[Hat Tip: RichardDawkins.net]
A number of studies have found that Ashkenazi Jews in the United States have a high average IQ. It has been proposed by Cochran, Hardy and Harpending (2006) that this can be explained by the occupational constraints imposed on the Ashkenazi for many centuries in Europe, when they were largely confined to money-lending. They propose that this selected for the high verbal and mathematical intelligence that has several times been found in American Ashkenazim. The current study investigates how far this theory holds for European and Oriental Jews in Israel. A review of studies shows that Oriental Jews in Israel have an average IQ 14 points lower than that of European (largely Ashkenazi) Jews. It is proposed that this difference can be explained in terms of the Cochran, Hardy and Harpending theory because Oriental Jews were permitted to engage in a much wider range of occupations and hence did not come under the selection pressure to develop the high verbal and mathematical intelligence that was present for Ashkenazim.It seems pretty silly to me but it still got published in the scientific literature. Jared Diamond has also favored explanations like this for the higher IQ of this population.
David, H. and Lynn, R. (2007) Intelligence differences between European and oriental Jews in Israel. J Biosoc Sci. 39:465-73.
In 1926, The (Theodor) Svedberg (1884-1971) won the Nobel Prize in Chemistry for his work on the behavior of molecules in solution. Svedberg is famous in the biological sciences for his development of the high speed ultracentrifuge and the technology for photographing the behavior of molecules during centrifugation. Many biochemical molecules are named for their sedimentation coefficients (e.g., 40S ribosomal subunits) in Svedberg units [The Compositon of Ribosomes]. The Svedberg equation used to be standard material in biochemistry courses but lately it has disappeared to make room for other techniques.Your Majesty, Your Royal Highnesses, Ladies and Gentlemen.
The Academy of Sciences has decided to award the Nobel Prize in Chemistry for 1926 to The Svedberg, Professor of Physical Chemistry at the University of Uppsala, for his work on disperse systems.
Almost a hundred years ago, or more accurately in 1827, the English botanist Robert Brown discovered with the aid of an ordinary microscope that small parts of plants, e.g. pollen seeds, which are slurried in a liquid, are in a state of continuous, though fairly slow movement in different directions. A more detailed study of this phenomenon during the last few decades has led to extremely interesting results. By means of the ultramicroscope it has been possible to observe a similar, only much livelier movement with very much smaller particles of a colloidal nature. As we have recently heard, Einstein evolved a theory for this so-called Brownian movement which was then developed to a high degree by the now late Smoluchowski. According to these scientists, the movement arises through the impacts of the molecules of the liquid against the particles slurried in the liquid, provided that the latter are sufficiently small. Taking a crude analogy: if a fly or a gnat flies against an elephant, the elephant will not noticeably alter its position, but this can occur if the fly or gnat collides only with a bee.The theory in question has been confirmed convincingly by experimental investigations of several colloid scientists among whom especially two of today's prize-winners, Perrin and Svedberg, have occupied and still occupy a leading position. Should it now be true that the movement of particles suspended in a liquid, which we can actually observe with the aid of our extremely highly magnifying instruments, can be explained only as a result of the movement of molecules beyond the limits of direct human vision, then this provides visual evidence for the real existence of molecules and consequently also for that of atoms, evidence which is all the more remarkable as not so long ago an influential school of scientists declared these particles of matter to be unreal fictions representing an obsolete viewpoint of science.
It is known that the opposition conducted by the colloid scientists so successfully against this so-called energetic view has been continued by others who have gone much farther in that according to this view not only what we call matter, but also electricity occurs solely as particles of a definite size - the so-called electrons - and even that energy at all is regarded as bound to larger or smaller multiples of a smallest unit, the so-called elementary quantum.
If one has once become convinced of the existence of atoms and molecules, the question as to their real size is naturally - this hardly needs stressing - a question of the very greatest interest. Whereas it was formerly possible to calculate this size only roughly from the properties of gases and in connection with the theory applying to them, the position was now, as happens so often in the history of science, that almost simultaneously several new and considerably more precise methods for determining the natural constant in question appeared. Among these methods those based on colloid-chemical phenomena occupy a special position through their vividness and persuasive power, even though they may be for the time being slightly superseded by other methods in regard to accuracy. Also in this field Svedberg and the school of eminent scientists trained by him, Swedes as well as nationals from more or less distant countries, have achieved extremely valuable results. This has been done in several ways, among others, by determining the speed at which colloidal particles migrate by themselves, or diffuse in a liquid, or by measuring the distribution of such particles in a column of liquid, the latter according to a method proposed originally by Perrin.
In accordance with the theory for the movement of gas and liquid molecules which, as just indicated, has also been applied to colloidal particles, it is assumed that the mean value of the momentum of molecules or particles has a definite magnitude at each temperature, but that the speeds of the individual particles can vary within wide limits. If we now consider a very small volume fraction, the result is that, as Smoluchowski has calculated in detail, the number of particles present simultaneously within this volume can change from one moment to another. Svedberg and his collaborators have been able to confirm this extremely interesting conclusion that a "few-molecular" system having definite limits within a large volume of a material with a definite mean temperature may contain a varying number of particles, partly by counting the colloidal particles, partly in the case of solutions of radioactive substances by counting the number of so-called scintillations, i.e. light flashes, which radioactive particles produce when they impinge upon a screen coated with zinc sulphide.
With the last investigation, however, we have gone beyond the field of actual colloid chemistry, although the solution of a radioactive substance, e.g. polonium chloride, can naturally be called a disperse system, though more accurately it is molecular-disperse because the substance dissolved in the solvent occurs here as molecules, not as molecular aggregates, as is the case in a colloidal solution.During the last few years Svedberg has completed an extremely ingenious invention, the so-called ultracentrifuge, which enables highly interesting investigations to be made also on such molecular-disperse systems. We know that when a slurry, an emulsion, is put into a rapidly rotating motion, its heavier constituents are thrown outwards in the direction of the periphery of the motion. This happens in the most used of all centrifuges, the milk separator, where the skimmed milk is pressed outwards whilst the lighter fat particles, the cream, accumulate inwards and can therefore be separated. Similarly in a solution, when centrifuging is sufficiently rapid, the molecules of the dissolved substance must accumulate outwards if they are considerably heavier than the molecules of the solvent. After overcoming exceptional experimental difficulties Svedberg succeeded in demonstrating this with the aid of an apparatus which allows the enormous speed of rotation of 40,000 revolutions per minute, and in which through a highly refined arrangement the progressive distribution of the particles within the extremely rapidly whirling solution can be observed and recorded photographically. The molecular weight of the dissolved material can be calculated from this distribution. This has already been done for certain proteins essential for organic life and for other substances allied to them. For example, the molecular weight of the red colouring agent of the blood, haemoglobin, has been determined as approximately 67,000 which assumes that there are in the region of 10,000 atoms in such a molecule.
In view of the fact that this year not less than three Nobel Prizes have been awarded for work in the field of colloid research, some people may ask whether this field really has a corresponding importance "for mankind".
By way of answer the following few remarks may be made.
Inorganic chemistry has revealed more and more cases where only a colloid-chemical approach was able to clarify the observed phenomena.
For physical chemistry colloids form a rich and rewarding field of research.
In organic chemistry we meet the perhaps most important colloids, the proteins and the polymeric carbohydrates, which cannot be studied without the aid of colloid research.
As all living matter is built up largely from organic colloids, the importance of colloid research for physiology and the medical sciences is obvious.
Finally, colloids play an important part in the various branches of chemical industry, such as in dyeing and tanning, in the cellulose, nitrocellulose, celluloid and textile industry, in rubber manufacture, in the pottery and cement industry, in the photographic industry, etc.
Professor Svedberg. With a feeling of sincere pleasure and justified pride the Academy of Sciences again sees itself able to recruit from the ranks of its own members the corps d'élite of researchers which has been set up by Alfred Nobel's legacy.
You have been able to accept on a previous occasion the assurance of the Academy on this together with its sincere congratulations.
In this festive hour we would now only add to this the hope that it may be made possible for you to carry out in your own country the important investigations which have already borne such fine fruit to the honour of Swedish research and which appear to be not less full of promise for the future.
[Photo Credit: Physical Chemistry: Uppsala University]
The ribosome is an important part of the translation machinery. (The others are mRNA, aminoacyl-tRNAs, and translation factors). The translation machine makes polypeptide chains according to the information encoded in the mRNA molecule
Over at Eye on DNA Hsien-Hsien Lei has given over her blog over to Jon Entine to promote his new book Abraham's Children [Books About DNA: Abraham’s Children by Jon Entine]. The book includes a chapter explaining the possible link between so-called Jewish diseases — certain neurological and LSD disorders, as well as DNA repair problems — and the high measured IQ of Ashkenazi (Eastern European origin) Jewry. Although this theory (most recently advanced by Gregory Cochran and Henry Harpending—two non-Jews—is best classified as informed speculation (as I acknowledge in the book) at the moment, it argues persuasively, I believe, that Ashkenazi Jews are a rather distinct population group in which positive selection pressures, balanced against the killer consequences of neurological disease mutations, have led to higher IQs. The “it’s environment and culture” argument are far less persuasive. This is only one chapter in the book–most of AC is a look at our shared Israelite ancestry and history–but it is the most provocative chapter. Wonder where others come down on this issue? Interestingly, “liberal” Jews (of which I’m one) are the one’s most uncomfortable about discussing or (even if they believe it) acknowledging this point.Leaving aside the truth of the premise, it seems very unlikely that there was selection for higher IQ. We're dealing with a polygenic trait (intelligence) in a population of about 100,000 (average) over a maximum of 70 generations and possibly less than 25 generations. It's very unlikely that the adaptive benefit of a 10% increase in IQ would have an effect in that time frame.
[Figure Credit: The image is Figure 2 in Behar et al. (2006)]
Behar, D.M. et al. (2006) The Matrilineal Ancestry of Ashkenazi Jewry: Portrait of a Recent Founder Event. Am. J. Hum. Genet. 78:487-497. [PubMed]
Feder, J., Ovadia, O., Glaser, B. and Mishmar, D. (2007) Ashkenazi Jewish mtDNA haplogroup distribution varies among distinct subpopulations: lessons of population substructure in a closed group. European Journal of Human Genetics 15:498–500. [PubMed]
Jerry Fodor publishes a critique of adaptationism in London Review of Books. The title is Why Pigs Don’t Have Wings and it's an excellent read. I wish I could write like this ... In fact, an appreciable number of perfectly reasonable biologists are coming to think that the theory of natural selection can no longer be taken for granted. This is, so far, mostly straws in the wind; but it’s not out of the question that a scientific revolution – no less than a major revision of evolutionary theory – is in the offing. Unlike the story about our minds being anachronistic adaptations, this new twist doesn’t seem to have been widely noticed outside professional circles. The ironic upshot is that at a time when the theory of natural selection has become an article of pop culture, it is faced with what may be the most serious challenge it has had so far. Darwinists have been known to say that adaptationism is the best idea that anybody has ever had. It would be a good joke if the best idea that anybody has ever had turned out not to be true. A lot of the history of science consists of the world playing that sort of joke on our most cherished theories.UPDATE: Read Jason Rosenhouse's take on the Foder essay [Fodor on Natural Selection]. Jason makes some good points but I think he misses the main idea; namely that many scientists (and philosophers) have an inordinate confidence in natural selection as the explanation for almost everything in biology that's important (to them).
[Hat Tip: Andrew Brown at Helmintholog: Adaptationism contested. Andrew is the author of "The Darwin Wars."]
[Photo Credit: Uncyclopedia.]
The 19th version of Mendel's Garden has just been posted on Discovering Biology in a Digital World [Mendel’s Garden: Halloween Edition]. I don't think Sandra Porter likes October very much but fortunately that didn't prevent her from posting an enlightened selection of blogs from the past month.
I'm a fan of Al Gore and I would have voted for him if I'd have been an American citizen in 2000. I'd vote for him today if I could. I think he's done a fabulous job of bringing the issue of global warming to the attention of the public. (I also like his latest book The Assault on Reason).
Many of the classic experiments are no longer taught to undergraduates. It's the nature of the beast, I suppose. Those experiments became classics because they showed us something we didn't know previously. That "something" was so important that it now seems obvious. We don't need to teach it.
Evolution: The Triumph of an Idea is a wonderful book by Carl Zimmer. The cover shows a bunch of different eyes ans it's meant to convey the idea that all these eyes have evolved from a common ancestor with primitive eyes. 
Hsp90 is a molecular chaperone that plays a role in the folding and assembly of other proteins. Current ideas suggest that it binds to substrate proteins at a "client" site and this either encourages folding into the proper conformation or prevents aggregation. The binding and release of polypeptides is accompanied by hydrolysis of ATP to ADP + Pi. 
The complete protein is a dimer of two identical subunits. Each monomer has three distinct domains; an N-terminal domain (N); a middle domain (M); and a C-terminal domain (C). The ATP hydrolysis site sits at the interface between the N and M domains. The C domains interact to form the dimer. The presumed site of binding for misfolded proteins ("client" site") is in the V-shaped pocket formed when the C domains come together.
Each of the structures seems to identify a protein in one of the conformations adopted in vivo. The most likely explanation is that the wings of the protein open and close to capture and release the substrate protein. This conformational change is induced by binding and hydrolysis of ATP.
Dollins, E.D., Warren, J.J., Immormino, R.M. and Gewirth, D.T. (2007) Structures of GRP94-Nucleotide Complexes Reveal Mechanistic Differences between the hsp90 Chaperones. Molec. Cell 28:41-56.
The editorial page of today's Toronto Star contains a column by Kathy English, who is identified as "Public Editor." The point of the article is to respond to people who criticized the paper's editorials against the Mixed Member Proportional voting system [Sparking needed debate on MMP].The heart of democratic politics is public debate of public concerns.No disagreement there. It is, indeed, the responsibility of The Toronto Star to provide accurate, unbiased information. Did it succeed in the case of the referendum issue?
During election campaigns, it is the media's role and responsibility to encourage this debate and to provide accurate, unbiased information about politicians, parties, policies and the electoral process so that citizens can cast informed votes.
Not surprisingly, our election coverage was not without its critics. One group in particular was highly critical of the Star – the supporters of electoral reform, specifically, the system known as "mixed-member proportional" that was soundly rejected in this week's referendum.Yes, there was criticism and I'm one of those who was highly critical [Toronto Star Trashes MMP, Again, The Toronto Star Endorses First-Pass-the-Post].
Dissatisfaction with our coverage of MMP began on the second day of the campaign when my office and our Letters page were blitzed by MMP supporters who took exception to the word "appointed" in a news story that explained how under MMP, 39 members of the Legislature would be selected from party lists.It's not just that the work "appoint" is loaded; it's factually incorrect. The list members are elected by democratic vote. It may not be the same kind of election as we're used to but that's because Canada is one of the few Western industrialized nations that retain the old first-past-the-post system.
I discussed this with National Editor Alan Christie, who directed our election news coverage and has worked on more than a dozen elections at every level of government in his 30 years at the Star. We realized that the word had become something of a political football in this highly polarized campaign. In the interests of our news coverage not being seen as biased for either side of this crucial debate, Christie then advised reporters that referendum articles should avoid stating that list members would be appointed. We told MMP supporters this, adding that columnists and editorials were entitled to their own interpretation of whether this word was apt.
Although the new system promises to deliver a legislature that mirrors the voters' intent, Tory notes it would also create two classes of members of the Legislature. Some would have a direct mandate from the voters; others could simply be appointed by party bosses.After only a few minutes of research it became clear that this statement was misleading to the point of being factually incorrect. The experience in other countries tells us that the list members will almost certainly be candidates who have been nominated in various ridings across the province. They will definitely not be appointed by party bosses and any statement to that effect reveals a profound ignorance of how the system works. The order of candidates on the list will be decided by the party but that's something different. Besides, all parties are committed to an open and democratic process for making up the list so even that part of the selection procedure will be open and transparent, and possibly democratic in the sense of requiring a vote by party members.
Meanwhile, the Star's editorial board, under the direction of Editorial Page Editor Bob Hepburn, was researching and debating electoral reform in order to decide and declare the Star's position on this important issue that could have radically changed the way we elect our politicians in Ontario.Some research! Did the editors really do a lot of "research" to conclude that the countries with proportional voting systems were all constantly chaotic? I'm sure that conclusion would come as a major surprise to most Europeans. I lived in Switzerland for four years and I didn't notice that the state was in constant chaos. I also missed the fact that the surrounding states (France, Germany, Italy, Austria) were in constant chaos. Isn't that strange?
On Sept. 30, the Star's lead editorial spoke out strongly against electoral reform. The board concluded that MMP could lead to constant electoral chaos and that our current system, though not perfect, is preferable.
That editorial also said that electoral reform would create two classes of MPPs – some with a direct mandate from voters and some who could be appointed. That raised the ire of the pro-MMP side. A press release issued by Vote For MMP accused the Star of "fear-mongering and inaccurate journalism." Some contacted my office demanding that the Star retract its editorial.The charge is accurate. The newspaper was presented with an opportunity to clarify it's position in a second editorial. It did publish a second editorial but it was no better than the first one. The inaccuracies and the fearmongering continued. As I pointed out in my second posting, "When people spread misinformation and fear for the first time you can put it down to ignorance. When they do it a second time there's something more serious going on."
Many did not seem to understand the difference between news coverage and editorial opinion. Editorials, which do not influence news coverage, represent a newspaper's institutional position on matters that affect its community.Don't be condescending, Kathy. We're all adults here and we know the difference between an editorial and a news item. The problem is not that we object to the editors publishing their opinion, it's that we object to the "facts" that they published. "Facts" upon which they based their opinion.
Effective editorials should provide leadership on divisive, important issues, as this one did. It was a studied, well-argued, sound assessment of much-debated – and disputed – facts. It was not inaccurate, nor do I believe it created fear about electoral reform.
Countries that have gone this route, including Israel, Italy, Germany and Belgium, have become notorious for chaotic, horse-trading minority governments and legislative gridlock.In what universe does this become a "fact"? And even if there was some truth to the statement why didn't they mention all the other states with PR where it wasn't true? Even better,why didn't they tell us about the states with MMP systems? Under no possible circumstances can you claim that this is a well-argued assessment of facts.
Eugene Koonin runs a large laboratory at the National Center for Biothechnology Information (NCBI) in Bethesda, MD. (USA) [Evolutionary Genomics ResearchGroup]. His group tends to focus on new ways of analyzing sequences databases and on interesting findings from database mining expeditions. In Biology Direct, we seek to live by the realities of the 21st century while addressing the issue of information overflow in a constructive fashion and offering a remedy for the ills of anonymous peer review. The journal will publish "essentially anything", even papers that receive three unanimously negative reviews, the only conditions being that three Editorial Board members agree to review (or solicit a review for) the manuscript and that the work qualifies as scientific (not pseudoscientific as is the case for intelligent design or creationism) – and, of course, that the author wants his/her paper published alongside the reviews it receives. Everything in Biology Direct will be completely in the open: the author will invite the referees without any mediation by the Editors or Publisher, and the reviews will be signed and published together with the article. The idea is that any manuscript, even a seriously flawed one, that is interesting enough for three respected scientists to invest their time in reading and reviewing will do more good than harm if published – along with candid reviews written by those scientists. Under the Biology Direct rules, an author is free to solicit as many members of the Editorial Board as s/he has patience for. The philosophy behind this approach is that what really matters is not how many scientists are uninterested in a paper (or even assess it negatively, which could be the underlying reason for declining to review) but that there are some qualified members of the scientific community who do find it worthy of attention. A manuscript will be, effectively, rejected only after the author gives up on finding three reviewers or exhausts the entire Editorial Board. We believe this is fair under the rationale that work that fails, after a reasonable effort from the author, to attract three reviewers is probably of no substantial interest, even if technically solid.The paper that concerns me here is Koonin (2007) The Biological Big Bang model for the major transitions in evolution. In all cases, the "problems" that Koonin addresses seem to be the rapid and unexplained appearance of novel characteristics, especially those that count as major transitions in evolution. Examples are the origin of cells and the Cambrian explosion.
I propose that most or all major evolutionary transitions that show the "explosive" pattern of emergence of new types of biological entities correspond to a boundary between two qualitatively distinct evolutionary phases. The first, inflationary phase is characterized by extremely rapid evolution driven by various processes of genetic information exchange, such as horizontal gene transfer, recombination, fusion, fission, and spread of mobile elements. These processes give rise to a vast diversity of forms from which the main classes of entities at the new level of complexity emerge independently, through a sampling process. In the second phase, evolution dramatically slows down, the respective process of genetic information exchange tapers off, and multiple lineages of the new type of entities emerge, each of them evolving in a tree-like fashion from that point on.The BBB model is clearly not gradualistic. Koonin attempts to ally himself with other advocates of episodic change such as Niles Eldredge and Stephen J. Gould. (Where necessary, I have converted Koonin's number references to ones in which the author and date is displayed.)
However, the evolution of life is, obviously, a non-uniform process as described, e.g., in Simpson's classic book [3,4], and captured, more formally, in the punctuated equilibrium concept of Gould and Eldredge [Eldredge and Gould, 1997; Gould and Eldredge, 1993]. Lengthy intervals of gradualist modification are punctuated by brief bursts of innovation that are often called transitions, to emphasize the fact that they culminate in the emergence of new levels of organizational and functional complexity [Maynard Smith and Szathmáry, 1997]I take issue with Koonin's description of punctuated equilibria (PE). PE is a pattern of evolution that describes speciation events. The morphological changes that characterize a new species are locked in place rapidly during cladogenesis (speciation by splitting). For the most part, these morphological changes are subtle and it often takes an expert to recognize them in the best documented cases. Furthermore, these small changes occur repeatedly in a number of distinct cladogenesis events spread out over tens of millions of years. The result is a very distinctive and well-defined phylogenetic tree that defines the punctuated equilibrium pattern. .
Before describing the six examples, we need to address the differences, if any, between Koonin's Biological Big Bang and the "net of life" model that is replacing the traditional tree of life at the deepest levels [The Three Domain Hypothesis (Part 5, Part 6)]. The similarities are obvious. In the net of life model the early stages of evolution involved massive exchanges of genetic information such that it is now impossible to construct a traditional tree relating the major groups of species such as prokaryotes and eukaryotes. What Koonin is doing is to generalize this event "by proposing that a phase of rapid, promiscuous evolution might underlie many, if not most of the major transitions in the history of life."1. Origin of protein foldsThere is no reason to postulate that all proteins sharing a common fold will share a common ancestor. Some of these proteins might well have arisen entirely independently and evolved to a common fold by convergence. In other words, the underlying assumption that the origin of protein folds represents evolution of some sort may be false. Furthermore, there is even less reason to think that groups with different folds have an evolutionary relationship. In order for this to be true there would have to have been a primordial protein with one kind of fold that gave rise to a protein with another kind of fold. Instead different polypeptides with little three-dimensional structure (random coils) may have independently evolved into proteins with particular folds.
There seem to exist ~1,000 or, by other estimates, a few thousand distinct structural folds the relationships between which (if existent) are unclear.
2. Origins of VirusesThe reason why there's no evidence of a common ancestor for all viruses may be because there is no common ancestor for all viruses.
For several major classes of viruses, notably, positive-strand RNA viruses and nucleo-cytoplasmic large DNA viruses (NCLDV) of eukaryotes, substantial evidence of monophyletic origin has been obtained. However, there is no evidence of a common ancestry for all viruses.
3. Origin of CellsThe existence of distinct bacterial and archaeal domains is hotly disputed. Many groups of bacteria have distinctive features that distinguish them from other groups. There is no need to postulate a radically new mechanism of evolution that accounts for bacteria and archaea if they really aren't much different than the major branches described below.
The two principal cell types (the two prokaryotic domains of life), archaea and bacteria, have chemically distinct membranes, largely, non-homologous enzymes of membrane biogenesis, and also, non-homologous core DNA replication enzymes. This severely complicates the reconstruction of a cellular ancestor of archaea and bacteria and suggests alternative solutions.
4. Origin of the major branches (phyla) of bacteria and archaeaIn addition to eurarchaeote and crenarchaeota there are other groups of prokaryotes that are easily resolved by current techniques (e.g., cyanobacteria, proteobacteria). It may be difficult to resolve the base of the tree because of extensive horizontal gene transfer as postulated in the "net of life" scenarios. This is the one case, along with #3, where the concept of an unusual type of evolution may be correct. I still don't like the term Biological Big Bang to describe it.
Although both bacteria and archaea show a much greater degree of molecular coherence within a domain than is seen between the domains (in particular, the membranes and the replication machineries are homologous throughout each domain), the topology of the deep branches in the archaeal and, especially, bacterial phylogenetic trees remains elusive. The trees conspicuously lack robustness with respect to the gene(s) analyzed and methods employed, and despite the considerable effort to delineate higher taxa of bacteria, a consensus is not even on the horizon. The division of the archaea into two branches, euryarchaeota and crenarchaeota is better established but even this split is not necessarily reproduced in trees, and further divisions in the archaeal domain remain murky.
5. Origin of the major branches (supergroups) of eukaryotesSubstantial progress has been made but the problem is very difficult because of the lack of reliable phylogenetic markers. That, plus the fact that we are trying to sort out events that took place more than one billion years ago. It is too early to conclude that our inability to reach consensus means that something strange must have been going on. That's a cop-out at this time.
Despite many ingenious attempts to decipher the branching order near the root of the phylogenetic tree of eukaryotes, there has been little progress, and an objective depiction of the state of affairs seems to be a "star" phylogeny, with the 5 or 6 supergroups established with reasonable confidence but the relationship between them remaining unresolved.
6. Origin of the animal phylaActually, the relationships between animal phyla are quite well understood at the molecular level. The lineages do not appear to be scrambled by excessive recombination between species as Koonin's hypothesis would require.
The Cambrian explosion in animal evolution during which all the diverse body plans appear to have emerged almost in a geological instant is a highly publicized enigma [32-35]. Although molecular clock analysis has been invoked to propose that the Cambrian explosion is an artifact of the fossil record whereas the actual divergence occurred much earlier [36,37], the reliability of these estimates appears to be questionable [38]. In an already familiar pattern, the relationship between the animal phyla remains controversial and elusive.
Koonin, E. (2007) The Biological Big Bang model for the major transitions in evolution. Biology Direct 2:21doi:10.1186/1745-6150-2-21.
[Photo Credit: The Tree of life is from Ford Doolittle's Scientific American article "Uprooting the Tree of Life" (February 2000). © Scientific American.]
