Answer to Question #146148 in Evolution for Keven Lacourse

Question

In 2000 and 2004, a University of Michigan palaeontologist discovered two well-preserved skeletons of a now-extinct species, about 47.5 million years old. He named this newly-discovered species Maiacetus inuus. He described them as skeletons of early whales that actually lived on land, before whales had evolved to become entirely aquatic like modern-day whales.

a) Explain how you would use the fossil record as evidence to suggest that Maiacetus inuus is an evolutionary ancestor of the modern-day whale.

b) Assume that traces of preserved DNA were discovered inside of the Maiacetus inuus fossils. Explain how this DNA could be used to show an evolutionary relationship between Maiacetus inuus and modern-day whales.

Answer 1

(a) First, where the fossils are found and the identity of other fossils found in the same area will suggest whether the species was found among sea creatures or land creatures.

We can then observe the fossil and compare with the skeleton modern-day whales. Areas of interest to observe include;

• middle ear bones
• Finger and toe bones
• Teeth, especially presence of incisor teeth only will suggest similarity, since that is uncommon in all other mammals except whales
• Elongated snout
• unique structures of the ankles.

All these structures is similar will suggest that the two species are evolutionary related.

(b) Comparing DNA evidence - through DNA hybridization technique, where DNA strands from both species are separated by heating to break up base pair hydrogen bonds between the strands. After which, the strands are chopped off (cut) into shorter segments and mixed up and allowed to recombine. Observations are made on the way this recombination occurs. Parts in which the base pairs will link up will suggest similarity, i.e. the more information that links up, the closer the two species.