Here is a question:
Is it common for biologists to believe in a “last universal common ancestor”? Is the general view that abiogenesis occured only once and life progressed from there, or that it possibly occured many many times? Did this “LUCA” look more or less like modern bacteria, i.e. did it have a genetic code?
I more or less understand (in the most basic sense of the word) the usual explanation of moves from replicating polymers to prebiotics to bacteria. It sort of blurs the line defining what “life” is, but it seems people agree the bacteria is where life started.
This post seems a little garbled to me…sorry about that. I guess I am trying to better define the origin of life.
That’s a great question and, AFAIK, the answer is yes, it happened only once. No life that I know of has been found that could be shown to not be related to other life. I think this has some interesting implications wrt ET life. If it happend on Earth only once it might be pretty rare, indeed. Or perhaps it did happen more than once, and only one “strain” did not go extinct a long time ago.
This is more of an ill-defined claim than a falsifiable one. The theory of evolution challenged the essentialism of “species/kind” and effectively exploded it. Abiogenesis suggests that the same may be said for life. That is, there is no reason to think that life has a distinct “minimal form” before which is non-life. There is no bright line between life and non-life.
As Darwin pointed out, this is a falsification of abiogenesis, not a grounds falisfication of ID. It has nothing, per se, to do with ID.
Abiogenesis, not evolution.
I agree. That is why no one thinks abiogenesis is a proven theory. In fact, most people suggest that it can never be historically supported the way evolution can, because the best we can do is come up with some possible mechanisms that make sense with as much as we know about the early conditions. We will probably never be able to prove that it actually happened that way in history.
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If I am postulating an intelligent designer that created the universe and the laws that govern it, it isn’t a stretch at all to say it also created life originally in a complex form. I admit that I cannot describe the mechanism, primarily because it is by definition supernatural.
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If I postulate a magical “I’m always right” device, I can be right, always. I can’t explain how it works, but it does explain why I’m always right.
In other words: postulate all you want. But don’t pretend you’re playing the game of science. If you want to just postulate things, I assure you we can have a lot more fun than just intelligent designers.
That may be. All we can say is that we have to continue looking for mechanisms, learning more about the world.
Standard abiogenesis explanation (there actually ISN’T one standard: there are many proposed theories). And maybe some or all will be precluded. I don’t see how that would be a victory for ID, however. It’s hard to feel sympathy for people who would crow at the failure of some people’s efforts in an extremely difficult field when they themselves haven’t even taken the first steps.
I agree with the concepts of evolution, and other concepts like speciation and natural selection that run hand in hand with evolution, only not to the same degree that scientists do.
They don’t agree with me, but rather I agree with them.
What is wrong with you? We are always in contact with the physical envirnment, and therfore a better skeletal structure will allow us to better interact with our physical envrionment. About vestigal structures and whatnot: they are either mutations of some sort that are not commonplace or structures still on their way out.
Well there are ancient whale-like creatures that used a hip bone. Prehaps the way those animals propeled themselves through the water was the very efficient, and so they were loosing to/evolved to be more like whales with a skeletal structure closer to the whales we see today. The hip-bone we see in modern whales is useless, but it does not harm the whale in any way. That combined with the fact that whales are k-stragists with relativly long lifespans means that it’s taking quite a while for the hip-bone to leave.
I think that is true. Just about all fish are similar in structure.
Again, while the use of a whale fin may be different than the use of a human hand, the fact remains the same that the skeletal design provides for a very efficient device. Also, because the function of a hand is different from the function of the fin, you get minor differences.
As for the other animals you mentioned: sometimes you have strange genetic mutatiosn, some structures are evolving their way into the organism, some structures are evolving their way out.
Fair enough.
Listen, someone asked me a question “If not because of common ansectory, then what?” and I answered. Sure, the physical envronment isn’t everything, but that wasn’t the focus.
I also have enjoyed my participation in this thread. My approach is usually an attempt at a laymens regurgitation of my understanding of a specific and/or complex idea. It is often a lacking approach but I can’t help but pipe up.
I can completely see the difficulties in applying evolutionary theory to abiogenesis, but I cannot help but think that there must be key similarities.
What are the current thoughts as to at what point abiogenesis ended and evolution began? Is one possibility a period of oozing back and forth between the two? Rudimentary life combining and recombining in and out of “live” existance within the primordial soup?
“Well there are ancient whale-like creatures that used a hip bone. Prehaps the way those animals propeled themselves through the water was the very efficient, and so they were loosing to/evolved to be more like whales with a skeletal structure closer to the whales we see today.”
Yes, that’s exactly it. Now go further back in time when the hip bone was used even more. Go further back in time and the animal had leds that actually worked OK on land, but not too well. Go back further…
Well I just lost a nice sized post so here is a retype.
To recap, I understand the difference in abiogenesis and evolution better thanks to Apos and Diogenes. Why is it called “Abiogenesis”? Wouldn’t that mean “without beginning of life”?
I don’t like to think of IDers attacking science. I will be the first to admit that the position has little it can do in the way of verification, but I think there is some parity.
When something unexplained comes up, and IDer will attribute it to the “magical ‘I’m always right’” device. A scientist will say it is simply a natural phenomena that we do not yet understand. The scientist basically has the advantage of being able to search for the natural phenomena and thus discredit the ID position. The ID position seems to be necessarily reactionary.
I’d like to think that IDers help keep science accountable and rigorous. If a biologist floats a bad theory and IDers help to show that it is bad, I think science is better off for it. Personally, I’d like us to understand the world and the way it works as well as possible, and I greatly admire the scientists who work toward that end.
Here is a hypothetical (repeat hypothetical): What would you (as in anyone interested in responding) think if complex life (bacteria) could be found to have existed immediately after earth left its molten state (or as soon as the ocean’s formed if you like)? Is there any point in time when you would no longer attribute it to natural processes?
And a few other questions that have not yet been answered: Am I right when I say we cannot extract any information about the genetic code from fossils? Do you believe in a single common ancestor and if so did it have a genetic code (more or less like we have today)?
A fossil is usually an impression in a material that, through various processes - that is, luck - was preserved, or a fossil can be an organism that was trapped in a similar way where the organic material later rotted away leaving just the impression. You can’t get genetic material from an imprint. On the other hand, in certain cases tissue samples, bones, pieces of skin are preserved, and you can sometimes get the information from those. Cecil discussed this in the column about dinosaur color. http://www.straightdope.com/classics/a1_010.html
“Abiogenesis” is the the development of living organisms from non-living matter. “Biogenesis” is the generation of organisms from other living organisms.
I’m not sure what it means: but that might actually be appropriate. Most theories of this sort make it clear that there is no bright line between life and unlife, and no distinct beginning.
That’s true, but remember that there is nothing special about ID itself in this respect: you don’t need to have an alternative, unfalsifiable pet theory to criticize an existing one.
Indeed, as critics, ID proponents have tended to do so in a very unhelpful way. They commonly make their case directly to a public audience prior to trying to float any evidence among the scientific community. In effect, they attempt to bypass the usual pathways by which claims are subjected to criticism, and present as knowledge, or convincing refuations of claims, ideas that have not been submitted for peer review and checked over by everyone else in the relevant fields. And the result is quite a number of sloppy and highly misleading claims that are very easy to convince the public of, but which turn out to be ridiculous when considered by experts in the relevant fields.
The truly silly thing about this is that criticism of ideas, claims, and theories of evolution happens all the time. ID proponents could almost certainly make more headway if they simply stuck to criticism of ideas without trying to then go and draw grand, utterly unsupported ad hoc conclusions. You aren’t going to find many articles in reputable journals of biology that discuss the problems with the current view of some obscure mechanism dealing with flagella or whatever… and then conclude “thus suggesting that god doesn’t exist.”
But these sorts of things happen all the time in the ID community: some tiny matter, where we can’t seem to figure out how a particular mechanism could have evolved, becomes grounds for asserting the existence of a being far more amazing an inexplicable than anything else that we’ve been trying to explain. Those just aren’t the sizes of steps it makes any sense to take in science without incredible amounts of evidence and solid theories.
I didn’t really make this clear in my previous comment, but I am not a “naturalist.” That is, I don’t see what sense it makes to delineate the unknown into “natural processes which we don’t yet know or understand, and supernatural processes.” To even label something a natural implies that we know what lies within the set of “natural” things and what doesn’t. But we don’t know what lies in the set of “natural” things. Indeed, I’ve never even heard a good account of what distinguishes the set from all other members or sets, if there are any. So I don’t even use the concept “natural processes” to describe anything other than the distinction between things intelligent do, and those they don’t do, and I rarely do even that.
That’s in part because “supernatural” is a non-concept, in my opinion. We can’t say what it is, only what it is not: which doesn’t bode at all well for it as a concept. How can we even talk about it? It seems a pointless distinction, because no one can even specify on WHAT it is that we are drawing the distinction.
Either something exists, or it doesn’t. Either something has an explanation, or it doesn’t. Maybe that explanation is an intelligent designer that is able to operate outside of the normal regularities of the universe. But if so, then that is an explanation, and I’m not sure what the distinction “natural” vs. “supernatural” gets us unless it is very very specifically construed. Especially since, once you are allowed to break all the rules, anything goes anyway. Given that, it makes quite a lot of sense that, if we can’t explain something, science asks us to leave it at that until we really can.
So I don’t really care much at all about the naturalism or supernaturalism of processes, because neither of those distinctions seem to tell me anything about the processes at all. And I want to know the processes.
Like I said, our more solid range of knowledge pretty much ends at “there were some bacteria back then that seemed to be very similar to each other, and could plausibly be said to have all come from a common few or one” After that, we really can’t say. We can’t say if there were other lines of bacteria that died out, other lines of pre-bacteria early life or even if the bacteria we found are even of the same line that presumably are the closest line to present life. We can outline some possible mechanisms, but we can’t establish for certain any particular line as “the” historical chain of events. Even if we discover a way to create early organic life/non-life precursors, or life, or whatever: even under the exact conditions we determine were present in the early earth, it will never prove conclusively that this is what actually happened. It could have been aliens. It could have been gods. It could have been a mindless slot-machine that seeds the universe with life just because that’s the way things work. We can’t ever rule out such things, because it is very very unlikely that we’re going to find a complete-enough fossilized map of the development of early life.
Thank you for the lengthy post Apos. I think I finally understand your position on the whole “supernatural” thing and understand your hang ups with my off the cuff “soul” statement in the creationism thread.
I think it is fair to say that we can’t be certain of anything. I don’t think science ever asks us to. We can be confident in some statement as being true though (on the 95% level or whatever). If we found geological evidence of prebiotic soup conditions on early earth and further evidence of prebiotic molecules and such, I’d be 95% confident that abiogenesis occured (through whichever process fit the observations).
I think you are correct that some, even many, IDers go about criticizing science the wrong way. I have been to southern school board meetings that devolved into shouting matches between the local university’s biology faculty and young earth fundamentalists. It is my opinion that the biologists became hardened early on from defending themselves against constant attack from creationist zealots and now are less likely to take seriously more scientific critiques coming from an IDer (no matter the IDer’s scientific background). I think that it is unfortunate that they have to spend a lot of time fighting off the less scientific, more emotional attacks.
Thanks to Diogenes and tomndebb for the origin of “abiogenesis.” That makes perfect sense.
Of course you would. All I see is the same old stuff we always get from IDists: the God of the Gaps. And the problem is, I’ve already explained that you don’t even have a Gap to sneak God into.
“Powerful evidence that an intelligent force was behind the formation of that code” would consist of somebody for once formulating ID as a detailed hypothesis which makes detailed predictions, instead of just the argument from ignorance.
So: what is your hypothesis, and what testable predictions does it make? How does it explain the evidence better than evolution does?
You yourself have now said several times that the current code is optimal or almost optimal. Guess what? “Almost optimal” is “suboptimal.”
I think I’ve already answered all your questions in my original post. Mainstream science has already shown that the current optimality of the code is the natural result of how the code developed to accomodate new amino acids. If your cite doesn’t mention that, then they’re not telling you the whole story. Since their bibliography cites the current literature, one could legitimately wonder whether the omission is accidental.
If you want more background on the origin of the genetic code, search for one of the earlier threads in which I posted my abiogenesis FAQ.
I don’t doubt that there are a fair number of things wrong with me, but they don’t hold much relevance to the current discussion…
Accepting, as you have claimed, natural selection, you must be aware the NS can only operate on phenotypes - that is, only those traits which actually can be “seen” by selection can be, well, selected. Vestigial traits, almost by definition, fall outside the purview of selection. Thus, the hip bones of whales cannot be explained by selection (and resulting adaptation) alone.
If those hipbones are “on their way out” (which, of course, is what current evolutionary theory predicts), then there must have been a point where they were “in”. And, indeed, we see these points in fossils of organisms which share many similarities with whales, but also possess more robust hind limbs, with associated pelvic girdles. If organism B has traits possessed by both A and C, why shouldn’t we conclude that B is something of an intermediate form between A and C?
Similarly, with respect to the digit bones of whales: typical “fish” fins are supported by numerous small structures known as either ceratotrichia, lepidotrichia, or actinotrichia, depending on the particular fish. These are typically made of keratin or dermal scales. Whale fins, however, have true bones, with digits similar to those of humans and other mammals. Again, if these two groups - whales and fish - live in the same environment, and their bodies are molded solely by the selective forces of those environments, then we should see the same structures in each group. But we don’t. Mere mutation is insufficient to explain their origins, since that only introduces the question of why we don’t see mutations of, say, ceratotrichia in whales, or boney fins in other fish.
The fact that they are k-strategists has little relevance here, as the distinction between k-selection and r-selection is only relevant with respect to reproductive effort and the care (or lack thereof) of offspring. It tells us nothing about how any particular trait came about.
As for your first couple of sentences there, well, as John Mace points out, that’s exactly what we’ve been saying. Early proto-whales had hind limbs, thus had hip bones. As selection operated on the ensuing generations, and they became subsequently more obligately aquatic, the need for those hind limbs decreased. Granted, the topic of degeneration (the gradual loss of structures, as opposed to their gain) is more complicated than that, but the general idea is that earlier relatives had them, and their descendants lost them over time.
However, whales are not fish. They may have the same streamlining, but are very different in many other ways. Not only in skeletal structure, but overall anatomy and physiology as well. Again, similar environments only allow for so much explanation with respect to convergence. The rest is explained through history.
I agree. But, if you reject the idea that humans and whales are even related, how can you argue for any similarity at all? One would rightly expect them to be very different, not have minor differences.
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And, again, the “evolving their way in” and “evolving their way out” points directly to an ancestor-descendant relationship between these various organisms. Birds still have the genes to make teeth and claws because they descended from other organisms which had teeth and claws: theropod dinosaurs. Whales still have hipbones because they descended from organisms which had hips and hind limbs.
But that did seem to be the focus of your “then what?” response. The point is that if you take organisms out of a historical framework which extends beyond a few generations of “simple” adaptation, many structures fail to make sense within that framework. The added layer of “deep time”, coupled with common descent of multiply-branching lineages provides a logical explanation for such structures.
You claim that you essentially accept evolution via natural seelction, yet rule out common descent. This seems to imply a belief in created “kinds”. Yet, by accepting that these kinds are not static entities - they can be changed through natural selection - the possibility exists that the kinds themselves may be divergent forms from a smaller set of kinds in the past. And so on, until you reach that “common ancestor”. Common descent follows logically from the evolution you accept.
Can you offer any evidence for either of these, other than the argument from ignorance? You can start by proving that a simple system of self-replicating RNAs can’t exist.
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“Well, Mr. Franklin, I refuse to believe this nonsense about electricity. Unless you can provide me with everything people will know about electrons in the 20th century, I’m going to have to assume that lightning is the magical weapon of a vengeful God. Are my demands for evidence really so unreasonable?”
Come on, Tertius. I’ve already given you some of the evidence for abiogenesis. If you read my FAQ, you’ll see even more. You’re being like the creationists who demand an IMAX film of the entire history of life up to the present day before they’ll believe in evolution.
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Sure, it’s a stretch, because you have to ignore all the evidence for the RNA world- not to mention the fact that we’re closing in on a self-replicating ribozyme. (Via in-vitro evolution, BTW.)
Plus, if you’re going to postulate an intelligent designer, why stop there? Why not believe in 6-day, young earth creationism? Or in geocentrism? Or in gravity fairies?
If your auto mechanic told you that the problems with your car were caused by gremlins, and that he therefore was unable to fix your car (primarily because gremlins are by definition supernatural,) what would your response be? Hail him as a genius? Or demand your money back?
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Yes, we do. We don’t have fossils in rocks, but we have molecular fossils. One example is all the evidence for the RNA world. For starters:
the centrality of RNA in the protein synthesis machinery
the existence of ribozymes
further RNA fossils in the recurring use of adenosine as a molecular handle (nicotinamide, ATP, etc.) and of GTP as a regulatory molecule (G proteins.)
everything I said about the genetic code in my previous post
Tertius, have you read anything about the mainstream scientific view on these matters from anyone but the opponents of mainstream science?
To answer your earlier question, Tertius, it’s hard to talk about how many times abiogenesis took place, because the dividing line is so fuzzy. I imagine there’s no reason several self-replicating RNA systems couldn’t have come about, although who knows how far they would have gotten before being eaten by others that were further along?
What’s clear is that there was, in fact, a last common ancestor. Some sort of bottleneck took place to prune away either all but one species, or all but one taxon. (you could envision the latter possibility as “Noah and his wife weren’t on the ark, but all of their grandchildren- and no one else- were.”) The reason I say this is mostly because the genetic code is pretty uniform, and the few changes we see (in mitochondrial codes) clearly fit into a taxonomic tree which only diverged later on.
One can conclude, then, that the last common ancestor had a functioning set of protein synthesis machinery. I would hesitate to speculate about whether it resembled modern bacteria. At that point in time, the cell membrane might have been pretty funky, given the big, big differences between the membranes of archaea, on the one hand, and everything else on the other hand.
What I don’t understand is why some people seem to believe you cannot believe in God and accept evolution. My awareness of the complexity of the process which had evolution produce the me, th crab apple tree outside my window, and the bees who’ll be pollinating it enhances my faith in God and my wonder, rather than detracting from it. Dostromin, if you could help out with this, too, I’d appreciate it.
I wasn’t trying to say that inferences aren’t science, but rather just note that we will probably never have the same sort of certainty for a particular theory of abiogenesis as we can have for things like common descent or mechanisms for evolution. The reason is that we lack historical evidence, and are left only with inference and plausibility.
I agree: some biologists are very touchy: perhaps too touchy, because of people like YEC. However, that doesn’t resolve the problem with ID proponents making grand unsupported claims, and taking them directly to the public in much the same way creationists did and do. So the similarity made is not exactly a mistake, especially since a lot of the major ID faces are very familiar people. Many of them aren’t even biologists: one of the most popular, Phillip Johnson, is a lawyer. So it’s no surprise that many people see the ID movement as just the latest incarnation of creationism, specially designed to try and get creationism back into science classrooms, or evolution out.
