Final answer:
In the past, 'physical makeup' referred to a person's outward physical characteristics, or phenotype. Currently, it denotes the genetic composition or genotype, which includes the inherited DNA that influences these physical traits.
Step-by-step explanation:
In the first half of the 20th century, physical makeup referred to physique; whereas now it refers to genes. In the past, physical makeup could have been understood as the observable traits of an individual (phenotype), which includes tangible characteristics such as height, skin color, and body shape. Back then, the genetic foundation of these traits (genotype) was not fully understood. However, with advancements in genetics and the discovery of DNA's role in heredity, scientists began to emphasize the importance of genetic makeup in determining physical traits.
The term genotype is defined as an individual's complete genetic makeup, based on the genetic material inherited from one's parents. This includes all genes present in the cells, which express themselves in various ways including physical, behavioral, and biochemical characteristics. In contrast, phenotype refers to the observable expression of these genes — the physical attributes we can see. Over time, the understanding of these concepts has drastically shifted from a focus on outward appearance to a deeper grasp of the underlying genetic causes of these appearances.