Tuesday, March 9, 2010

Whale and Hippopotamus Prove Duane Gish Wrong

"Duane Gish, an American creationalist, is renowned for his lively and popular (if wildly misguided) lectures attacking evolution" (pg. 47). Gish made fun of evolutionists that thought that whales descended from land animals related to cows. He did not believe that it was possible for an animal that could live in both an aquatic and terrestrial environment to have evolved. Explain how it is possible for an animal to have been naturally selected to live in both an aquatic and terrestrial environment and how the transition between aquatic and terrestrial environments proves that evolution is possible. Use the example of the hippopotamus to support your explanation. Use outside resources to provide other examples of transitional species that prove the existence of species that evolved and had the ability to live in both aquatic and terrestrial environments.


  1. Being able to survive in water and on land can be one of the most selective features for some animals since there are more options for mating, habitat selection, and predation. Jerry Coyne highlights this fact by describing hippopotami and whales in an effort to combat Duane Gish's argument that evolution of a semi-aquatic organism never could have occurred. Many people consider hippos to be mainly land dwelling animals, but Jerry suggests that hippos are on the path of evolving into totally aquatic, whalelike creatures. Most of their day is spent in the water, including times of mating and giving birth. To me it seems that hippos have evolved to more of a whalelike creature because of the amount of activity in water versus on land; their babies can swim before they walk. Hippos have also been documented to have specific adaptations for going on land although they may have first been strictly terrestrial organisms. For instance, they are prone to sunburn, so they secrete an oily red fluid containing hipposudoric acid that essentially serves as sunscreen during the day and an antibiotic. Also, they avoid sunburn since they usually feed at night.

    Whales "Are warm-blooded, produce live young whom they feed with milk, and have hair around their blowholes" (48). DNA evidence from whales has shown that their rudimentary pelvis and hind legs prove the fact that their ancestors lived on land (species of the artidactyls: the group of mammals that have an even number of toes). In fact, modern-day biologists have concurred their belief that the closest living relative of the whale is the hippopotamus.

  2. Besides the DNA evidence, fossil findings from the Middle East have also allowed scientists to trace the unique features of whales today: "absence of rear legs, front limbs that are shaped like paddles, a flattened flukelike tail, a blowhole... , a short neck, simple conical teeth... , special features of the ear that allow them to hear underwater, and robust projections on top of the vertebrae to anchor the strong swimming muscles of the tail" (49). 48 million years ago, a small, racoon-like organism called Indohyus was an artiodactyl that displayed the special features of the ears and teeth of modern whales and their aquatic ancestors. With this fossil, scientists were able to determine that it was at “least partially aquatic” because “its bones were denser than fully terrestrial animals” (49). This may have not been the ancestor of whales, but for sure its cousin. On page 50, there is a diagram showing the transitional forms in the evolution of modern whales. The pattern starts with the Indohyus and is preceded by Pakicetus (52 m.y.a; simpler teeth and whalelike ears), Ambulocetus (50 m.y.a; elongated skull and reduced but still robust limbs, thought to have waddled on land like a seal), Rodhocetus (47 m.y.a; stout extentsions on the backbone, small pelvis and hindlimbs), Dorudon (40 m.y.a; fully aquatic mammal→ short neck and blowholes placed at top of skull), and as of now the Balaena. This is great evidence of how it is possible for a terrestrial organism to become semi-aquatic and eventually totally aquatic, which seems to be occurring for hippos.

    Another example of evolution supporting how animals can develop to be amphibians is observed in amniotes. “Amniotes are named for the major derived characer of the clad, the amniotic egg, which contains four specialized membranes: the amnion, the chorion, the yolk sac, and the allantois” (Campbell et al., 2008). According to http://sci.waikato.ac.nz/evolution/AnimalEvolution.shtml, this adaptation proved to be the determining factor of allowing reptiles to move away from waterside habitats into dry regions. The allantois is the disposal sac for metabolic waste produced by the embryo and works with the chorion to aid in gas exchange between the embryo and air. Next, the amnion protects the embryo in a fluid-filled cavity to cushion any mechanical shock. Lastly, the yolk sac contains yolk, which provides the embryo its nutrients from blood vessels. This evidence could in fact be just as strong as the whale and hippopotamus because it allowed organisms to be able to develop qualities of becoming amphibians or simply creatures that completely changed their respective habitats from water to land.