Question

Horse skeleton fossils indicate that the size of horses increased over time. Which statement best explains this fossil record?

A. Smaller horses bred with larger horses, creating hybrids.
B. Smaller horses were infected by a fatal virus early in their history.
C. Larger horses consumed the food supply of the smaller horses.
D. Larger horses produced a slightly greater number of surviving offspring.

Answer 1

The increase in size of horses over time as seen in the fossil record is best explained by the fact that larger horses produced more surviving offspring, an outcome of evolution and natural selection.

Step-by-step explanation:

The fossil record of horses indicates an increase in size over time, and the best explanation for this observation is option D: Larger horses produced a slightly greater number of surviving offspring. This aligns with the principles of evolution and natural selection, where advantageous traits that improve survival and reproduction tend to be passed on to successive generations. As the environment changed from a forested landscape to prairie, horses evolved with adaptations such as changes in teeth shapes for grazing, and foot and leg anatomy for running to escape predators. These evolutionary changes are well-supported by the rich fossil records, showing transitional species and anatomical adaptations that led to the modern genus Equus.