A Folha de São Paulo não explica o dilema de Darwin: o registro fóssil

Em 1859 Darwin sabia: a inexistência de zilhões de elos transicionais no registro fóssil era um argumento poderoso contra as suas especulações transformistas através de um processo evolutivo lento e gradual.

Um século e meio depois da publicação de Origem das Espécies e dois séculos após o nascimento de seu autor, Charles Darwin (1809-82), a explicação tida como mais racional e objetiva do mundo não é corroborada pelas evidências encontradas no registro fóssil. Teriam sido inteiramente perdidos os 150 anos de teoria da evolução por seleção natural, a grande contribuição de Darwin para as ciências da vida e para o pensamento contemporâneo como indagou a Folha de São Paulo?

Desde 1859 um exército de dedicados e renomados paleontólogos e paleobiólogos foram à caça de tais evidências que corroborariam a teoria de Darwin. E o que eles encontraram? Eles ainda estão encontrando o mesmo dilema de Darwin: estase, inequívoca antítese da evolução — nenhuma evidência dessas mudanças lentas e graduais.

Para livrar a cara de Darwin no contexto de justificação teórica — Niles Eldredge e Stephen Jay Gould popularizaram a teoria do equilíbrio pontuado em 1972, e outros cientistas elaboraram numerosas razões “racionais” sobre por que o registro fóssil não mostra a evidência evolutiva predita e esperada por Darwin e discípulos.

Será que Marcelo Leite, colunista da Folha de S.Paulo, mostrou realmente neste livro como que a teoria darwiniana veio a tornar-se a melhor e mais resistente explicação para o fenômeno da vida tal como a conhecemos hoje? Vamos dar uma olhada retrospectiva nos livros e na literatura especializada sobre o que os paleontólogos disseram a respeito do registro fóssil.

Sorry, periferia, mas está em inglês:

“In all major lineages, the earliest known members had already achieved the basic body plan of their living descendants. They differed in details, but most can be readily allied with their modern descendants ... Few fossils are yet known of plausible intermediates between the invertebrate phyla, and there is no evidence for the gradual evolution of the major features by which the individual phyla or classes are characterized.”

Carroll, Robert in Patterns and Processes of Vertebrate Evolution. Cambridge University Press, (1997), p. 4.

“The introduction of a variety of organisms in the early Cambrian, including such complex forms of the arthropods as the trilobites, is surprising. ... The introduction of abundant organisms in the record would not be so surprising if they were simple. Why should such complex organic forms be in rocks about six hundred million years old and be absent or unrecognized in the records of the preceding two billion years? If organisms evolved, it should have taken a long time for them to have developed into forms such as arthropods. Many suggestions have been made. They may have had soft bodies, structures that were not resistant enough to be preserved as fossils. As we will see, remarkably well-preserved records of soft-bodied Cambrian organisms are known in Alberta-animals that otherwise are not known through the geological record because they have so rarely been preserved. ... If there has been evolution of life, the absence of the requisite fossils in the rocks older than the Cambrian is puzzling.”

Kay, Marshall, and Edwin H. Colbert in Stratigraphy and Life History. John Wiley & Sons, New York, London, Sydney, NY (1965), p. 102-103.

“One might suppose that Darwin, like his modern intellectual descendants, saw in the fossil record a confirmation of his theory — the literal documentation of life's evolution from the Cambrian to the present day. In fact, the two chapters devoted to geology in The Origin of Species are anything but celebratory. On the contrary, they constitute a carefully worded apology in which Darwin argues that evolution by natural selection is correct despite an evident lack of support from fossils.”

Knoll, Andrew H. in Life on a Young Planet. Princeton University Press, (2003), p. 11.

“Most paleontologists today give little thought to fossiliferous rocks older than the Cambrian, thus ignoring the most important missing link of all. Indeed the missing Pre-Cambrian record cannot properly be described as a link for it is in reality, about nine-tenths of the chain of life: the first nine-tenths.”

Ladd, H.S. in Geological Society of America Memoir, Vol II. (1967), p. 7.

“Since there is considerable question as to just when plants did come from water onto land-estimated dates varying from early Cambrian to Silurian times — it is clear that no one actually knows much about the actual events. There is no tangible evidence whatsoever in the fossil record. Supposedly somewhere within the group called algae lay the sources of the higher plants, the vascular groups. Whatever these ancestors may have been, they seem to have been irrevocably lost in the vastness of time.”

Olson, Everett C. in The Evolution of Life. The New American Library, New York and Toronto, (1965), p. 160,161.

“Ediacarian fossils provide the earliest evidence of metazoan life on Earth. All are impressions of soft-bodied organisms that lived in shallow seas over 600 million years ago, about 50 million years preceding the Cambrian. ... At any rate, they shed little light on the question of which phyla were ancestral to other phyla, or if, indeed, animals have a common ancestry.”

Pearse, V., J. Pearse, M. Bushsbaum, and R. Buchsbaum “Chapter Thirty: Animal Relationships” in Living Invertebrates. Blackwell Scientific Publications, Palo Alto, CA (1987), 2nd edition, p. 764.

“The known phyla of living animals...number well over 30, each with a characteristic body plan. ...There are few convincing intermediate species that might serve as bridges between the phyla.”

Pearse, V., J. Pearse, M. Bushsbaum, and R. Buchsbaum “Chapter Thirty: Animal Relationships” in Living Invertebrates. Blackwell Scientific Publications, Palo Alto, CA (1987), 2nd edition, p. 753.

“A record of pre-Cambrian animal life, it appears, simply does not exist. Why this lamentable blank? Various theories have been proposed; none is too satisfactory. It has been suggested, for example, that all the Pre-Cambrian sediments were deposited on continental areas, and the absence of fossils in them is due to the fact that all the older animals were sea-dwellers. But that all these older sediments were continental is a theory which opposes, without proof, everything we know of deposition in later times. Again, it is suggested that the Pre-Cambrian seas were poor in calcium carbonate, necessary for the production of preservable skeletons; but this is not supported by geochemical evidence. Yet again, it is argued that even though conditions were amenable to the formation of fossilizable skeletal parts, the various phyla only began to use these possibilities at the dawn of the Cambrian. But it is, a priori, hard to believe that the varied types present in the early Cambrian would all have, so to speak, decided to put on armour simultaneously. And, once again, it has been argued that the whole evolution of multicellular animals took place with great rapidity in late Pre-Cambrian times, so that a relatively short gap in rock deposition would account for the absence of any record of their rise. Perhaps; but the known evolutionary rate in most groups from the Cambrian on is a relatively leisurely one, and it is hard to convince oneself that a sudden major burst of evolutionary advance would be so promptly followed by a marked ‘slowdown’. All in all, there is no satisfactory answer to the Pre-Cambrian riddle.”

Romer, A.S. in The Procession of Life. The World Publishing Co, Cleveland, OH (1968), p.19-20.

“The models we consider are of three sorts: those that extrapolate processes of speciation to account for higher taxa via divergence, those that invoke selection among species, and those that emphasize that many higher taxa originated as novel lineages in their own right, not only as a consequence of species-level processes. It is in this latter class of model that we believe the record favors. ... many of the large populations should have been preserved, yet we simply do not find them. Small populations are called for, then, but there are difficulties here also. The populations must remain small (and undetected) and evolve steadily and consistently toward the body plan that comprises the basis of a new phylum (or class). This is asking a lot. Deleterious mutations would tend to accumulate in small populations to form genetic loads that selection might not be able to handle. Stable intermediate adaptive modes cannot be invoked as a regular feature, since we are then again faced with the problem of just where their remains are. We might imagine vast arrays of such small populations fanning continually and incessantly into adaptive space. Vast arrays should have produced at least some fossil remains also. Perhaps an even greater difficulty is the requirement that these arrays of lineages change along a rather straight and true course — morphological side trips or detours of any frequency should lengthen the time of origin of higher taxa beyond what appears to be available. Why should an opportunistic, tinkering process set on such a course and hold it for so long successfully among so many lineages?”

Valentine, J., and Erwin, D. “Interpreting Great Developmental Experiments: The Fossil Record” in Development as an Evolutionary Process, Raff, Rudolf A. and Elizabeth C. Raff, ed. Alan R. Liss, Inc., New York, NY (1985), p.71.

“We conclude that the extrapolation of microevolutionary rates to explain the origin of new body plans is possible, but does not accord with the primary evidence.”

Valentine, J., and Erwin, D. “Interpreting Great Developmental Experiments: The Fossil Record” in Development as an Evolutionary Process, Raff, Rudolf A. and Elizabeth C. Raff, ed. Alan R. Liss, Inc., New York, NY (1985), p.95.

“It is certain that the multicellular animals, like the two other multicellular kingdoms, the Fungi and Plantae are the descendants of the unicellular (or acellular) eukaryote protists. But there the certainty ceases. Most of the animal phyla that are represented in the fossil record first appear, fully formed, in the Cambrian some 550 million years ago...The fossil record is therefore of no help with respect to the origin and early diversification of the various animal phyla.”

Barnes, R.S.K., P. Calow, P.J.W. Olive, and D.W. Golding in The Invertebrates: A New Synthesis. University Press, Cambridge, (1993).

“We must still address the phylogenetic origin of the molluscs themselves. The excellent fossil record of molluscs extends back some 500 million years and indicates that the origin of this phylum lies hidden in Precambrian history, and we may never know with much certainty what the first mollusc was like.”

Brusca, Richard C. & Gary J. Brusca in Invertebrates. Academic Press, New York, NY (1990), p. 764.

“The origin of insect flight, like the origins of wings and flight in vertebrates, is a wonderful mystery yet to be completely solved. The basic problem is one of explaining the intermediate stages ... The earliest known insect fossils include both winged and wingless types — but no intermediates or partly winged fossil forms have yet been found... .”

Brusca, Richard C. & Gary J. Brusca in Invertebrates. Academic Press, New York, NY (1990), p. 562.

“The fossil record of amphibians in the Lower Carboniferous is very incomplete and little is known of the specific interrelationships of the numerous lineages.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 188.

“The origin and relationships of salamanders and caecilian remain uncertain. The presence of pedicellate teeth in all three groups and the operculum-opercularis complex in frogs and salamanders suggest that the modern amphibian groups share a common ancestry from among the Paleozoic amphibians. However, no fossils are known that support this hypothesis, and all three groups may have evolved separately from distinct ancestral groups.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 189.

“The early amniotes [birds, reptiles, mammals] are sufficiently distinct from all Paleozoic amphibians that their specific ancestry has not been established.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 198.

“By the early Permian, pelycosaurs made up 70 per cent of the known amniote genera and had diversified into a number of distinct families. Unfortunately, remains from the Carboniferous, when these groups underwent initial differentiation, are still poorly known, and specific interrelationships of these families continue to be in dispute.”

Carroll, Robert in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 364.

“All birds that we know from the Cenozoic appear to share a common ancestry above the level of the toothed Hesperornithiformes and Ichthyornithiformes. The fossil record demonstrated that at least some of the modern orders had already differentiated by the end of the Mesozoic, but their remains are so incomplete that it is not possible to establish the common skeletal pattern from which they evolved or to establish their interrelationships (empahsis added).”

Carroll, Robert in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 364.

“Because of their great numbers and wide range of anatomical diversity, it is a monumental problem to establish phylogenetic relationships among the teleosts [ie, fish] ... No fossils are known of an immediate common ancestor that might have given rise to crossopterygians and Dipnoi...”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 113.

“Despite extensive study of exceptionally well-preserved fossils of sarcopterygian fish near the beginning of their radiation in the Devonian, considerable controvery remains regarding their relationships.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 153.

“Olson (1962, 1974) described fossils from the early Upper Permian that have some features in common with therapsids, but their remains are too fragmentary to provide information regarding the transition between the two groups. “

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 369.

“Unfortunately, the record of the immediate ancestors of mammals becomes less complete in the Upper Triassic. The trithelodonts provide only a tantalizing glimpse of small forms that may be derived from the chiniquodontids. The tritylodonts provide good evidence of the final stages in the evolution of the therapsids, but their highly specialized dentition indicates that they are not close to the ancestry of mammals.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 392.

Sobre os Captorhinomorphs...

“Each of these derivative groups is already well differentiated when it first appears in the fossil record, and the specific times of their derivation has not been established.”

Carroll, Robert “Evolution” in Vertebrate Paleontology and Evolution. W.H. Freeman and Co., New York, NY (1988), p. 202.

“Every time I write a paper on the origin of life, I determine I will never write another one, because there is too much speculation running after too few facts.”

Crick, Francis in Life Itself: Its Origin and Nature. Touchstone Book, publicado por Simon & Schuster, New York, NY (1981), p. 153.

“Unfortunately evidence of the crucial steps leading to the origin of insects have not yet been found in the fossil record. Wings have contributed more to the success of insects than any other anatomical structures, yet the historical origin of wings remains largely a mystery. The earliest insect fossils that have been discovered, from the Pennsylvanian Period, were already winged...Thus the body structures that developed into wings, the steps in the evolution, and the ecological circumstances that favored wings are debatable.”

Daly, H.V., J.T. Doyen, and P.R. Ehrlich. in Introduction to Insect Biology and Diversity. McGraw Hill, New York, NY (1978), p. 274.

“Some scientists say, just throw energy at it and it will happen spontaneously. That is a little bit like saying: put a stick of dynamite under the pile of bricks, and bang, you've got a house! Of course you won't have a house, you'll just have a mess. The difficulty in trying to explain the origin of life is in accounting for how the elaborate organisational structure of these complex molecules came into existence spontaneously from a random input of energy. How did these very specific complex molecules assemble themselves.”

Davies, Paul C.W. and Adams, Philip in More Big Questions. ABC Books, Sydney, (1998), p. 53-54, 47-48.

“It is easier to understand the stages by which the reptiles evolved temporal fenestrae and other distinguishing skeletal characters than to imagine the steps that led to the development of the ‘land egg.’ Paleontologists continue to speculate upon the way in which the enclosure of the embryo came about, however, because the matter is central to the broad question of reptilian origins. Study of the eggs laid by living reptiles has provided little insight into the evolution of the extraembryonic structures which gave protoreptiles their first advantage over other tetrapods. Rather than recapitulating the process of its evolution, the ‘land egg’ develops in a specialized manner derived, no doubt, by abbreviation and reordering of an earlier procedure. ... All the extraembryonic membranes in the ‘land egg’ of a modern reptile must complete their formation normally if the embryo is to sustain itself. The yolk sac is of crucial importance, because nutritive materials from the yolk mass can enter the body only by passing through the vessels in its surface. The allantois also cannot fail: it serves as the respiratory organ for the embryo, since blood coursing through it loses carbon dioxide and receives oxygen by diffusion through the adjacent chorion and porous shell. In addition, its central cavity stores nitrogenous wastes produced by the actively metabolizing, embryonic cells. Blood reentering the embryo from the allantoic vessels restores to the body water that has been resorbed from the excreted waste and also adds some that passes into the egg from the environmental air. The exterior of the embryo is kept wet by a liquid that accumulates within the amnion. Unlike pond water, to which it is often compared, the amniotic fluid does not act as an oxygen-bearing medium for the embryo. It is an adaptation for protecting the developing, animal against shock and for preventing it from resting against the membranes in the shell and sticking to them. Despite the difficulty of explaining how the embryo might have been served while the ‘land egg’ was evolving to its present state, Szarski has suggested a series of steps by which the reptilian structure may have arisen.”

Stahl, Barbara J. “The Rise and Fall of the Reptiles” in Vertebrate History: Problems in Evolution. Dover, New York, NY (1985), 2nd edition, p. 269-270.

“Paleontologists are quite certain of the relationship between the rhipidistians and the amphibians even though they have not discovered the animals intermediate between the finned and limbed forms. The remains of the oldest tetrapods in their collections leave no doubt about the derivation of the axial skeleton from fishes of the rhipidistian group. Since the fossil material provides no evidence of other aspects of the transformation from fish to tetrapod, paleontologists have had to speculate how legs and aerial breathing evolved and why a group of fishes produced forms that habituated themselves little by little to life on land.”

Stahl, Barbara J. in Vertebrate History: Problems in Evolution. Dover, New York, NY (1985), 2nd edition, p. 194-195.

“The lack of fossil specimens intermediate between anurans or urodeles and the older amphibians has forced paleontologists and students of the living animals to base their speculations about the evolution of the group upon evidence from the anatomy and embryology of modern species. This approach has presented difficulties that have so far proved insurmountable . The structure of the existing amphibians is so specialized that the more generalized condition from which it derived is almost completely obscured.”

Stahl, Barbara J. in Vertebrate History: Problems in Evolution. Dover, New York, NY (1985), 2nd edition, p. 240-241.

“If sufficient fossil material were available, paleontologists think that the turtles would be traceable...almost directly to the early cotylosaurs. Because turtles enter the record in a nearly modern state in the Triassic period, the supposition rests on inferences from the anatomy of their skull rather than on evidence of known transitional forms.”

Stahl, Barbara J. in Vertebrate History: Problems in Evolution. Dover, New York, NY (1985), 2nd edition, p. 284-285.

“...frogs and toads...have been found as fossils, but known extinct forms are essentially modern in structure and give no hint of the older amphibians from which they have descended.”

Stahl, Barbara J. in Vertebrate History: Problems in Evolution. Dover, New York, NY (1985), 2nd edition, p. 240.

“The great diversity of these opinions reflects their largely subjective nature. Individual viewpoints often reveal idealogical, philosophical, or religious biases more than they express objective appraisals, for the simple reason that not enough elements are available for objective analysis.”

de Duve, Christian “Chance or Necessity” in Blueprint for a Cell: The Nature and Origin of Life. Neil Patterson Publishers, Burlington, NC (1991), 1st edition, p. 212.

“Paleontologists just were not seeing the expected changes in their fossils as they pursued them up through the rock record. ... That individual kinds of fossils remain recognizably the same throughout the length of their occurrence in the fossil record had been known to paleontologists long before Darwin published his Origin. Darwin himself, ... prophesied that future generations of paleontologists would fill in these gaps by diligent search ... One hundred and twenty years of paleontological research later, it has become abundantly clear that the fossil record will not confirm this part of Darwin's predictions. Nor is the problem a miserly fossil record. The fossil record simply shows that this prediction is wrong.
The observation that species are amazingly conservative and static entities throughout long periods of time has all the qualities of the emperor's new clothes: everyone knew it but preferred to ignore it. Paleontologists, faced with a recalcitrant record obstinately refusing to yield Darwin's predicted pattern, simply looked the other way.”

Eldredge, N. and Tattersall, I. (1982), The Myths of Human Evolution, Columbia University Press, p. 45-46

“The gaps in the fossil record are real, however. The absence of a record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods; species seldom and genera never show evolution into new species or genera but replacement of one by another, and change is more or less abrupt.”

Wesson, R., Beyond Natural Selection, MIT Press, Cambridge, MA, 1991) p. 45.

Como que a teoria da evolução por seleção natural é “a melhor e mais resistente explicação para o fenômeno da vida tal como a conhecemos” se desde 1859 até hoje o registro fóssil continua dizendo um sonoro não para as especulações transformistas de Darwin?

A Folha de São Paulo não explicou, mas poderia explicar o verdadeiro status de robustez epistêmica da “melhor e mais resistente explicação” teórica se “ouvisse o outro lado” das evidências: no contexto de justificação teórica o livro “Darwin” é mais retórica ufanista. Com um agravante: desprovido das evidências que justifiquem o caráter heurístico proposto por Darwin – o de explicar a origem das espécies.

O registro fóssil corrobora as especulações transformistas de Darwin? As pedras clamam e dizem “Não”! O que é gritante é que os autores de livros didáticos de Biologia do ensino médio não abordam esta questão teórica fundamental, e os alunos tem sua cidadania violentada: acesso à informação científica objetiva e não distorcida. Alô MEC/SEMTEC/PNLEM, o nome disso é desonestidade acadêmica!

Marcelo Leite, está faltando mais Bacon na Folha: ir à natureza, fazer perguntas a ela e seguir as evidências aonde elas forem dar!