4 Types of Early Hominoids-Differences and Similarities Explained!


December 21, 2018 admin 0 Comment

In certain dental characters Ramapithecus is markedly different from Dryopithecus. In Ramapithecus the incisors and canines are smaller in relation to molar, but it is not in Dryopithecus. The Dryopithecus pattern of molar cusps is not seen in Ramapithecus.

The upper jaw of Ramapithecus is shortened; it does not protrude forward but is long vertically. The palate of Ramapithecus is arched, it is wider behind than in front and in this respect also, it differs from Dryopithecus and approaches man.

The short, deep face of Ramapithecus has led some anthropologists to suggest that perhaps it could not use teeth as weapons to the same extent as Dryopithecus, and that Ramapithecus used hands for hunting and defence.

That implies that Ramapithecus was probably an
erect biped with hands free. Following this line of argument some scholars want to say that perhaps Ramapithecus is most likely the ancestor of Homo sapiens.

It is quite probable that Ramapithecus line was separated from the Dryopithecus lineage in the Miocene epoch. The separation was complete by the Pliocene time.

2. Australopithecus africanus:

Remains of Australopithecus consisting of an almost complete skull of a young individual, probably not more than five years of age were first discovered in 1924 at Taungs in Bechuanaland, South Africa, and were studied by Prof. Raymond Dart. The skull contained twenty milk teeth and four permanent first molars in good condition.

The geological age of the Taungs ape is not very certain. In the opinion of Broom, it belongs to the Middle Miocene or Lower part of the Upper Pliocene. Others attribute it to the Lower Pleistocene age.

Characteristics:

Some important characteristics of Australopithecus are as follows:

1. The size of the cranium and facial portion closely resembles that of the chimpanzee. The head is dolichocephalic.

2. Seen in profile the face is concave as in the orang.

3. The premaxilla is well marked as in the apes.

4. The flat nasal bones resemble that of the chimpanzee.

5. There is no ridge to separate the floor of the nose from the upper jaw—a simian character.

6. The face is prognathous as in the chimpanzee.

7. A diastema is present in the upper jaw between the lateral incisor and the canine. The cranial capacity as estimated by Dart was 520 c.c.

Difference from the Present Apes:

In the following characters Australopithecus differs from the present apes the face is small; the nasal aperture is high (in apes it is wider than its height); the nasal bones are short, broad and separated by intranasal suture; in general appearance the face is more in harmony with the head.

Similarities with the Present Apes:

Again Australopithecus approaches man in the character of the enlarged cranium; highly arched forehead; position of the orbits; downward face: position of uncial plane; faint supraorbital ridges; relatively interiorly placed foramen magnum, etc. Hooton, however, pointed out that “young apes have smaller brow-ridges, higher foreheads; lesser jaw projection, and a more horizontal and forward position of the foramen magnum than the adults of the species.”

The jaw is massive. In some characters it resembles that of the apes while in others it differs. The molar teeth are very large but quite humanoid. The canines are small and their crowns are in the same level along with that of the other teeth. The incisors are small in size and almost vertical in position, while in apes it is sloped.

3. Australopithecus boisei (Zinjanthropus):

Zinjanthropus is very interesting and important for us because he is considered to be the earliest known man, who could make tools. It is not perfectly known whether he was capable of speech, but it may be said that he could express and communicate simple ideas in sound.

The tool maker Zinjanthropns was a food-gatherer. While gathering vegetables he, however, collected small animals also. But his diet was still largely vegetarian. This is supported by the wear of his teeth also. At this stage man was still a food-gatherer and not a hunter of large animals.

A. Discovery:

The remains were discovered by Mrs. and Dr. L. S. B. Leaky in the year 1959 from a lower Pleistocene deposit in Olduvai Gorge, Tanganyika Territory, East Africa.

B. Materials:

The skeletal material consists of an almost complete skull without mandible, and the larger part of the tibia.

C. Associated finds:

From the same bed several primitive stone artefacts, including 9 choppers, 1 hammerstone, 5 natural stones and 176 flakes were unearthed. Associated with the skeletal materials were found remains of snake, lizard, frog, rat, mouse, bird, baby pig, etc.

D. Age:

Zinjanthropus dates back to some 600,000 years. They belong to the upper part of the lower Pleistocene.

E. Description:

The skull belongs to a youth whose age varies between 16 and 18 years. The cranial capacity is somewhat over 600 c.c.

F. Characteristics:

1. The postorbital constriction is marked thus, making the temporal fossae large.

2. The sagittal crest is well developed.

3. The supraorbital torus is massive.

4. The interorbital region is of enormous size. The face is long and broad.

5. The facial and zygomatic portions of the maxilla are large.

6. The plate is very high.

7. The nasal bones are long and narrow; the superior end is broader than the inferior.

8. The dental series is regular without any premaxillary diastema.

9. The canines are not larger than those of contemporary man; so also the incisors.

10. The right lateral incisor is somewhat smaller than the left. This condition is occasionally met with in contemporary man, but rarely seen among the anthropoids.

11. The premolars and molars are very large. The third molars which had not yet erupted are smaller than the second molar (as in man).

12. The mastoid process is well developed (as in man).

13. The nuchal crest, though strongly developed, is hominid in its form.

14. The foramen magnum is situated more anteriorly than it is in the skull of contemporary man. This suggests that Zinjanthropus habitually walked erectly.

15. Stature is estimated at not more than 4 feet 9 inches.

4. Australopithecus robustus:

Middle Pleistocene deposits of Kromdraai, two miles east of Sterkfontein, yielded fossil remains of two individuals to which Dr. Broom gave the scientific name Paranthropus robustus. It was represented by a part of skull, parts of some long bones like humerus and ulna, some carpel and tarsal bones, etc.

The cranial capacity is estimated at 600 c.c. Of the other characters the cheek bones are projecting forward, premaxilla is marked off from maxilla, diastema is present, high degree of prognathism is noticed.