INVESTIGATING GENESIS SERIES ©2003  by Gerard Wakefield    http://www.creationism.org/wakefield/ (This article may be copied for educational purposes only.)

In the 1980s and 1990s, numerous fossils were found, particularly in Pakistan, which allegedly demonstrated that whales evolved from land-dwelling, carnivorous mammals called mesonychids. A slew of fossils seemed to indicate an unmistakable progression from the land-dwelling Pakicetus ("Pakistan whale") all the way up to modern whales in a traditionally Darwinian step-by-step manner. It turns out, however, that paleontologists were seeing in these fossils what they wanted to see, rather than what actually was there.
 
While these fossils were being unearthed, geneticists in the US, Belgium, and Japan analyzed the DNA of living whales and determined that the mesonychid-to-whale progression, supposedly so obvious in the fossils, was false. These tests suggested that whales did not descend from mesonychids at all, but are members of a mammal family called the artiodactyls, which include hippopotami. At first, whale paleontologists firmly dismissed the findings. However, more meticulous DNA testing led by Norihiro Okada at the Tokyo Institute of Technology strengthened the findings considerably, and paleontologists dropped their objections (Wong 2002: 78).
 
Later, excavations in Pakistan turned up foot bones of Pakicetus and another alleged ancestor of today's whales, Ichthyolestes, and the mesonychid theory was finally dropped, despite what had appeared to be overwhelming fossil evidence in its favor. The reason was that all members of the artiodactyl family have a unique feature in their anklebones known as a "double-pulleyed astragalus." The anklebones of both Pakicetus and Ichthyolestes were found to have this unique feature, identifying them as members of the artiodactyl family, not as mesonychids (Wong 2002: 78-79).
 
Scientific American reported that the mesonychid theory soon went the way of countless other evolutionary theories that were once touted as practically undeniable:

"What of the evidence that seemed to tie early whales to mesonychids? In light of the new ankle data, most workers now suspect that those similarities [between mesonychids and whales] probably reflect convergent evolution rather than shared ancestry and that mesonychids represent an evolutionary dead end" (Wong 2002: 79).
 
Two points must be raised here. First, the similarities between mesonychids and early whales do not automatically have to be interpreted as "convergent evolution," but could just as well be credited to Intelligent Design. Second, evolutionists are now falling into the same trap that they fell into with their mesonychid theory: just because two extinct creatures, Pakicetus and Ichthyolestes, were highly similar to whales, it does not necessarily mean that they are the evolutionary ancestors of whales, but merely that they are related to them.
 
Although scholars of whale origins still cling to the theory of macroevolution (major changes leading to brand-new species), the failure of the mesonychid theory displays the extreme danger of using fossils to determine evolutionary ancestry. For 20 years, the findings in Pakistan and other places were touted as solid evidence for the evolution of whales from mesonychids, but later finds proved them wrong. This accentuates the essentially unreliable nature of trying to use the fossil record as proof of macroevolution, and it also demonstrates how paleontologists convince themselves to see what they want to see in the fossil record, rather than what is actually there.
 

References:

Wong, K. 2002. “The Mammals that Conquered the Seas.” Scientific American 286, no. 5.