Evolution – Where did gorillas come from? Are gorilla apes? When did gorillas first appear on earth? When were gorillas found?
The history of the primates has at least 65 million years. Today there are more than 500 species distributed around the world in America, Asia, and Africa, but it took several million years for the early ancestors to evolve into modern gorillas. There are more than 500 species of primates around the world today. All members from the Primate order originate from animals which spent much of their time in the trees of tropical forests. It is likely they originated in Africa, from proto-primates who lived at the end of the Cretaceous period. Purgatorius is the name of a genus of animals that some scientists thought were the earliest proto-primates, but there is a debate on this theory, and recent findings have proved they could belong to another genus. Their appearance was not similar to modern monkeys or apes because they looked more like rats.
About fifteen million years ago, apes and many other of its forms evolved. What the large apes gained in brute strength, they lost in agility (Kimbel & Martin 1993). They lost the ability to move through the branches. Early apes swung along by their arms from tree to tree, many evolving short legs and arms to suit this mode of travel (Kimbel & Martin 1993). The tail was also eventually lost, which was needed mostly for balance (Kimbel & Martin 1993). The apes then moved through wide distribution when Africa drifted into Asia. Asian apes diverged from the African apes 12.5 million years ago, which then gave rise to the orangutans and gibbons. Between four and eight million years ago, at which point man, chimps, and gorillas began to evolve along three independent paths (Kimbel & Martin 1993).
Primate ancestry is not easy to research about since it involves the evolution of man. The fossil record begins with teeth from Montana, dated about seventy million years ago (Uchida 1996). Most likely, they were small and rodent-like. They probably ate insects, but then developed a taste for the abundant fruit to be found in moist tropical rain forests (Uchida 1996). We are not sure what the early relative of the gorilla was, but it can be traced back to an early ape known as Proconsul Africans. Roughly the size of a mandrill, it leaped or ran about the forests of East Africa, feeding on fruit (Kimbel & Martin 1993). The chart on the last page details the development of primates. From what science knows, all primates started developing during the Paleocene era (58-63 million years ago). Gorillas developed during the Pleistocene era (2 million years ago).
A few years ago, it was thought that all gorillas belonged to a single species, and there were three subspecies, but now, the latest research concluded that there are two species:
- Eeastern gorilla and
- Western gorilla
Each species has two subspecies
Both species diverged about 2 million years ago and were separated by the Congo River. Gorillas comprise the eponymous genus Gorilla, the large sized primate genus in terms of physical expression. Gorillas are predominantly land dwelling animals which largely feed on vegetation and no wonder they inhabit the forest tracts of Bwindi and the Virunga Volcanoes, the world’s re-known gorilla trekking destinations. Gorillas belong to the following classification Subspecies; Gorilla. beringei beringei, Species; Gorilla beringei, Genus; Gorilla, Family; Hominidae, Order; Primates, Class; Mammalia, Phylum; Chordata, Kingdom; Animalia,
After the divergence of Gibbons, members of the genus Pongo, orangutans, also separated from the others about 14 million years ago. During the late Miocene, about 11 million years ago, apes that were the ancestors of the modern hominids were abundant in Africa. Some reached incredible height, such as the Gigantopithecus, a genus of great apes that reached up to 3 meters high. Possibly the Gigantopithecus were ancestors of modern gorillas, but also other apes could be. Humans, chimpanzees, and gorillas shared a common ancestor in a lineage where orangutans were not there anymore.
Gorillas are closely related to Homo sapiens, but less than chimpanzees. However, the closest relatives of the Gorillas are chimpanzees. The gorillas were separated from the other hominids about 7 million years ago, although some sources indicate that began to populate Africa around 11 million years ago. With the extinction of other great apes, gorillas became the largest primates in the world.
The gorillas’ habitat is restricted to central Africa. The two species are separated by the Congo River.
Minor differences between the lowland and mountain forms suggest that the divergence between the two occurred in the past. The present distribution of the two subspecies also suggests that at one point the population was continuous throughout a rain forest belt from western Africa to central Africa, north of the Congo River (Schaller 1963). There seems to be two primary factors that limit the growth of gorillas as a species. First, gorillas frequent only humid forested areas where succulent herbs and vines are readily available for forage (Schaller 1963). Secondly, gorillas are apparently unable to swim and hesitate to wade in water (Schaller, 1963). Rivers are barriers to gorillas. In the past gorillas may have been a single population, but due to climatic change, their population has become changed. Maybe at one time, central and western Africa were combined as one and free from stretch of rain forest. Due to climatic change where there was a much drier period caused the rain forest to be in pockets
This change in habitat is likely to reflect different dietary adaptations acquired during the isolation (Uchida 1996). Western lowland gorillas have relatively wide incisors, relative to both molar size and body weight, while mountain gorillas have large, high-crowned molars with expanded crushing basins (Uchida, 1996). From the development of teeth, we can note that the lowland gorillas have a varied diet of leaves and fruits, while the mountain version is adapted to eating mainly leaves and shoots of the higher elevation. The habitat disjunction is related to the landscape change due to climate, which has allowed the three subspecies to evolve into different types of gorilla.
Many different scientists have a different view of how the gorillas evolved. Some say it is due to climate change and some say it is due to the availability of food. This may be a combination of both. For sure it has to do with its diet and habitat. According to data from various studies, the lowland gorilla has more numbers (the eastern) and mountain races and is more widely spread. The western race of gorilla lives in the central.
The eastern lowlands gorilla is ten times rarer than the western lowlands gorilla. The range of this ape is considerably smaller than its western cousin. It lives on patches of lowland rain forest and in the western foothills of the Rift Valley, all within eastern Zaire (Nowark 1988). On some mountain slopes, it lives on altitudes of around 6,560-8,200 feet. The easy way to determine the habitats of the gorillas is to note that the lowlands version stays in a hot and wet climate, whereas the mountain version stays in a cool, temperate climate.
At about 400,000 years ago, the mountain gorillas separated from the eastern lowland and these two subspecies separated from the western gorillas over 2 million years ago. Though the debate about the classification of mountain gorillas is still unresolved, they were first regarded as Troglodytes in 1847 and later returned to gorilla in 1852. In 1967, Colin gloves suggested that all gorillas should be considered as one species Gorilla gorilla with Gorilla gorilla gorilla, gorilla gorilla graueri and Gorilla gorilla beringei as the three sub species. In return, the IUCN conducted a review that classified gorillas into two species Gorilla gorilla and Gorilla beringei in 2003.