Claim CC200:
There are no transitional fossils. Evolution predicts a continuum between each fossil organism and its ancestors. Instead, we see systematic gaps in the fossil record.
Response:
1. There are many transitional fossils. The only way that the claim of their absence may be remotely justified, aside from ignoring the evidence completely, is to redefine "transitional" as referring to a fossil that is a direct ancestor of one organism and a direct descendant of another. However, direct lineages are not required; they could not be verified even if found. What a transitional fossil is, in keeping with what the theory of evolution predicts, is a fossil that shows a mosaic of features from an older and more recent organism.
2. Transitional fossils may coexist with gaps. We do not expect to find finely detailed sequences of fossils lasting for millions of years. Nevertheless, we do find several fine gradations of fossils between species and genera, and we find many other sequences between higher taxa that are still very well filled out.
The following are fossil transitions between species and genera:
1. Human ancestry ( http://www.talkorigins.org/indexcc/CC/CC050.html ). There are many fossils of human ancestors, and the differences between species are so gradual that it is not always clear where to draw the lines between them.
2. The horns of titanotheres (extinct Cenozoic mammals) appear in progressively larger sizes, from nothing to prominence. Other head and neck features also evolved. These features are adaptations for head-on ramming analogous to sheep behavior (Stanley 1974).
3. A gradual transitional fossil sequence connects the foraminifera Globigerinoides trilobus and Orbulina universa (Pearson et al. 1997). O. universa, the later fossil, features a spherical test surrounding a "Globigerinoides-like" shell, showing that a feature was added, not lost. The evidence is seen in all major tropical ocean basins. Several intermediate morphospecies connect the two species, as may be seen in the figure included in Lindsay (1997).
4. The fossil record shows transitions between species of Phacops (a trilobite; Phacops rana is the Pennsylvania state fossil; Eldredge 1972; 1974; Strapple 1978).
5. Planktonic forminifera (Malmgren et al. 1984). This is an example of punctuated gradualism. A ten-million-year foraminifera fossil record shows long periods of stasis and other periods of relatively rapid but still gradual morphologic change.
6. Fossils of the diatom Rhizosolenia are very common (they are mined as diatomaceous earth), and they show a continuous record of almost two million years which includes a record of a speciation event (Miller 1999, 44-45).
7. Lake Turkana mollusc species (Lewin 1981).
8. Cenozoic marine ostracodes (Cronin 1985).
9. The Eocene primate genus Cantius (Gingerich 1976, 1980, 1983).
10. Scallops of the genus Chesapecten show gradual change in one "ear" of their hinge over about 13 million years. The ribs also change (Pojeta and Springer 2001; Ward and Blackwelder 1975).
11. Gryphaea (coiled oysters) become larger and broader but thinner and flatter during the Early Jurassic (Hallam 1968).
The following are fossil transitionals between families, orders, and classes:
1. Human ancestry. Australopithecus, though its leg and pelvis bones show it walked upright, had a bony ridge on the forearm, probably vestigial, indicative of knuckle walking (Richmond and Strait 2000).
2. Dinosaur-bird transitions ( http://www.talkorigins.org/indexcc/CC/CC214.html ).
3. Haasiophis terrasanctus is a primitive marine snake with well-developed hind limbs. Although other limbless snakes might be more ancestral, this fossil shows a relationship of snakes with limbed ancestors (Tchernov et al. 2000). Pachyrhachis is another snake with legs that is related to Haasiophis (Caldwell and Lee 1997).
4. The jaws of mososaurs are also intermediate between snakes and lizards. Like the snake's stretchable jaws, they have highly flexible lower jaws, but unlike snakes, they do not have highly flexible upper jaws. Some other skull features of mososaurs are intermediate between snakes and primitive lizards (Caldwell and Lee 1997; Lee et al. 1999; Tchernov et al. 2000).
5. Transitions between mesonychids and whales ( http://www.talkorigins.org/indexcc/CC/CC216_1.html ).
6. Transitions between fish and tetrapods 9 http://www.talkorigins.org/indexcc/CC/CC212.html ).
7. Transitions from condylarths (a kind of land mammal) to fully aquatic modern manatees. In particular, Pezosiren portelli is clearly a sirenian, but its hind limbs and pelvis are unreduced (Domning 2001a, 2001b).
8. Runcaria, a Middle Devonian plant, was a precursor to seed plants. It had all the qualities of seeds except a solid seed coat and a system to guide pollen to the seed (Gerrienne et al. 2004).
9. A bee, Melittosphex burmensis, from Early Cretaceous amber, has primitive characteristics expected from a transition between crabronid wasps and extant bees (Poinar and Danforth 2006).
The following are fossil transitionals between kingdoms and phyla:
1. The Cambrian fossils Halkiera and Wiwaxia have features that connect them with each other and with the modern phyla of Mollusca, Brachiopoda, and Annelida. In particular, one species of halkieriid has brachiopod-like shells on the dorsal side at each end. This is seen also in an immature stage of the living brachiopod species Neocrania. It has setae identical in structure to polychaetes, a group of annelids. Wiwaxia and Halkiera have the same basic arrangement of hollow sclerites, an arrangement that is similar to the chaetae arrangement of polychaetes. The undersurface of Wiwaxia has a soft sole like a mollusk's foot, and its jaw looks like a mollusk's mouth. Aplacophorans, which are a group of primitive mollusks, have a soft body covered with spicules similar to the sclerites of Wiwaxia (Conway Morris 1998, 185-195).
2. Cambrian and Precambrain fossils Anomalocaris and Opabinia are transitional between arthropods and lobopods ( http://www.talkorigins.org/indexcc/CC/CC220.html ).
Claim CC200.1:
Given all the species that exist and have existed, there should be billions of transitional fossils in the fossil record; we should have found tens of thousands at least.
Response:
1. Some important factors prevent the formation of fossils from being common:
* Fossilization itself is not a particularly common event. It requires conditions that preserve the fossil before it becomes scavenged or decayed. Such conditions are common only in a very few habitats, such as river deltas, peat bogs, and tar pits. Organisms that do not live in or near these habitats will be preserved only rarely.
* Many types of animals are fragile and do not preserve well.
* Many species have small ranges. Their chance of fossilization will be proportionally small.
* The evolution of new species probably is fairly rapid in geological terms, so the transitions between species will be uncommon.
Passenger pigeons, once numbered in the billions, went extinct less than 200 years ago. How many passenger pigeon fossils can you find? If they are hard to find, why should we expect to find fossils that are likely from smaller populations and have been subject to millions of years of potential erosion?
2. Other processes destroy fossils. Erosion (and/or lack of deposition in the first place) often destroys hundreds of millions of years or more of the geological record, so the geological record at any place usually has long gaps. Fossils can also be destroyed by heat or pressure when buried deep underground.
3. As rare as fossils are, fossil discovery is still rarer. For the most part, we find only fossils that have been exposed by erosion, and only if the exposure is recent enough that the fossils themselves do not erode.
As climates change, species will move, so we cannot expect a transition to occur all at one spot. Fossils often must be collected from all over a continent to find the transitions.
Only Europe and North America have been well explored for fossils because that is where most of the paleontologists lived. Furthermore, regional politics interfere with collecting fossils. Some fabulous fossils have been found in China only recently because before then the politics prevented most paleontology there.
4. The shortage is not just in fossils but in paleontologists and taxonomists. Preparing and analyzing the material for just one lineage can take a decade of work. There are likely hundreds of transitional fossils sitting in museum drawers, unknown because nobody knowledgeable has examined them.
5. Description of fossils is often limited to professional literature and does not get popularized. This is especially true of marine microfossils, which have the best record.
6. If fossilization were so prevalent and young-earth creationism were true, we should find indications in the fossil record of animals migrating from the Ark to other continents.