Brain Evolution in the Human Species

Brain Evolution in the Human Species Introduction Hominid evolution is marked by a very significant increase in relative brain size. Because relative brain size has been linked to energetic requirements, it is possible to look at the pattern of encephalization as a factor in the evolution of human foraging and dieting (Foley et al., 1991). Major expansion of the brain is associated with the Homo species rather than the Hominidae as a whole, where the energetic costs are likely to have forced prolongation of growth rates and secondary altriciality (Foley et al., 1991). Paleontological evidence indicates that rapid brain evolution occurred with the emergence of Homo erectus 1.8 million years ago and was associated with important changes in diet, body size, and foraging behavior (Leonard et al., 2007). Energy Requirements Extensive energy is required for brain growth and functioning. Parker (1990) analyzes intelligence and encephalization from the perspective of life history strategy theory, which is based on the premise that evolutionary selection determines the timing of major life cycle events-especially those related to reproduction-as the solution to energy optimization problems. Foley and Lee (1991) analyze the evolutionary pattern of encephalization with respect to foraging and dieting strategies. In considering the development of human foraging strategies, increased returns for foraging effort and food processing may be an important prerequisite for encephalization, and in turn a large brain is necessary to organize human foraging behavior. Dietary quality is also correlated with brain size. Foley and Lee (1991) first consider brain size vs. primate feeding strategies, and note that folivorous diets (leaves) are correlated with smaller brains, while fruit and animal foods (insects, meat) are correlated with larger brains. Overall, the genetic costs of brain maintenance for modern humans are about three times that of a chimpanzee. The first dietary shift is seen beginning within the genus Hom o, which began to include meat in the diet. It may be argued that meat-eating represents an expansion of resource breadth beyond that found in non-human primates (Foley and Lee, 1991). Therefore, Homo and its encephalization may have been the product of the selection of capable of exploiting energy- and protein-rich resources as the habitat expanded. While the evolutionary causes of the enlarging human brain themselves are thought to have been due to factors that go beyond diet alone (increasing social organization being prime among the proposed factors usually cited), a diet of sufficient quality would nevertheless have been an important prerequisite. That is, diet would have been an important hurdle, or limiting factor, to overcome in providing the necessary physiological basis for brain enlargement to occur within the context of whatever those other primary selective pressures might have been. Leonard and Robinson (1994: add page numbers for direct quote) conclude: These results imply that changes in diet quality during hominid evolution were linked with the evolution of brain size. The shift to a more calorically dense diet was probably needed in order to substantially increase the amount of metabolic energy being used by the hominid brain. Thus, while nutritional factors alone are not sufficient to explain the evolution of our large brains, it seems clear that certain dietary changes were necessary for substantial brain evolution to take place.

Homicide - Black males age 17-25 Research Paper

Homicide - Black males age 17-25 - Research Paper Example In history, premeditated or deliberate killing of an individual by another was termed as Felonious homicide which is related to murder. The biggest percentage of homicide committed in the United States is done by victims’ intimate partners. In the recent years, the overall rate of homicide in the US has been reported to remain constant. However the there has been an increased homicide among young black males aged between 17 and 25. Generally between 1999 and 2005 homicides rate in the US remained at around six deaths per one million people as suggested by Anderton, Barrett and Bogue (1997). However there was an increase in 2001 as a result of terrorist attacks which happened during this period. Homicide committed by the use of the gun occurred mostly around metropolitan areas. Homicide rates increased in the past one decade in most of the US cities with some experiencing around one thousand homicide per one million people. This situation was experienced in Richmond and Washing ton in 1994 among the black males aged between 18 and 24. In the subsequent years the homicide levels in the same age range in Washington, Richmond and New Orleans were twice those of other cities. The prevalence of homicide in metropolitan areas of the US in 2005 was twice that in non-metropolitan areas. ... Trait Theory Trait theory is a theory which explains matters of crime with regard to the individual. It was developed by Lonnie Athens explaining how parents or peer brutalization in childhood results to violent crimes later in life. In trait theory, the psychological perspective focuses on behavioral, personality and cognitive processes related to homicide. Individuals at the o age of 17-25 are associated with a lot of emotions which account a lot to their behavior and decision making. In United States this can be seen in the black males at this age group and it is attributed to their increased incidence of homicide. Personality disorders may result from brutality in adulthood and according to trait theory. This is because such disorders affect the way the individual perceives others in the society and above all how to react in pressure. For instance a child brought up in a society where there is a lot of crime he may end up committing crimes. This dictates why black males at the ag e of 17-25 in the United States due are likely to engage in homicide. This is associated with terrorist incidences which have affected the country leading to young individuals engaged in war. Trait theory also upholds homicide especially in United States, due to the children’s early age exposure to guns according to Levinson (2002). In United States due to development, possessing a gun it is not big deal which perceived as an item for solving conflicts. In connection with this, at the age of 17 to 25 individuals are said to be anxious in facing reality. As a result, as learned in childhood individuals at this age especially male as they are said to be more aggressive may engage homicides in solving conflicts. Personal traits such as social isolation and aggression also commuting to