Which of the following are examples of lowly heritable traits?

• A. Height, length
• B. Reproduction, health, survival
• C. Milk production
• D. Bone and fat content

Answer: (B)

Heritability is the fraction of the variation in a trait among individuals that is due to genetic differences, given a specific population and environment. Traits like height or length are strongly influenced by many genes, so the differences we see among individuals are largely genetic. Milk production has a genetic component as well, but management, nutrition, and lactation factors often have a big influence, making its heritability moderate rather than high. Bone and fat content also involve genetics, but diet and overall metabolic state can shift these traits substantially, so their heritability tends to be moderate to low depending on context. Reproduction, health, and survival, however, are heavily shaped by the environment—nutrition, disease exposure, stress, and management practices—so the genetic contribution to their variation is relatively small. That environmental dominance is what makes reproduction, health, and survival the best examples of lowly heritable traits.