Introduction
Evolution is the process by which different organism develop and diversify from earlier forms. Evolution explains the origin of species and gives justifications for the variation among species. Through evolution, we can understand the relationship between different species. On the other end, intelligence refers to cognitive ability. Intelligence enables the reasoning, planning, problem-solving and learn in addition to comprehending complex concepts. As different species evolve, their intelligence also increases to enable them to adapt and relate to their environment for survival. Different theories have been advanced to explain the origin and variation of species as a justification for evolution. It has been noted that social organization or behavior is an indicator of primates’ intelligence. Similarly, the brain volume or size of the primates show a correlation with their intelligence. Social intelligence hypothesis links foraging challenges to the development of bigger brain size to ensure survival. Evolution meant to provide species with advantageous traits that would help them survive the changes in ecological conditions as well as climatic conditions. Such advantageous traits could include changes in gestation period as well as social organization. This paper explains evolution and intelligence among the Lemuroids, Tarsiers, Monkeys, Apes and Man by explaining their changes that occur in their intelligence through primate evolution. In explaining the intelligence, the paper uses parameters like brain size, gestation period, social organization and mating patterns which vary with the intelligence of an animal to highlight the changes that occurred in evolution in primates.
Discussion
Grade I: The lemuroids
Lemurs are small primates found majorly in Madagascar Island. The lemurs are very intelligent, and it is believed they went to Madagascar about 40-50 million years ago (Zimmermann, & Radespiel, 2014). Over the past, it was believed that the brain size of the primates gets bigger through their evolution. However, while that may be true for some primates, a few of them have shown that brains have grown smaller in size. One them is the lemur. The brains of the lemur have shrunk significantly. Compared to the ancestor Lemur, the nocturnal Lemur of Madagascar has shown a 27% decrease in brain size (Zimmermann, & Radespiel, 2014). The smaller brain size has made the animals more intelligent.
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The lemuroids social organization has evolved in a similar way to other primates’ social evolution. During the millions of years, the evolutionary mechanisms have made the lemurs a more socially organized group of apes. The Lemurs have evolved from solitary nocturnal to the diurnal activity which has resulted in changing from solitary foraging to group foraging (Zimmermann, & Radespiel, 2014). The social and ecological factors contributed to the variation.
Grade II: Tarsiers
The tarsiers are a unique type of primates mostly found in the Southern and Eastern parts of Asia. They have up to 18 different subspecies although they all look similar. They majorly inhabit mangroves, scrubs, and low forests. The family of Tarsiers is today listed among the endangered species due to hunting, loss of habitat as well as the introduction of new species that threaten their existence (Hartig, Churakov, Warren, Brosius, Makałowski, & Schmitz, 2013).
The Tarsiers have a very small brain size. The size of their brains is smaller than their eye. The small size brain has an enormous visual cortex that helps in processing the information from the large goggling eyes. The current Tarsier has an EQ of 1.53 (Hartig, et. al, 2013). During the evolution process, it is evident that the increase in brain size took place in the pretentious and Necrolemur groups. These were from the 10th to the seventieth percentile (Hartig, et. al, 2013). The recent Tarsier is however from the 95th percentile in a similar range.
Hartig, et al., (2013) explains that Tarsier have a gestation period of 6 moths and give birth to one baby. In some cases, the gestations are always controlled by season like in the case of the Eastern Tersia. Different Tarsier species have different social behaviors. The western ones have displayed a more solitary behavior only coming together to mate while the Eastern Tarsier are very social often keeping together. Tarsiers are very vocal animals and use that as a communication tool between the different species. Animals that socialize are usually more intelligent than those that are solitary. Their calls as vocal creature differ across species. The ability of an animal to socialized and operate in organized groups is an indicator if a high level of intelligence.
Grade III: Monkeys
Monkeys belong to the group of haplorhine primates. This group comprises of primates that have tails. The monkeys can range in sizes and are about 3.3 Ft. long (Fleagle, 2013). Although monkeys share a few characteristics, they also have a variety of differentiating characteristics. For example, the new world monkey has a prehensile tail whereas the old monkey has a non-prehensile monkey. Others have a trichromatic vision while others have dichromatic or monochromatic vision.
The intelligence of the monkeys can be assessed by the changes in brain size across their evolution. The old world monkey had a tiny and complex brain compared to the new world monkey. For instance, the ancient monkey referred to as victoriapithecus whose 15million-year-old skull was discovered around Lake Victoria was investigated and the brain found to be tiny and wrinkled up. In addition, the brain was complex as opposed to the new monkey’s brain. The new world monkeys, however, have a different brain size. During the adaptive radiation of new monkeys to respond to the different ecological dimensions, the brain has changed to become bigger (Fleagle, 2013).
The old world monkeys also had longer gestation periods. They lived longer and their gestation period ranged from five to nine months. However, the new world monkeys have evolved to have shorter gestation periods. Their gestation period ranges from 4 – 5 months.
On their mating pattern, the new world monkey has the polygynous mating pattern (Fleagle, 2013). One male monkey has his female mates that constitute a mating and child rearing group. The new world monkeys do not operate in solitary life but rather form social groups. It is no wonder they have the polygynous mating pattern. The social organization into groups is important for facilitation of social learning through information transferee. It, therefore, follows that monkeys who operate in social groups become more intelligent. The social organizations can be seen in the chimpanzee population where they organize themselves to do ant dipping. Also, others could be seen to have a different tradition like termite fishing. It is the social intelligence that is acquired through groups or social organization that enables the monkeys to keep together to facilitate its transmission. Socializing enables the monkeys to thrive in their environment. Some of the forms of socialization in the new world monkeys include vocalization.
Grade IV: The Apes and Man
Kaas, (2013) explains: Apes and man are primates only different from the rest due to a few characteristics. Man and Apes unlike other Primates do not have tails. Among all primates, the most intelligent of them is man and apes. There are also other internal body differences that man and ape have that distinguish them from other primates. The man is the most dependent being of all primates. Some examples of the apes include Gibbon and Orangutans. The gap between man and ape is very narrow when a deeper analysis is done among primates. Man does not differ so much from other primates especially when a considerable observation is made on how they walk, stand or even grab stuff.
The brain size: the human brain size has increased over time across the evolution phase making them the most intelligent of primates. In 6 - 2 million years ago there was a slight increase in the brain size of a man, and as such, they began making simple crude tools. Between 2 million – 800,000 years ago, the human brain there was a further increase in brain size due to an increase in their body size and thus enabled Human to move around the globe. From 800,000 t0 200,000 years ago, the human brain evolved most rapidly. Their brains became larger enabling them to interact t more freely with their counterparts as well as with their surroundings. The improved size of the brain is better for humans due to increased storage capacity for information; increased the speed of collection, storage, and processing of information in a matter of seconds. Also, the bigger brain enables humans to solve problems a lot easier. Apes like chimpanzee which is closer to humans have brains a third the size of the human brain. Humans have the largest volume of the frontal cortex usually between 238.8cm3 – 329.8cm3 (Kaas, 2013).
There also is a fundamental difference between humans and Apes with regards to socialization, a principle indicator of intelligence. The differences also relate to humans social behavior and are influenced by cognition. It, therefore, follows that the level of intelligence determines the difference in social behavior of man from other apes or primates. Humans organize themselves into the political system, trade groups. Humans have evolved to cope with more fissioning. As such, within the human community, there are organized groups with a common dialect, leadership, and tradition. The social and cognitive apparatus of humans that have evolved have provided the mechanisms for such organizations. Human society can be described as chimp society with exploded fusion. More importantly is the aspect of kinship that runs as a thread in the human evolution.
Another aspect is mating patterns. According to Byrd-Craven, Vigil, and Geary (2004), among humans, most women are very choosy when selecting their mating or marriage partners. Men also depict the mammalian pattern by chasing multiple mates. In mammals, the sexual relationships are often short term while man has evolved to have a lasting relationship. Byrd-Craven, Vigil, and Geary (2004) notes that, according to the evolution logic, women often choose individuals with good genes as well as the ability to invest their potential in their children and them. Basically, physical attractiveness plays a major role in selecting of mates among humans, however, for men, the mating choices vary based on the anticipated length of the relationship. Apes mostly have the polygynous mating pattern which occurs within the groups and one male mates with a couple of other females.
The gestation periods of humans are nine months. In terms of evolutionary survival value. For instance during the hunting and gathering period. Men did the hunting while women gathered fruits. Also, during sporting women who did marathon often lost their periods and thus interfered with their fertility. However, today, the humans have evolved to be able to run marathons and still give birth. Orangutans and Chimps have the same gestation period, an indication of the closeness of Apes to man. Charles Darwin theory of evolution explains bets the relationship of man and ape.
Conclusion
Primates are very recent animals. They have evolved from their original forms and continue to evolve acquiring different traits for survival. Man and apes for instant looks are very much alike. However, there are other differences they have mostly internal and behavioral. This paper has explained evolution and intelligence among the Lemuroids detailing how they have experienced a decrease in brain size, hence, becoming more intelligent. The brains of the lemur have shrunk significantly, and the ancestor Lemur has shown a 27% reduction in brain size. The smaller brain size has made the animals more intelligent. Tarsiers, on the other hand, have experienced an increase in brain size with an EQ of 1.53. Tarsiers, especially the Eastern ones are very social often keeping together and very vocal animals and use that as a communication tool between the different species. They social organize themselves into groups an important factor for facilitation of social learning through information transfer. Monkeys have also witnessed a change in brain size. The old world monkey had a tiny and complex brain compared to the new world monkey. Moreover, they have had a reduced gestation period. Finally, Apes and Man. These are the most closely related primates. They have a lot of similarities although different. Humans have the largest volume of the frontal cortex usually between 238.8cm3 – 329.8cm3 which is three times bigger than that of its closest apes like a chimpanzee. In humans, most women are very choosy regarding the selection of their mating or marriage cohorts while Men also depict the mammalian pattern by chasing multiple mates. Humans are also more socially organized expressing a high level of intelligence. By explaining their changes that occur in their intelligence through primate evolution the paper has used these parameters: intelligence, brain size, gestation period, social organization and mating patterns which vary with the intelligence of an animal to highlight the changes that occurred in evolution in primates.
References
Byrd-Craven, J., Vigil, J., & Geary D. C. (2004). Evolution of human mate choice. Journal of sex research , 41 (1), 27-42.
Kaas, J. H. (2013). The evolution of brains from early mammals to humans. Wiley Interdisciplinary Reviews: Cognitive Science , 4 (1), 33-45.
Fleagle, J. G. (2013). Primate adaptation and evolution . Massachusetts: Academic Press.
Hartig, G., Churakov, G., Warren, W. C., Brosius, J., Makałowski, W., & Schmitz, J. (2013). Retrophylogenomics place tarsiers on the evolutionary branch of anthropoids. Scientific reports , 3 .
Zimmermann, E., & Radespiel, U. (2014). Species concepts, diversity, and evolution in primates: lessons to be learned from mouse lemurs. Evolutionary Anthropology: Issues, News, and Reviews , 23 (1), 11-14.
