Biological and cultural factors in human evolution ?
The first step is to remind ourself of the definition of the term “evolution”. Evolution is most often defined as “any change in allele frequency in a population”.
Forces that drive evolution
Categorizing the processes that affect allele frequencies might be subject to issues of semantics. Without going into the details, we generally recognize 4 forces that drives evolution
- Natural selection
- Natural selection refers to the deterministic change in allele frequency due to a differential in fitness among different genotypes. Sexual selection and artificial selection are typically considered as part of natural selection (although that may vary from author to author)
- Genetic Drift
- Genetic Drift refers to the stochastic sampling process of individuals
- A mutation refers to any spontaneous change (substitution, indel, chromosome duplication, etc…) in an individual’s genotype.
- Gene flow (aka. migration)
- Gene flow refers to the transfer (migration) of DNA sequences among populations.
Source of Information:
Culture has driven changes to the human digestive systems making many digestive organs, like our teeth or stomach, smaller than expected for primates of a similar size, and has been attributed to one of the reasons why humans have such large brains compared to other great apes. This is due to food processing. Early examples of food processing include pounding, marinating and most notably cooking. Pounding meat breaks down the muscle fibres, hence taking away some of the job from the mouth, teeth and jaw. Marinating emulates the action of the stomach with high acid levels. Cooking correctly breaks down food and makes it more easily digestible. Food enters the body effectively partly digested, and as such food processing reduces the work that the digestive system has to do. This means that there is selection for smaller digestive organs as the tissue is energetically expensive, those with smaller digestive organs can process their food but at a lower energetic cost than those with larger organs. Cooking is notable because the energy available from food increases when cooked and this also means less time is spent looking for food. Humans living on cooked diets spend only a fraction of their day chewing compared to other extant primates living on raw diets. American girls and boys spent on average 8 and 7 percent of their day chewing respectively, compared to chimpanzees who spend more than 6 hours a day chewing.
Source of Information:
a. Ability of humans to learn on its own and as well as from one another, living together etc. leads to effective culture exchange between humans than other living species
b. Use of fire and cooking leads to changes in teeth structure and internal digestive system of the body
c. Change in skin color of people living in africa to save them from sun rays, change in the lung size of people according to their place of living like the ones that lives in mountains have more lung capacity than the ones living in plain areas, then in they have more blood circulation that leads to their red and pink cheeks in comparison to people of plain areas etc.
d. The the evolution of opposable thumb of humans that leads to better picking up capability of objects
e. Tool making that leads ease in many other works of daily life like hunting.
f. Culture of writing on leaves and than later on on paper, making artefacts on stones etc. that leads to culture transfer from generation to generation and hence better evolution of human being in terms of better culture and improved thinking capability over time