Departing the Vacuousness
Started by Tank, May 16, 2011, 07:30:05 PM
QuoteIda is the most complete early primate fossil ever found, and scientists believe that she could be one of our earliest ancestors. She is a remarkable link between the first primates and modern humans and despite havinglived 47 million years ago, her features show striking similarities to our own.
QuoteAbstractBackgroundThe best European locality for complete Eocene mammal skeletons is Grube Messel, near Darmstadt, Germany. Although the site was surrounded by a para-tropical rain forest in the Eocene, primates are remarkably rare there, and only eight fragmentary specimens were known until now. Messel has now yielded a full primate skeleton. The specimen has an unusual history: it was privately collected and sold in two parts, with only the lesser part previously known. The second part, which has just come to light, shows the skeleton to be the most complete primate known in the fossil record.Methodology/Principal FindingsWe describe the morphology and investigate the paleobiology of the skeleton. The specimen is described as Darwinius masillae n.gen. n.sp. belonging to the Cercamoniinae. Because the skeleton is lightly crushed and bones cannot be handled individually, imaging studies are of particular importance. Skull radiography shows a host of teeth developing within the juvenile face. Investigation of growth and proportion suggest that the individual was a weaned and independent-feeding female that died in her first year of life, and might have attained a body weight of 650–900 g had she lived to adulthood. She was an agile, nail-bearing, generalized arboreal quadruped living above the floor of the Messel rain forest.Conclusions/SignificanceDarwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative 1of the early haplorhine diversification.
QuoteOverview of the E. coli long-term evolution experimentThe inexorable rhythm of the project is as follows:1. Every day, the cultures are propagated;2. Every 75 days (500 generations), mixed-population samples are frozen away; and3. Mean fitness, relative to the ancestor, is estimated using the mixed-population samples. Note that "3" can be done anytime after "2". Each of these tasks is described in detail below.For all aspects of this project, unless otherwise stated, the following standards are maintained:1. The liquid culture medium is DM supplemented with 25 mg/l of glucose;2. Cells are spread on TA plates; and3. Liquid cultures and agar plates are incubated at 37C.Two types of back-ups for the long-term populations are available in the event of a mishap:4. After each daily transfer, cultures are saved in the refrigerator for one day; and5. The mixed-population samples are stored indefinitely and can be used to re-start the cultures. 1. Daily transfers* Daily transfers should be made 22-26 hours after the previous day's transfer.* Label 12 flasks as A+1 through A+5 and A-1 through A-6. (Check flasks and beaker tops for cracks.) Add 9.9 ml of DM25 to each flask.* Remove 12 flasks from shaking incubator. Visually confirm (slight) turbidity of each.* Propagate 12 cultures by transferring 0.1 ml from previous day's cultures into fresh DM25. While transferring, strictly alternate between + and - cultures. This maximizes our ability to detect any inadvertent cross-contamination.* Incubate the new flasks in the shaking incubator at 37C and 120 rpm.* Save the old flasks for one day in the refrigerator, discarding the previous day's flasks. (In the event that a flask has cracked, or some other mishap, use the previous day's flasks from the refrigerator, setting the transfer number back by one day.)* Be sure to record each day in the notebook by day number. 2. Storing mixed-population samples* Every 75th day ( = 500 generations), the evolving populations are themselves stored away in the ultra-low freezer at -80C.* Perform the daily transfer as always. Also, plate for colonies to check for contamination.* Number and label 12 large and 12 small freezer vials. Numbering should begin after the last number used for the entire freezer collection. The large and small freezer vials receive duplicate numbering; the small vials provide back-ups. In addition to putting number stickers on top, use a blue marker to write numbers and strain identifiers on the vials. Record the strain numbers and identifications in the lab notebook, noting in particular that these are "mixed-population samples" (not clonal isolates).* To each of the previous day's cultures, add glycerol (about 1 ml) from the small tubes. Swirl to mix the glycerol well with the culture; this takes some effort owing to the viscous nature of the glycerol.* Using an individually wrapped, sterile bulb-pipette for each culture, transfer 1 ml to the appropriate small vial and 5 ml to the corresponding large vial. The vials are then stored away in the appropriate freezer boxes.
QuoteAbstract: The role of historical contingency in evolution has been much debated, but rarely tested. Twelve initially identical populations of Escherichia coli were founded in 1988 to investigate this issue. They have since evolved in a glucose-limited medium that also contains citrate, which E. coli cannot use as a carbon source under oxic conditions. No population evolved the capacity to exploit citrate for >30,000 generations, although each population tested billions of mutations. A citrate-using (Cit+) variant finally evolved in one population by 31,500 generations, causing an increase in population size and diversity. The long-delayed and unique evolution of this function might indicate the involvement of some extremely rare mutation. Alternately, it may involve an ordinary mutation, but one whose physical occurrence or phenotypic expression is contingent on prior mutations in that population. We tested these hypotheses in experiments that ''replayed'' evolution from different points in that population's history. We observed no Cit+ mutants among 8.4 X 1012 ancestral cells, nor among 9 X 1012 cells from 60 clones sampled in the first 15,000 generations. However, we observed a significantly greater tendency for later clones to evolve Cit+, indicating that some potentiating mutation arose by 20,000 generations. This potentiating change increased the mutation rate to Cit+ but did not cause generalized hypermutability. Thus, the evolution of this phenotype was contingent on the particular history of that population. More generally, we suggest that historical contingency is especially important when it facilitates the evolution of key innovations that are not easily evolved by gradual, cumulative selection.
Quote from: Sweetdeath on July 12, 2011, 07:30:56 AMSweetjeebus!Thank you for posting this goldmine of delicious knowledge. <3
QuoteBack in late 2009, we started offering free evolution book excerpts on the NCSE web site and via Facebook. The excerpts—often complete chapters—were culled from a range of tomes, from illustrated versions of the Origin to textbooks (such as Douglas Futuyma's Evolution) to kids books (such as Evolution: How We and All Living Things Came to Be).These excerpts are still accessible for your delectation:
Quote from: xSilverPhinx on March 09, 2012, 03:26:43 AMIMO Dawkins is very good at explaining evolutionary theory to laypeople (even those who haven't had any high school classes on the subject) quite well. The problem is since many people are a bit...erm...hostile towards him they don't really give what he says due attention. If you want to broaden it to the topic of skepticism in general, then Sagan is the best. I suggest you read the material she's been reading first, and get to know creationist tactics well before you try and refute them. Focus heavily on the ideas she has on what evolutionary theory is first, before you focus just on the objective evidence. If she doesn't know first that all the creationist arguments are ridiculous strawmen, then she might be more susceptible to confusion. I like using the 'shock and awe' approach to do this. You could come out and say something like "if ducks would mate with crocodiles and produce crocoducks, then that would mean that there is something really wrong with evolutionary theory. It doesn't predict such a thing. Same thing for two ducks giving birth to a crocoduck. If that were ever to happen then something is patently false and the whole theory would need massive readjusting. That is not what transitional species are all about. And btw, only species evolve, not individuals (gene frequency in populations). And also, the common-sense idea that people have about evolution is basically a Lamarckist one, which was proven to be false (except for epigenetic inheritence) long ago. Larmarckism would say that an individual feels the need to evolve for a certain purpose, does, and passes the trait on. The common giraffes stretching their necks to reach higher branches scenario. It's also good to be keenly aware of the fact that most creationists are coming from a know-more-than-those-who-actually-do-know stance and are confident in their ignorance (or disinformation). To those who don't know enough to know otherwise, that's a point in the creationist's favour. Someone spewing out their dribble with confidence makes that person more of an expert than an actual expert in the eyes of the ignorant and scientifically illiterate (if you ever watch debates... ), so if you're unable to refute her points or answer her questions well, you might do more harm than good and push her more into creationism. There's a YouTube Channel which compiles some documentaries on evolution. You might want to check out Talk Origins for refutations to creationist claims, propaganda and misinformation too. I'm assuming you already have a good understanding of evolutionary theory, but I just thought I'd add the link in case anybody else is reading this. If you or your mom don't have the time to watch hour-long documentaries, then there are a few good summerised youtube videos (made by people who frequently deal with creationists). Potholer's 'Made easy' series are really good. Natural Selection Made EasyThe Theory of Evolution Made EasyHuman Evolution Made EasyHe also has other good videos worth checking out too. Another excellent YouTube series is AronRa's Foundational Falsehood of CreationismQualia Soup's 'Evolution' is good too, but it might be a bit rushed for someone who doesn't have a very basic idea of what evolution is. I would also recommend Creationism - Penn & Teller Bullshit! because it's fun
QuoteReplicators are the fundamental units of any process of natural selection. They were first defined by evolutionary biologist Richard Dawkins as any entities of which copies are made. The concept of replicators has diverse applications in a variety of areas, including biology, sociology, linguistics, and philosophy.