genes, and Non-genetic Inheritance
Birth parents and their offspring are linked to some of the factors that are harmful to their offspring. Molecular and epidemiology research now infers that there are some dietary that behaviors can influence gene expressions and human genome evolution. Some of the association with diet and evolution was recognized during the deviation of humans and chimpanzees 4.7 million years ago. Experiments that were conducted to analyze epigenetic effects of the genes of the liver were done to shed light on the effects of diets on liver genes. This experiment was carried out in mice because mice, humans, and chimpanzees have similar genes and expressions that are located in similar areas in the genome. The result of this experiment showed that genes that had different expressions among humans and chimpanzees were traced back to the divergence of both humans and chimpanzees. Results also show that, due to the divergence, human evolution recognized a reduced gut size and an increased brain size which is a result of the increase in high-quality diet and cooking. .

Research, that was conducted by a British biologist Conrad Waddington in the the 1900s, suggests that the interactions between diet genes and other environmental factors are a result of epigenetic changes that take place in the environment. Epigenetic diet changes that occur due to dietary shifts begin when offspring are embryos throughout their lifespan development, until death. These changes are then carried on to subsequent generations. Epigenetic changes occur in animals. Examples of these epigenetic changes are DNA methylation and histone modification.

DNA methylation and histone modification can be altered which can result in the addition or detachment of signals to our DNA that can influence the phenotypes that we express. Epigenetic changes that are inherited are caused by environmental factors. Certain plant flavones or food chemicals are key instruments in altering DNA methylation levels and histone modification which leads to tags on DNA that can alter gene expressions. An expecting mother that indulges in unhealthy eating habits while pregnant can increase the probability of their offspring experiencing maladies like childhood obesity and gestational diabetes. However, this predicament can change by the mother counteracting her eating habits to a healthy one while breastfeeding the child. According to research studies, a healthy mother with a healthy diet routine breastfeeding can lead to healthy changes in the offspring. This is possible because the initial alterations that took place were environmental changes and not genetically inherited changes; therefore, these environmental epigenetic changes that manifested in the offspring can be reversed.

Gene-diet Interactions
The United States is a country that possesses diverse individuals from different ethnic groups and racial populations. These groups have different metabolic processes because there are different individuals from different ancestries that reside in the country. The result of these diverse populations that have inherited different kinds of metabolic processes began in Africa 100,000 years ago, where the relationship between diet-based genetic variation started. Modern humans migrated to different parts of the world where they settled, and experienced natural selection in regards to environmental factors like climate, and food sources that developed in the environment. The migration brought rise to population or region-specific genetic variations through natural selection. Individuals that have origins of the same continent experience the same nutrition issues compared to individuals from different continents. The dramatic change in nutrient interactions of a certain demographic can create harmful gene-diet interactions that can affect the way some genes that are in charge of metabolism are expressed. Therefore, leading to a generation of a change in the expression of an individual's molecular phenotype. The three components of gene interactions include ;


 * One, gene-diet interactions can be instigated by introducing a nutrient into a diverse population that is unfamiliar with the nutrient or the diverse population in question has not evolved to be accustomed to that nutrient. The introduction of a nutrient that is unfamiliar to a population can be deleterious to the health of the individuals in that population. The after-effects of this introduction are a change in the molecular phenotypes that control the metabolic processing of the foreign nutrients. For example, the transition from the consumption of saturated fatty acids to polyunsaturated fatty acids in the United States in 1961 lead to an overwhelmed polyunsaturated biosynthesis pathway which was hypothesized to lead to inflammation and inflammation increased diseases.


 * Two, a particular group in a diverse population that cannot digest chemical compounds which are found in certain foods in diverse populations is as a result of the foreign population not evolving in the environment where the food compounds are found. The foreign population is not selected to be adapted to the food compounds. The variants near the LCT locus that codes for lactase enzymes exemplify this component of gene-diet interactions. Populations from Northern Europe, African, and Asian descent have minute to no alleles that code for the enzyme which generates lactase, therefore leading to lactose-intolerant groups in a diverse population . Variations of the alleles around the LCT locus arose from the selection of traits that possess alleles for generating lactase that took part in the cattle domestication 500-100,000 years ago.
 * Three, epigenetic DNA modifications can switch the expressions of the genes that code for metabolic processes. These modifications do not alter the DNA sequence, they alter or reverse biological processes to become beneficial or harmful to the environment or offspring.

Evolution of Human Nutrition
Paleoanthropologists have answered the question of what humans are adapted to eat in three ways first, that the dietary lineage of humans have been traced to meat eating because most of the diets that have evolved to include meat were first supported 2.6 million years ago in the times of the early Homo. Although the majority of humans have adapted to meat-eating, our need for other essential nutrients indicates that we cannot solely survive on a carnivore diet. Second, the theory that one of the major food components that humans have adapted to is starch is challenged. Starch consumed in modern days and the starch consumed in the age of the early humans are different and are not necessary for survival. There is little evidence to bolster the theories that starch is the main nutrient for consumption for humans. Third, humans can thrive with or without starch and meats which may lead to the hypothesis that our diets could be based on variability. Studies have shown that the variability of the human diet palette is minuscule compared to other mammals. To bring these three theories together with the help of studies of evolution and genetics, the verdict is that what humans are adapted to eat will depend on the human genome, environmental factors, and how it processes the food components.

Nutrition in Human Evolution
The human dietary lifestyle has undergone genetic adaptations that have shaped and marked the human genome into what it is today. The marks on our genome and adaptations are a result of food ingested over the years. These marks aid in the understanding of human evolutionary history. Three dietary transitions have occurred during human evolution history. The early hominids ate mainly plant-based diets, then the Australopithecus which migrated to environments with open landscapes and also changed dietary lifestyle from grass-based to hard foods found on land. The environmental change came with the dietary shifts and change in the methods and required tools used to eat the foods found on land. Finally, the homo began to use the resources available to them to provide food for themselves. These adaptations to dietary lifestyle changes are the signatures on our genes.

Examples
Illustrations of diet-related adaptations show us how humans have evolved and why several variations occur. These are important diet adaptations that have shaped human evolution and relationships to certain nutrients.


 * AMY1 gene is responsible for encoding salivary amylase which is used for starch digestion. The populations that consume high starch diets became prevalent for the AMY1 gene . The populations who are adapted to eating meat do not have the gene. In the genome of populations that are meat-based, there is less copy number of the gene as a result of the low starch diet consumed. The low starch consumers are the rainforest dwellers that get their energy from fruits and meats, whereas the starch-dependent population is open foresters that eat tuber crops.


 * Eastern and Western Asians have been hypothesized to have a lower tolerance for alcohol since they have mitochondrial mutations in certain genes that lead to low acetyl aldehyde dehydrogenase production.


 * Folate is known to be significant in the Northern Eurasian groups because of the MHTFRC677T polymorphism which can be associated with reduced activity and higher homocysteine levels . Dietary folate depends on several factors like climate and temperature, and soil fertility. Lack of this enzyme can bring about neural tube defects.


 * The adaptations for vitamin D originated from the intense sun exposure in Africa, whereas light skin originated as a result of the sun moving away from the equator. Vitamin D is needed for calcium metabolism. Deficiency in vitamin D resulting from populations moving to higher latitudes with lower incident sunlight leads to bone malformations and immune system deficiencies.