Recent Problems in Evolution - 1998

Table of Contents

Interdependent genes demonstrate limits to evolution

Irreducible complexity is something many evolutionists say does not exist in nature. The "reductionists" believe that there are no limits to an organism's variability and its ability to evolve. However, a new report demonstrates that when three characters are affected by a gene, the gene cannot change, but is constrained by the dependency of the other characteristics. Therefore, evolution is now falsifiable if organisms can be found that have broken this principle. In addition, this study demonstrates that the ability of organisms to evolve is limited. (Gunter Wagner. 1998. EVOLUTION: Complexity Matters Science 279:1158) and David Waxman, Joel R. Peck. 1998. Pleiotropy and the Preservation of Perfection Science 279: 1210.)

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Extreme fine tuning and design in enzymes

Molecular Biology has greatly added to our ability to understand the how the cell functions at the molecular level. A recent report used genetic selection and "directed molecular evolution" to redesign a bacterial enzyme (chorismate mutase) from its natural dimeric (2 subunit) structure to a monomeric complexly folded enzyme with nearly identical activity to the natural enzyme. The surprising thing to the researchers was that of all the The order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequencesthey designed, only 0.05% of those redesigned enzymes expressed appreciable enzymatic activity. What does this tell us? Since evolution is based upon random A permanent structural alteration in DNA, consisting of either a substitution, insertion or deletion of nucleotide bases.mutation, the probability of randomly designing this enzyme is extremely unlikely. It is probable that other enzymes will be designed to similar levels of precision. (MacBeath, G., P. Kast, and D. Hilvert. 1998. Redesigning enzyme topology by directed evolution. Science 279: 1958.)

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Lack of eukaryotic cytoskeleton Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins or precursors in bacteria

Evolutionary theory states that eukaryotes evolved from, and derived all of their metabolic and structural genes from related Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins of eubacteria ("normal" bacteria) and/or archaebacteria (ancient bacterial group). However, no microbial Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins hjave been found that are homologous to the eukaryotic cytoskeleton-the framework of An organic compound made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.protein filaments that give a cell its shape and ability to move (Doolittle, R. F. 1995. Phil. Trans. R. Soc. Lond. B 349: 235-240). These Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins consist of tubulin and actin and many other cytoskeletal Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins. According to the author, " The absence of The order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequencesclosely related to the slowly changing Organic compounds made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.proteins of the eukaryotic cytoskeleton remains unsettling, and the origin of the cytoskeleton cannot easily be accounted for by simple chimaeric mergers of a eubacterium and an archaebacterium."

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Rapid repopulation of life forms following Permium extinction event

The earth's largest extinction (at the end of the Permium period) now appears to have taken place over a period as short as 10,000 years and not millions, as previously thought. During this time nearly 90% of all species became extinct. Even so, life reappeared rapidly after this catastrophic event. The new study examined the ratio of carbon-13 to carbon-14 in the rocks, the layers of which were dated by the uranium-lead method. A rapid shift in carbon-13 to carbon-14 ratio over a short period of time indicated that much of the carbon originally associated with living organisms became part of the inorganic carbon pool for a short period of time associated with the end of the Permium period. A rapid restoration of the carbon-13 to carbon-14 ratio indicates that living organisms rapidly repopulated the earth after this catastrophic extinction event. (Kerr, R. 1998. Biggest extinction looks catastrophic. Science 280: 1007 and S. A. Bowring, * D. H. Erwin, Y. G. Jin, M. W. Martin, K. Davidek, W. Wang. 1998. U/Pb Zircon Geochronology and Tempo of the End-Permian Mass Extinction. Science 280: 1039.)

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Large human brains pose energy problem for evolutionists

Modern humans have brain sizes larger than any other placental mammal relative to body size. The human brain uses a tremendous amount of energy - up to 60% of total energy consumed in newborns. A recent study suggests that the large increase in brain size was balanced by a similar reduction in the size of the gastrointestinal tract. However, other mammals, such as pigs, with small intestines don't have brains as large as ours. In addition, the theory doesn't hold for birds or bats. The presence of large brains in humans presents a problem to evolutionists, since it presents a large energy drain upon the species, especially before the advent of agriculture and reliable food supplies. (Ann Gibbons. 1998. Solving the brain's energy crisis. Science 280: 1345.)

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No transitional brain sizes between Homo and Australopithecines

One of the problems in the theories of human evolution has been the huge difference between the brain capacity of our genus (Homo) and the genus of our supposed ancestors (Australopithecus). A recent discovery of a large Australopithecine skull was anticipated to lessen the gap between the two genera. However, a recent study, using computerized tomography technology has determined that the new skull (Stw 505) has a brain capacity no larger than the size of the largest published value. However, in doing the measurements and checking their validity, the group determined that nearly all of the brain capacities of Australopithecine skulls is inflated. In reality, many Australopithecine skulls have brain capacities no larger than those of chimpanzees. Thus, there exists a huge difference between the brain capacity of the oldest Homo specimen and the largest Australopithecine skull. (Dean Falk. 1998. Hominid brain evolution: looks can be deceiving. Science 280: 1714 and Conroy, G.C., G.W. Weber, H. Seidler, P.V. Tobias, A. Kane, and B. Brunsden. 1998. Endocranial capacity in an early hominid cranium from Sterkfontein, South Africa. Science 280: 1730-1731.)

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Transition between dinosaur and birds appears 20 million years after first bird

Archaeopteryx has been described as a link between birds and dinosaurs, although it is remarkably similar to modern birds. Attempts to find more primitive intermediates have been unsuccessful - until now - so say a group of paleontologists (see the July, 1998 issue of National Geographic). The group has found two turkey-sized dinosaurs that have both downy and modern flight feathers on their arms and tail. Their skeletal structure is similar to theropod dinosaurs (short arms - too short to be useful in flight, serrated teeth, theropod-like pelvis, etc.). The conclusions are obvious. Right? However, other researchers dispute the claims. They point to shortened tail and fused sternum, arguing that they are more advanced than Archaeopteryx. These researchers believe that the intermediates are actually flightless birds. Oh, did I mention that the new fossils are dated to have appeared at least 20 million years after the appearance of the first Archaeopteryx? Those little details do get in the way of evolutionary theory, don't they! For more information on some of the controversies, see Demise of the "Birds are Dinosaurs" Theory, located on this site. (Ann Gibbons. 1998. Dinosaur fossils, in fine feather, show link to birds. Science 280: 2051.)

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Sudden appearance of mammals

At the recent meeting of the International Symposium on the Origin of Mammalian Orders, scientists presented evidence testifying of the rapid appearance of mammals in the fossil record during the beginning of the Tertiary period. During the first 16 million years of the Tertiary period, 18 orders of mammals appeared. Many scientist had claimed that gaps in the fossil record could account for the apparent sudden appearance of mammals. However, Dr. David Archibald (San Diego State University), looked at the numbers of fossil site spanning the period of 5 million years before and after the Cretaceous-Tertiary boundary. Dr. Archibald found that sampling was equal for periods before and after the boundary, although only 11 genera were found in the 5 million years before the beginning of the Tertiary compared to 139 genera in the 5 million years following. As he stated, "Something happened to cause this explosion of speciation." The results of the fossil record are not confirmed by molecular clocks reported earlier this year. Dr. John Allroy, a paleontologist at the National Museum of Natural History (Washington D.C.) stated, "If molecular analysts can't find evidence of this explosion in speciation, then they don't know anything about the evolutionary process."

Dennis Normile. 1998. MAMMALIAN EVOLUTION MEETING: New views of the origins of mammals. Science 281: 775.

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Whales lose ancestors?

The discovery of two 50-million-year-old whales from the family Pakicetidae suggest that the previously thought link between the mesonychians and whales seems unlikely, according to Dr. Hans Thewissen (Northeastern Ohio Universities College of Medicine). The fact that these fossils have more primitive teeth than the mesonychians from which they were supposed to have evolved led Dr. Thewissen to conclude that there was "considerable doubt" that cretaceans (whales) are closely related to mesonychians. Paleontologists now are attempting to link whales with the hippopotamus (artiodactyls). However, Dr. Maureen O'Leary (State University of New York) stated, "it's difficult to connect hippos with whales in the fossil record."

Dennis Normile. 1998. MAMMALIAN EVOLUTION MEETING: New views of the origins of mammals. Science 281: 775.

More information can be found at the Scientific American website:

CETACEAN CREATION New fossils leave researchers wondering where whales come from

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No link between ecology and evolution?

Evolutionary theory predicts that ecology should profoundly effect evolution within groups of related species. A recent study examined the ecological dominance of two bryozoan clades (Cyclostomata and Cheilostomata) and how that related to evolutionary success over the last 140 million years. The results indicated that "evolutionary success and ecological dominance can be decoupled and profoundly different, even over tens of millions of years." Previous studies had shown that the Permium and Triassic mass extinctions had removed other byrozoan clades that had much higher ecological diversities than Cyclostomata and Cheilostomata (Taylor, P.D., and G.P. Larwood, in Extinction and Survival in the Fossil Record, G.P. Larwood, Ed. (Clarendon, Oxford, 1988), pp. 99-119.

McKinney, F.K., S. Lidgard, J.J. Sepkoski, Jr., and P.D. Taylor. August 7, 1998. Decoupled temporal patterns of evolution and ecology in two post Paleozoic Clades. Science 281: 807-809.

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The "very long leap"

"It's a very long leap from [mineral] surface chemistry to a living cell." (Norman Pace, evolutionary biologist, University of California, Berkeley, from Vogel, G. 1998. A sulfurous start for An organic compound made of amino acids arranged in a linear chain, joined together by peptide bonds between the carboxyl and amino groups of the adjacent amino acid residues.protein synthesis? Science 281: 627-628.)

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Ancient animals regain their youth

Three weeks ago in the pages of Science, paleontologists claimed to have pushed back the origins of multicellular life by 400 million years to a startling 1.1 billion years ago, based on ancient fossilized tracks found in central India (Adolf Seilacher, Pradip K. Bose, and Friedrich Pfl�ger. 1998. Triploblastic Animals More Than 1 Billion Years Ago: Trace Fossil Evidence from India. Science 282: 80-83). But a paper published about the same time in the Journal of the Geological Society of India indicates that these same rocks date to about 540 million years ago, roughly the time of the Cambrian explosion. (Kerr, R.A. 1998. PALEONTOLOGY: Fossils Challenge Age of Billion-Year-Old Animals. Science 282: 601.)

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Recent human origins from One of the two sex chromosomes that determines maleness in mammals, carried and passed down from males to males.Y chromosome study

A worldwide survey of 67 men from five continents representing 19 distinct populations showed that most males have both DAZ variants of a One of the two sex chromosomes that determines maleness in mammals, carried and passed down from males to males.Y chromosomegene. The authors concluded that the human race originated 55,000-200, 000 years ago. (Agulnik AI, Zharkikh A, Boettger-Tong H, Bourgeron T, McElreavey K, Bishop CE. 1998. Evolution of the DAZ gene family suggests that Y-linked DAZ plays little, or a limited, role in spermatogenesis but underlines a recent African origin for human populations. Hum. Mol. Genet. 7: 1371-1377.)

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Species sorting = species extinction

Punctuated equilibrium is dependent upon the accumulation of Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations within a large population that gets "sorted" into an isolated small population that interbreeds the new Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. A new study destroys this idea. Instead of becoming a new species, populations that suffer drastic reductions in numbers are characterized by decreased genetic variability and an accumulation of detrimental genes. This happens because normally Possessing two different forms of a particular gene, one inherited from each parent.heterozygous (containing 2 different Variant forms of a gene at a particular locus, or location, on a chromosome.alleles of each gene) individuals become Possessing two identical forms of a particular gene, one inherited from each parent.homozygous, due to inbreeding. As a result, detrimental, non-expressed, A genetic disorder that appears only in patients who have received two copies of a mutant gene, one from each parent.recessive genes become Possessing two identical forms of a particular gene, one inherited from each parent.homozygous and, therefore, are expressed, resulting in a less fit population. The study examined the effect of a 35-year population decline of greater prairie chickens on their fitness and fertility. The results showed that population decline and isolation of the prairie chicken led to decreased genetic variability, reduced egg viability (from near 100% to less than 80%), and a decline of fertility rates (from 93% to 74%). Only after human intervention (which brought in genetically diverse individuals from other areas) did the population begin to recover. This study calls into serious question the punctuated equilibrium concept of species sorting. (Soul�, M.E. and L.S. Mills. 1998. No need to isolate genetics. Science 282: 1658 and Wetermeirer, R.L., J.D. Brawn, S.A. Simpson, T.L. Esker, R.W. Jansen, J.W. Walk, E.L. Kershner, J.L. Bouzat, and K.N. Paige. 1998. Tracking the long-term decline and recovery of an isolated population. Science 282: 1695.)

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Last updated January 2, 1999

 

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