Whale Evolution

This animated video depicts a sperm whale hunting prey, including a giant squid, by echolocation.

Until recently the consensus opinion among biologists was that whales evolved from land animals, but recent finds have made this view increasingly untenable. Not only is the window of available time for all the requisite changes to adapt a terrestrial creature to a marine environment very narrow, but the sheer number and scope of the changes strains credulity. Here are a few of the changes that would need to have occurred within the span of about 3-5 million years:

• Counter-current heat exchanger for intra-abdominal testes
• Ball vertebra
• Tail flukes and musculature
• Blubber for temperature insulation
• Ability to drink sea water (reorganization of kidney tissues)
• Fetus in breech position (for labor underwater)
• Nurse young underwater (modified mammae)
• Forelimbs transformed into flippers
• Reduction of hindlimbs
• Reduction/loss of pelvis and sacral vertebrae
• Reorganization of the musculature for the reproductive organs
• Hydrodynamic properties of the skin
• Special lung surfactants
• Novel muscle systems for the blowhole
• Modification of the teeth
• Modification of the eye for underwater vision
• Emergence and expansion of the mandibular fat pad with complex lipid distribution
• Reorganization of skull bones and musculature
• Modification of the ear bones
• Decoupling of esophagus and trachea
• Synthesis and metabolism of isovaleric acid (toxic to terrestrial mammals)
• Emergence of blowhole musculature and their neurological control

Here's another video, courtesy of Uncommon Descent, which highlights some of the problems with the consensus view:

Whale Evolution vs. The Actual Fossil Evidence from Philip Cunningham on Vimeo.

The problem of transitional forms remains a serious difficulty for any kind of "molecules to man" evolutionary hypothesis, as this article at Evolution News and Views illustrates. It may have happened that all forms of life on earth are descended from a single ancestral form, but it seems that the more we discover the less evidence there is for it.