AUSTRALOPITHECUS AFRICANUS: CHARACTERISTICS, EVOLUTION - CULTURE VOCABULARY - 2024

The Australopithecus africanus is an extinct hominid species discovered in Africa. In 1924 Raymond Dart identified fragments of the face and jaw of a bipedal ape in its juvenile stage. At first, the fossils that Dart discovered were not considered to belong to a precursor species of man.

However, the similarities of Australopithecus africanus characteristics to apes and humans showed that the first hominins were bipedal apes rather than quadruped humans.

Australopithecus Africanus skull lifeder. Tiia Monto, from Wikimedia Commons

It is a hominid that, according to estimates made by scientists, developed on the planet between two geological periods: the Upper Pliocene and the Lower Pleistocene.

Tests have been made to determine more exactly what is the dating of the remains found; however, it has been difficult considering the state of these fossils. Due to this context, there is no agreement among scientists regarding the biological age of this hominid: estimates range from 2 million to 3 million years old.

The discovery of this species was decisive for understanding the evolution of the human being as a species, and implied a paradigm shift in the conception of humanity in the genetic field.

Raymond Dart, the original discoverer

Dart was born in Toowong, a suburb of Brisbane, Australia, on February 4, 1893. He was the fifth of nine children, the son of a merchant and farmer. His childhood was divided between his farm property in Laidley and his store in Toowong.

Young Dart attended Toowong State School and later obtained a scholarship to study at Ipswich School from 1906 to 1909. Dart considered becoming a medical missionary in China and wanted to study medicine at the University of Sydney; however, his father persuaded him to study at the University of Queensland.

At the University of Queensland, where he studied Geology and Zoology, Dart was awarded a scholarship. She then studied Medicine at the University of Sydney in 1917, from which she graduated ten years later.

Dart and the postwar

In 1918, Dart served in World War I as a captain and medic in the Australian Army in England and France. After the conflict ended, Dart served as a professor at University College London, in 1920.

This was followed by a grant from the Rockefeller Foundation at Washington University, in St. Louis, Missouri. Shortly thereafter, Dart returned to London to work at University College, and in 1922 he decided to take a teaching position at the University of the Witwatersrand, in Johannesburg, South Africa.

The find

In 1924, at a time when Asia was considered the cradle of humanity, the discovery of the Taung boy (recovered in Africa near the Kalahari desert) supported Charles Darwin's prediction: our ancestors would be discovered on the old continent..

The skull that Dart discovered was classified into a specimen of a new genus and species: Australopithecus africanu or the "southern African ape." His claim of a creature possessing a brain the size of an ape and with teeth and posture similar to those of humans was met with skepticism.

The reason for this initial opposition was due to the fact that Dart's theory supports the principle of Mosaic evolution; that is, the development of some characteristics before others. His thesis also differs from that of Elliot Smith, who claimed that the hominization process began with an increase in cranial capacity.

However, Dart lived to see his theories corroborated by additional discoveries of other Australopithecus specimens at Makapansgat in South Africa in the late 1940s, as well as later discoveries made by Louis Leakey, which established Africa as the cradle of humanity.

Discovery

Australopithecus africanus was discovered in excavations carried out in South Africa and within 80 years the remains of more than 200 individuals have been found. Many of these fossils were found accidentally in caves used for mining; These caves were formed due to the underground activity of the water.

The fossilization of Australopithecus africanus was facilitated by the calcification of the bones that generated the constant dripping of water on the remains of the hominids.

Over millennia, water activity generated a large number of mineral deposits, and when the surface eroded, the underlying deposits were exposed and then excavated for fossils.

The discovery of Australopithecus africanus is attributed to Raymond Dart, who in 1924 found the first remains of this species. His now famous "Taung boy" was named after the place of his discovery.

The Taung boy is a specimen of approximately two or three years, of which only his face, jaw, skull fragments and brain were found. Dart also worked at the Makapansgat archaeological site, where he found more remains of Australopithecus africanus.

In Makapansgat, a small jasper stone belonging to an Australopithecus africanus was found, considered the first symbolic element. It is important to clarify that this rock is considered the oldest sculpture even though it has not been deliberately carved, as it was not modified.

Other discoveries

Robert Broom, a South African paleontologist contemporary with Dart, worked in the Sterkfontein Caves. There he discovered an entire Australopithecus africanus skull, belonging to a female specimen. This specimen was christened "Mrs. Ples". More fossils of the species were also found at Sterkfontein.

Broom also worked on the Kromdraai and Swartkrans excavations; in the last one he discovered another hominin: Paranthropus robustus. For his part, Charles Kimberlin Brain, a South African paleontologist and taphonomist, conducted extensive research at Sterkfontein.

Brain rejected Dart's view of the Austrolopithecus as "killer apes." Instead, he argued that the bones found alongside the hominid remains belonged to large cat prey or were taken to caves by rodents in search of food.

Killer ape theory

This is a Dart theory that holds that the long bones of animals, as well as the jaw fragments found along with the remains of the Austrolopithecus africanus fossils, were used as weapons to fight and kill each other.

However, today it is known that these hominids were characterized by their opportunism, as they hunted small prey and lived on gathering and carrion.

Why have fossils been found in caves?

Many of the Australopithecus africanus specimens may have accidentally perished in the caves when trapped in the caves. Remains such as those of the Sterkfontein caves, preserved in good condition, confirm this thesis.

Instead of being taken to the caves as prey, Australopithecus africanus is believed to have been attracted to the water coming from them; at Drimolen, one of the most recently discovered sites, remains of approximately 80 specimens were found. Gladysvale is also one of the sites where remains of these hominids have been found.

Evolution

Austrolopithecus africanus has traditionally been considered the immediate ancestor of the Homo lineage, specifically Homo habilis. However, Australopithecus afarensis is considered by some researchers to be the common ancestor of the africanus and the Homo lineage. This last hypothesis has become more popular in recent years.

Many of the fossils found in South Africa between 1930 and 1940 were given different names, such as: Australopithecus transavaalensis, Plesianthropus transvaalensis and Australopithecus prometheus.

The fossils discovered in 2008 in Malapa, South Africa, were heralded as a new species: Austrolipthecus sediba.

However, many other paleontologists consider these fossils to be a chronospecies of the africanus. In other words, the anatomical differences between the new fossils and the previous ones were generated throughout the 500,000 years that this species lived.

characteristics

Australopithecus africanus have all the adaptations in the lower limbs corresponding to a common biped.

They also retained features in their limbs belonging to a climbing hominid, with upward-facing shoulder joints, long arms compared to their legs, and long curved fingers. In general, their hands more closely resembled those of a human than Australopithecus afarensis.

The latter were characterized by the primitive condition of their long arms and long, curved fingers.

However, their hands had a similarity to those of humans, specifically their thumbs, which gave them greater grip and grip strength. This was achieved thanks to better developed thumb muscles than those of their ancestors.

These hominins are considered common bipeds. However, Australopithecus africanus is thought to have been more arboreal than afarensis.

Regarding sexual dimorphism, the Africanus did not present as many differences as their cousins: the males measured an average of 138 centimeters and weighed about 40 kilograms, while the females measured 115 centimeters and weighed 29 kilograms.

Skull

While its brain was small compared to later species, Australopithecus africanus was not only more encephalized than its ancestors (with a cranial capacity of 450 cc), but also possessed a larger cerebral cortex in the frontal and parietal regions.

His encephalization quotient was 2.7. This quotient is a method used to compare brain size between different species.

A quotient greater than 1 equates to a larger brain size than would be expected based on body size; the modern human encephalization quotient is approximately 7.6.

Drill area

Broca's area is an area on the left side of the frontal cortex that is related to the production and development of language. This area is found in all Old World monkeys and apes; it was also present in Australopithecus africanus. In the latter, the size of Broca's crust was larger.

These developments mentioned support the idea that Australopithecus africanus possessed greater capacities to process ideas, as well as better abilities to communicate.

It is worth noting that there is a debate about whether the lunate sulcus - a fissure on both sides of the occipital lobe related to vision - is more similar to that of a human or an ape.

The outer skull reflects the cerebral expansion of Australopithecus africanus in its round shape and broad forehead. The face of this species tended to exhibit a high degree of prognathism and a concave midface region. The face and teeth of this species were specially designed to chew harder food.

Habitat

The Austrolopithecus africanus is considered to have developed in fairly open spaces with a dry climate. Investigations have shown that it probably lived in the same spaces as Austrolopithecus afarensis, since it became its substitute thanks to its greater hunting skills.

The specific geographic space that this hominid occupied is located in East Africa, encompassing the current territories of Tanzania, Kenya and Ethiopia.

The facial and molar robustness of Austrolopithecus africanus suggests that its diet was more plant-based than earlier hominins. Its climbing adaptations, inherited from its ancestors, allowed it to use trees as shelter, as well as to sleep and feed quietly.

While on the ground, this species is thought to be foraging, feeding on plants and small animals, as well as carrion.

As mentioned above, it is possible that Australopithecus africanus fell into the caves accidentally. However, although there is no evidence, some researchers suggest that they used these sites as a refuge.

Tools

Very primitive stone tools were found in the Sterkfontein and Makapansgat caves alongside the remains of Australopithecus africanus. Although there is no evidence that they made tools, it appears that they used stones for hammering and cutting.

It is also speculated that they used tubers in their diet and that they extracted them with sticks in a similar way to modern Africans, such as the tribes of the Kalahari desert.

Feeding

In nature, gatherers have relatively large brains. Some examples within the primate world are the aye-aye, which hunts insects with a combination of hearing and extraction; and capuchin monkeys, which steal young animals from holes in trees and extract insects from the bark of trees.

Other examples are baboons, which dig the earth for tubers. Orangutans and chimpanzees can also be mentioned, who use a variety of tools to extract ants, honey, and other foods. Chimpanzees also use the branches to hunt small animals.

Bipedalism may have been a response to an increasingly resource-poor habitat, and encephalization a response to the need to locate and learn about how to process new foods.

Since Australopithecus africanus, researchers have found a tendency for the portions of the brain involved in association and complex thinking to expand, as well as for the strength and manual dexterity required to manipulate food and objects.

References

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