From Eli Haltov, Israel:
What is a transitional form? And is it correct to say that there are no transitional forms in the fossil record?
Eli, as with all things, definitions are important. In evolutionary biology, the term “transitional intermediate” is ambiguous and can assume one of two meanings.
Many people understand this term to refer to one or more of the organisms that comprise the stepwise, evolutionary transition of one species (or taxon) into another. At times, evolutionary biologists do employ this definition. Quite frequently, however, they use transitional intermediates to refer to the entire ensemble of organisms between two time points in the fossil record.
Evolutionary biologists will often use this second definition when they have no real understanding of the precise evolutionary pathway that connects two organisms. Yet, in spite of their uncertainty, they are convinced that an evolutionary pathway must exist. They are equally convinced that they will eventually identify that pathway. In the meantime, they deem all the organisms that exist between two time points in the fossil record as transitional forms, irrespective of whether or not they are actually part of an evolutionary sequence.
In my opinion, if the evolutionary paradigm is to be considered a valid model, then the fossil record needs to be replete with transitional forms documenting the actual transformation of one taxon into another, as defined by the first meaning. Remarkably, there are very few examples of these types of transitional intermediates. For example, paleontologist Christopher R. C. Paul states in The Adequacy of the Fossil Record,
With the benefit of hindsight, I am amazed at how long we accepted that gradual morphological change was the norm when data to support this belief were so sparse and the discrepancy had been known since Darwin’s time. Examples of gradual evolutionary trends in the fossil record can be counted on our fingers and we simply ignored countless examples that do not show the expected pattern. Lack of morphological change was equated with lack of data and the few examples of trends were with the truth…the few known examples of gradual trends are no more than random walks that just happen to be more or less linear.1
When creationists and intelligent design proponents highlight this significant problem, evolutionary biologists are quick to assert that the fossil record possesses an abundance of transitional forms. But they are using the second definition, not the first. So whether there is a dearth or there is an abundance of transitional forms in the fossil record all depends on the definition one employs.
To be fair, the fossil record does include some well known examples of transitional forms that correspond to the first definition, such as the fishapods (presumably documenting the emergence of tetrapods from lobe-finned fish) and feathered dinosaurs (presumably the evolutionary ancestors to birds). Even so, when we consider the details of these high-profile examples, some rather uncomfortable problems surface for the evolutionary paradigm. For example, both the tetrapod and bird evolutionary sequences suffer from what paleontologists call a temporal paradox, in which the transitional forms (i.e., fishapods and feathered dinosaurs) appear in the fossil record after the evolutionary end products (i.e., tetrapods and birds, respectively).
The bottom line is that when the fossil record is considered in its entirety, the patterns found therein find perfect explanation from a creation model vantage point, rather than from an evolutionary one. For a detailed discussion of the temporal paradox and other problems associated with the evolutionary models for tetrapod and bird origins, check out the following articles:
- "Is There a Controversy about Evolution?"
- "Out of Order"
- "Tetrapod Transitions: Evidence for Design"
For more on transitional forms, check out these two short videos, part of RTB’s Through the Lens series on evolution: