Talk:Paleontology/GA1

GA Review

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Initial comments

• Watson and Crick did not confirm DNA's role in inheritance, this was shown much earlier by Frederick Griffith. The discovery of the double helix structure instead showed how DNA acts as the genetic material.

Dna#History_of_DNA_research makes it an even more complex story - Griffith did not actually say that DNA was the "transforming principle", and DNA's role was pinned down mid-1940s to mid-1950s (decade following the formulation of modern synthesis). Since Paleontology needs to be very brief about everything (!),would this do?

Within the next few years the role and operation of DNA in genetic inheritance were discovered, leading to what is now known as the "Central Dogma" of molecular biology.

• Genetic drift does not provide variation, it instead reduces variation by removing alleles from a population.
• Similarly, speciation does not provide variation, it is a result of evolution.

Could I suggest:

Increasing awareness of Gregor Mendel's pioneering work in genetics led first to the development of population genetics and then in the mid-20th century to the modern evolutionary synthesis, which explains evolution as the outcome of events such as mutations and horizontal gene transfer providing genetic variation and genetic drift and natural selection driving changes in this variation over time.

You're right, this attempt on my part to squeeze a quart into a pint pot wasn't too successful. Specifically re genetic drift, I was thinking of how it can force organisms off an existing adaptive peak and towards a new one, which AFAIK is its role in Punctuated equilibrium theory and allopatric speciation. Your phrasing leaves that door open and I can't see any way to improve on it. So I've edited it in - many thanks! --Philcha (talk) 13:04, 6 November 2008 (UTC)

1. It is reasonably well written.

   a (prose):

   • In the lead the 2 sentences on the history of the subject are separated and not well integrated, I'd suggest moving the one starting "Although 5th century BC and medieval thinkers.." to merge with the one saying "The final quarter of the 20th century.." and provide a linker between the two. — response below
   • Saying "Fossils found in China since the 1990s.." is moving from a general description of the subject, to this specific fact, and then back to generalities. Best to remove this sentence, since it doesn't seem critical. — response below
   • The idea that atmospheric oxygenation triggered an increase in complexity may be true, but I don't think this is certain enough to be stated as a fact. Later PMID 15005799 is used to reference this, but this paper suggests this idea as a model and does not prove this to be true. Just need to say "May have caused.." and that's OK — Yes, done. --Philcha (talk) 12:30, 12 November 2008 (UTC)
   • "During the time of the dinosaurs, mammals' ancestors could survive only as small, mainly nocturnal insectivores" - again possibly true, or perhaps this was just chance. Unless we do the experiment over again a few times we can't say things were "impossible", just that they didn't happen. Maybe just say "mammals' ancestors were small, mainly nocturnal.." — response below
   • "paleontology focuses not on life but on fossils, its main source of evidence found in rocks." - are fossils its main source of evidence, or are they just the main source of evidence that are found in rocks and other main sources exist that are not found in rocks? — response below
   • In molecular phylogenetics the article says "..although this approach is controversial because of doubts about the reliability of the "molecular clock"" - are you saying molecular phylogenetics in general is controversial (I'd disagree) or that the specific application of using these techniques to derive precise dates is controversial? — response below
   • "The sparseness of the fossil record means that organisms are expected to exist long before.." - merge into first paragraph of this section. — Yes, done. --Philcha (talk) 12:30, 12 November 2008 (UTC)
   • "some apparent scientific disputes have arisen from misunderstandings over names" - I don't understand what "apparent" means here. I'd be tempted to cut it out, but I'm not sure exactly what you mean.
     • "Many recent debates between paleontologists and neontologists have been based more on miscommunication than an on real conflict between data sets. The "conflict" between molecular and fossil estimates on the age of the taxon Crocodylus, for example, was based entirely on conflicting meanings of the name; ..." (Brochu and Sumrall, 2001; cited) --Philcha (talk) 22:20, 16 November 2008 (UTC)

   Does this cover it? The point I'm trying to deal with is that the disputes were real, just the basis was a misunderstanding. Tim Vickers (talk) 00:50, 17 November 2008 (UTC)

   b (MoS):

   Fine.

2. It is factually accurate and verifiable.

   • Be careful about using the archaean lipid data to date the emergence of eukaryotes, a paper this year (PMID 18948954) questioned this analysis. — | response below
   • "Stratigraphy and biostratigraphy can in general provide only relative dating" - can they ever provide absolute dating? Why do you say "in general"?
     • Theoretically one could get lucky and find a thin radiometrically-datable ash layer in a well-correlated sequence of sediments, which would give usable absolute dates for the overyling and underlying layers, and all those that correlate with them. A slim chance, but non-zero, so making it an absolute "... can only ..." would be asking for trouble. --Philcha (talk) 22:28, 16 November 2008 (UTC)

   Wouldn't these would still be relative dates though? In this case relative to the ash layer?

   • "Multicellular life is composed only of eukaryotic cells" not strictly true, see myxobacteria for example and PMID 15040179
     • I agree "multicellular" can be a tricky term, and Evolutionary_history_of_life#Multicellularity goes a bit deeper than this, incl citing the entertaining grumbles of a mycologist about anthropocentrism, plus an example of a slime mould solving a maze. In the limited space available here I'm going for the usual meaning of having specialised cells, for which Volvox is often cited as the simplest instance - and it's a eukaryote, as are all plants, fungi and metazoa. --Philcha (talk) 22:20, 16 November 2008 (UTC)

   True, this is a very broad overview, so a few exceptions are OK

   a (references):

   • "..the story of Anomalocaris is an example of this" - needs a citation
     • Now cites Gould's Wonderful Life --Philcha (talk) 22:20, 16 November 2008 (UTC)

   b (citations to reliable sources):

   Lots!

   c (OR):

   None I can spot.

3. It is broad in its coverage.

   a (major aspects):

   "In 1822 the word "paleontology" was invented by the editor of a French scientific journal" - would be good to add his name. - response below

   b (focused):

   Useful examples

4. It follows the neutral point of view policy.

   Fair representation without bias:

   Yes.

5. It is stable.

   Yes.

6. It is illustrated by images, where possible and appropriate.

   a (images are tagged and non-free images have fair use rationales):

   Yes.

   b (appropriate use with suitable captions):

   Needs a good lead image, a dinosaur or a fossil would be traditional

   I've WP:BOLDly gone for the big picture. If you think that's a bit much,, there's a more modest alternative (hidden by HTML comment tags) below it. --Philcha (talk) 23:07, 16 November 2008 (UTC)

7. Overall:

Pass, excellent work!

Discussion of recent comments

I dont' want to clutter the checklist, so:

Lead

• If by "The final quarter of the 20th century.." you mean the one about mol phylo (end of 2nd para), I'm really not sure about this. The latter sentence is specifically about the latest in a series of techniques for uncovering evolutionary history. The former sentence is meant to be equivalent to "After a long prehistory, paleo got established in the late 18th cent". To me inserting mol phylo into the first para would jarringly fragment the overview of techniques. Maybe we should consider what signalling / signpost phrases might be better. --Philcha (talk) 12:30, 12 November 2008 (UTC)
• The recent torrent of Chinese fossils is hugely significant. The most notable of their many notable contributions is throwing more light on the Cambrian explosion, which is the second biggest issue in paleontology (after the origin of life) and I suspect the more likely to be resolved. --Philcha (talk) 12:30, 12 November 2008 (UTC)
• "During the time of the dinosaurs, mammals' ancestors could survive only as small, mainly nocturnal insectivores" is a slight over-simplification, as some late Jurassic and Cretaceous mammaliforms / mammals reached the size of badgers, and some took to the air or water. However all known early Jurassic mammaliforms are smaller than modern rats and are mostly shrew-sized. "small, mainly nocturnal insectivores" is so widely-accepted that it has prompted consideration of whether the downsizing accelerated evolution of mammalian characters. --Philcha (talk) 12:30, 12 November 2008 (UTC)
  • The problem is saying "could", which is a statement about what was possible, not a statement about what occurred. If you "rewound the tape" as Gould put it, mammals might have become dominant earlier - we can't say that outcome was impossible. I'd have no problem saying that the mammals were small at this point, but I'm not happy with the statement that this was the only possible outcome. Tim Vickers (talk) 16:49, 12 November 2008 (UTC)
  • "survived only as"? The point of this is the contrast with their mid-late Permian dominance of at least temperate latitudes and their significant position among mid-large land animals in the early Triassic.--Philcha (talk) 17:08, 12 November 2008 (UTC)
    • • Yes, that's fine, since it doesn't imply nothing else might have happened. Tim Vickers (talk) 17:15, 12 November 2008 (UTC)
      • Done. Also made similar change in "Overview of the history of life". --Philcha (talk) 18:24, 12 November 2008 (UTC)

Related sciences

• I can see what "paleontology focuses not on life but on fossils ..." is supposed to mean, but the phrasing's bloody awful and I'm desperately looking for someone else to blame :-(  How about:

Paleontology lies on the boundary between biology and geology since paleontology focuses on life but fossils, its main source of evidence, are found in rocks.

• • I've edited in the re-wording. --Philcha (talk) 21:59, 16 November 2008 (UTC)
    • It's mean to suggest "one foot in biology and the other in geology" --Philcha (talk)
• Re "..although this approach is controversial because of doubts about the reliability of the "molecular clock"": At this level of summarisation I think it's fair to say mol phylo is controversial on both counts. Re the structure of the family tree: it's taken a while to identify the "Goldilocks" genes that change fast enough to be useful but not so fast that "static" causes misleading results, especially in "deep time" analyses; AFAIK the Afrotheria issue is unresolved, and that was raised by mol phylo; I've recently found WP:RS indicating that botatists are less happy than zoologists about cladistics (Talk:Clade#Sources_-_recognised_scientific_publications), which is the basis of mol phylo. Re the dates, it's controversial: divergence dates of mammalian orders; stages in evolution of animals; etc. OTOH we might need to re-examine this in a year's time, as increasingly large datasets processed and sensitivity-tested on increasingly powerful computers appear to be improving mol phylo's credibility by the day. WP:OR: I predict that the next problem will be getting the cladistics software to explain its conclusions to mere mortals, a problem that AI researchers encountered in the 1980s. --Philcha (talk) 12:30, 12 November 2008 (UTC)

Phylogenetics seems very well-accepted in the literature I read, but I suppose I'm used to dealing with more modern organisms, rather than deep time. If that's what you intended to say then no problem. Tim Vickers (talk) 17:18, 12 November 2008 (UTC)

Overview of the history of life

• The Nature article "Reassessing the first appearance of eukaryotes and cyanobacteria" is a tasty catch, and fresh too (Oct 2008). Paleontology#Overview_of_the_history_of_life currently says "While eucaryotes, cells with complex internal structures, may have been present earlier, their evolution speeded up when they acquired the ability to transform oxygen from a poison to a powerful "fuel" for their metabolisms, a development that may have started with their capturing oxygen-powered bacteria as endosymbionts." and I think "may" is the saving grace here, at this level of summarisation. However I'll check out the corresponding bits of Evolutionary history of life right now - many thanks!
  BTW The Nature article "Reassessing the first appearance of eukaryotes and cyanobacteria" says "Our findings also negate the use of cyanobacterial and eukaryotic biomarkers from 2.7- to 2.5-Gyr-old rocks as calibration points for molecular clocks and the universal tree of life." --Philcha (talk) 13:07, 12 November 2008 (UTC)

History of paleontology

• BTW re your initial comments about DNA, I've proposed an alternative wording - what do you think? --Philcha (talk) 12:49, 12 November 2008 (UTC)

Reads fine. Tim Vickers (talk) 19:53, 16 November 2008 (UTC)

Edited in. --Philcha (talk) 21:52, 16 November 2008 (UTC)

Origin of "paleontology"

• According to History of paleontology it was Henri Marie Ducrotay de Blanville, editor of Journal de Phisique, in 1817 (although the lead says 1822!). I've edited this in, using 1817.
  I don't have the cited book and it is not available in Google Books. The Encyclopedia of Language and Linguistics, p. 2907 credits Charles Lyell (1838), but that was presumably first use in English. --Philcha (talk) 21:56, 16 November 2008 (UTC)