Final answer:
Heritability is the extent to which genetic differences account for variations in traits among individuals in a population. Higher heritability means that traits are more influenced by genetics and can be subject to the processes of evolution. This concept is crucial in understanding how traits are passed down and how populations can change over time.
Step-by-step explanation:
Heritability refers to the fraction of phenotype variation in a population that can be attributed to genetic differences among individuals, also known as genetic variance. This means that the more heritable a trait is, the greater the chance that it can be affected by evolutionary forces such as natural selection. For instance, when looking at a population's phenotypic variation—the observable traits—it's important to identify the proportion of that variation that is due to the genetic makeup of the individuals. Natural selection can only act on these heritable traits. If a trait is not genetically based, it cannot be passed down and thus, cannot be acted upon by evolution.
Studies like the Minnesota Study of Twins Reared Apart have shown that certain personality traits have a significant genetic component, with heritability ratios of more than 0.50. Examples include leadership and resistance to stress. This points to the fact that genetics can play a large role in determining certain aspects of our personalities, although it is crucial to remember that traits are influenced by multiple genes and epigenetic factors, not a single gene.
When discussing heritability, it is imperative to differentiate between genetic variation and other forms of variation, such as those caused by environmental factors. While environmental influences like nutrition can affect traits such as height, they do not cause changes in the genetic code and are therefore not heritable. Only genetic attributes can be passed down to offspring and potentially influence future generations.