Final answer:
Heritability is the fraction of variation in a trait within a population that is due to genetic differences among individuals. High heritability means genetics significantly influence that trait, although it is usually not due to a single gene but multiple genes and epigenetic factors.
Step-by-step explanation:
Heritability refers to the extent to which trait differences among individuals are attributable to genetic variations. It is a measure of how much of the variation in a trait within a population can be attributed to the differences in genes among individuals. Higher heritability indicates that genetics play a greater role in the variation of that trait. For example, through the Minnesota Study of Twins Reared Apart, researchers found that some personality traits such as leadership and obedience have a heritability ratio of more than 0.50, implying a significant genetic contribution. However, it's crucial to understand that traits are influenced by multiple genes and epigenetic factors, and are not determined by a single gene alone. This is especially true for polygenic traits, such as height or weight, which involve multiple genes and can be influenced by environmental factors.