- Dec 25, 2003
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I present four evidences for whale evolution, two genetic, one physiological and one embryological.
1. If whales evolved from land mammals we would expect them to have numerous physical characteristics including a mammalian jaw. We indeed find those characteristics one of which is the up and down movement characteristic of mammals in contrast with the side to side movement of reptiles and fish. if whales were specially created they could just as easily move side to side and have a vertical tail fluke as opposed to a horizontal one (see Ichthyosaurs).
2. Cetacean embryos develop hind limb buds that are absorbed (except in cases of atavisms) during fetal development. This is due the interaction of two genes that normally would grow hind limbs (see below). If cetaceans never lived on the land, why do they develop limb buds during the embryonic stage?
http://etb-whales.blogspot.com/2012/03/dolphin-hind-legs-hind-limb-bud-images.html
3. The sleek, hydrodynamic bodies of whales are due to a broken interaction between the genes Sonic Hedgehog and Hand2. Hand2 normally grows hind limbs in terrestrial mammals. If cetaceans didn't evolve from terrestrial mammals, why do they have the Hand2 gene?
http://news.ufl.edu/archive/2006/05...-legs-got-sleek-and-conquered-the-oceans.html
4. The evolution of cetacean forelimbs into flippers is controlled by two genes - Hoxd12 and Hoxd13.
http://www.ncbi.nlm.nih.gov/pubmed/19074008
These are just 4 of the many evidences making whale evolution one of the most compelling and supported lineages we can look at.
1. If whales evolved from land mammals we would expect them to have numerous physical characteristics including a mammalian jaw. We indeed find those characteristics one of which is the up and down movement characteristic of mammals in contrast with the side to side movement of reptiles and fish. if whales were specially created they could just as easily move side to side and have a vertical tail fluke as opposed to a horizontal one (see Ichthyosaurs).
2. Cetacean embryos develop hind limb buds that are absorbed (except in cases of atavisms) during fetal development. This is due the interaction of two genes that normally would grow hind limbs (see below). If cetaceans never lived on the land, why do they develop limb buds during the embryonic stage?
http://etb-whales.blogspot.com/2012/03/dolphin-hind-legs-hind-limb-bud-images.html
3. The sleek, hydrodynamic bodies of whales are due to a broken interaction between the genes Sonic Hedgehog and Hand2. Hand2 normally grows hind limbs in terrestrial mammals. If cetaceans didn't evolve from terrestrial mammals, why do they have the Hand2 gene?
http://news.ufl.edu/archive/2006/05...-legs-got-sleek-and-conquered-the-oceans.html
4. The evolution of cetacean forelimbs into flippers is controlled by two genes - Hoxd12 and Hoxd13.
http://www.ncbi.nlm.nih.gov/pubmed/19074008
These are just 4 of the many evidences making whale evolution one of the most compelling and supported lineages we can look at.