Human Evolution: From Australopithecus to Homo Sapiens
Human Evolution
Australopithecus
The first hominids were just over one meter tall, with long ape-like arms. However, their spine, pelvis, and lower limbs were adapted for bipedal locomotion. They were vegetarians with large molars, thick jaws, and a pronounced cranial crest. Bipedalism freed the powerful muscles of their arms and hands for other actions. They walked on their hind legs.
Homo habilis
Homo habilis lived in Africa alongside australopithecines. Similar in appearance to australopithecines but somewhat larger, they had increased cranial capacity and a new skill: toolmaking. Their diet was more varied than australopithecines; they were scavengers and predators, feeding on bone marrow.
Homo erectus
Homo erectus made more elaborate stone tools, such as axes, cleavers, and picks. They were the first hominids to control fire and the first to leave Africa. Remains have been found in Africa, Asia (Java), and Europe. They exhibited social behavior, hunting large animals, requiring organization, communication, and planning. They walked upright.
Homo antecessor
Homo antecessor shows signs of cannibalism, not ritualistic but for food. They had older characteristics, especially in the face, with flattened facial bones. Remains have been found on the border between Asia and Europe.
Homo neanderthalensis
Homo neanderthalensis had a robust skeleton and was stronger than modern humans. They had a high cranial capacity, but their brains were different from ours. They lived in Europe and western Asia. They buried their dead and developed tools for different uses. They probably could obtain fire and survived in an extremely hostile environment.
Homo sapiens
Homo sapiens emerged in Africa. They possess a modern bone structure: high forehead, retracted face, weak brow ridges, and a prominent chin. Their jaw structure and cranial volume are similar to modern humans. They are the only hominids to develop verbal language. They are the only mammals that can breathe and swallow at the same time. They made specialized tools. With better climatic conditions, humans expanded across the continents, colonizing Asia, Africa, Australia, and finally, via the Bering Strait, the Americas and Europe.
Biological Evolution
Fijist Theories
Fijist theories contend that the world and life forms are static and immutable since creation. The discovery of fossils of extinct life forms challenged fijism. The diluvian theory proposed that fossils were remains of animals that did not survive a universal flood. Cuvier proposed the cataclysmic theory to explain the existence and extinction of animals.
Evolutionary Theories
Taxonomy revealed similarities between living beings worldwide. Lamarck introduced the concept of adaptation, a mechanism for organisms to withstand environmental changes. He proposed the law of use and disuse: the use of an organ leads to its development, while disuse leads to atrophy or disappearance.
Current Debates Around Evolution
- Direction of evolution: Is it random or directional?
- Causes of evolution: Environmental or internal factors?
- Rate of evolution: Gradualism or punctuated equilibrium?
- Role of natural selection: Primary or assisted by other agents?
- Adaptive value: The significance of adaptation.
Darwin and Wallace’s Theory of Evolution by Natural Selection
Darwin’s theory of natural selection involves: great variability among individuals in a population; the age of the Earth; and the struggle for existence in an environment with limited resources. Natural selection is the mechanism by which species change over time. Key evolutionary theory points are: a) variation among individuals in a population; b) natural selection, where advantageous characters allow reproduction and transmission to the next generation; and c) gradualism, where individuals with adaptive characters become the majority in the population.