Transitional form

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A transitional form is a fossil or living organism that is intermediate between two other organism in an evolutionary sequence. A transitional form that has not yet been found is colloquially called a 'missing link'.

Creationists claim that transitional forms between different kinds of creatures are systematically absent. Anti-creationists typically reject this claim. One such attempted rebuttal is that by Kathleen Hunt who created a Transitional Vertebrate Fossil FAQ.

The lack of transitional forms

Many scientists have admitted the lack of transitional fossils.

The late paleontologist Stephen Jay Gould said in 1977:

The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology.

And in 1984:

The absence of fossil evidence for intermediary stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution.

The senior palaeontologists at the British Museum of Natural History, Colin Patterson, agreed with Gould, when asked why he didn't have any illustrations of transitional forms in his book:

I fully agree with your comments on the lack of direct illustration of evolutionary transitions in my book. If I knew of any, fossil or living, I would certainly have included them. ... Yet Gould and the American Museum people are hard to contradict when they say there are no transitional fossils. I will lay it on the line- there is not one such fossil for which one could make a watertight argument.

See also

• Missing link
• Transitional fossil
• Theory of Punctuated Equilibrium