Question

chimpanzees exhibit 99% genetic similarity to humans. cows share approximately 80% of their dna sequence with humans. scientists can predict the relative age of a common ancestor using dna sequences. which of the following statements regarding molecular clocks is true?
○ cows do not share a common ancestor with chimpanzees and humans, and any genetic relatedness is by chance.
○ molecular clocks cannot provide information regarding the relatedness of organisms or how distantly related common ancestors are from descendant species.
○ the common ancestor of cows, chimpanzees, and humans lived more recently than the common ancestor of chimpanzees and humans.
○ chimpanzees, humans, and cows were at one time more closely related, but due to genetic drift have become more distantly related from one another.
○ the common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.

Explanation:

Molecular clocks use genetic similarity to estimate the timing of common ancestors. Higher genetic similarity (chimpanzees-humans: 99%) indicates a more recent common ancestor than lower similarity (cows-humans: 80%). Thus, the chimpanzee-human common ancestor is more recent than the shared ancestor of all three species.

Answer:

The common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.