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Whale Transitions

Welcome to the Whale Transitions page. These links are provided as additional information to go along with the topics covered on my website. At the time of this posting, the links are all in working order, but if you come across one that doesn't work, please contact me at WWDD.

The Journey from Land to Sea

The cladogram depicting whale evolution is from the book Evolution: The Triumph of an Idea by Carl Zimmer. The artist was Deborah Perugi. The book is a companion to the PBS series of the Evolution Project, a coproduction of the WGNH/NOVA Science Unit and Clear Blue Sky Productions. Please visit the extensive website for this production, and you can read my review of the book at Book of the Month, April 2004.

It was not until 1979 that paleontologists had their first indisputable evidence about whale transition. Pakicetus was discovered by Philip Gingerich in Pakistan. Later, in 1995, Hans Thewissen found Ambulocetus. Whales with legs are now known from Pakistan, India, Egypt and the U.S.A.

It took less than 15 million years for the whale lineage to move from land, through shallow bays and coastal waters, to deep marine environments. By 40 million years ago whales had become essentially the animals we know today.

The evolution of whales involved much more than legs becoming flippers or vestigial organs. The fossil series demonstrates how their breathing apparatus changed, their ears changed and other body parts changed. If you are interested in detailed taxonomic descriptions, click on an animal illustrated at right to be taken to another website with that information.

Whales did not turn into fish. Inside every flipper is found the bones of the mammalian hand. They swim like otters by undulating the mammalian spine. The tail fluke is not a fish fin. Evolution works by modifying existing body plans to fit new conditions of life, and is often constrained by developmental pathways. No longer limited by gravity and strength of bones, whales could become giants of the sea.

To learn more about whale evolution and the many transitional forms, use the hotlinks in the image to the right or in the bibliography given below.

As Stephen Gould concludes, "If you had given me a blank piece of paper and a blank check, I could not have drawn you a theoretical intermediate any better or more convincing than Ambulocetus. Those dogmatists who by verbal trickery can make white black, and black white, will never be convinced of anything, but Ambulocetus is the very animal that they proclaimed impossible in theory."
Natural History magazine, May 1994.

Side view of the inner ears of, left to right, a land mammal (bushbaby), a land-living early whale from Pakistan (50-million-year-old Ichthyolestes), a marine early whale from India (45-million-year-old Indocetus), and a modern dolphin. The latter two aquatic species have much smaller semicircular canals than the former two. Image reconstructed from computed tomography scans, adjusting for body size differences between the animals. Each inner ear would easily fit on a penny. [Image by F. Spoor using Voxel-man] Researchers Discover Clues to Whale Evolution

Cetaceans have unique semicircular canals that allow them to be highly acrobatic swimmers without becoming dizzy. By investigating this organ in ancient fossils, the researchers found that early whales acquired this special trait quickly and early on in their evolution. This was a defining event that likely resulted in their total independence of life on land. Another news item may be seen here.

The research paper by Spoor F. et al., Vestibular Evidence for the Evolution of Aquatic Behaviour in early Cetaceans, Nature 417:163-166 (2002), is available here in .pdf format.

More Information

Ancient Walking Whales

Rodhocetus Sheds Light on Ancestry of Ocean Giants. National Geographic.

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Cetacean Evolution

This overview of information through 1994 may be objectionable to some creationists because it counters arguments by Duane Gish.

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PBS on Whale Evolution

A 7-minute video describes two lines of evidence, fossil and molecular, which contribute to our picture of evolution. It focuses on whales, which provide an excellent opportunity to examine the transition between species because so many intermediate fossils have been found.

Recent Journal Publications

River Dolphins Add Branches to Family Tree. by Dennis Normile. Science 2001 Mar. 30; 291: 2531-2532.

Origin of Whales from Early Artiodactyls by P. D. Gingerich etal. Science 2001, 293: 2239-2242.

The Ancestry of Whales by Kenneth D. Rose. Science 2001, 293: 2216-2217.

Culture and Genetic Evolution in Whales. Science 1999 Jun. 25; 284: 2053

Whale Origins by Maureen A. O'Leary & John E. Heyning. Science 1999 Mar. 12; 283: 1641.

Whale Origins -- Conquering the Seas by John E. Heyning. Science 1999 Feb. 12; 283: 943.

New Views of the Origins of Mammals by Dennis Normile. Science 1998 Aug. 7; 281: 774-775.

Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales. by J. Thewissen, etal., Science 263:210-212, 1994.

Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales. by P. Gingerich, etal., Science 249: 154-157, 1990.

Origin of Whales in Epicontinental Remnant Seas. by P. Gingerich, etal., Science 220: 403-406, 1983.

Vestibular Evidence for the Evolution of Aquatic Behaviour in Early Cetaceans by F. Spoor etal., Nature 417: 163-166, 09 May 2002.

Walking With Whales by Christian de Muizon, Nature 413: 259-260, 20 Sep 2001.

Evolution: In Search of the Whales' Sisters by Z. Luo, Nature 404: 235-239, 16 Mar. 2000.

Evolution of Cetacean Osmoregulation. by J. Thewissen, etal., Nature 381: 379-380, 1996.

New Whale from the Eocene of Pakistan and the Origin of Cetacean Swimming. by P. Gingerich, etal., Nature 368: 844-847, 1994.

Origin of Underwater Hearing in Whales. by J. Thewissen & S. Hussain, Nature 361: 444-445, 1993.

Phylogenetic Aspects of Cetacean Origins: a Morphological Perspective. by J. Thewissen, Journal of Mammalian Evolution 2: 157-184, 1994.

Origin of Whales & Role of Behavioral Changes in Terrestrial-aquatic Transition. by M. O'Leary & M. Uhen, Paleobiology 25: 534-556, 1999.

A New Eocene Archaeocete from India and the Time of Origin of Whales. by S. Bajpai & P. Gingerich, Proc. Nat. Acad. Sci. 95: 15464-15468, 1998.

Estimation of Time of Origin of Cetacea & Time of Divergence of Cetacea & Artiodactyla. by P. Gingerich & M. Uhen, 1998