ARDIPITHECUS: DISCOVERY, CHARACTERISTICS, SKULL - BIOLOGY - 2025

Ardipithecus is a genus of fossil hominid, which probably existed between 4.4 and 5.6 million years ago. The etymology of the word Ardipithecus has two different origins, where Ardi comes from the Afar language and means soil, while pithecus is of Greek origin, and means monkey.

According to morphological data, it is thought to be one of the closest ancestors (from an evolutionary point of view) to the genus Australopithecus. However, some researchers believe that it is, rather, the last common ancestor between chimpanzees and humans.

Ardipithecus ramidus. Taken and edited from: Tiia Monto.

Members of this genus differ from other hominins by the shape and size of their canine teeth, and because a marked sexual dimorphism has not been observed. The shape of the pelvis, and also the bones of the feet, indicate that they possessed a locomotion very different from that of any hominid, living or extinct.

Discovery

The first finds of Ardipithecus date from explorations made in the town of Aramis in Ethiopia, in the early 90's. According to chronological records, the Aramis area had previously been explored in 1981, but in 1992 a team of paleontologists led by Tim White made the first discoveries.

Tim White and his colleagues decided to work in an area where sediments from two volcanic zones converge, approximately 4.4 million years old. Among these sediments they found a great variety of fossils, among which small mammals, antelope horns, as well as birds stood out.

They also found what appeared to be the first 4.4 million-year-old primate fossils. Between 1992 and 1993 they found more hominid material at the site and in 1994 they announced the discovery of the new species of the Australopithecus genus, Au. ramidus.

A year later (1995), after new analyzes and revisions of the material, the species was relocated to a new genus, which would be called Ardipithecus, being until that date a monospecific genus (genus represented by a single species), a situation that would change for 1997 with the discovery of another species.

In 2009, paleontologists announced the discovery of a skeleton much more complete than all the findings made since the description of the species in 1994; The fossil was a female specimen of about 50 kilograms, which the scientists called Ardi.

characteristics

Representatives of the genus Ardipithecus were characterized by relatively large canine teeth compared to the premolars and molars; all teeth had thin enamel. They also had a hallux or big toe quite characteristic and adapted to move and climb trees.

Apparently the brain was small. Their teeth indicate that they were omnivorous organisms. No marked sexual dimorphisms have been observed to date and even the canines of males and females were sub-equal, something that distinguishes them from what for some is their closest group, the chimpanzees.

According to recent discoveries, an average female should measure about 120 centimeters and weigh approximately 50 kilograms. According to some scientists, the shape of the pelvis indicates that they could have had a bipedal or semi-bipedal locomotion, although not all researchers share this hypothesis.

Ethology

Some paleontologists suggest that, depending on some morphological traits, certain behaviors can be predicted. For example, it is believed that the presence of sub-equal canine teeth in males and females (A. ramidus) suggests that they could be organisms with little violence or with reduced agonistic behavior.

Another example related to the denture, suggests that the wear of the rear teeth of Ardipithecus kaddaba and also the size of these (larger than in A. ramidus), indicate a diet rich in fibrous foods and the absence of fruit consumption (no they were frugivores).

Reconstruction of an Ardipithecus spp. Taken and edited from: Ori ~.

Cranial capacity

As mentioned in the characteristics of the genus, paleontologists believe that Ardipithecus had a small brain. This assumption is based on the fact that it had a cranial capacity of 300 to 350 cubic centimeters. This volume represents only 20% of the human cranial capacity.

Because the genus information is based on fossil discoveries, the cranial capacity data for this genus is based on the species with the most complete material, Ardipithecus ramidus.

Feeding

According to its morphology, the estimation of the environment where the Ardipithecus species developed, and also according to the fossil fauna and flora discovered and dated from the same geological age, it can be inferred that the genus was more omnivorous than its current descendants (chimpanzees and gorillas).

The diet of the species that make up the genus varied between meat, fruits, leaves and flowers. They also consumed fibrous plant matter, such as foliage, roots, and some tubers, even nuts.

Species

Two species of the genus Ardipithecus have been described to date:

Ardipithecus ramidus

It was described in 1994 as Australopithecus ramidus, but later renamed Ardipithecus ramidus in 1995. According to the fossil record, it is believed to have lived about 4.4 million years ago. The epithet ramidus is of Afar origin and means root.

Of the two species, this is the best known, due to the greater number of fossil records found, including Ardi, which is the most complete specimen of this genus that has been discovered so far.

It is believed that it inhabited savanna environments, very similar to what are today the African savannas. In other words, it lived in grasslands with little precipitation and patches of deciduous trees, among other characteristics.

Ardipithecus kaddaba

This species was discovered in 1997, but its description was delayed until 2001. At that time it was classified as a subspecies of Ardipithecus ramidus (A. ramidus kaddaba).

In 2004, thanks to new scientific evidence, paleontologists reevaluated this subspecies and elevated it to species status, now calling it Ardipithecus kaddaba. The epithet kaddaba comes from the Afar language and means father of a family.

It is known that it lived about 5.6 to 5.8 million years ago. For several reasons, among which the analysis of phylogeny, isotopes and morphology stand out, the scientists concluded that this species is a possible ancestor of A. ramidus.

Both predictive analysis and geological and paleontological evidence make scientists think that this species lived in wooded savannas, with areas of grasslands, lakes and swamps. Some suggest that it inhabited areas with very similar characteristics to those later inhabited by A. ramidus.

References

1. TD White, G. Suwa, B. Asfaw (1994). Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia. Nature.
2. Ardipithecus ramidus. Smithsonian Institution. Recovered from humanorigins.si.edu.
3. Ardipithecus. Recovered from en.wikipedia.org.
4. Ardipithecus kadabba. Recovered from en.wikipedia.org.
5. Human Ancestors - Ardipithecus Group. Recovered from thoughtco.com.
6. Ardipithecus, fossil hominin genus. Encyclopædia Britannica. Recovered from britannica.com.
7. ST Francisco & SA Quiroz Barroso (2010). Fossil record and evolution of hominids. Sciences
8. Ardipithecus ramidus. Recovered from mclibre.org.