>The longest running criticism of Darwin's theory is by St. Georges Mivart,
>and is called Mivart's dilemma. Shortly after the publication of _Origins_
>Mivart stated that natural selection is incompetent to account for incipient
>stages of useful structures. Take for example, the case of the whale
>transition from a small terrestrial mammal to a large aquatic one. The
>lineage had to pass through many incipient stages in which there were neither
>legs nor flippers. The criticism is how natural selection would ever get
>started and continue changing presumably well adapted legs, through incipient
>stages that were neither legs nor flippers and less well adapted than the
>legs, and into future useful flippers.
But these transition are well documented in the fossil record. Documented
transitions include the origin of tetrapods from panderidicthyids, the
transition from primitive ungulates to whales, and the transition from
terrestrial anguimorph lizards to mosasaurs. There are quite a range and
diversity of environments that are neither terrestrial nor marine and it is
in these environments that the transitional species are quite well adapted.
For example, it seems quite clear now that the earliest tetrapods were not
terestrial and that limbs evolved for clambering in shallow water.
Keith B. Miller
Department of Geology
Kansas State University
Manhattan, KS 66506
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