Question

question 3 of 9
the fossil record indicates that the earliest known ancestor of horses has four toes. modern horses have only one. which of the following best explains why this occurred?
because the ancestors did not use all of their toes, their offspring were born with fewer toes.
environmental pressures selected for four toes over one dominant central toe over millions of years.
gradually, over the course of many generations, the four toes merged together to form a single toe.
offspring with genetic mutations resulting in fewer toes were more likely to survive and reproduce.
over the course of a lifetime, ancestors would lose toes due to the stresses of prairie life, such as predation and injury.

Explanation:

This aligns with natural selection: genetic variations (mutations) leading to fewer toes conferred a survival/reproductive advantage, so these traits became more common over generations. Other options are incorrect (e.g., disuse inheritance is Lamarckian, not evolutionary theory; merging toes isn’t the mechanism; environmental pressure selected for fewer toes, not four; lifetime injury doesn’t pass to offspring).

Answer:

D. Offspring with genetic mutations resulting in fewer toes were more likely to survive and reproduce.