[Campbell Biology P.597] Regarding the evolution of horses described in the text, which stat... | Practice Question

Regarding the evolution of horses described in the text, which statement is most accurate?

  • A: The fossil record clearly shows a straight-line progression from Hyracotherium to the modern single-toed Equus.
  • B: Hyracotherium was larger than present-day horses, with fewer toes.
  • C: Phylogenetic analyses show that all horse lineages, including grazers and browsers, are closely related to Parahippus.
  • D: The evolution of horses is best described as a branching tree or bush rather than a straight line, with Equus being the sole surviving twig.

Explanation

The text strongly emphasizes that 'Extracting a single evolutionary progression from the fossil record can be misleading' and that 'The genus Equus did not evolve in a straight line; it is the only surviving twig of an evolutionary tree that is so branched that it is more like a bush.' This directly supports option D.