Human Evolution Milestones: Anatomical and Behavioral Shifts
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Hominization Stages
The evolutionary process leading to modern man is characterized by two main stages:
- The first stage marks purely animal existence.
- The second stage involves the ability to perform prehuman cooperative behavior, leading to the emergence of language.
The first stage was significantly longer than the second. Remains found have led paleoanthropologists to conclude that changes in habitat caused behavioral shifts. The greatest threat on the ground strengthened solidarity among them, forcing them to move and adapt to adverse conditions, favoring an upright posture.
This liberation of the hands allowed them to carry objects, leading to anatomical, physiological, and psychological improvements.
Anatomical Improvements: Bipedalism
Bipedalism Improvements
Vision became a central organ for the activity of early hominids. There was a congenital development of structures supporting an erect posture, such as the structure of the lower extremity, the five fingers, bulging joints beneath them, narrowing of the pelvis, and the appearance of a hole between the leg bones.
Liberation of Hands
Going upright allowed for the development of hand dexterity through increased innervation. The hands retained all five toes but developed harmonic motion and the opposition of the thumb.
Brain Development
The vertical position meant the hominid no longer needed to defend itself primarily with its mouth; this could be done with the hands. Consequently, large, powerful jaws and facial muscles were no longer as functional and began to disappear. This shift favored the development of the central nervous system and the production of a growing brain. Cephalization evolved alongside cerebration.
Physiological Improvements
Changes in Food
Man became omnivorous.
Neoteny
The need to protect fire and prepare useful items for camping led hominids to seek protected places that were easier to watch. Neoteny refers to the slow development of newborns. The speed of bodily development decreased due to the increased dependency ratio of the young relative to the adult.
Psychic Improvements
Cooperative work activity and social activity stand out as key social characteristics, alongside the appearance of language.
Second Stage
This stage is characterized by the inflection toward word use in hominids, making them very similar to modern humans under actual circumstances. The discovery and use of fire were decisive influences, protecting them from carnivores. While natural selection and organic evolution underpin culture, once the capacity for culture fully developed, major variations ceased to appear.
The appearance of language, a system of universal semantic communication, had a great repercussion on evolution. The transition from screaming to language was a significant evolutionary step.