rhinoceros
Archon
Gender: 
Posts: 1318
Reputation: 8.40
Rate rhinoceros
My point is ...
  
|
 |
Galapagos 2005: The Woodstock of Evolution
« on: 2005-06-28 09:26:26 » |
 |
The World Summit on Evolution - Galapagos 2005
The Woodstock of Evolution
http://www.skeptic.com/eskeptic/eskeptic05-06-24.html
This is Michael Shermer's report from Galapagos. I have already copied the full text in the Evolution section of the BBS. Here are some teasers:
<snip>
In the subsequent discussion session, Bill Schopf asked all the speakers the Gouldian question: if we reran the tape of life would we end up with something like what we have today? The collective response was that it depends on how the question is defined, as in “what do you mean by ‘something like’?” There is evolutionary convergence, so clearly some things would be preserved (like eyes and wings). The experiment has been run in that sense. Fortey said that such “what if” questions are meaningless, but that’s not true, since counterfactual history is a legitimate form of reasoning about cause and effect relationships
<snip>
One of the best talks of the conference was delivered by the U.C. Berkeley paleoanthropologist Timothy White, in which he opened with a prediction made by Stephen Jay Gould in the late 1980s: “We know about three coexisting branches of the human bush. I will be surprised if twice as many more are not discovered before the end of the century.” A glance at the extant fossil record looks like Gould was right. There are at least two dozen fossil species in six million years of hominid evolution. But the bush is not so bushy, says White. The problem lies in the difference between “lumpers” and “splitters” in species classification, and the social pressures to publish extraordinary new discoveries. If you want to get your fossil find published in Science or Nature, and you want the cover illustration, you cannot conclude that your fossil is yet another Australopithicus africanus, for example. You better come up with an interpretation indicating that this new find you are revealing for the first time to the world is the most spectacular discovery of the last century and that it promises to overturn hominid phylogeny and send everyone back to the drawing board to reconfigure the human evolutionary tree. Training a more skeptical eye on many of these fossils, however, shows that many, if not most of these fossils belong in already well-established categories. White says that the specimen labeled Kenyanthropus platyops, for example, is very fragmented and is most likely just another Australopithicus africanus. “Name diversity does not equal biological diversity,” White elucidated.
White then concluded his talk with a fascinating discussion of the recent discovery of fossil dwarf humans on Flores Island in the Malay Archipelago, located on the outside of Wallace’s Line, meaning that even during the last ice age they could only have gotten there by boat. (White did note, however, that after last December’s tsunami people were rescued from large floating rafts of natural debris, so it is possible that the founding population of Flores rafted there by accident and not design.) Found in Liang Bua cave, the type specimen of Homo floresensis was dated at 18,000 years old, meaning that they had to be modern humans because all other hominid species had long ago gone extinct. But with a cranial capacity of only 300cc — about the same size as that of Lucy and modern chimpanzees — this means that they were able to fashion complex tools (and possibly boats) with tiny brains; the implication is that brain architecture, not size, is what counts for creating higher intelligence. A second published specimen put to rest the pathology hypothesis that Homo floresensis was a microcephalic human. The best evidence, says White, points to insular dwarfing, a rapid punctuation event out of Homo sapiens that led to a shrinkage of these isolated people. Such dwarfing effects can be seen on this and other islands, where large mammals get smaller (like the dwarf elephant), and small reptiles get larger (like the Komodo Dragon). The chances of any living members of this species still existing in the hinterlands of Flores are extremely remote, but some observers have noted that the indigenous peoples of Flores recount a myth of small hairy humans who descend from the highlands to steal food and supplies.
<snip>
The next lecture would have sent Darwinian fundamentalists into skeptical paroxysms, as Leticia Aviles, a zoologist at the University of British Columbia, summarized the evidence for “multilevel selection.” Darwinian fundamentalists (an intentionally pejorative term coined by Stephen Jay Gould) believe that the individual organism is the sole target of natural selection. Aviles said that below the individual, selection may occur at the level of genes, chromosomes, organelles, and cells. Above the individual, selection may occur at the level of social groups, demes, species, and multispecies communities. In that sense, Aviles said, “individual” depends on the frame of reference. She then applied multilevel selection to research on sex ratios, cooperation among non-relatives, and multicellularity. Social spiders are an example of group selection, Aviles continued. And sex ratios that depart from 1:1 cannot be accounted for by inbreeding alone, so group selection is here invoked. Likewise, the equilibrium of sex ratios is explained by both within-group selection and between-group selection. “When cooperation is not costly, groups, grouping, and cooperation evolve readily. But with increasing costs of cooperation, levels of cooperation decrease.”
<snip>
the penultimate lecture of the conference by the acknowledged star of the weekend, Lynn Margulis, famous for her pioneering research on symbiogenesis. Margulis began graciously by acknowledging the conference hosts and saying, “This is the most wonderful conference I’ve ever been to, and I’ve been to a lot of conferences.” She then got to work, pronouncing the death of neo-Darwinism. Echoing Darwin, she said “It was like confessing a murder when I discovered I was not a neo-Darwinist.” But, she quickly added, “I am definitely a Darwinist though. I think we are missing important information about the origins of variation. I differ from the neo-Darwinian bullies on this point.” She then outlined the basis of her theory of the origin of the cell nucleus as a fusion between archaebacteria (thermoplasma) and Eubacteria (Spirochaeta). “We live on a bacterial planet,” she reflected.
<quote>
The cell is the fundamental unit of life. A minimal cell has DNA, mRNA, tRNA, rRNA, amino acylating enzymes, polymerases, sources of energy and electrons, lipoprotein membranes, and ion channels, all contained within a cell wall, and is an autopoietic (self-regulating feedback) system.
</quote>
The biggest break in life, she explained, was between the prokaryotes (cells with nucleoids: monera, prokaryota; archaebacteria, eubacteria) and eukaryotes (cells with nuclei: protoctista, fungi, plantae, animalia).
In this framework, Margulis continued, all of life’s history can be divided into three major eons: Archean (3,500–2,500 million years ago), Proterozoic (2,500–540 Ma), and Phanerozoic (540–0 Ma). “Most evolutionary biologists deal with the Phanerozoic, which is like saying that history began in 1909 when the Ford Motor Company opened shop in Dearborn, MI,” Margulis quipped. The major steps in evolution involved symbiogenesis, which Margulis described succinctly as “the inheritance of acquired genomes” and more formally in its relationship to symbiosis, “the long-term physical association between members of different types (species).” The problem with neo-Darwinism, Margulis concluded, is that
<quote>
Random changes in DNA alone do not lead to speciation. Symbiogenesis — the appearance of new behaviors, tissues, organs, organ systems, physiologies, or species as a result of symbiont interaction — is the major source of evolutionary novelty in eukaryotes — animals, plants, and fungi.
</quote>
There were no direct challenges to Margulis in the discussion period that followed, so I once again queried a number of the experts in this area after the lecture. The overall impression I received was that Margulis goes too far in her rejection of neo-Darwinism, but because she was right about the role of symbiogenesis in the origin of the first eukaryote cells, they are taking a wait-and-see approach. One scientist added that since Margulis was to receive an honorary doctorate that afternoon, it seemed inappropriate to challenge her in this venue.
<snip>
The final talk was delivered by evolutionary biologist Joan Roughgarden, from Stanford University. Evolutionary skepticism must have been in the air, for on the heals of Margulis’ pronouncement of the death of neo-Darwinism, Roughgarden proclaimed the death of Darwin’s theory of sexual selection. Darwin said that males have stronger passions than females, that females are coy, and that females choose mates who are more attractive, vigorous and well-armed. “People are surprised to learn how much sex animals have for purely social reasons (including same-sex sexuality in over 300 species of vertebrates),” Roughgarden explained,
<quote>
and how many species have sex-role reversal in which the males are drab and the females are colorfully ornamented and compete for the attention of males, and that most plants and perhaps a quarter of all animal species have individuals that cannot be classified as male or female.
</quote>
In response, University of Georgia evolutionary biologist Patricia Gowaty noted that Roughgarden is right in identifying the exceptions to Darwin’s theory and that there is much we still do not know, but added that since Darwin’s time much has been learned about mate selection and competition that should not be dismissed.
<snip>
Futuyma explained that he had agreements with everyone on some aspects of the various debates and controversies under discussion, but that in the end more research and more data will resolve some issues and open up new ones.
Herein lies science’s greatest strength: not only the ability to withstand such buffeting, but to actually grow from it. Creationists and other outsiders contend that science is a cozy and insular club in which meetings are held to enforce agreement with the party line, to circle the wagons against any and all would-be challengers, and to achieve consensus on the most contentious issues. This conclusion is so wrong that it cannot have been made by anyone who has ever attended a scientific conference. The World Summit on Evolution, like most scientific conferences, revealed a science rich in history and tradition, data and theory, as well as controversy and debate. From this I conclude that the theory of evolution has never been stronger.
|
Author
Logged
