Human Evolution: From Primates to Modern Homo Sapiens
- Forelimbs endowed with great mobility: Prehensile toes, flat nails, opposable thumb, which promotes dexterity.
- Stereoscopic vision: The position of the eyes in front, to calculate distances.
- Unspecialized digestive system, which can have a very varied diet: plants, carrion, meat, insects.
- A very limited number of descendants: With large units of the mother after birth, thereby developing a complex social behavior.
Genetic Changes Conditioning the Human Species: Hominization
It is a complex biological process of natural selection and adaptation.
It is linked to a major global climate change that occurred between 3 and 2.5 million years, where large areas of forest were replaced by African savanna, which had to abandon some primates’ arboreal life.
Hominization
- Or erect bipedal stance: Establishes the vision above the level of plants, and frees your hands to get tools, hunting weapons or even climb trees.
- They lengthen the legs, the pelvis widens and shortens, the femur is directed inward and amending the knee joint, thus facilitating the upright position, the toe longer opposable toes now only used for walking. Changes in the spine, which takes the form of S.
- The hands become more mobile and get progressively increasing accuracy, become precision tweezers (not pressure). That along with hand-eye coordination, and the vertical position will promote further development of the brain.
- Diversified diet, including meat and reshapes the teeth, gradually reducing the teeth, suffering less wear. The skull is more graceful reducing the facial area, the lower jaw and the binding sites of the jaw muscle.
- Increases the degree of encephalization, which is the relationship between brain size and body size, as influences:
- A rich and varied diet with nutritional value.
- Development of social and communication activities necessary for hunting, sharing food, etc. culminating in the development of language, a major milestone in human evolution.
The Human Brain
The brain is the part of the brain responsible for higher functions related to intelligence. It has two hemispheres, LH and RH, and each with four lobes: frontal, temporal, parietal and occipital. The outermost part of the brain is the cortex with a large number of interconnected neurons.
In the cortex there are two parts:
Paleocortex: Related to the reception of olfactory stimuli.
Neocortex: Characteristic of mammals and in humans is well developed gyri and sulci that increase the surface allowing great expertise.
- And in whose features include:
- Existence of different functional areas responsible for specific areas, and lateralization, each hemisphere has some functions.
The Evolution of Hominids
It is considered that started 6 or 7 million years in Africa a common ancestor to humans and some other primates today. Among these are several species:
Orrorin tugenensis, Australopithecus, Paranthropus, Homo habilis, Homo rudolfensis, Homo ergaster, Homo erectus, Homo antecessor, Homo neanderthalensis and Homo sapiens
The Human Evolutionary Tree
It is difficult to identify the evolutionary lines of hominids.
Its origin was in Africa, where the largest deposits (H. ergaster, H. erectus) and then expanded into Europe and Asia.
In Atapuerca (Burgos) is situated the H. antecessor and H. heidelbergensis, where the H. neanderthal seem to come and H. sapiens.
Technological and Cultural Development
The story of Homo sapiens is an evolutionary success story without precedent, a few populations living in balance, we have now to reach equilibrium in balancing that characterizes life.
Technological advances such as stone, metal, fire, resulted in a rapid evolution of hominids, which has also been reflected in cultural and social progress.
From the Neolithic Age 10,000 years ago, starting a gradual population growth, which leads to contact groups, share knowledge, improved study skills, teamwork, creativity, innovation, making a collective resource of knowledge assets all mankind.
The Diversity of Homo Sapiens
The migrations of Homo sapiens led to the diversification of the species, found in every place different climatic and environmental conditions for a partial geographic isolation of populations, without in any way be reproductive isolation. Today there is geographical isolation, even if cultural barriers.
Mitochondrial Eve and Y Chromosome Adam
Mitochondrial DNA is inherited only from the mother, that’s who contributes the mitochondria, this comes from an ancestor who lived 200,000 years ago, so it is called mitochondrial Eve. DNA mutations that allow migration and further elucidate relationships between human groups.
Something similar happens with the Y chromosome that is passed from father to sons.
The Result of Evolution: Biodiversity
Life presents a great biodiversity as a result of the evolutionary process. Every form of life on Earth is classified as a species, defined as all organisms that have morphological similarities can reproduce giving rise to a fertile offspring and have a reproductive isolation from other species.
Process of Speciation
The individuals of a species are grouped to form populations or demos can be played and give fertile offspring. If there are physical barriers is the phenomenon of speciation by geographical isolation, where populations are separated (the appearance of mountains, tectonic drift, rivers, etc.).
The hinny is a hybrid resulting from crossing horses with donkeys.
The mule is a hybrid resulting from crossing a donkey with a mare.
Both are sterile, then donkeys and horses are different species, have different numbers of pairs of chromosomes, they can not mate.
The Classification of Living Things
Taxonomy is the branch of biology responsible for the classification and naming of living things. All the millions of species are divided into five kingdoms:
R. Monera: Bacteria and cyanobacteria.
R. Protoctista: Protozoa and algae.
R. Fungi: Mushrooms.
R. Metafitas: Plants.
R. Metazoa: Animals vertebrates and invertebrates
Binomial System
Linnaeus established the binomial system, provides that the name of a species consists of two Latin words written in italics, the first corresponds to the genre. The human species is called Homo sapiens, and belongs to the genus Homo.
Species: Homo sapiens
Genus: Homo
Family: Hominidae
Order: Primates
Class: Mammals
Subphylum: Vertebrates
Phylum: Chordata
Kingdom: Metazoa
Similar species are grouped in the same
Gender, gender in
Families, households
Orders, orders in
Classes, classes in
Subphylum these in
Phylum, and these in
Kingdoms