Here is a very good FAQ on transitional fossils (to use the layman's term) which includes long lists (with cites) of the intermediate stages of development in many types of species:
http://www.talkorigins.org/faqs/faq-transitional.html
But here are a couple of very useful sections from the introduction. the first explains how Creationists "quote mine" scientists when discussing PE and then misleadingly use it out of context to support their own agenda. The second explains what the theory of evolution REALLY predicts and what we should expect to see if YEC was correct:
Misunderstanding of quotes about punctuated equilibrium What paleontologists do get excited about are topics like the average rate of evolution. When exceptionally complete fossil sites are studied, usually a mix of patterns are seen: some species still seem to appear suddenly, while others clearly appear gradually. Once they arise, some species stay mostly the same, while others continue to change gradually. Paleontologists usually attribute these differences to a mix of slow evolution and rapid evolution (or "punctuated equilibrium": sudden bursts of evolution followed by stasis), in combination with the immigration of new species from the as-yet-undiscovered places where they first arose.
There's been a heated debate about which of these modes of evolution is most common, and this debate has been largely misquoted by laypeople, particularly creationists. Virtually all of the quotes of paleontologists saying things like "the gaps in the fossil record are real" are taken out of context from this ongoing debate about punctuated equilibrium. Actually, no paleontologist that I know of doubts that evolution has occurred, and most agree that at least sometimes it occurs gradually. The fossil evidence that contributed to that consensus is summarized in the rest of this FAQ. What they're arguing about is how often it occurs gradually. You can make up your own mind about that. (As a starting point, check out Gingerich, 1980, who found 24 gradual speciations and 14 sudden appearances in early Eocene mammals; MacFadden, 1985, who found 5 cases of gradual anagenesis, 5 cases of probable cladogenesis, and 6 sudden appearances in fossil horses; and the numerous papers in Chaline, 1983. Most studies that I've read find between 1/4-2/3 of the speciations occurring fairly gradually.)
Predictions of creationism and of evolution
Before launching into the transitional fossils, I'd like to run through the two of the major models of life's origins, biblical creationism and modern evolutionary theory, and see what they predict about the fossil record.
http://www.talkorigins.org/faqs/faq-transitional.html
But here are a couple of very useful sections from the introduction. the first explains how Creationists "quote mine" scientists when discussing PE and then misleadingly use it out of context to support their own agenda. The second explains what the theory of evolution REALLY predicts and what we should expect to see if YEC was correct:
Misunderstanding of quotes about punctuated equilibrium What paleontologists do get excited about are topics like the average rate of evolution. When exceptionally complete fossil sites are studied, usually a mix of patterns are seen: some species still seem to appear suddenly, while others clearly appear gradually. Once they arise, some species stay mostly the same, while others continue to change gradually. Paleontologists usually attribute these differences to a mix of slow evolution and rapid evolution (or "punctuated equilibrium": sudden bursts of evolution followed by stasis), in combination with the immigration of new species from the as-yet-undiscovered places where they first arose.
There's been a heated debate about which of these modes of evolution is most common, and this debate has been largely misquoted by laypeople, particularly creationists. Virtually all of the quotes of paleontologists saying things like "the gaps in the fossil record are real" are taken out of context from this ongoing debate about punctuated equilibrium. Actually, no paleontologist that I know of doubts that evolution has occurred, and most agree that at least sometimes it occurs gradually. The fossil evidence that contributed to that consensus is summarized in the rest of this FAQ. What they're arguing about is how often it occurs gradually. You can make up your own mind about that. (As a starting point, check out Gingerich, 1980, who found 24 gradual speciations and 14 sudden appearances in early Eocene mammals; MacFadden, 1985, who found 5 cases of gradual anagenesis, 5 cases of probable cladogenesis, and 6 sudden appearances in fossil horses; and the numerous papers in Chaline, 1983. Most studies that I've read find between 1/4-2/3 of the speciations occurring fairly gradually.)
Predictions of creationism and of evolution
Before launching into the transitional fossils, I'd like to run through the two of the major models of life's origins, biblical creationism and modern evolutionary theory, and see what they predict about the fossil record.
- Most forms of creationism hold that all "kinds" were created separately, as described in Genesis. Unfortunately there is no biological definition of "kind"; it appears to be a vague term referring to our psychological perception of types of organisms such as "dog", "tree", or "ant". In previous centuries, creationists equated "kind" to species. With the discovery of more and more evidence for derivation of one species from another, creationists bumped "kind" further up to mean higher taxonomic levels, such as "genus", or "family", though this lumps a large variety of animals in the same "kind". Some creationists say that "kind" cannot be defined in biological terms.
- Predictions of creationism: Creationists usually don't state the predictions of creationism, but I'll take a stab at it here. First, though there are several different sorts of creationism, all of them agree that there should be no transitional fossils at all between "kinds". For example, if "kind" means "species", creationism apparently predicts that there should be no species-to-species transitions whatsoever in the fossil record. If "kind" means "genus" or "family" or "order", there should be no species-to-species transitions that cross genus, family, or order lines. Furthermore, creationism apparently predicts that since life did not originate by descent from a common ancestor, fossils should not appear in a temporal progression, and it should not be possible to link modern taxa to much older, very different taxa through a "general lineage" of similar and progressively older fossils.
Other predictions vary with the model of creationism. For instance, an older model of creationism states that fossils were created during six metaphorical "days" that may each have taken millenia to pass. This form of creationism predicts that fossils should be found in the same order outlined in Genesis: seed-bearing trees first, then all aquatic animals and flying animals, then all terrestrial animals, then humans.
In contrast, many modern U.S. creationists believe the "Flood Theory" of the origin of fossils. The "Flood Theory" is derived from a strictly literal reading of the Bible, and states that all geological strata, and the fossils imbedded in them, were formed during the forty-day flood of Noah's time. Predictions of the Flood Theory apparently include the following:- most rock should be sedimentary and indicative of cataclysmic flooding. There should be no rock formations that indicate the passing of millenia of gradual accumulation of undisturbed sediment, such as multi-layered riverbed formations. There should be no large lava flows layered on top of each other, and definitely not with successively older radiometric dates in the lower levels.
- terrestrial animal fossils should either not be sorted at all, or should be sorted by some "hydrodynamic" aspect such as body size, with, for instance, extinct elephants and large dinosaurs in the lowest layers, and small primitive dinosaurs in the upper layers. Terrestrial animal fossils should not be sorted by subtle anatomical details (such as, say, the number of cusps on the fourth premolar).
- marine animals are a puzzle, since it is unclear that a Flood would cause any extinctions of aquatic animals. If such extinctions did occur, aquatic fossils would perhaps be "sorted" by body size or ecological niche (bottom-feeder vs. surface swimmer). For instance, plesiosaurs, primitive whales, and placoderm fishes (relatively slow-swimming and quite large) should end up in the same layers. Ichthyosaurs and porpoises (smaller, faster swimmers with almost identical body shapes and similar diets) should also occur in the same layers.
- there should be no sorting of large rooted structures such as coral reefs and trees. There should likewise not be differential sorting of microscopic structures of the same size and shape, such as pollen grains.
- sorting, if it occurs at all, should be quite imperfect. With only 40 days for sorting, there should be occasional examples of individual fossils that ended up in the "wrong" layer -- the occasional mammal and human fossil in Paleozoic rocks, for instance, and the occasional trilobite and plesiosaur in Cenozoic rocks.
- sorting should not correlate with date of the surrounding rocks. If all fossils were created by Noah's flood, there is no conceivable reason that, for instance, lower layers of fossils should always end up sandwiched between lava rocks with old radiometric dates.
- Modern evolutionary theory holds that the living vertebrates arose from a common ancestor that lived hundreds of millions of years ago (via "descent with modification"; variety is introduced by mutation, genetic drift, and recombination, and is acted on by natural selection). Various proposed mechanisms of evolution differ in the expected rate and tempo of evolutionary change.
- Predictions of evolutionary theory: Evolutionary theory predicts that fossils should appear in a temporal progression, in a nested hierarchy of lineages, and that it should be possible to link modern animals to older, very different animals. In addition, the "punctuated equilibrium" model also predicts that new species should often appear "suddenly" (within 500,000 years or less) and then experience long periods of stasis. Where the record is exceptionally good, we should find a few local, rapid transitions between species. The "phyletic gradualism" model predicts that most species should change gradually throughout time, and that where the record is good, there should be many slow, smooth species-to-species transitions. These two models are not mutually exclusive -- in fact they are often viewed as two extremes of a continuum -- and both agree that at least some species-to-species transitions should be found.
