[Campbell Biology P.598] The caption for Figure 25.30 states that tracing the yellow line 'c... | Practice Question

The caption for Figure 25.30 states that tracing the yellow line 'creates the illusion of a progressive trend.' What does this statement imply about horse evolution?

  • A: Horse evolution was a simple, linear progression from *Hyracotherium* to *Equus*.
  • B: *Equus* is the only surviving lineage from a complex evolutionary history with many divergent branches.
  • C: The primary evolutionary pressure on horses was always towards increased size and reduced toes.
  • D: Grazing behavior evolved independently in several horse lineages.

Explanation

The caption explains that the yellow line, while useful for showing a sequence, creates an 'illusion' because Equus is actually the 'only surviving twig of an evolutionary bush with many divergent trends.' This means horse evolution was characterized by many different lineages evolving simultaneously, with only one that of Equus surviving to the present day, making the simple linear progression an oversimplification.