Evolution and Human Origins: A Comprehensive Study
Evolution: Key Concepts and Evidence
Neutral Theory of Molecular Evolution
Independent: The Japanese scientist Motoo Kimura suggested that most mutations that occur during evolution are neutral, indifferent to natural selection. For the same reason, their distribution in a population corresponds to a purely random factor. According to the neutral theory, natural selection is not pure chance but allows for several populations in which a particular mutated gene can be dispersed without any selective advantage.
Punctuated Equilibrium
The punctuated equilibrium suggests that the absence of intermediate steps in the fossil record is not because it is incomplete, but because evolution sometimes occurs in leaps.
Morphological Studies
Morphological study, based on comparative anatomy, allows us to know the similarities and differences that the same organ displays in different species.
Homologous and Analogous Organs
Homologous organs are the result of divergent evolution from a common ancestral organ that differed as a result of organic adaptation. Analogous organs, such as a butterfly wing, have their origins in a process of adaptation to develop a similar function (flight) and are examples of convergent evolution.
Paleontological Evidence
Paleontological studies examine fossils in sedimentary rocks.
Embryological Evidence
Embryological studies examine the early development of organisms. These studies have shown that different vertebrates are very similar in their first weeks and gradually differentiate. This led Ernst Haeckel to propose the principle of recapitulation, which states that embryonic development is a summary of the evolution of its species.
Taxonomic Classification
Taxonomic groups have similar characteristics that follow a common evolutionary process.
Comparative Biochemistry and Cell Biology
The chemical unit of living things is the genetic code, which establishes the relationships between the sequence of nucleic acids and proteins. ATP is the molecule that provides metabolic energy to cells, irrespective of the type of body concerned. The metabolic and physiological processes are common to most major groups of living things, even very different ones.
Proteins and DNA Sequences
Comparing nucleotide sequences of the same gene or amino acid sequences of the same protein in different species reveals similarities.
DNA Hybridization
DNA hybridization is the capacity to renature and reconstruct the hydrogen bonds between the bases of their chains after having undergone a process of denaturation.
Speciation and Reproductive Isolation
Species Definition
A species is a set of organisms that has morphological similarities, can reproduce resulting in fertile offspring, and has reproductive isolation from other species.
Reproductive Isolation
Reproductive isolation is the inability of organisms to reproduce with each other, and when it appears between different populations of a species, it leads to speciation.
Demos and Speciation
Demos are the same group of individuals or populations of a species, within which reproduction occurs. The process of speciation occurs when insulation between members of a species leads to reproductive isolation between populations of the same species, resulting in the appearance of two or more different species. The most important factor is geographic isolation.
The Classification of Living Things
The classification of living things: Taxonomy is the branch of biology responsible for the classification and nomenclature of living things and is done through a hierarchical system.
Human Origins and Evolution
The Origin of the Human Species: Order Primates
Order Primates are an order of mammals whose origin dates back some 75 million years. Its features are forelimbs endowed with great mobility, stereoscopic vision that can calculate distances, a digestive system specialized for feeding from a relatively varied diet, and a very limited number of offspring dependent on the mother after birth.
The Process of Humanization
The process of humanization is characterized by the following changes:
- Adopting a bipedal posture or erect lower extremities.
- Legs become longer.
- Hands become more mobile and get progressively greater accuracy.
- The diet is diversified and includes increased meat consumption.
- Encephalization (brain size relative to body size) increases.
Originally driven by the following factors:
- A rich and varied diet.
- Development of social activities and communication.
- Increased rate of brain growth during gestation.
- Prolongation of childhood and infancy.
Evolution of Hominids
The evolution of hominids: Australopithecus > Homo habilis > Homo erectus > Homo antecessor > Homo neanderthalensis > Homo sapiens.
The Human Brain
The human brain is the part of the brain responsible for higher functions related to intelligence. It has two hemispheres, right and left. Salient features of the brain:
- The existence of distinct functional areas responsible for specific tasks, and lateralization.
- The great development of the frontal lobe that controls motor functions and developing intellectual capacities.
- The temporal and prefrontal areas that are related to language.