Talk:Extinction event

From Wikipedia, the free encyclopedia

This article is part of WikiProject Extinction, an attempt at creating a standardized, informative, comprehensive and easy-to-use resource on extinct animals, extinct plants and extinction in general. If you would like to participate, you can choose to edit this article, or visit the project page for more information.

Contents 1 K-T Extinction 2 The Oxygen Revolution Extinctions 3 The Sixth Mass Extinction? 4 Other Issues 5 Remove verneshot paragraph 6 We're missing one. 7 Timeframes 7.1 Extinction events vs Mass extinctions 8 Timeline graphic 9 Wilkes Land Crater 10 Extinction Theory Fallacy 11 List of doomsday scenarios 12 Need to restructure set of pages about mass extinctions 13 Discussion on end of civilization

[edit] K-T Extinction

From the K-T extinction blurb: " including the dinosaurs." I personally feel that the evolutionary lineage of birds from dinosaurs is clear, so feel that this should be amended to say "including the non-avian dinosaurs." I realize that this may be contentious for some, so, before doing so, I wanted to hear what the community felt. Baryonyx 04:25, Sep 28, 2004 (UTC)

__________________________________________________________________

I didn't notice anyone mention the advent of electricity and the industrial revolution playing very real roles in the acceleroration of such a hypothetical instance as extinction occurring now. As with all else pertaining to the development of society, the advent of electricity and the industrial revolution has hastened the process.... in which ever directions a person chooses to recognize it as having proceded.

[edit] The Oxygen Revolution Extinctions

I remember having read about a (widely accepted?) theory that the second (or the first) mass extincting was caused by the development of photsynthesis in the evolution of life: The new organism capable of doing photosynthesis thrived and rapidly increases the abundance of oxygen in the atmosphere from only traces before to several tens of percents as now. As oxygen is highly corrosive (remember: there was no oxidation before) most organism died expect for those that developped protection against oxidation in time.

Does anybody know details? Is this correct? If so there should it go? -- sanders_muc

The original poster is talking about the idea that many of the original microbes of the Earth's early life evolved in the near complete abscene of oxygen in the atmosphere, and hence the oceans. The rise and expansion of the cyanobacteria would have posed a significant evolutionary pressure upon these organisms as oxygen began to increase in the oceans and in the atmosphere. It is believed that the Oxygen Revolution, as the buildup of oxygen during the Archean and Proterozoic is called, would have led to the extinction of organisms that could not cope with this oxygen-rich world, at least those that did not successfully move to anoxic areas or adapt. I have not seen it cited as counting as one of the Big Five, though. I would argue that it is an evolutionarily significant extinction: even if not Big Five material, it marks an important change in the history of life. As such, it probably merits mention.Baryonyx 04:25, Sep 28, 2004 (UTC)

[edit] The Sixth Mass Extinction?

Some people claim that we are living in the middle of another, man-made extinction event right now. However, humanity's effects are trivia compared with the extinction events shown in the fossil record.

Is that a fact? I've seen estimates on damage that are comparable to the smaller or intermediate sized mass extinctions, if nothing like the boundaries that end the Mesozoic and Palaeozoic eras.

If those are the same estimates that I've seen -- that something like 50,000 species a year are dying out -- they are not particularly reliable. The ones I've seen have all been created by organizations like the Sierra Club and people like Al Gore and Paul Ehrlich who have large, flaming political agenda that such figures are constructed to support. Over the past 500 years, almost 90 per cent of the forest along the Atlantic coast of Brazil has been cleared. However, no one has found a single known species that could be declared extinct. According to the "mass extinction" figures, about half the known species in that Brazilian forest should have been lost.

But if you can cite figures commonly accepted by paleontologists -- figures that, say, appeared in a peer-reviewed journal -- feel free to enter them! --The Epopt

Do a search for something like "current mass extinction" in google, and you will find a great number of hits, including articles in Nature and Science. It looks to me like the mass extinction view is closer to a consensus than to a minority of politically motivated views. At the very least there is enough here to remove the sentence from the article, which I'm doing.

We should move this discussion to Holocene extinction event anyway.

It should also be noted that some scientists have begun to refer to the period from 18th century forward as a new geological epoch, the Anthropocene, mainly because of the impact we are having on the planet. It is by no means in common use though, but wanted to note it.Baryonyx 04:25, Sep 28, 2004 (UTC)

So, do we actually have a common unbiased point of view that there is, in fact, another extinction event currently going on? If so, is there a wikipedia entry or other material we could link to? Because I, frankly, remain skeptical and would like to see more scientific evidence (on both sides of the argument). Cema 22:39, 12 Nov 2004 (UTC)

---

Recently, 24.7.97.222 removed this section:

Other scientists view this estimate as exaggerated, however. For example it can be noted that only 9 species of mammals have gone extinct in North America since Columbus' discovery. Of these, 7 are small rodents [1]. Compared to a background global extinction rate of roughly 2 mammal species per millenia, this is quite high, but probably not enough by itself to make dire predictions about. The most species rich environment on Earth are the rainforest, and their destruction could lead to major losses. However, though 12.5% of the amazon rainforest have been cleared, studies suggest that only a far smaller fraction of its diversity has been destroyed. Because animals and plants can frequently be found in many distant locales within the rainforest, it may be possible to preserve most of the rainforest's diversity in an area 1/3 to 1/2 its original size. Hence conservation efforts may be able to save a majority of these species.

and replaced it with:

A survey by the American Museum of Natural History in 1998 found that the vast majority of biologists agreed with Wilson's assessment, and numerous confirmatory studies in the years since then-- led by the IUCN's annual "Red List" of threatened species-- have now produced a scientific concensus on the subject.[2]

Obviously this is a change in perspective for that section of the article and not one I am entirely happy about. I don't doubt that there is a "mass extinction" ongoing in terms of humanity's reorganization of the environment and ensuing loss of diversity. However, from a paleontological perspective, the extinctions we have caused are no where near the scale of any of the major mass extinctions listed in the article. Maybe our impact could reach that level, but in my honest opinion, most of the near-term dire predictions are grossly overblown. In particular, they frequently apply the species-area relation in a context that has never been empirically verified. In doing so, they predict a number of extinctions based solely on the amount of habitat that was destroyed. However, I have never seen a single field study that concluded that the actual impact even approached the level predicted.

Frankly, this article has a problem in that it only talks about the truly major extinction events, which had profound effects even on global disperse and well-adapted taxa. While the Holocene extinctions might well qualify as a man-made event, to date, they simply aren't in the same category as the major mass extinctions. Perhaps we can discuss extinctions as having a gradiation between local/regional extinction events to those of global scale, and also discuss more of the minor/moderate mass extinctions that have occured in the past. In my opinion, the Holocene extinctions are basically minor so far. Whether they can graduate to major is obviously a matter of debate and should be portrayed as such.

Dragons flight 22:52, Dec 31, 2004 (UTC)

---

I'm the one (24.7.97.222) who made the change you just described. Did you look at the reference link I provided?[3] The issue is not the extinctions that humans have caused so far-- it is the extinctions that are about to take place as a result of the staggering growth in human population and consumption over the past two centuries. It is this impending mass extinction that the world's biologists are warning about. And it certainly does rival the great mass extinctions of the past: the most recent estimate I heard at the California Academy of Sciences two weeks ago was that half of all species will be extinct in 50 years-- i.e., twice as fast as E.O. Wilson's estimate.

Check the list in the ref provided by our anonymous poster, it is quite impressive. I've upped the ante a bit by including the current or Holocene extinction event as #7. No doubt some skeptics will be unhappy and probably claim that its all some large, flaming political agenda as someone so eloquently put it earlier. So be it. Vsmith 03:17, 1 Jan 2005 (UTC)

Vsmith, you cited IUCN, without realizing that their own rate estimate of 2300 species extinctions a year predicts the extinction of only 1% of species in the next 50 years. (This compares with Wilson's 27000 - 100000 species extinctions a year, which is certainly on the high side of views held by scientists). Secondly, the 1998 AMNH study only showed that most biologists agreed that the current rate of extinction is historically very high, not that they endorsed Wilson's position. And they are right, a 1% turn over would be phenomenally high since 1% would be more typical of a million years. I don't disagree that the extinction rate is currently enormous. But I don't believe there exists a consensus that the current rate is high enough to lead to a MAJOR mass extinction in the near term.

Wilson holds an extreme position in a field where the scale of the problem is still being actively debated. I will provide more documentation for the more moderate position before updating this further. Dragons flight 03:58, Jan 1, 2005 (UTC)

Dragons flight (this is 24.7.97.222 speaking!): The AMNH study said "The majority (70%) polled think that during the next thirty years as many as one-fifth of all species alive today will become extinct, and one third think that as many as half of all species on the Earth will die out in that time."[4] And the IUCN estimates that one in four mammals, one in three amphibians, and one in eight birds are now threatened with extinction.[5] I don't know where you got your figure for the IUCN estimating "2300 species extinctions a year." Can you give a reference? I don't recall the IUCN ever giving an estimate of the total number of species they believe are going extinct per year-- in fact, they seem to systematically avoid such global estimates, carefully limiting themselves to talking only about the groups of species (mammals, birds, and now amphibians) that they have fully evaluated.

Maybe what you're talking about is the increase of 3,300 threatened species between the 2003 and 2004 Red Lists (from 12,259 to 15,589). However, this figure of 3,300 is not even remotely the total number of species that the IUCN scientists think might be going extinct per year-- it is simply the increase between 2003 and 2004 in the number of species that the IUCN was able to fully evaluate and to conclude are threatened. But the number of species the IUCN has fully evaluated is only a microscopic fraction of the total number of species on earth. As the Executive Summary of the 2004 Red List says, "this figure (15,589) is an underestimate of the total number of threatened species as it is based on an assessment of less than 3% of the world’s 1.9 million described species"[6]-- and even the 1.9 million "described species" are only a small fraction (roughly 10%) of the total number of species on earth, which the IUCN estimates as being between 10 and 30 million.

A good example of how far the figure of 15,589 understates the magnitude of the extinction crisis is found in the fact that the 2004 Red List evaluated only 771 insect species out of the almost 1,000,000 insect species it says have been described[7] (by the way, of these 771 insect species, 559-- 73%-- were found to be threatened). And the 1,000,000 insect species that have been described are only a small fraction of the total number of insect species, which is now estimated at between 4 and 6 million[8]

So let's do the math (just a rough ballpark figure): the IUCN says 15,589 species are threatened, but it has evaluated only 3% of described species-- and described species are only about 10% of the total number of species on earth. So that means the IUCN has evaluated about .3% of the total number of species on earth, and has found that roughly 15,000 of those are threatened with extinction. So if we extrapolate to a ballpark figure, 15,000 X 300 = 4,500,000 species threatened with extinction. Granted that's just a ballpark figure, but the order of magnitude shows why the IUCN scientists and almost every other biologist in the world now think we're facing a mass extinction on the same scale as the other great extinction events in the earth's history.

New edit: Think of processes, of a graph with the numbers of species going down from 100% to 98% over millennia and then rapidly to about 95% in 2000. Then think of the momentum that such a 'system' posesses - to coast along to 90%, to 80%, to 50%, could be easy - do nothing new. The extinction debate should be about what counter forces can Humans begin to apply now so as not only to equal the forces driving extinctions, but to reverse the trend. Only then will the graph bottom out, and a painful, slow recovery begin.

I've made a small 'change of balance' edit and hope to do more. This first point is to reinstate the 'taxonomy' of the sixth extinction. The person who carefully, and I assume factually, records 1/, 2/ ... 6/ and 7/ mass extinction events, with 7/ being the sixth extinction should be - well the word is close to the tip of my tongue )- That person was being devious. I would be grateful to him for removing this confusion from the Article.

I've also removed a line that implied that someone (or more) had received a science research grant to search for a past total extinction! I hope he was alone when he earned his reward. Stanskis 04:10, 12 July 2005 (UTC)

[edit] Other Issues

Out of curiosity, is "extinction event" really the standard biological terminology here? Anyone know where the phrase originated? --Ryguasu 22:31 Dec 2, 2002 (UTC)

Yes "extinction event" is what biologists and geologists use. I don't think there is any special story behind the origin of the term since scientists often speak of "events." --mav

---

Although many life forms may become extinct, this does not necessarily imply that all life ceases to exist…

This seems like an awfully weak statement. If I'm not mistaken, no recorded or even theorized extinction event has ever implied that "all life cease[d] to exist". Sure, it could happen, but even a man-made nuclear winter or other catastrophic climate change would probably leave quite a bit of life, even if it destroyed all of our favorite genera. Surely this could be rephrased more meaningfully. -- Jeff Q 04:07, 19 May 2004 (UTC)

I'd vote for it to be removed. The summaries of the extinctions should make this pretty clear. If there really is a need to note this type of sentiment, it should be something more describing the sheer impossibility of wiping out all forms of life, because of life's resilience and the variability already shown on Earth. Remove oxygen... anoxic forms will take over. Nuclear winter? Bacteria, many arthropods, and probably a great deal of deep sea or chemical-processing organisms will be just fine. Hell... blow up the entire planet, and odds are most bacteria will adapt. This comment only begins to address the problem with viewing everything from a megafaunal PoV. Baryonyx 04:25, Sep 28, 2004 (UTC)

[edit] Remove verneshot paragraph

I removed the following questionable material. Verneshot is more untested hypothesis or wild speculation than theory. Google search brings up some bizzare sites. Don't think it belongs here.

An even more recent theory, which is still being evaluated, is that periodic large scale vulcanism along continental rifts may include eruption events named verneshots which launch gigatonnes of rock into sub-orbital trajectories. The consequent impacts are expected to have very similar effects to asteroid impacts. This theory explains the periodicity of extinction events as well as the apparently coincidental occurrence of large-scale impacts and vulcanism for at least three of the extinction events without relying on coincidence in the way that the asteroid impact theory does.

Vsmith 15:03, 31 Dec 2004 (UTC)

If this has a good Reference, use it, and the item can stay in place. It's a long-shot theory to help balance peoples' views against the inevitability of the processes that we take for granted as right an proper - CO_{2, and all that. Stanskis 04:16, 12 July 2005 (UTC)}

[edit] We're missing one.

The Eocene Mass Extinction, about 36(?) million years ago. I don't know too many details, but I do know there was a drop in average temperature and a die-off of some mammal groups. Somebody who knows more could fill it in.--Rob117 03:48, 3 September 2005 (UTC)

Missing more than that (though the Eocene is minor on geological time scales). Raup and Sepkoski's Big 5 are End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous. To that one could easily add End Eocene, End Jurassic, End Middle Permian, End Silurian, Middle Carboniferous, Dresbachian (late Cambrian), and Botomanian (middle Cambrian). Depending on which author one chooses to cite there may be more than 20 discernable extinction "events" since the start of the Phanerozoic. Wiki's coverage of extinction events in general is just plain weak (not that I presently have the time to improve it). Dragons flight 05:13, September 3, 2005 (UTC)

Its weak...but you can't do anything about it. Thanks for stopping by. RealityCheck 06:23, 3 September 2005 (UTC)

[edit] Timeframes

I have seen various figures for how many years ago each event happened. There seems to be a rough margin of error of about 1 - 3%. And also, some events occured over a few million years, so I think there should be some way to clearly note this on the page. Phaldo December 12, 2005

[edit] Extinction events vs Mass extinctions

I agree with Phaldo that there should be a note in the article drawing attention to the margin of error for estimates of when extinction events occurred. In the External links section, The Sixth Extinction by Niles Eldredge (American Institute of Biological Sciences) puts the dates of the five previous mass extinctions at circa 65, 210, 245, 370 and 440 million years ago. The University of Hawaii's College of Natural Sciences says 65, 208, 245, 360 and 438 mya. A History of the Universe timeline on the University of California's website says 67, 205, 251, 370 and 440 mya. I've also seen a variety of alternative names for the most recent geologic periods. I think these discrepancies should be noted and explained. Non-specialist visitors might feel confused if the article seeks to establish one set of event dates and period/epoch names as difinitive when they've already seen alternative dates and names on other websites which they consider authoritative (universities, encyclopedias).

I found this article after a Google search for info on the five major mass extinctions. I was redirected from Wikipedia's superseded "Mass extinction" article. This article addresses Extinction events in general and includes a list of seven events. I feel there should be a specific section on the five major mass extinctions. I'm not well versed on the subject, which is why I resorted to Wikipedia for a quick summary. There are probably many non-scientists and highschool students who arrive at this article for the same reason.

I was trying to find reliable dates for the five major mass extinctions to include in a chart. I've included the current version of the chart, which I donated to Wikipedia. -- Bookish 12:40, 17 May 2006 (UTC)

[edit] Timeline graphic

I just removed Image:MassExtinctionTimeline.png from the article and restored the EasyTimeline version it had replaced. I figured I should elaborate on my reasoning. The EasyTimeline version is much easier to edit, the layout can be customized to different presentation formats (printed versions, for example, or link maps) with arbitrary resolution, and even as it currently stands it's more precice - the image version has a scale marked only at hundred million year intervals whereas the EasyTimeline is set to ten million year intervals. Bryan 07:24, 15 February 2006 (UTC)

[edit] Wilkes Land Crater

Added detail on recent report of putative P-T linked crater/mascon finding in Wilkes Land, Antarctica.

[edit] Extinction Theory Fallacy

The following text was inserted by 72.195.144.113 (talk • contribs). It is not suitable for a scientific discussion of extinction, but it is cogent and might be suitable for some philosophical or metaphysical article, so I am preserving it here in case anyone knows a suitable place for it. Dragons flight 04:31, 27 June 2006 (UTC)

==Extinction Theory Fallacy==

Certain geotheorists and vitalistic philosophers (vide Buffon, Lamarck, de Luc, Pareto, Sorel, Deleuze, et al) have elaborated theories of eternal life-sustainability or infinite life-resilience in the process of constructing a philosophical problematics of life on earth (vide geosophy). Many of these theories maintain a common speculative or propositional assertion or claim of faith that life in all its manifestations, stages, and permutations is a "permanent integer," an inexpugnable factor in the quanta that envelope, permeate, embody, and constitute all energy. All of these theories contend that all theories of species (as opposed to population) extinction constitute non-malicious fallacies based on the dependence in the biological sciences on empirical proofs of presence or being. These theorists contend that life in its individual instance leaves an eternel, inerradicable, energetic presence-print or residue on the dimensions of time and space, one which grants each cell and thus each creature eternal presence in time and space– essentially eternal life. Such a presence or life would of course not be entirely equatable or identical to the life of, for example, new-born animals, for the simple reason that new-born animals would not have passed through the psychic, systemic, and energetic "trauma" of physical disintegration known as death, but it would nevertheless constitute a continuation of individual presence, not to mention an envolving state of energetic existence, another phase of life. The process of energy utilization would be different in both cases, and this difference would result in post-thanatic (vide thanatos) life being largely removed from and invisible to pre-thanatic life, although it would leave the possibility, if perhaps not the probability, of pre-thanatic life's detection of post-thanatic beings.

A related theory holds that all animals (and one assumes plants) that ever existed from the earliest unicellular life form, to the dinosaurs, to the latest mutant strain of avian flu, continue to exist in some zone or area of the planet and will continue to do so (although perhaps in greatly diminished numbers) until the earth itself ceases to exist. This theory contends that once life assumes a certain form through the processes of evolutionary change that form will eternally abide as an inerradicable part of the biological diversity of the earth through the organism's own undefeatable processes of preservation either as cellular or mitochondrial memory in the body of another organism or by actually finding the most impenetrable enviromental niches permitting its continued survival as a living relic, in certain cases with a relic population consisting of two individuals, or simply a pregnant female or even just a hermaphroditic specimen.

[edit] List of doomsday scenarios

Could use votes to save this article, thanks MapleTree 22:26, 28 September 2006 (UTC)

[edit] Need to restructure set of pages about mass extinctions

I think the set of pages about mass extinctions needs to be restructured, and in particular detailed discussion of particular extinctions should be removed from the general "mass extinction" page:

• Before I recently edited it, the general "mass extinction page" presented just 1 theory for the P/T and K/T extinctions. i.e. it was not objective.
• Adding further theories about P/T and K/T has made the page too long but the analysis of causes is still superficial and not very objective.
• Meanwhile the page is unbalanced because there's no mention of causes of other extinctions.
• The length of the page and the space taken up by the causes pf particular extinctions squeezes out disussion of other topics and makes it difficult to add other mass extinctions.

Topics that should be added to the general "mass extinction page" include:

• The role of mass extinctions in evolution - competitive displacement of dominant groups appears to be rare and mass extinctions create openings for new or previously obscure groups of organisms. The P/T and K/t extinctions are spectacular examples of this.
• The role of extinctions in evolutionary theory - supporters of punctuated equilibrium place more emphasis on mass extinctions than gradualists do.
• The distinction between mass extinctions that change ecosystems and mass extinctions that simply kill a lot of species. I remember seeing a web page where a researcher argued that the late Devonian extinction(s) did not change the ecosystem. On the other hand the P/T and K/T extinctions did, even more in the seas than on land - before P/T 67% of known marine organisms were sessile, during the Mesozoic 50% were sessile, after K/T only 33% are sessile.
• The related concept of key species (I can't remember if that's the right term) - if a lot of key species die the ecosystem changes, otherwise there's a temporary reduction in species but the ecosystem remains much the same.
• The fact that the background extinction rate appears to have declined over time. Is this real or is it an artefact of e.g. fossilisation or how fossils are discovered?
• The difficulty of deciding whether an extinction was abrupt or gradual because of the Signor-Lipps effect. This is a large feature of debates about the K/T extinction.
• A list of all the proposed mass extinctions, including those whose status is under debate. This provides an opportunity to link to pages about each one, and to invite contributions for those which have no detail pages. One good example is the late Pre-Cambrian extinction which killed off the Ediacaran biota (this one is important for both the history and the theory of evolution - see for example Gould's Wonderful Life).
• A list of hypothetical mass extinctions, i.e. those where we can see adequate causes but have little / no paleontological evidence. For example the O2 extinction and the extinction(s) likely to have been caused by the supercontinent Rodinia.

I also suggest that the "Marine genus diversity" diagram should be reversed - I've seen many presentations with time runing left to right and no other ones with time running right to left, and I think Wikipedia runs the risk of confusing readers if it remains the odd one out. Philcha 07:50, 6 October 2006 (UTC)

I agree, the text you added is much too long and the detail should appear in the specific articles, not here. I do think however, that is there is a leading cause (or causes) then it should be mentioned here, but all the details about what effect it would have or argument about different explanations should be at the subpage not here. Dragons flight 18:27, 6 October 2006 (UTC)

[edit] Discussion on end of civilization

Editors input would be appreciated at Talk:End_of_civilization. There seems to be some disagreement what the end of civilization actually means. nirvana2013 17:44, 10 November 2006 (UTC)