Recent Problems in Evolution - 2002

Table of Contents

Review of inbreeding discredits "species sorting" of punctuated equilibrium

Punctuated equilibrium claims that new species arise rapidly due to accumulated Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations that get expressed during "species sorting," when populations plummet due to natural disasters, climatic changes, etc. However, new data from wild populations and molecular and analytical tools for tracing patterns of relationship and inbreeding have determined that "inbreeding depression" (decreased fitness) occurs among diverse taxa. According to the recent review:

"This work reveals that levels of inbreeding depression vary across taxa, populations and environments, but are usually substantial enough to affect both individual and population performance. Data from bird and mammal populations suggest that inbreeding depression often significantly affects birth weight, survival, reproduction and resistance to disease, predation and environmental stress. Plant studies, based mostly on comparing populations that differ in size or levels of genetic variation, also reveal significant inbreeding effects on seed set, germination, survival and resistance to stress. Data from butterflies, birds and plants demonstrate that populations with reduced genetic diversity often experience reduced growth and increased extinction rates. Crosses between such populations often result in heterosis. Such a genetic rescue effect might reflect the masking of fixed Having a harmful of bad effect.deleterious Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. Thus, it might be necessary to retain gene flow among increasingly fragmented habitat patches to sustain populations that are sensitive to inbreeding."

Although the authors did not relate their study to the theory of punctuated equilibrium, it has obvious implications. Species sorting, as a mechanism of producing new species, has never been shown to be anything other than a theoretical concept. This and previous studies suggest that the only "sorting" consistently resulting from decreases in population numbers is extinction. Although this may "make room" for new species, it certainly cannot be claimed to be a creative force in evolution.

Lukas F. Keller and Donald M. Waller. 2002. Inbreeding effects in wild populations. Trends in Ecology & Evolution 17: 230-241.

Oceanic hydrothermal vents out as origin of life site

The most common abiogenesis theories claim that life arose at hydrothermal vents in the ocean. However, recent studies show that polymerization of the molecules necessary for cell membrane assembly cannot occur in salt water (1). Other studies show that the early oceans were at least twice as salty as they are now (2). Therefore, the oceans could not be the site at which the first life was assembled. Although crude membranes can undergo assembly in fresh water, there would be a very limited source of organic molecules present in those waters - certainly not enough to form anything on the verge of living.

  1. Monnard, P.-A, C. L. Apel, A. Kanavarioti and D. W. Deamer. 2002. Influence of ionic solutes on self-assembly and polymerization processes related to early forms of life: Implications for a prebiotic aqueous medium. Astrobiology 2: 213-219.
  2. Knauth, L.P. 2000. Life on Land in the Precambrian and the Marine vs. Non-Marine Setting of Early Evolution. First Astrobiology Science Conference, April 3-5, 2000, NASA Ames Research Center, 403 (Abstract 353).
    Knauth, L.P. 2002. Early Oceans: Cradles of Life or Death Traps? Astrobiology Science Conference 2002, April 7-11, NASA Ames Research Center. p. 9.

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Really quickly evolving dinos

A recent study has demonstrated that reptiles disappeared and the giant carnivorous dinosaurs replaced them within a period of  less than 10,000 years of the Triassic-Jurassic boundary and only 30,000 years after the last Triassic taxa, which were eliminated by a mass extinction event, probably due to an asteroid collision. The rate of evolution of these dinosaurs is almost beyond belief. Of course, it all fits into one or another of the current evolutionary theories. Maybe we should try to short-circuit a near-earth asteroid to repeat the experiment and see if evolution really works that fast!

P. E. Olsen, et al. 2002. Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary. Science 296: 1305-1307.

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Rapid "evolution" of the human brain

Studies as early as1975 showed that the sets of 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 found in the brains of chimpanzees and humans were virtually identical. The question naturally arose as to why humans and chimpanzees are so different. A new study provides at least a partial answer to the question. Researchers collected brain, liver, and blood samples from humans, chimps, macaques, and orangutans, isolated Ribonucleic acid: a chemical that directs the manufacture of proteins and sometimes codes for the genetic material within certain organisms.RNA from each sample and calculated the amount of Ribonucleic acid: a chemical that directs the manufacture of proteins and sometimes codes for the genetic material within certain organisms.RNA produced for 12,000 genes. Little difference was found among the species for the liver and blood samples. However, big differences were detected in gene expression between humans and chimpanzees, although gene expression between chimpanzees' and the other An order of mammals including man, apes, monkeys, etc., often characterized by large brains and flexible hands and feet.primates' brains was about the same. The results show that regulation of gene expression is unique in the human brain compared to all other An order of mammals including man, apes, monkeys, etc., often characterized by large brains and flexible hands and feet.primates.

Pennisi, E. 2002. Gene Activity Clocks Brain's Fast Evolution. Science 296: 233-235.
Enard, W, et al. 2002. Intra- and Interspecific Variation in An order of mammals including man, apes, monkeys, etc., often characterized by large brains and flexible hands and feet.Primate Gene Expression Patterns. Science 296: 340-343.

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Of mice and men - little genetic difference!

Previous genetic studies have shown that chimpanzee and humans Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA differs by only 1.5%. This was said to be powerful evidence of common descent. Scientists are now sequencing the murine (mouse) genome and have come upon some rather startling data regarding a comparison of the murine and human genomes. So far, only One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosome 16 has been fully Determining the order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequenced in both species. However, the results show that human and murine Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA differ from each other by only 2.5%. This is very surprising, since, according the evolutionary theory, the two species diverged 90 million years ago. The problem for the theory of evolution is that this small difference between mice and humans makes the difference between humans and chimpanzees look huge. Whereas it took 90 million years of evolution to produce 2.5% difference in Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA The order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequence, humans and chimpanzees diverge 1.5% in less than 10 million years. Why has evolution sped up so much during the evolution of An order of mammals including man, apes, monkeys, etc., often characterized by large brains and flexible hands and feet.primates? Maybe 1.5% is a really big difference?

Just 2.5% of Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA turns mice into men. New Scientist, May 30, 2002.
R. J. Mural et al. 2002.A Comparison of Whole-Genome Shotgun-Derived Mouse One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.Chromosome 16 and the Human Genome. Science 296: 1661.

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Of chimps and men - more genetic difference!

Previous genetic studies have shown that chimpanzee and humans Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA differs by about 1.5%. However, this difference was determined by examining the Two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds.base pair The order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequence Replacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one amino acid in a protein by another amino acid.substitutions within certain Determining the order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequenced Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes. Recently, the human genome was completely Determining the order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequenced and sequencing of the chimpanzee genome is well on its way. Preliminary results confirm previous results regarding Two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds.base pair Replacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one amino acid in a protein by another amino acid.substitutions (estimated at 1.4%). However, sequencing reveals that Chromosomal abnormalities in which a DNA sequences are inserted into genes, disrupting the normal structure and function of those genes.insertions and deletions result in another 3.4% difference between human and chimp Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA. Therefore, the overall difference between chimp and human Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA is nearly 5%, which represents an almost insurmountable amount of rapid evolution.

Britten, R.J. 2002. Divergence between samples of chimpanzee and human Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA The order of nucleotides in a DNA or RNA molecule, or the order of amino acids in a protein molecule.sequences is 5%, counting indels. Proc. Natl. Acad. Sci. USA 99: 13633-13635.

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Last updated January 2, 2003

 

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