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Author | Topic: fossilization processes | |||||||||||||||||||||||
NosyNed Member Posts: 9004 From: Canada Joined: |
The science here is called taphonomy. Google that and search here and you will find a lot.
Generally, I think the "mini-catastrophes" is correct. Even bones don't last long in the open so it requires something special to preserve something long enough to fossilize.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Randman, you gave specific quantities for the numbers of fossils that should be found.
You have been asked to show your development of those numbers or retract them. Do you have time yet?
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NosyNed Member Posts: 9004 From: Canada Joined: |
Let's see if we can make some estimates on how complete the fossil record might be:
from : Canadian Biodiversty: Species There are currently about 4,500 mammal species alive today. Let's assume a species "lives" for an average of 5 Myrs (I read it somewhere -pick another number if you don't like it). That suggests that since the end of the cretaceous and the "age of mammals" starting we should have had about (65/5) * 4500 = 58,000 separate mammal species. Subtract 4500 for the current ones gives 53,500 extinct species. Now the question is how many have we found? That is a harder answer to track down. You suggested the answer should be 90% or 48,000. I suggest that you are off by about an order of magnitude. I'm not at all sure of how to prove that though.
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NosyNed Member Posts: 9004 From: Canada Joined: |
from: http://www.madsci.org/.../archives/aug97/871343510.Ev.r.html
Of the 100,000,000 extinct animal species, only around 100,000 species have been discovered and described. That means that only around 1/10 of 1% of all animal species that have ever lived have been discovered! (And remember that each species may be represented by hundreds of millions of individuals.) I don't know where they get the underlying numbers but this is a start. Of course, species that are larger, lived later etc. are more likely to be preserved I would guess.
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NosyNed Member Posts: 9004 From: Canada Joined: |
I did? In what why? All I am working with is that there were very different forms of mammals around at different times in the past? I didn't say how they got there or changed in the next snapshot. Do you have a problem with that?
That's comparing observed species with observed fossils. That, imo, is real science. That is strongly biased in two ways:1) more recent species will have some recent remains thus biasing the sample to show a larger percentage. 2) it may be that NONE of the samples are fossils that could be expected to survive even centuries talk about millionso of years thus biasing the answer to very low percentage of preservation. Since it is clear that there have been totally different forms of life at different times we must use an estimating technique that allows us to consider the time frames and conditions.
My guess is that with such strong evidence, based on statements of fossils found of all whale families, if not all whale species, well-represented in the fossil record, that fossilization per mammal family at least is not that rare, and occurs at such a rate that we are likely to have seen all mammal families represented, or most, and that we even find multiple examples of each. now you are guessing and working with families. Does that mean your previously supplied numbers are in the dust bin? I agree that the whole thing is interesting. We should continue to try to dig up what we can find. This message has been edited by NosyNed, 08-07-2005 10:42 PM
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NosyNed Member Posts: 9004 From: Canada Joined: |
I suppose the question is do their bones sink, as the article suggests, and does the carcass sink intact regularly. If so, then we really ought to be able to find just about every theorized step in whale evolution, imo, since semi-aquatic and aquatic species should create an abundance of fossils. You are making what may be unwarrented assumptions about preservation rates here. The relative rate for aquatic and semi aquatic may be high but the rate for dry land based forms is dammed near zero. This means the aquatic rate doesn't have to be that high. Simply stating that is is high means zip. We need to dig a bit more to see what evidence there is. I await your reasoning for why the 0.1 % number is not a good place to start working. This message has been edited by NosyNed, 08-07-2005 10:56 PM
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NosyNed Member Posts: 9004 From: Canada Joined: |
It appeared to me you were starting with a number of species not based on observed species, but on an assumption based on how many species there should be, including most which are not observed. LOL, , of course! Do you miss the whole point of the collecter's curve. We are sampling something with an unknown number of different items. We are attempting to estimate the nature of the population from that. There have been, so far, a couple of ways of getting there presented here. One is the collector's curve and the other is based on assuming biological diversity something like todays. The collector's curve has yet to be shown to be applied to any fossils that we have discussed yet. You have just shown the basic concept. Someone already noted that for dinosaur's the collector's curve says we are still a long way from finding most of the samples. Since almost all whale-thingies have been found in the last decade or two it appears we are also a long way from the flat part of that curve too. But then we don't have numbers so we are just guessing on that. For most people it isn't very interesting -- they are much more interested in finding the next exciting specimen than worrying about how many their are left. You have been making your own assumptions about how many species there "should be" from post 1. Why do you object to trying to come to as reasonable estimate as possible instead of just guessing -- which is all you have been doing so far? Got a better way of arriving somewhere?
Except that the most recent species have had less time to fossilize. So that may off-set the effect of erosion in balancing out more recent fossils with older fossils. I don't understand this. Care to explain more fully? You didn't answer the pair of my points just sort of this one. As I noted the very most recent remains will almost all not be "fossils" at all. So there are none that are recent. But we then have to define what the heck we mean by "fossil" for that to make sense.
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NosyNed Member Posts: 9004 From: Canada Joined: |
You are confused. The curve should be built from real numbers, comparing actual numbers of fossils found with the number of new species found. The idea is there is a law of diminishing returns, that with more and more new fossils we find less and less, eventually, new species. I'm sorry I was a bit unclear. There are two different things being discussed. The estimates from biodiversity are not numbers to be put in to the collector's curve. They are separate ways of attempting to arrive at an estimate of the number of species left to be found.
Moreover, since you have no problem estimating the number of species it toto, why could you not estimate the number of transitionals needed to evolve a whale from a land mammal? Why avoid totally that question? I have, based on your rough idea of what each step would be agreed that something like 1,000's isn't too bad a number. However, any such estimate is very dodgey at best. It is entirely possible that two or 3 changes occured together in one population so it isn't clear if we call those 1 step (only one 'speciation') or 3. Some of the changes are simply "more of". That is, when a limb is being used as a paddle it may become more paddle-like in very, very small steps. These may spread through a population rapidly or slowly. The population with slightly longer paddles may be able to interbreed (in fact are pretty much sure to be able to interbreed) with those with shorter. There has been no speciation yet. The long paddle form may dominate or be 100% in the population but still there has been no barrier to interbreeding (if the others were still around). The same can be said for many of the changes needed. (blow hole position, backbone flexibility, rib arrangement, ear structure and so on). You are asking questions which don't seem to be very sensible with any understanding of the processes involved. That is one reason why there is not firm number. It is also, for reasons given, not an number that you can be sure of pining down with any certainty. What we do know from taphonomy is that very, very few individuals fossilize (none if they live in a habitate that is really hard on bones -- like rain forests). We also know that some land forms have been eroded to sand and dust -- including any fossils in them. In other words there are a ton of good reasons for expecting fossilization to be rare. So far you haven't given any good reasons (and no numbers) as to why it should be otherwise.
On younger species, presumably the current number of species have an lived on average, at best considering the extinction and depopulation rate due to man particularly with whale hunting, only half of their "normal" geologic time as a species on earth. ... So even if some species are far older, they will in general have lived out their complete geologic time on the earth. So let's say we estimate due to erosion, etc,...that fossils from 120 million to 30 million years ago have been reduced in half via erosion, but had on average twice the life-span of species from 30 million to the present. Is that reasonable? If that was the case, then we should expect equal numbers of fossils for ancient pre-whales that we would expect for the crop of current whales. Right? I don't get this? I need more detail of what you are getting at. The comment about man's effect is irrelevant I think. The major impact on whales is only over the last century. I don't see how it ties in?
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NosyNed Member Posts: 9004 From: Canada Joined: |
I'll do some work on backing it up when you have caught up with backing up your 90% for whales. My opinion there is based on the bit of reading in taphonomy that I have done (not a lot). Also others have pointed out to you that we have examples in bison and the passenger pigeon where millions and even billions of individuals left very few (1,000's for bison toward zero for passenger pigeons).
I did read, quickly, your reference but can't find it right now. Could you both re suppy it and show how you got from specific items in it to 90% please. I am pretty darn sure that you number is a guess with no back up of any kind but I'm waiting to see otherwise.
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NosyNed Member Posts: 9004 From: Canada Joined: |
It appears that this is telling us something useful. I'd interpret it as saying that we have found all the species that we are going to find not that we have found all the species that every were. Which is their interpretation too.
So how does this help us arrive at the number of species that were there? It seems it doesn't help with that.
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NosyNed Member Posts: 9004 From: Canada Joined: |
I'm prepared to change views when shown something that requires that.
I think you are saying that there are a lot of missing whale fossils -- if whale evolution occured as hypothosized --- and that there should be many more of those fossils there. I think that there are a lot of gaps with fossils missing and I think that it is not surprising that they have not (and maybe won't be ) been found. If you can convince me that they should be there then I would have to wonder why they are missing. One possibility is that the evolution of whales did not take place as hypothosized. I would then be interested in how you do think that modern whales arose.
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NosyNed Member Posts: 9004 From: Canada Joined: |
...relatively common fossils ... The above is all I see as input information. You then move this to:
We should see about the same percentage of these transitional semi-aquatic and land mammal fossils that we do see of whales. Why? Unless you think the transition took place multiple times we would expect the founder population to be much smaller than the diverged populations some 10's of millions of year later.
problem finding an abundance of whale fossils of existing species and species in the same family How did you get from "relatively common" to "an abundance". We are supposed to be looking at numbers and you haven't found any numeric values yet.
But we don't have massive numbers of the transitionals? Now it has gone from an abundance to "massive". How did you getthere? Note that you are jumping around between species and families. That is careless too. It is much easier to represent a family than each species in it. You're not being intellectually honest here.
but it seems like whales and fish would most likely have similar aspects of fossilization. If that is true, then we should have found a corresponding percentage of whale fossils that we find of land mammals, particularly the land mammals that evolved into whales. Even if that were true, and there are obvious reasons for thinking it is not, what percentage of fish are fossilized? The article itself comments on reasons for different levels of fossilization. What this article is telling us is that the diversity of different groups appears to be reasonably well representated. That our older understanding of the nature of the evolutionary pathways was pretty good and that what we have now is enough to suggest there will not be any surprises in the future. As far as whales go you don't have enough information of any kind to draw conclusions yet. In fact you have darned little information at all.
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NosyNed Member Posts: 9004 From: Canada Joined: |
If the transition were one or 2 speciation events, or let's say families of species arising, you might have a point, but the differences between land mammal and whales would suggest numerous such events, imo, hundreds, and each new family of species would undoubtedly be evolving, according to ToE, into different branches, etc,... As noted several times but you have ignored there may well be NO speciaion "events" involved. Zero, zip, nada and none you have not discussed that further and don't seem to have read the discussions on that issue. In the few snapshots we have there is no suggestion that I see that there had to be any clearly deliminated "events". We have never defined event carefully. I am useing the word the way you have previously. Many of the early changes needed to get to fully or nearly fully aquatic may have happened in a small, localized population (and for changes to fix in a population we know that there must be significant selective pressure and/or smaller populations). Now to get this back on topic (fossilization). If there has been a smallish (1,000's of individuals), localized (one area and niche in the world) population that has undergone evolutionary change with no sudden (less than 100's of generations) speciation "events" then we will not have as many potential individuals to fossilize as you seem to think. In addition, I just realize, you have been mixing two very different numbers (or we all have): one is the number of fossils that should have been formed the other the number that we should have found. They are very, very far from the same thing. The number of fossils formed and intact depends on things like the number of individuals that every exisited, the type of environment they lived in, the extent of their geographic spread and what has happened geologically since they would have been laid down. The number found depends on how much effort has been expended and the geologic changes that have happened (to expose or not expose the sediments for example). You have not yet developed anything like a reasonable numberical estimate of what we should expect to find.
So there is no reason to think the "founder species" would be smaller than the current group of whale species since in reality, there would be dozens if not hundreds of families of species needed to arise in order to create the transition, and there is absolutely no reason to assume they would all be small, and a good bit of reason to think they should have thrived long enough to continue to evolve, and in so doing have created far larger numbers than the species of whales we see today. This does not follow. What stops several of the changes needed to make the transition happening in one small population, in one area together. That is, as has already been noted to you, you can change the location of the nostril, have a more flexibile backbone, make feet more paddle like, reduce the external ear all within individuals in one population at about the same time. This could all happen with one or a few species extant at anyone time without specific speciation events occuring just a gradual change in a population over time.
It takes many dead-ends presumably of transitionals that go extinct in leading to a form existing today. I don't see how this follows.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Message 14
Is the reply since it is off topic in this thread. Please do not ignore it I have given you a warning about using QM mumbo-jumbo there which is both off topic and nonsense.
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