HOMINIZATION PROCESS: CHARACTERISTICS AND PHASES - BIOLOGY - 2025

The process of hominization is the evolutionary development of human characteristics that differentiate hominids from their ancestors the primates. In simpler terms, it could be said that the word "hominization" refers to the different transformations that the common ancestor of primates and hominids underwent (through different species) to "produce" human beings as we know them today. (Homo sapiens sapiens).

This term was initially restricted to the description of the emergence process of modern man, however, today it is a bit broader, since it includes all aspects of the structural and behavioral changes that occurred in the hominid line and that they ended up with the man of today.

Representation of the hominization process. Image by LAURENCE ROUAULT at www.pixabay.com

Different authors agree, then, that the most outstanding changes that occurred in this lineage can be summarized in five fundamental points:

- The development of bipedalism (walking on the two hind limbs)

- The improvement of manual handling and the manufacture and use of tools

- Modification of the jaw and teeth

- The increase in brain mass and

- Changes in the vocal cords, the development of language and communication

It is proposed that such a process of hominization began in Africa, more or less 6 million years ago, when some ancestral primates left fossil traces of their ability to use certain types of "tools".

Characteristics of hominization

The hominization process was defined by some characteristic events that occurred in the different species of the lineage and that led to the development of modern man. These characteristics are summarized in 5 main milestones:

- Bipedalism

- The anatomy of the hands and the use of tools

- Modification of the jaws and teeth

- Increased brain mass

- The development of language and communication

Bipedalism

The ability to walk upright on the lower limbs is, perhaps, one of the oldest characteristics shared by all hominids and that appeared in the most primitive ancestors, belonging to the Australopithecus genus.

This statement is consistent with the fossil records of about 4 million years ago, which correspond to a female of the genus discovered in Ethiopia in 1974, who was baptized "Lucy", and with the analysis of fossils of Australopithecus africanus, Australopithecus afarensis, Australopithecus ramidus and Australopithecus anamensis, also of the same genus.

Australopithecus afarensis (Source: Australopithecus_afarensis.JPG: User: 1997derivative work: Rafaelamonteiro80 / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.5) via Wikimedia Commons)

The ability to walk upright involved a series of important skeletal modifications, which were necessary for the transition from a life on trees to a life in the African savannas. Among these modifications we can highlight:

- the lengthening of the lower limbs and "flattening" of the soles of the feet

- the shortening of the upper limbs, including the fingers of the hands

- the widening of the palms of the hands and development of an opposable thumb

- the “restructuring” of the spine into an “S” shape to support the head in a vertical position and

- the narrowing and strengthening of the pelvis to support the viscera (internal organs)

In this phase of the hominization process it is good to establish that hominoids belonging to the Australopithecus genus had small brains, prominent faces, as well as their teeth, and arms much shorter than their legs.

Anatomy of the hands and the use of tools

The ability to use hands with some precision (different from that of apes and more similar to that of members of the genus Homo) was first observed in Australopithecus afarensis, a species of hominoid that had hands of similar proportions to that of humans, but with more "curved" digits, from which it is deduced that it had a greater "grip" capacity.

Facial reconstruction of A. afarensis. Cicero Moraes / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

The literature agrees that the acquisition of a greater grasping capacity than that of apes, but less than that of humans, could have meant a significant expansion of the ecological niche for members of the Australopithecus genus.

The next "phase" of the hominization process is represented by paleontological findings of the species Homo habilis, according to which there is indisputable evidence that the manufacture of stone tools occurred more than 2 million years ago, before the appearance of brains more large and complex.

Homo habilis is the first known species of the genus Homo. They were short hominids (less than 1.50 m), with slightly larger brains and smaller teeth than those of Australopithecus. The epithet "habilis" was assigned thanks to his known ability to carve stones.

After H. habilis, about 1.8 million years ago and up to 200 thousand years ago, representatives of the species Homo erectus lived on the earth.

H. erectus not only had the ability to make more sophisticated tools, but also learned to control fire, which had great ecological significance, as it acquired the possibility of:

- cook your food

- keep warm at night and in cold seasons

- drive away predators and

- light up your paths in the dark

In addition, it had a brain capacity even greater than that of Homo habilis and with them the earth saw the light of the first social organizations that allowed a thick development of communication through the spoken language in hominids, which spread to the most temperate Eurasia.

There is evidence that Neanderthals, belonging to the species Homo sapiens neanderthalensis, which inhabited Europe and Western Asia about 60 thousand years ago, had religious practices.

Furthermore, the Cro-Magnons, the European representatives of Homo sapiens sapiens, built their homes and maintained stable communities some 40,000 years ago or less.

The domestication of plants and animals, the development of agriculture and the appearance of the first civilizations did not take much longer to characterize the modern human being.

Modification of the jaws and teeth

The differences between the jaws and teeth of apes and hominids are quite significant. The former have large, thick enameled teeth, with prominent canines and molars, as well as a large jaw (as are their associated muscles).

Compared to Australopithecus, for example, apes have a higher ratio of tooth area to body weight.

Australopithecus radimus, had teeth similar to those of some representatives of the genus Homo: small teeth, with a thin layer of enamel and short canines, similar to chimpanzees in certain respects.

Australopithecus afarensis, on the other hand, had traits shared between apes and hominids: incisors like those of chimpanzees, but canines like those of Australopithecus africanus. Homo habilis had teeth more or less similar to those of Australopithecus afarensis.

The variation of the teeth among these hominids had the peculiar characteristic of being accompanied by a gradual reduction in the size of the front teeth and an increase in the size of the lateral teeth (closer to the cheeks).

It is thought that this was related to certain climatic changes, which undoubtedly could have modified the plant and animal composition of the environment in which these organisms lived, also modifying their eating habits.

Increased brain mass

Many paleontologists consider that the "evolution" of the brain from the earliest hominids to modern man occurred shortly after the onset of bipedalism and once the changes in the teeth and jaws were complete.

With the increase in brain mass, there was also an increase in body size and this process of "encephalization" was also accompanied by other characteristic changes of hominids.

Homo habilis had a much larger brain volume than Australopithecus, but different computerized studies have shown that the increase was not gradual.

The period between 4 and 2 million years ago showed negligible changes in brain volume, at least for Australopithecus afarensis and Australopithecus africanus, who shared brains smaller than 450 cc; while Homo habilis, 2 or 1.5 million years ago, had brains between 650 and 700 cc.

From the above it is understood that the evolution of the hominin brain actually occurred at a time in history about 2-1.5 million years ago.

Language and communication development

- Communication

The phonetic apparatus of humans has two components: the "subglottal" system (under the glottis), which consists of the lungs and their muscles, and the larynx, which communicates the subglottal system with the upper tract of the latter.

Human supra-laryngeal pathways are different from those of other primates, since in humans the palate is "backward" and the larynx is "downward," which allows the unique "construction" of a supra-laryngeal pathway different from that of other primates.

Furthermore, the fact that the human tongue can move in the space defined by the palate and the spinal column makes it possible to generate the frequency patterns that the sounds of vowels and consonants achieve.

The structures and the nervous control mechanism necessary for the establishment of human speech evolved 1.8 million years ago in Homo erectus, according to what is suggested by studies of comparative anatomy between current primates and the fossils of hominids found.

- language

Language is a unique adaptation of humans, as it evolved in the human brain, although there is no anatomical evidence of the acquisition of any new "organ", different from the predecessors of modern man; a fact that makes it difficult to study its origin.

Anthropologists differ in their opinion as to when language first appeared. Some claim that its origin accompanied the emergence of modern Homo sapiens, with the size of the modern brain and a fully formed descending vocal tract.

Others, on the contrary, place the appearance of language in the times of Homo habilis, with the first records of the tools and the beginning of the increase in brain mass.

However, the different adaptations found for the development of language and its deep integration with human nature seem to indicate that this had its origin many millions of years ago, and it has been suggested that the first forms of language included songs and gestures.

Phases of the hominization process

The phases of the hominization process correspond to the different species of which fossil records are kept, according to whose characteristics the pertinent conclusions have been drawn in relation to the origin of modern human beings.

These are the species of the hominization process:

Of the genre

Commonly known as "australopithecines," these are perhaps the oldest hominoids ever found, from which hominids are thought to have arisen.

Australopithecines inhabited the African savannas about 4 million years ago and, as discussed, they walked upright on their hind limbs (they were bipedal).

According to paleontological studies (of fossils), these early hominoids had an appearance and physical build more similar to that of an ape than a human and, based on the size of their brains, they are believed to be as intelligent as modern chimpanzees.

Various species of this genus are known that may have existed in the temporal space corresponding to 4-2.5 million years ago:

- Australopithecus afarensis

- Australopithecus africanus

- Australopithecus deyiremeda

- Australopithecus garhi

- Australopithecus sebida

- Australopithecus anamensis

- Australopithecus bahrelghazali

Homo habilis

Homo habilis (Source: Reconstruction by W. Schnaubelt & N. Kieser (Atelier WILD LIFE ART) Homo_habilis.JPG: Photographed by User: Lillyundfreya) / CC BY-SA (https://creativecommons.org/licenses/by-sa/ 2.5) via Wikimedia Commons)

The first representative of the genus Homo is Homo habilis, which existed 2.5 million years ago. It has already been commented on their ability to make tools and their social behaviors, in addition to their greater brain capacity (compared to australopithecines).

Homo ergaster

Facial reconstruction of Homo ergaster. Wolfgang Sauber (photograph); E. Daynes (sculpture) / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Homo ergaster lived 1.8 million years ago and, like Homo habilis, had the ability to make tools for different purposes, including hunting, so the consumption of meat from this species is thought to be greater than of its predecessors.

Fossils of this species have been recorded in Asia, Europe and North Africa, and it has been determined that its cranial capacity was even greater than that of Homo habilis.

Homo erectus

Homo erectus (Source: reconstruction by John Gurche; photographed by Tim Evanson / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0) via Wikimedia Commons)

Like Homo ergaster, Homo erectus lived 1.6 million years ago and maintained the ability to make hunter's tools and utensils. As mentioned above, these hominids managed to master fire and perhaps communicated with a kind of primitive language.

Homo antecessor

Facial reconstruction of Homo antecessor. Milena Guardiola / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

The Homo antecessor is considered the oldest hominid species found in Europe, which inhabited the earth makes about 900 thousand or 1 million years.

They had smaller brains than modern humans, were larger in build than earlier hominins, and are believed to have preceded Homo sapiens.

Homo sapiens

Representation of a Homo sapiens. Source:, via Wikimedia Commons Representatives of Homo sapiens were found between Europe and Asia a little more than 200 thousand years ago, so it is thought that they coexisted with other representatives of the genus.

They had greater cranial capacity (more than 1,000 cc) and could make more elaborate or sophisticated tools and weapons. They built their homes, which had a certain organization, and practiced funeral rituals for their deceased.

Homo sapiens sapiens

Homo sapiens sapiens, Neolithic reconstruction. MUSE / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

It corresponds to modern men, but it appeared 160 thousand years ago, with the Cro-Magnon man, who had a cranial capacity of almost 2,000 cc.

The earliest fossil records suggest a great capacity for making stone, wood and bone household tools and utensils. They were the first to present complex social organizations (tribes) and to make language and communication more complex.

In this species creativity arose and with it art, which is deduced by the cave paintings found in the caves of Altamira, in Spain.

Cave drawing of a bison in the Altamira caves (Image from Welcome to all and thank you for your visit! ツ at www.pixabay.com)

Later, the processes of culturization and civilization took place, which marked a before and after in the history of humanity as we know it today.

References

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