BLA - Evolution

2.2 The Biological Level of Analysis: Genetics and Behavior

Adaptation
The environment presents challenges to the individual. In order to survive, these individuals needed to adapt best to the environment.
By adapting, individuals would have greater chances of:

• Surviving
• Reproducing
• Passing genes on to offspring

Charles Darwin's theory of evolution and natural selection explains how species acquire adaptive characteristics to survive in ever-changing environments. According to Darwin's theory of natural selection, members of a species that are able to adapt to the environment are more likely to breed and pass on their genes to offspring.

During his travel to the Galapagos Islands, Charles Darwin noticed that the finches on different islands had slightly different beak shapes. He found out that each type of finch had the beak-type that was most advantageous to its own environment - better suited to eat the food that was available on its island.

Therefore, Darwin concluded that adaptation was a process that helps species develop characteristics that make it more competitive in that environment. However, when Darwin presented this theory in his journal, On the Origin of Species, he was not aware of the biological factors through which traits and characteristics can be inherited.

^Principle: "there are biological correlates to behavior"

Animal Researches and Evolution

Charles Darwin also laid the foundation for psychologists and biologists that animal research and studies can help gain insight to human behavior. Humans have a number of traits and principles that are similar to animals, especially apes and monkeys. The similarities include:

• Mate selection
• Maternal love
• Self-preservation

Darwin also noted that there are facial expressions and emotions that humans have that are in concordance to apes.

Study: Tetsuro Matsuzawa (Kyoto University) 2007

Brief: A study on spatial memory on chimps

Three pairs of chimps were selected and taught to memorize the numbers 1-9 on a monitor. Humans and chimps were placed to sit in front of a computer monitor, where the numbers 1-9 would appear (in a random order) for a brief period, and disappear, only to be replaced by blank slates. Subjects were directed to select the slates in the order which the numbers appears at their respective locations. They had to touch the slates in the appropriate sequence.

Result: As the time that the numbers on the screen appeared shortened, humans were unsuccessful in remembering the sequential order and selecting the correct slates in order. They made many errors. The chimps showed a remarkable spatial memory ability - selecting the correct slates even when the time that the numbers were shown was shortened.

Interpretation: Chimps had strong spatial memory abilities because they need the skill to survive in the jungle. They need to remember where food resources and dangers are in the rain-forest. Humans, on the other hand, do not need as much of this skill because of their urban environment. As agriculture developed, the skill of spatial memory was no longer an essential skill for human survival. However, to compensate, humans have a remarkable language ability that chimps do not. It appears that the memory skills of each organism were used in different ways - humans with language, chimps with spatial recognition. The organisms adapted to become more suitable to their respective environments.

^Principle: "animal researches can help us understand human behavior"

Evolutionary Psychology

Evolutionary psychology is based on the belief that as genes mutate, those that are advantageous are passed down to new generations. This is based on the belief of natural selection.
Evolutionary psychologists attempt to find human behaviors that can be used as proof of how our species has developed over time. Natural selection can select for mechanisms and functions that are correlated to behavior.

Study: Fessler et. al (UCLA) 2006.

Brief: A study on the sensation of disgust in first trimester pregnancy. "The sensation of disgust helped our ancestors avoid illnesses that are food-borne and survive long enough to produce offspring. These ancestors then passed on these genes to us." (Fessler, 2006)

Aim: To investigate if the sensation of disgust in the first trimester of pregnancy was elevated. (= Hypothesis)

Procedure: Web-based survey that was completed by 691 women who are pregnant. These women were recruited via pregnancy-related sites on the internet. No compensation was provided in this experiment. The subjects were (on average) 28.1 years old.

496 subjects' answers on the survey were used. (They had to be healthy with no chronic illness, above 18 and below 50 years of age, and answer all questions on the survey.) The subjects stated their level of nausea on a 16 point scale. Then, they answered a questionnaire to test their disgust sensitivity in 8 areas.

Result: Women in their first trimester of pregnancy had elevated levels of disgust, generally in all areas. However, the level of disgust was highest in the area that involved food. Food-borne diseases are especially harmful to women in first trimester pregnancy. Consumption of spoiled foods (etc.) could result in illness, or death, to both the mother and child. Nausea and vomiting when in contact with food is an adaptive behavior that was acquired from evolution in order to prevent mothers from eating dangerous foods.

Evaluation: Subjects were liable to lie due to the method of the study. Many samples were acquired, presumably accurate data processing.

Things to Consider / Studies of Evolutionary Psychology:

• Difficult to test theories because we do not know about the lives of early humans
• Researchers interpret the data in a way they expect: confirmation bias
• Evolutionary psychology underestimates cultural influences of behavior

Resources used: 

Psychology Course Companion (Crane)

Psychology for the IB Diploma (Pearson Education)

Course Companion Outcomes Glossary