Jonathan M. is breaking it down chapter by chapter at Evolution News. Chapter 2 is on fossils. In his response to chapter 2, he covers fish/amphibian evolution, bird/dinosaur evolution and whale evolution.
Here’s a snippet about the whale series:
The next transitional series alluded to by Coyne is the whale series. One of the most notable problems with the evolution of the whale is the extremely abrupt timescale over which it is supposed to have occurred. The sheer force of this conundrum is only properly appreciated when one considers the multiple feats of anatomical novelty, innovative engineering and genetic rewiring necessary to change a terrestrial mammal like Pakicetus into a fully aquatic whale. Indeed, evolutionary biologist Richard Sternberg has argued that even many of the relatively minor changes are extremely unlikely to have occurred in the time-frame allowed. Consider the following small sample of necessary modifications:
- 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
According to Richard Sternberg’s calculations, and based on the equations of population genetics applied in a 2008 paper by Durrett and Schmidt in the Journal of Genetics, one may reasonably expect to see two coordinated mutations achieve fixation in the timeframe of around 43.3 million years. When one considers the magnitude of the engineering feat, such a scenario can only be ruled incredible. The problem is accentuated further when one considers that the majority of anatomical novelties unique to aquatic cetaceans (Pelagiceti) appeared during just a few million years — probably within 1-3 million years.
[…]More recently, however, a jawbone was discovered that belonged to a fully aquatic whale dating to 49 million years ago, only four million years afterPakicetus! This means that the first fully aquatic whales now date to around the time when walking whales (Ambulocetus) first appear. This substantially reduces the time window — to 4 or 5 million years, perhaps even less — that may be allotted to the Darwinian mechanism to accomplish truly radical engineering innovations and genetic rewiring. It also suggests that this fully aquatic whale existed before its previously presumed semi-aquatic archaeocetid ancestors.
If you missed chapter 1, it’s here. And chapter 3 is out soon.