Well, trying to prove the concepts of evolution with a non-evolutionary model isn't very effective. LOL
Please work on your reading comprehension, you're just wasting both your and my time -- as was already explained to you, the cloud/snow example was not employed "trying to prove the concepts of evolution". It was introduced in order to refute the false claim you made about the "laws of nature" in general. Here, again, is the paragraph you obviously either didn't bother to read, or didn't understand:
the cloud/snow example was not brought in as an example of an "evolutionary model". It was brought in as a counterexample to your (false) claim that there's some sort of "natural law" which requires all things to "go from order to disorder". Not only is there no such law, but ordinary natural processes manage to "go from disorder to order" all the time, contrary to your misunderstandings about nature, laws, and science. He gave you one example in order to point out how trivially wrong you were.Are we clear now, or are you going to insist on misunderstanding this simple point for a *third* time?
Look, if you're not going to bother to read or understand what people say to you, why even post at all?
[Rigorously define "more complex organization".]
I did. See the brief list of examples.
No, you didn't. A list of vague "examples" doesn't even *begin* to rigorously define a concept, nor is it "precise" as I requested. Are you dodging, or do you really not understand the first thing about defining your terms in a scientifically precise way?
[Evolutionary processes require three things in order to work: 1) reproduction, 2) variation, 3) selection.]
Great! So why don't we see evolution at work with those 3 things?
We do.
Where are all the transisitional freaks and mutants?
Once again, you're basing your "knowledge" on some sort of bizarre comic-book version of evolution, not the actual biological science. While evolution (the real thing, that is) will technically produce "mutants", they won't be what one would consider "freaks", nor are transitional forms "freakish" in any way -- they're as fully formed as any other organism.
We just can't seem to find any living examples, or any in the fossil record.
Actually, there are countless transitional examples.
God must be hiding the evidence to test our faith, right? ROFL
Only in the "there are none so blind as he who will not see" sense.
Do you REALLY believe that fish can transform into an amphibian or a dinosaur into a bird or an ape into a man?
Yes, because the evidence that they have is clear and overwhelming. Too bad you're apparently quite unfamiliar with it -- not that this lack of knowledge prevents you from pontificating on the subject anyway...
Hey, want to see an evolutionary sequence from fish to elephants? If a fish to an elephant is illustrative enough to address your question, then here you go (all of the listed specimens are actual fossils):
(Most of the above text is from the link provided at the start of this post, and is the result of hard work by Kathleen Hunt, who deserves the credit. I've just extracted the relevant individual portions and assembled them into one direct fish-to-elephant sequence.) If you like that, here are a few hundred more.Fish to Amphibian transition: 1. Cheirolepis, (early Devonian, 400 million years ago) -- Primitive bony ray-finned fishes that gave rise to the vast majority of living fish. Heavy acanthodian-type scales, acanthodian-like skull, and big notocord.
2. Osteolepis (mid-Devonian, 390 million years ago) -- One of the earliest crossopterygian lobe-finned fishes, still sharing some characters with the lungfish (the other lobe-finned fishes). Had paired fins with a leg-like arrangement of major limb bones, capable of flexing at the "elbow", and had an early-amphibian-like skull and teeth.
3. Eusthenopteron, Sterropterygion (mid-late Devonian, 380 million years ago) -- Early rhipidistian lobe-finned fish roughly intermediate between early crossopterygian fish and the earliest amphibians. Skull very amphibian-like. Strong amphibian- like backbone. Fins very like early amphibian feet in the overall layout of the major bones, muscle attachments, and bone processes, with tetrapod-like tetrahedral humerus, and tetrapod-like elbow and knee joints. But there are no perceptible "toes", just a set of identical fin rays. Body & skull proportions rather fishlike.
4. Panderichthys, Elpistostege (mid-late Devonian, about 370 Mya) -- These "panderichthyids" are very tetrapod-like lobe-finned fish. Unlike Eusthenopteron, these fish actually look like tetrapods in overall proportions (flattened bodies, dorsally placed orbits, frontal bones! in the skull, straight tails, etc.) and have remarkably foot-like fins.
5. Obruchevichthys(middle Late Devonian, about 370 Mya -- Discovered in 1991 in Scotland, these are the earliest known tetrapod remains. The humerus is mostly tetrapod-like but retains some fish features. The discoverer, Ahlberg (1991), said: "It [the humerus] is more tetrapod-like than any fish humerus, but lacks the characteristic early tetrapod 'L-shape'...this seems to be a primitive, fish-like character....although the tibia clearly belongs to a leg, the humerus differs enough from the early tetrapod pattern to make it uncertain whether the appendage carried digits or a fin. At first sight the combination of two such extremities in the same animal seems highly unlikely on functional grounds. If, however, tetrapod limbs evolved for aquatic rather than terrestrial locomotion, as recently suggested, such a morphology might be perfectly workable."
6. Hynerpeton, Acanthostega, Ichthyostega (late Devonian, 360 Mya) -- A little later, the fin-to-foot transition was almost complete, and we have a set of early tetrapod fossils that clearly did have feet. The most complete are Ichthyostega, Acanthostega gunnari, and the newly described Hynerpeton bassetti (Daeschler et al., 1994). (There are also other genera known from more fragmentary fossils.) Hynerpeton is the earliest of these three genera (365 Ma), but is more advanced in some ways; the other two genera retained more fish- like characters longer than the Hynerpeton lineage did. Acanthostega still had internal gills, adding further support to the suggestion that unique tetrapod characters such as limbs with digits evolved first for use in water rather than for walking on land. Acanthostega also had a remarkably fish-like shoulder and forelimb. Ichthyostega was also very fishlike, retaining a fish-like finned tail, permanent lateral line system, and notochord. It turns out that Acanthostega's front foot had eight toes, and Ichthyostega's hind foot had seven toes, giving both feet the look of a short, stout flipper with many "toe rays" similar to fin rays. All you have to do to a lobe- fin to make it into a many-toed foot like this is curl it, wrapping the fin rays forward around the end of the limb. In fact, this is exactly how feet develop in larval amphibians, from a curled limb bud. Hynerpeton, in contrast, probably did not have internal gills and already had a well-developed shoulder girdle; it could elevate and retract its forelimb strongly, and it had strong muscles that attached the shoulder to the rest of the body (Daeschler et al., 1994).
7. Labyrinthodonts (eg Pholidogaster, Pteroplax) (late Dev./early Miss., 355 Mya) -- These larger amphibians still have some icthyostegid fish features, such as skull bone patterns, labyrinthine tooth dentine, presence & pattern of large palatal tusks, the fish skull hinge, pieces of gill structure between cheek & shoulder, and the vertebral structure. But they have lost several other fish features: the fin rays in the tail are gone, the vertebrae are stronger and interlocking, the nasal passage for air intake is well defined, etc.
Amphibian to Reptile transition: 8. Pholidogaster (Mississippian, about 330 Ma) -- A group of large labrinthodont amphibians, transitional between the early amphibians (the ichthyostegids, described above) and later amphibians such as rhachitomes and anthracosaurs.
9. Proterogyrinus (late Mississippian, 325 Mya) -- Classic labyrinthodont-amphibian skull and teeth, but with reptilian vertebrae, pelvis, humerus, and digits. Still has fish skull hinge. Amphibian ankle. 5-toed hand and a 2-3-4-5-3 (almost reptilian) phalangeal count.
10. Limnoscelis, Tseajaia (late Carboniferous, 300 Mya) -- Amphibians apparently derived from the early anthracosaurs, but with additional reptilian features: structure of braincase, reptilian jaw muscle, expanded neural arches.
11. Solenodonsaurus (mid-Pennsylvanian) -- An incomplete fossil, apparently between the anthracosaurs and the cotylosaurs. Loss of palatal fangs, loss of lateral line on head, etc. Still just a single sacral vertebra, though.
12. Hylonomus, Paleothyris (early Pennsylvanian) -- These are protorothyrids, very early cotylosaurs (primitive reptiles). They were quite little, lizard-sized animals with amphibian-like skulls (amphibian pineal opening, dermal bone, etc.), shoulder, pelvis, & limbs, and intermediate teeth and vertebrae. Rest of skeleton reptilian, with reptilian jaw muscle, no palatal fangs, and spool-shaped vertebral centra. Probably no eardrum yet.
13. Paleothyris (early Pennsylvanian) -- An early captorhinomorph reptile, with no temporal fenestrae at all.
14. Protoclepsydrops haplous (early Pennsylvanian) -- The earliest known synapsid reptile. Little temporal fenestra, with all surrounding bones intact. Had amphibian-type vertebrae with tiny neural processes. (reptiles had only just separated from the amphibians)
15. Clepsydrops (early Pennsylvanian) -- The second earliest known synapsid.
Reptile to Mammal transition: 16. Archaeothyris (early-mid Pennsylvanian) -- A slightly later ophiacodont. Small temporal fenestra, now with some reduced bones (supratemporal). Braincase still just loosely attached to skull. Slight hint of different tooth types. Still has some extremely primitive, amphibian/captorhinid features in the jaw, foot, and skull. Limbs, posture, etc. typically reptilian, though the ilium (major hip bone) was slightly enlarged.
17. Varanops (early Permian) -- Temporal fenestra further enlarged. Braincase floor shows first mammalian tendencies & first signs of stronger attachment to rest of skull (occiput more strongly attached). Lower jaw shows first changes in jaw musculature (slight coronoid eminence). Body narrower, deeper: vertebral column more strongly constructed. Ilium further enlarged, lower-limb musculature starts to change (prominent fourth trochanter on femur). This animal was more mobile and active. Too late to be a true ancestor, and must be a "cousin".
18. Haptodus (late Pennsylvanian) -- One of the first known sphenacodonts, showing the initiation of sphenacodont features while retaining many primitive features of the ophiacodonts. Occiput still more strongly attached to the braincase. Teeth become size-differentiated, with biggest teeth in canine region and fewer teeth overall. Stronger jaw muscles. Vertebrae parts & joints more mammalian. Neural spines on vertebrae longer. Hip strengthened by fusing to three sacral vertebrae instead of just two. Limbs very well developed.
19. Dimetrodon, Sphenacodon or a similar sphenacodont (late Pennsylvanian to early Permian, 270 Ma) -- More advanced pelycosaurs, clearly closely related to the first therapsids (next). Dimetrodon is almost definitely a "cousin" and not a direct ancestor, but as it is known from very complete fossils, it's a good model for sphenacodont anatomy. Medium-sized fenestra. Teeth further differentiated, with small incisors, two huge deep- rooted upper canines on each side, followed by smaller cheek teeth, all replaced continuously. Fully reptilian jaw hinge. Lower jaw bone made of multiple bones & with first signs of a bony prong later involved in the eardrum, but there was no eardrum yet, so these reptiles could only hear ground-borne vibrations (they did have a reptilian middle ear). Vertebrae had still longer neural spines (spectacularly so in Dimetrodon, which had a sail), and longer transverse spines for stronger locomotion muscles.
20. Biarmosuchia (late Permian) -- A therocephalian -- one of the earliest, most primitive therapsids. Several primitive, sphenacodontid features retained: jaw muscles inside the skull, platelike occiput, palatal teeth. New features: Temporal fenestra further enlarged, occupying virtually all of the cheek, with the supratemporal bone completely gone. Occipital plate slanted slightly backwards rather than forwards as in pelycosaurs, and attached still more strongly to the braincase. Upper jaw bone (maxillary) expanded to separate lacrymal from nasal bones, intermediate between early reptiles and later mammals. Still no secondary palate, but the vomer bones of the palate developed a backward extension below the palatine bones. This is the first step toward a secondary palate, and with exactly the same pattern seen in cynodonts. Canine teeth larger, dominating the dentition. Variable tooth replacement: some therocephalians (e.g Scylacosaurus) had just one canine, like mammals, and stopped replacing the canine after reaching adult size. Jaw hinge more mammalian in position and shape, jaw musculature stronger (especially the mammalian jaw muscle). The amphibian-like hinged upper jaw finally became immovable. Vertebrae still sphenacodontid-like. Radical alteration in the method of locomotion, with a much more mobile forelimb, more upright hindlimb, & more mammalian femur & pelvis. Primitive sphenacodontid humerus. The toes were approaching equal length, as in mammals, with #toe bones varying from reptilian to mammalian. The neck & tail vertebrae became distinctly different from trunk vertebrae. Probably had an eardrum in the lower jaw, by the jaw hinge.
21. Procynosuchus (latest Permian) -- The first known cynodont -- a famous group of very mammal-like therapsid reptiles, sometimes considered to be the first mammals. Probably arose from the therocephalians, judging from the distinctive secondary palate and numerous other skull characters. Enormous temporal fossae for very strong jaw muscles, formed by just one of the reptilian jaw muscles, which has now become the mammalian masseter. The large fossae is now bounded only by the thin zygomatic arch (cheekbone to you & me). Secondary palate now composed mainly of palatine bones (mammalian), rather than vomers and maxilla as in older forms; it's still only a partial bony palate (completed in life with soft tissue). Lower incisor teeth was reduced to four (per side), instead of the previous six (early mammals had three). Dentary now is 3/4 of lower jaw; the other bones are now a small complex near the jaw hinge. Jaw hinge still reptilian. Vertebral column starts to look mammalian: first two vertebrae modified for head movements, and lumbar vertebrae start to lose ribs, the first sign of functional division into thoracic and lumbar regions. Scapula beginning to change shape. Further enlargement of the ilium and reduction of the pubis in the hip. A diaphragm may have been present.
22. Dvinia [also "Permocynodon"] (latest Permian) -- Another early cynodont. First signs of teeth that are more than simple stabbing points -- cheek teeth develop a tiny cusp. The temporal fenestra increased still further. Various changes in the floor of the braincase; enlarged brain. The dentary bone was now the major bone of the lower jaw. The other jaw bones that had been present in early reptiles were reduced to a complex of smaller bones near the jaw hinge. Single occipital condyle splitting into two surfaces. The postcranial skeleton of Dvinia is virtually unknown and it is not therefore certain whether the typical features found at the next level had already evolved by this one. Metabolic rate was probably increased, at least approaching homeothermy.
23. Thrinaxodon (early Triassic) -- A more advanced "galesaurid" cynodont. Further development of several of the cynodont features seen already. Temporal fenestra still larger, larger jaw muscle attachments. Bony secondary palate almost complete. Functional division of teeth: incisors (four uppers and three lowers), canines, and then 7-9 cheek teeth with cusps for chewing. The cheek teeth were all alike, though (no premolars & molars), did not occlude together, were all single- rooted, and were replaced throughout life in alternate waves. Dentary still larger, with the little quadrate and articular bones were loosely attached. The stapes now touched the inner side of the quadrate. First sign of the mammalian jaw hinge, a ligamentous connection between the lower jaw and the squamosal bone of the skull. The occipital condyle is now two slightly separated surfaces, though not separated as far as the mammalian double condyles. Vertebral connections more mammalian, and lumbar ribs reduced. Scapula shows development of a new mammalian shoulder muscle. Ilium increased again, and all four legs fully upright, not sprawling. Tail short, as is necessary for agile quadrupedal locomotion. The whole locomotion was more agile. Number of toe bones is 2.3.4.4.3, intermediate between reptile number (2.3.4.5.4) and mammalian (2.3.3.3.3), and the "extra" toe bones were tiny. Nearly complete skeletons of these animals have been found curled up - a possible reaction to conserve heat, indicating possible endothermy? Adults and juveniles have been found together, possibly a sign of parental care. The specialization of the lumbar area (e.g. reduction of ribs) is indicative of the presence of a diaphragm, needed for higher O2 intake and homeothermy. NOTE on hearing: The eardrum had developed in the only place available for it -- the lower jaw, right near the jaw hinge, supported by a wide prong (reflected lamina) of the angular bone. These animals could now hear airborne sound, transmitted through the eardrum to two small lower jaw bones, the articular and the quadrate, which contacted the stapes in the skull, which contacted the cochlea. Rather a roundabout system and sensitive to low-frequency sound only, but better than no eardrum at all! Cynodonts developed quite loose quadrates and articulars that could vibrate freely for sound transmittal while still functioning as a jaw joint, strengthened by the mammalian jaw joint right next to it. All early mammals from the Lower Jurassic have this low-frequency ear and a double jaw joint. By the middle Jurassic, mammals lost the reptilian joint (though it still occurs briefly in embryos) and the two bones moved into the nearby middle ear, became smaller, and became much more sensitive to high-frequency sounds.
24. Cynognathus (early Triassic, 240 Ma; suspected to have existed even earlier) -- We're now at advanced cynodont level. Temporal fenestra larger. Teeth differentiating further; cheek teeth with cusps met in true occlusion for slicing up food, rate of replacement reduced, with mammalian-style tooth roots (though single roots). Dentary still larger, forming 90% of the muscle-bearing part of the lower jaw. TWO JAW JOINTS in place, mammalian and reptilian: A new bony jaw joint existed between the squamosal (skull) and the surangular bone (lower jaw), while the other jaw joint bones were reduced to a compound rod lying in a trough in the dentary, close to the middle ear. Ribs more mammalian. Scapula halfway to the mammalian condition. Limbs were held under body. There is possible evidence for fur in fossil pawprints.
25. Diademodon (early Triassic, 240 Ma; same strata as Cynognathus) -- Temporal fenestra larger still, for still stronger jaw muscles. True bony secondary palate formed exactly as in mammals, but didn't extend quite as far back. Turbinate bones possibly present in the nose (warm-blooded?). Dental changes continue: rate of tooth replacement had decreased, cheek teeth have better cusps & consistent wear facets (better occlusion). Lower jaw almost entirely dentary, with tiny articular at the hinge. Still a double jaw joint. Ribs shorten suddenly in lumbar region, probably improving diaphragm function & locomotion. Mammalian toe bones (2.3.3.3.3), with closely related species still showing variable numbers.
26. Probelesodon (mid-Triassic; South America) -- Fenestra very large, still separate from eyesocket (with postorbital bar). Secondary palate longer, but still not complete. Teeth double-rooted, as in mammals. Nares separated. Second jaw joint stronger. Lumbar ribs totally lost; thoracic ribs more mammalian, vertebral connections very mammalian. Hip & femur more mammalian.
27. Probainognathus (mid-Triassic, 239-235 Ma, Argentina) -- Larger brain with various skull changes: pineal foramen ("third eye") closes, fusion of some skull plates. Cheekbone slender, low down on the side of the eye socket. Postorbital bar still there. Additional cusps on cheek teeth. Still two jaw joints. Still had cervical ribs & lumbar ribs, but they were very short. Reptilian "costal plates" on thoracic ribs mostly lost. Mammalian #toe bones.
28. Pachygenelus, Diarthrognathus (earliest Jurassic, 209 Ma) -- These are trithelodontids. Inflation of nasal cavity, establishment of Eustachian tubes between ear and pharynx, loss of postorbital bar. Alternate replacement of mostly single- rooted teeth. This group also began to develop double tooth roots -- in Pachygenelus the single root of the cheek teeth begins to split in two at the base. Pachygenelus also has mammalian tooth enamel, and mammalian tooth occlusion. Double jaw joint, with the second joint now a dentary-squamosal (instead of surangular), fully mammalian. Incipient dentary condyle. Reptilian jaw joint still present but functioning almost entirely in hearing; postdentary bones further reduced to tiny rod of bones in jaw near middle ear; probably could hear high frequencies now. More mammalian neck vertebrae for a flexible neck. Hip more mammalian, with a very mammalian iliac blade & femur. Highly mobile, mammalian-style shoulder. Probably had coupled locomotion & breathing.
29. Sinoconodon (early Jurassic, 208 Ma) -- The next known very ancient proto-mammal. Eyesocket fully mammalian now (closed medial wall). Hindbrain expanded. Permanent cheekteeth, like mammals, but the other teeth were still replaced several times. Mammalian jaw joint stronger, with large dentary condyle fitting into a distinct fossa on the squamosal. This final refinement of the joint automatically makes this animal a true "mammal". Reptilian jaw joint still present, though tiny.
Proto-mammal to Placental Mammal transition: 30. Kuehneotherium (early Jurassic, about 205 Ma) -- A slightly later proto-mammal, sometimes considered the first known pantothere (primitive placental-type mammal). Teeth and skull like a placental mammal. The three major cusps on the upper & lower molars were rotated to form interlocking shearing triangles as in the more advanced placental mammals & marsupials. Still has a double jaw joint, though.
31. Eozostrodon, Morganucodon, Haldanodon (early Jurassic, ~205 Ma) -- A group of early proto-mammals called "morganucodonts". The restructuring of the secondary palate and the floor of the braincase had continued, and was now very mammalian. Truly mammalian teeth: the cheek teeth were finally differentiated into simple premolars and more complex molars, and teeth were replaced only once. Triangular- cusped molars. Reversal of the previous trend toward reduced incisors, with lower incisors increasing to four. Tiny remnant of the reptilian jaw joint. Once thought to be ancestral to monotremes only, but now thought to be ancestral to all three groups of modern mammals -- monotremes, marsupials, and placentals.
32. Peramus (late Jurassic, about 155 Ma) -- A "eupantothere" (more advanced placental-type mammal). The closest known relative of the placentals & marsupials. Triconodont molar has with more defined cusps. This fossil is known only from teeth, but judging from closely related eupantotheres (e.g. Amphitherium) it had finally lost the reptilian jaw joint, attaing a fully mammalian three-boned middle ear with excellent high-frequency hearing. Has only 8 cheek teeth, less than other eupantotheres and close to the 7 of the first placental mammals. Also has a large talonid on its "tribosphenic" molars, almost as large as that of the first placentals -- the first development of grinding capability.
33. Endotherium (very latest Jurassic, 147 Ma) -- An advanced eupantothere. Fully tribosphenic molars with a well- developed talonid. Known only from one specimen. From Asia; recent fossil finds in Asia suggest that the tribosphenic molar evolved there.
34. Vincelestes neuquenianus (early Cretaceous, 135 Ma) -- A probably-placental mammal with some marsupial traits, known from some nice skulls. Placental-type braincase and coiled cochlea. Its intracranial arteries & veins ran in a composite monotreme/placental pattern derived from homologous extracranial vessels in the cynodonts. (Rougier et al., 1992)
35. Kennalestes and Asioryctes (late Cretaceous, Mongolia) -- Small, slender animals; eyesocket open behind; simple ring to support eardrum; primitive placental-type brain with large olfactory bulbs; basic primitive tribosphenic tooth pattern. Canine now double rooted. Still just a trace of a non-dentary bone, the coronoid, on the otherwise all-dentary jaw. "Could have given rise to nearly all subsequent placentals." says Carroll (1988).
Placental mammal to elephant transition: 36. Protungulatum (latest Cretaceous) -- Transitional between earliest placental mammals and the condylarths (primitive, small hoofed animals). These early, simple insectivore- like small mammals had one new development: their cheek teeth had grinding surfaces instead of simple, pointed cusps. They were the first mammal herbivores. All their other features are generalized and primitive -- simple plantigrade five-toed clawed feet, all teeth present (3:1:4:3) with no gaps, all limb bones present and unfused, pointy-faced, narrow small brain, eyesocket not closed.
37. Minchenella or a similar condylarth (late Paleocene) -- Known only from lower jaws. Has a distinctive broadened shelf on the third molar.
38. Phenacolophus (late Paleocene or early Eocene) -- An early embrithopod (very early, slightly elephant-like condylarths), thought to be the stem-group of all elephants.
39. Pilgrimella (early Eocene) -- An anthracobunid (early proto-elephant condylarth), with massive molar cusps aligned in two transverse ridges.
40. Unnamed species of proto-elephant (early Eocene) -- Discovered recently in Algeria. Had slightly enlarged upper incisors (the beginnings of tusks), and various tooth reductions. Still had "normal" molars instead of the strange multi-layered molars of modern elephants. Had the high forehead and pneumatized skull bones of later elephants, and was clearly a heavy-boned, slow animal. Only one meter tall.
41. Moeritherium, Numidotherium, Barytherium (early-mid Eocene) -- A group of three similar very early elephants. It is unclear which of the three came first. Pig-sized with stout legs, broad spreading feet and flat hooves. Elephantish face with the eye set far forward & a very deep jaw. Second incisors enlarged into short tusks, in upper and lower jaws; little first incisors still present; loss of some teeth. No trunk.
42. Paleomastodon, Phiomia (early Oligocene) -- The first "mastodonts", a medium-sized animals with a trunk, long lower jaws, and short upper and lower tusks. Lost first incisors and canines. Molars still have heavy rounded cusps, with enamel bands becoming irregular. Phiomia was up to eight feet tall.
43. Gomphotherium (early Miocene) -- Basically a large edition of Phiomia, with tooth enamel bands becoming very irregular. Two long rows cusps on teeth became cross- crests when worn down. Gave rise to several families of elephant- relatives that spread all over the world. From here on the elephant lineages are known to the species level.
44a. The mastodon lineage split off here, becoming more adapted to a forest browser niche, and going through Miomastodon (Miocene) and Pliomastodon (Pliocene), to Mastodon (or "Mammut", Pleistocene).
44b. Meanwhile, the elephant lineage became still larger, adapting to a savannah/steppe grazer niche:
45. Stegotetrabelodon (late Miocene) -- One of the first of the "true" elephants, but still had two long rows of cross-crests, functional premolars, and lower tusks. Other early Miocene genera show compression of the molar cusps into plates (a modern feature ), with exactly as many plates as there were cusps. Molars start erupting from front to back, actually moving forward in the jaw throughout life.
46. Primelephas (latest Miocene) -- Short lower jaw makes it look like an elephant now. Reduction & loss of premolars. Very numerous plates on the molars, now; we're now at the modern elephants' bizarre system of one enormous multi-layered molar being functional at a time, moving forward in the jaw.
47. Primelephas gomphotheroides (mid-Pliocene) -- A later species that split into three lineages, Loxodonta, Elephas, and Mammuthus:
The Pleistocene record for elephants is very good. In general, after the earliest forms of the three modern genera appeared, they show very smooth, continuous evolution with almost half of the speciation events preserved in fossils. For instance, Carroll (1988) says: "Within the genus Elephas, species demonstrate continuous change over a period of 4.5 million years. ...the elephants provide excellent evidence of significant morphological change within species, through species within genera, and through genera within a family...."
- Loxodonta adaurora (5 Ma). Gave rise to the modern African elephant Loxodonta africana about 3.5 Ma.
- Elephas ekorensis (5 Ma), an early Asian elephant with rather primitive molars, clearly derived directly from P. gomphotheroides. Led directly to:
- Elephas recki, which sent off one side branch, E. hydrusicus, at 3.8 Ma, and then continued changing on its own until it became E. iolensis.
- Elephas maximus, the modern Asian elephant, clearly derived from
- E. hysudricus. Strikingly similar to young E. hysudricus animals. Possibly a case of neoteny (in which "new" traits are simply juvenile features retained into adulthood).
- Mammuthus meridionalis, clearly derived from P. gomphotheroides. Spread around the northern hemisphere. In Europe, led to M. armeniacus/trogontherii, and then to M. primigenius. In North America, led to M. imperator and then M. columbi.
Species-species transitions among the elephants:
- Maglio (1973) studied Pleistocene elephants closely. Overall, Maglio showed that at least 7 of the 17 Quaternary elephant species arose through smooth anagenesis transitions from their ancestors. For example, he said that Elephas recki "can be traced through a progressive series of stages...These stages pass almost imperceptibly into each other....In the late Pleistocene a more progressive elephant appears which I retain as a distinct species, E. iolensis, only as a matter of convenience. Although as a group, material referred to E. iolensis is distinct from that of E. recki, some intermediate specimens are known, and E. iolensis seems to represent a very progressive, terminal stage in the E. recki specific lineage."
- Maglio also documented very smooth transitions between three Eurasian mammoth species: Mammuthus meridionalis --> M. armeniacus (or M. trogontherii) --> M. primigenius.
- Lister (1993) reanalyzed mammoth teeth and confirmed Maglio's scheme of gradual evolution in European mammoths, and found evidence for gradual transitions in the North American mammoths too.
Similar fossil sequences can be listed for the majority of other major-group transitions.
(Did I hear a creationist in the back row say something about "no transitional fossils?")
Also note that the changes between any two sequential transitionals are small enough that most creationists would write them off as only "microevolution" -- and yet those 50-or-so "microevolutionary" steps turn a fish into an elephant, which even the most stubborn creationist would have to concede is "macroevolution".
Let's take a brief look at ONE example. What structural and physiological transformations must occur to change, say a dinosaur, into a bird? Well, WINGS would be the most obvious. The proposed ancestors of birds are thought to have walked on their hind legs. Their diminutive forelimbs had digits similar to a hand, but consisting only of digits one, two, and three. Bird forelimbs consist of digits two, three, and four.
No, actually, they don't. Because the other two digits are suppressed almost entirely in birds, it has actually been rather difficult to determine exactly which three digits actually go into constructing the bird wing. Experiments with ostriches a few years ago seemed to indicate that it might have been digits II, III, and IV, but genetic analysis has now determined pretty inarguably that birds actually use digits I, II, and III -- just like the theropod dinosaurs, you'll note.
Birds have dinosaur wings: The molecular evidence. Alexander O. Vargas, John F. Fallon; J. Exp. Zool. (Mol. Dev. Evol.) 304:000-000, 2004.So there. I'll bet your creationist source(s) tried to make the "which digits" issue sound like a resolved issue, and like an insurmountable contradiction for evolutionary biology, didn't it? Neither is true.Abstract: Within developmental biology, the digits of the wing of birds are considered on embryological grounds to be digits 2, 3 and 4. In contrast, within paleontology, wing digits are named 1, 2, 3 as a result of phylogenetic analysis of fossil taxa indicating that birds descended from theropod dinosaurs that had lost digits 4 and 5. It has been argued that the development of the wing does not support the conclusion that birds are theropods, and that birds must have descended from ancestors that had lost digits 1 and 5. Here we use highly conserved gene expression patterns in the developing limbs of mouse and chicken, including the chicken talpid2mutant and polydactylous Silkie breed (Silkie mutant), to aid the assessment of digital identity in the wing. Digit 1 in developing limbs does not express Hoxd12, but expresses Hoxd13. All other digits express both Hoxd12and Hoxd13. We found this signature expression pattern identifies the anteriormost digit of the wing as digit 1, in accordance with the hypothesis these digits are 1, 2 and 3, as in theropod dinosaurs. Our evidence contradicts the long-standing argument that the development of the wing does not support the hypothesis that birds are living dinosaurs.
Today, most hold that ground-dwelling theropods learned to run fast and jump to catch insects and eventually used arms with frayed scales to fly. (Ok, I'm trying not laugh here, but it is NOT easy!)
Proverbs 29:9: "If a wise man has an argument with a fool, the fool only rages and laughs, and there is no quiet."
"Most hold" that scenario because the evidence supporting it is solid, plentiful, and convincing.
The cladogram for the evolution of flight looks like this:
(Note -- each name along the top is a known transitional fossil; and those aren't all that have been discovered.) Here's a more detailed look at the middle section:
Fossils discovered in the past ten years in China have answered most of the "which came first" questions about the evolution of birds from dinosaurs.
We now know that downy feathers came first, as seen in this fossil of Sinosauropteryx:
That's a close-up of downy plumage along the backbone. Here's a shot of an entire fossil
Sinosauropteryx was reptilian in every way, not counting the feathers. It had short forelimbs, and the feathers were all the same size. Presumably, the downy feathers evolved from scales driven by a need for bodily insulation.
Next came Protarchaeopteryx:
It had long arms, broad "hands", and long claws:
Apparently this species was driven by selection to develop more efficient limbs for grasping prey. One of the interesting things about this species is that the structure of the forelimb has been refined to be quite efficient at sweeping out quickly to grab prey, snap the hands together, then draw them back towards the body (mouth?). The specific structures in question are the semilunate carpal (a wrist bone), that moves with the hand in a broad, flat, 190 degree arc, heavy chest muscles, bones of the arm which link together with the wrist so as to force the grasping hands to spread out toward the prey during the forestroke and fold in on the prey during the upstroke. Not only is this a marvelously efficient prey-grabbing mechanism, but the same mechanism is at the root of the wing flight-stroke of modern birds. Evolution often ends up developing a structure to serve one need, then finds it suitable for adaptation to another. Here, a prey-grasping motion similar in concept to the strike of a praying mantis in a reptile becomes suitable for modifying into a flapping flight motion.
Additionally, the feathers on the hands and tail have elongated, becoming better suited for helping to sweep prey into the hands.
Next is Caudipteryx:
This species had hand and tail feathers even more developed than the previous species, and longer feathers, more like that of modern birds:
However, it is clear that this was still not a free-flying animal yet, because the forelimbs were too short and the feathers not long enough to support its weight, and the feathers were symmetrical (equal sized "fins" on each side of the central quill). It also had very reduced teeth compared to earlier specimens and a stubby beak:
But the elongation of the feathers indicates some aerodynamic purpose, presumably gliding after leaping (or falling) from trees which it had climbed with its clawed limbs, in the manner of a flying squirrel. Feathers which were developed "for" heat retention and then pressed into service to help scoop prey were now "found" to be useful for breaking falls or gliding to cover distance (or swooping down on prey?).
Next is Sinornithosaurus:
Similar to the preceding species, except that the pubis bone has now shifted to point to the back instead of the front, a key feature in modern birds (when compared to the forward-facing publis bone in reptiles). Here are some of the forearm feathers in detail: 
Long feathers in detail:
Artists' reconstruction:
Next is Archaeopteryx:
The transition to flight is now well underway. Archaeopteryx has the reversed hallux (thumb) characteristic of modern birds, and fully developed feathers of the type used for flight (long, aligned with each other, and assymetrical indicating that the feathers have been refined to function aerodynamically). The feathers and limbs are easily long enough to support the weight of this species in flight. However, it lacks some structures which would make endurance flying more practical (such as a keeled sternum for efficient anchoring of the pectoral muscles which power the downstroke) and fused chest vertebrae. Archaeopteryx also retains a number of clearly reptilian features still, including a clawed "hand" emerging from the wings, small reptilian teeth, and a long bony tail. After the previous species' gliding abilities gave it an advantage, evolution would have strongly selected for more improvements in "flying" ability, pushing the species towards something more resembling sustained powered flight.
Next is Confuciusornis:
This species had a nearly modern flight apparatus. It also displays transitional traits between a reptilian grasping "hand" and a fully formed wing as in modern birds -- the outer two digits (the earlier species had three-fingered "hands") in Confuciusornis are still free, but the center digit has now formed flat, broad bones as seen in the wings of modern birds.
Additionally, the foot is now well on its way towards being a perching foot as in modern birds:
It also has a keeled sternum better suited for long flight, and a reduced number of vertebrae in the tail, on its way towards becoming the truncated tail of modern birds (which while prominent, is a small flap of muscle made to look large only because of the long feathers attached).
From this species it's only a small number of minor changes to finish the transition into the modern bird family.
(Hey, who said there are no transitional fossils? Oh, right, a lot of dishonest creationists. And there are a lot more than this, I've just posted some of the more significant milestones.)
There's been a very recent fossil find along this same lineage, too new for me to have found any online images to include in this article. And analysis is still underway to determine exactly where it fits into the above lineage. But it has well-formed feathers, which extend out from both the "arms" and the legs. Although it wasn't advanced enough to fully fly, the balanced feathering on the front and back would have made it ideally suited for gliding like a flying squirrel, and it may be another link between the stage where feathers had not yet been pressed into service as aerodynamic aids, and the time when they began to be used more and more to catch the air and developing towards a "forelimbs as wings" specialization.
So in short, to answer your question about how flight could have developed in birds, the progression is most likely some minor refinement on the following:
1. Scales modified into downy feathers for heat retention.
2. Downy feathers modified into "straight" feathers for better heat retention (modern birds still use their body "contour feathers" in this fashion).
3. Straight feathers modified into a "grasping basket" on the hands (with an accompanying increase in reach for the same purpose).
4. Long limbs with long feathers refined to better survive falls to the ground.
5. "Parachute" feathers refined for better control, leading to gliding.
6. Gliding refined into better controlled, longer gliding.
7. Long gliding refined into short powered "hops".
8. Short powered flight refined into longer powered flight.
9. Longer powered flight refined into long-distance flying.
Note that in each stage, the current configuration has already set the stage for natural selection to "prefer" individuals which better meet the requirements of the next stage. Evolution most often works like this; by taking some pre-existing ability or structure, and finding a better use for it or a better way to make it perform its current use.
But flight requires fully formed, interlocking feathers and hollow bones, not to mention the flight muscles and keeled sternum to anchor the muscles.
No, it most certainly does not. Such things help improve the efficiency of flight, but they are not "required".
And of course wings are made of feather, which are not at all similar to scales.
Where do you get that nonsense? They are similar in a large number of ways to scales. See for example:
Evo-Devo of feathers and scales: building complex epithelial appendagesYou seem to "forget" that modern birds have scales (most often on the feet) *and* feathers, and that you can see one transition into the other in the regions where they meet. And from the above paper:
Retinoic acid can cause feather formation on all the three types of foot scales, suggesting a chemical basis for the conversion [41••]. On the other hand, retinoic acid added to cultured feather explants converted feather buds into scale-like appendages [42]. Regional differences of the Hox expression pattern on chicken skin led us to propose that the skin Hox code is related to regional specificity of skin appendages [43•,44]. Retinoic acid indeed caused the expression pattern of Hox D13 in the foot to disappear, approximating it more to that of the feather dermis [44]. With the development of RCAS-mediated gene transduction, the ectopic expression of several genes was observed to produce interesting phenotypes when injected into the leg buds. A dominant negative form of the BMP receptor resulted in ptilopody of the scuta and scutella, but not reticulate scales [45••] —suggesting that BMP may be one of the suppressors of feather formation for the leg dermis. â-catenin is another important molecule that can cause the outgrowth of feathers from the scale epidermis [46••] and apteric skin [47•]. Analysis showed that, in each case, the scale epidermis became activated during the conversion to feathers, and the distribution of molecular markers such as SHH, NCAM and Tenascin-C were characteristic of feather buds. The ectopic feathers form follicle sheaths, dermal papillae and barb ridges [46••]. In mouse, LEF1, a â-catenin molecular partner, caused hair to grow out from the gum region [48], and â-catenin caused new hair formation [49••]. These results suggest that activation of the â-catenin pathway can activate the versatile appendageforming potentials of epidermal cells. Notch and its ligands are known to be involved in cell-fate decisions and the misexpression of Delta-1 in the leg bud also caused feather- like outgrowths from scales [50].So not only are you incorrect when you say that feathers are "not at all similar to scales", but in fact one can be induced to actually grow into the other when triggered with the appropriate signalling chemicals.
A *lot* is already known about the evolution of feathers. Although many of the specific details still need to be nailed down, the fundamentals are pretty already known. See for example:
The morphogenesis of feathersAnd so onAvian skin development and the evolutionary origin of feathers
Molecular biology of feather morphogenesis: A testable model for evo-devo research
When did theropods become feathered? - evidence for pre-archaeopteryx feathery appendages
Even if scales were frayed, they would not be interlocking and impervious to air as are feathers. (Ok, I'm flat out laughing now)
Laugh in your ignorance if you want, or go read up on the actual research on this topic and *learn* something about it for a change. Hint: Reading creationist materials is not the same as reading science journals.
Actually, feathers are more similar to hair follicles than scales.
Feathers, scales, and hair are all integumentary modifications. This "problem" you see just isn't the obstacle that you mistakenly think it is.
Birds have delicate, hollow bones to lighten their weight while dinosaurs had solid bones.
So? Did you have some sort of point here? Yes, the bird lineage evolved several adaptations to improve their flight efficiency. This is classic Darwinian evolution due to selective pressures.
For example, the heavy tail of dinosaurs (needed for balance on two legs) would prohibit any possible flight (Can't you just picture a big dino running and trying to fly and looking back disdainfully at his heavy tail? LOL).
...which is why the bony tail progressively becomes more vestigial as the bird lineage evolves. Just as you'd expect by evolution...
And besides, the theropods were "lizard-hipped" dinosaurs, not "bird-hipped" as would be expected for bird ancestors.
Change over time is called "evolution", son. Thanks for making my point for me.
Ah, let's see...Oh yes, birds are warmblooded with exceptionally high metabolism and food demands. While dinosaur metabolism is in question, all modern reptiles are cold-blooded with a more lethargic life style. Birds are unique among land-dwelling vertebrates in that they don't breathe in and out. The air flows continually in a one-directional loop supporting the bird's high metabolism. Reptilian respiration is entirely different, more like that in mammals. The soft parts of birds and dinosaurs, in addition to the lungs, are totally different. A recent "mummified" dinosaur, with soft tissue fossilized, proved to be quite like a crocodile, and not at all like a bird.
Evolution changed these things. And yes, both the fossil evidence and the DNA evidence show clear transitional steps along the sequence of changes (see the above cladograms). Please learn some *science* instead of parroting creationist tracts for a change.
Thus, the dinosaur-to-bird transition is blocked by many major obstacles, not just the acquisition of feathers.
No it isn't, nor have you actually identified even a single "obstacle" -- you just rambled about how birds have ended up with several differences from their dinosaur ancestors, without ever demonstrating that any of them would be any sort of "obstacle". Care to try again?
Furthermore, you have ignored (probably out of true ignorance) all the evidence that yes, indeed, birds *have* evolved from dinosaurs in the way biologists describe. They don't just pull these scenarios out of a hat, you know -- they develop them as a result of what all the *evidence* indicates. Too bad you're entirely unfamiliar with it...
It gets even worse, for in order to make the transition, most if not all of the definitive characteristics must be acquired simultaneously.
...because...? Now you're just making things up.
They all must be present or else none serves a valid purpose.
See the cladograms, Einstein... Or pay attention to the fossil sequences for once in your life. Each new adaptation was, by itself, advantageous.
Now if you want to believe in such leaps of faith, go right ahead, but YOU are the one off the scientific reservation, not I.
I, like the biologists, am familiar with the vast amounts of evidence (along multiple independent lines and from multiple independent sources) which indicates in great detail the path which the bird lineage took in its evolution from dinosaur ancestors to modern birds. Thus no "faith" is required, just knowledge and understanding -- things you're clearly lacking on this topic.
You may want to read up on Dr. Michael Denton. He's an agnostic but a decided non-evolutionist who compiled a chart on "The Adequacy of the Fossil Record" in his book, Evolution: A Theory In Crisis,
Actually *YOU* "may want to read up on Dr. Michael Denton", because he is NO LONGER "a decided non-evolutionist. His "theory in crisis" book was already outdated when it was published in the 80's, and has only become even more blown away by all the detailed DNA analsysi which has been done since. From one of Denton's more recent books:
"it is important to emphasize at the outset that the argument presented here is entirely consistent with the basic naturalistic assumption of modern science - that the cosmos is a seamless unity which can be comprehended ultimately in its entirety by human reason and in which all phenomena, including life and evolution and the origin of man, are ultimately explicable in terms of natural processes. This is an assumption which is entirely opposed to that of the so-called "special creationist school". According to special creationism, living organisms are not natural forms, whose origin and design were built into the laws of nature from the beginning, but rather contingent forms analogous in essence to human artifacts, the result of a series of supernatural acts, involving the suspension of natural law. Contrary to the creationist position, the whole argument presented here is critically dependent on the presumption of the unbroken continuity of the organic world - that is, on the reality of organic evolution and on the presumption that all living organisms on earth are natural forms in the profoundest sense of the word, no less natural than salt crystals, atoms, waterfalls, or galaxies."And:
"One of the most surprising discoveries which has arisen from DNA sequencing has been the remarkable finding that the genomes of all organisms are clustered very close together in a tiny region of DNA sequence space forming a tree of related sequences that can all be interconverted via a series of tiny incremental natural steps [...] So the sharp discontinuities, referred to above, between different organs and adaptations and different types of organisms, which have been the bedrock of antievolutionary arguments for the past century (3), have now greatly diminished at the DNA level. Organisms which seem very different at a morphological level can be very close together at the DNA level."
by comparing the number of living types to fossil types, gleaning information from Romer's classic book, Vertebrate Paleontology. He found that 97.7% of living orders of terrestrial vertebrates are found as fossils. Approximately 95% are marine invertebrates, with the rest being mostly plants, fish, and insects.
You're not making much sense here.
When we look at the invertebrates, we see separate and distinct categories (i.e., clams, corals, trilobites, etc.) existing in the earliest strata with NOT A HINT of ancestors or of intermediates.
Oh look, precambrian trilobite precursors:
Care to pull the other leg now?
We find clams by the trillions, with a lot of variety among them, but no evolution.
You're lying again: http://en.wikipedia.org/wiki/Bivalvia
Furthermore, we have no idea how vertebrate fish could have arisen from any invertebrate.
Maybe *you* don't have any idea... However, biologists have no problem understanding how vertebrate fishes could have arisen from *chordate* invertebrates...
Where there are good data, we see no evolution.
Your either hallucinating, or parroting nonsense from some creationist site. There are countless good evolutionary sequences in the paleontological record, not to mention the massive DNA evidence for evolution.
The fossil record is voluminous and apparently substantially complete.
ROFL!!! What have you been smoking?
Yet no evolution is seen.
Again, is this God testing our faith in evolution?
No, but you're testing my patience with your ignorant and false proclamations.
If you remember nothing else, never forget that Mutations never add information to the DNA code, as would be necessary for major evolutionary advancement.
Gene duplication is just one of the many ways that mutations "add information to the DNA code". See for example:
Koch, AL: Evolution of antibiotic resistance gene function. Microbiol Rev 1981, 45:355378.You've obviously made the mistake of reading creationist lies -- and believing them.Velkov, VV: Gene amplification in prokaryotic and eukaryotic systems. Genetika 1982, 18:529543.
Romero, D & Palacios, R: Gene amplification and genomic plasticity in prokaryotes. Annu Rev Genet 1997, 31:91111.
Stark, GR & Wahl, GM: Gene amplification. Annu Rev Biochem 1984, 53:447491.
Reinbothe, S, Ortel, B, & Parthier, B: Overproduction by gene amplification of the multifunctional arom protein confers glyphosate tolerance to a plastid-free mutant of Euglena gracilis. Mol Gen Genet 1993, 239:416424.
Gottesman, MM, Hrycyna, CA, Schoenlein, PV, Germann, UA, & Pastan, I: Genetic analysis of the multidrug transporter. Annu Rev Genet 1995, 29:607649.
Schwab, M: Oncogene amplification in solid tumors. Semin Cancer Biol 1999, 9:319325.
Widholm, JM, Chinnala, AR, Ryu, JH, Song, HS, Eggett, T, & Brotherton, JE: Glyphosate selection of gene amplification in suspension cultures of three plant species. Physiol Plant 2001, 112:540545.
Otto, E, Young, JE, & Maroni, G: Structure and expression of a tandem duplication of the Drosophila metallothionein gene. Proc Natl Acad Sci USA 1986, 83:60256029.
Maroni, G, Wise, J, Young, JE, & Otto, E: Metallothionein gene duplications and metal tolerance in natural populations of Drosophila melanogaster. Genetics 1987, 117:739744.
Kondratyeva, TF, Muntyan, LN, & Karvaiko, GI: Zinc-resistant and arsenic-resistant strains of Thiobacillus ferrooxidans have increased copy numbers of chromosomal resistance genes. Microbiology 1995, 141:11571162.
Tohoyama, H, Shiraishi, E, Amano, S, Inouhe, M, Joho, M, & Murayama, T: Amplification of a gene for metallothionein by tandem repeat in a strain of cadmium-resistant yeast cells. FEMS Microbiol Lett 1996, 136:269273.
Sonti, RV & Roth, JR: Role of gene duplications in the adaptation of Salmonella typhimurium to growth on limiting carbon sources. Genetics 1989, 123:1928.
Brown, CJ, Todd, KM, & Rosenzweig, RF: Multiple duplications of yeast hexose transport genes in response to selection in a glucose-limited environment. Mol Biol Evol 1998, 15:931942.
Hastings, PJ, Bull, HJ, Klump, JR, & Rosenberg, SM: Adaptive amplification: an inducible chromosomal instability mechanism. Cell 2000, 103:723731.
Tabashnik, BE: Implications of gene amplification for evolution and management of insecticide resistance. J Econ Entomol 1990, 83:11701176.
Lenormand, T, Guillemaud, T, Bourguet, D, & Raymond, M: Appearance and sweep of a gene duplication: adaptive response and potential for new functions in the mosquito Culex pipiens. Evolution 1998, 52:17051712.
Guillemaud, T, Raymond, M, Tsagkarakou, A, Bernard, C, Rochard, P, & Pasteur, N: Quantitative variation and selection of esterase gene amplification in Culex pipiens. Heredity 1999, 83:8799.
End of sentence. End of evolution.
Little do you know how little you know.
I must yet again repeat the advice I have to give way too many anti-evolutionists: Please *learn* something about evolutionary biology and the evidence for it before you attempt to critique it, lest you make a fool of yourself, and spread misinformation from unreliable creationist sources.