Changes

==Evolutionary claims==

==Evolutionary claims==

The question of how whales and their relatives could have evolved from terrestrial [[mammal]]s has intrigued evolutionary biologists since [[Charles Darwin]]'s suggestion that they may have evolved from ancient mammals. He suggested that their development may have been started by something similar to a behavior observed in bears. <blockquote>"In North America the black bear was seen . . . swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale."</blockquote><ref>Charles Darwin, [http://www.gutenberg.org/ebooks/1228 Origin of species] 1st edition</ref>

The question of how whales and their relatives allegedly evolved from terrestrial [[mammal]]s has intrigued evolutionary biologists since [[Charles Darwin]]'s suggestion that they may have evolved from ancient mammals. He suggested that their development may have been started by something similar to a behavior observed in bears. <blockquote>"In North America the black bear was seen . . . swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale."</blockquote><ref>Charles Darwin, [http://www.gutenberg.org/ebooks/1228 Origin of species] 1st edition</ref>

Evolutionary biologists estimate the last ancestor of whales and hippos lived about 25 million years ago.<ref>[http://evolution.berkeley.edu/evosite/lines/IAtransitional.shtml] UCLA Berkley Understanding Evolution for Teachers website</ref>, with a more recent suggestion that modern whales and their relatives arose from ancient [[Artiodactyla|artiodactyls]] (even-toed ungulates such as [[deer]] and [[hippopotamus|hippopotami]]).<ref>[http://www.redorbit.com/news/science/41080/molecular_clock_divergence_estimates_and_the_fossil_record_of_cetartiodactyla/index.html] Theodore, JM (2004) Molecular Clock Divergence Estimates And The Fossil Record Of Cetartiodactyla '' The Journal Of Paleontology'' '''78''':39-44</ref>

Evolutionary biologists estimate the last ancestor of whales and hippos lived about 25 million years ago.<ref>[http://evolution.berkeley.edu/evosite/lines/IAtransitional.shtml] UCLA Berkley Understanding Evolution for Teachers website</ref>, with a more recent suggestion that modern whales and their relatives arose from ancient [[Artiodactyla|artiodactyls]] (even-toed ungulates such as [[deer]] and [[hippopotamus|hippopotami]]).<ref>[http://www.redorbit.com/news/science/41080/molecular_clock_divergence_estimates_and_the_fossil_record_of_cetartiodactyla/index.html] Theodore, JM (2004) Molecular Clock Divergence Estimates And The Fossil Record Of Cetartiodactyla '' The Journal Of Paleontology'' '''78''':39-44</ref>

More specifically, they believe that whales evolved from Pakicetus through Aetiocetus, because of the similarities in their bone structure. For example, ''Pakicetus'' has nostrils at the front of its skull, ''Aetiocetus'' has nostrils in the middle of its skull, and the modern gray whale has nostrils at the top of its skull<ref>[https://evolution.berkeley.edu/evolibrary/article/lines_03]University of California, Berkeley, ''Understanding Evolution''</ref>. This kinship has been termed the whippo hypothesis.<ref>http://www.sciencenews.org/pages/pdfs/data/1999/15619/15619-10.pdf</ref>

More specifically, they believe that whales evolved from Pakicetus through Aetiocetus, because of the similarities in their bone structure. For example, ''Pakicetus'' has nostrils at the front of its skull, ''Aetiocetus'' has nostrils in the middle of its skull, and the modern gray whale has nostrils at the top of its skull<ref>[https://evolution.berkeley.edu/evolibrary/article/lines_03]University of California, Berkeley, ''Understanding Evolution''</ref>. This kinship has been termed the whippo hypothesis.<ref>http://www.sciencenews.org/pages/pdfs/data/1999/15619/15619-10.pdf</ref>