Lions are competing with zebras to survive. Lions evolve to become more efficient hunters and zebras evolve to become better survivors. This is what drove the Cambrian explosion. It was the result of an arms race between the predators and the prey.
Nonsense. Evolution is driven by variation not by natural selection. Natural selection is only a filter so it cannot drive anything. Thus it makes much more sense that the Cambrian explosion was driven by a new source of variation. That must always be the source of an explosive increase in species and changes. In this case, the new source of variation was at one level the development of multi-cellular organisms and all the new possibilities this opened up. However, I strongly suspect that this development itself was the result of a more fundamental increase in genetic variation in the cellular process of sexual reproduction – some mechanism like chromosomal crossover.
There are several proposed triggers for the Cambrian explosion but one of them was the development of predation. Animals developed skeletons for protection and vision, simple eye spots, to detect the approach of predators. Before the explosion animals were soft bodied and fed on bacteria mats. There are also marked changes in the behavior of the animals.
Note: I am not saying that natural selection drove these changes. Animals that could escape a predator survived and animals that could catch a meal also survived.
It an unsupportable hypothesis since predation was around for at least a billion years, 460 million years before the Cambrian explosion. The appearance of multi-cellular organisms is closer to the Cambrian explosion by 400 million years and thus close enough to be within the error limits of these time estimates. But even if the multicellularity preceded the Cambrian explosion by 60 million years, that just tells us that it is a different source of variation (opportunistic or genetic) which is the cause of this explosive increase of variation in form and species.
Frankly I think this predation idea/hypothesis was concocted by those with an ideological agenda to emphasize the so called “survival of the fittest” aspect of evolution because it justifies the very worst of philosophical trends such as social Darwinism and eugenics. Thus this nonsense about society’s protection of the weak standing in the way of human evolution. The very opposite is the case. The protection of the weak by the cooperative community accelerates evolution by introducing an increase in variation. In the case of human evolution, everyone no longer has to be a Daniel Boone – self sufficient survialist. Instead the human community has become our new survival environment supporting all the developments of technology requiring people in specialized roles with specialized abilities (just like the development of multicellular organisms).
Starting to sound like the YEC folk who argue in a similar fashion.
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Let’s take that as a hypothesis. What kind of evidence would it take to support or refute this hypothesis?
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I have given you the opportunity to demonstrate how your understanding of evolution is batter than mine with an actual example, dinosaurs to birds. You have ignored this opportunity, but rather raised a series of unfounded charges.
You are right in that ecological natural selection is not the same as conflict survival of the fittest selection. It is much better than Darwin and Dawkins’ Selfish Gene.
I have never denied the role of genes in the process of Variation as Dawkins has denied the role of ecology, which is the reason your criticism of my view makes no sense. .
If the lions were able to wipe out the zebras, what would be the benefit? If zebras survived 100%, what would be the benefit?
Predation is part of an interdependent ecological adaptation that benefits all if it is appropriate to the environment. Lions and zebras cannot live in Australia.
Evolution needs both Variation and Natural Selection. Variation which does not meet an ecological need is selected out. Changes in the ecology create changes in ecological needs. Life forms have changed as the surface of the earth has changed.
We can readily observe this when we see how climate change made most of the dinosaurs go extinct and led others to be transformed into birds. Therefore we can see that changes in the ecology have driven changes in alleles that have been transformed by ecological changes. .
No that comment wasn’t the argument I gave. Frankly it is the way you ignored the evidence I gave and jumped on that comment instead that sounds like so much like the YEC folk.
What kind of evidence would you like? Shall we run evolution experience on Drosophila comparing those where we inhibit chromosomal crossover? But tell me… Why would we doubt that a source of genetic variation produces greater evolutionary variation any more than we would doubt 1+1 = 2 enough to run experiments on that as if we expect that putting one jelly bean in an empty bowl and then another is ever going to give us a bowl with other than two jelly beans?
But the real problem here is that adding a filter like natural selection can never increase variation. How about a jelly bean experiment that puts a filter through which you pour jelly beans? Will you ever expect more jelly beans rather than less to end up in the bowl. Why isn’t the simple indisputable logic not enough in this case? Now… changing the filter to something less restrictive and increasing survival would increase the numbers like I explain below…
Actually no, it doesn’t. That is wrong. With variation alone you will get a branching tree. The addition of natural selection only means that some of the branches are cut.
Correct! Not all sources of variation are equal. For very simple organisms radiation might be an effective source of variation but for more complex organisms you need something considerably less random. And yes, changes in the environment/ecology can boost the process by making some variations beneficial where they were not so before. That is what I called opportunistic sources of variation, like the example of the human community protecting the weaker members meaning that we don’t all have to be Daniel Boone survivalists. But all of this assumes that the basic genetic sources of variation are already there, for without that there is no evolution whatsoever.
That’s pretty much up to the one proposing the hypothesis.
I don’t see how that would address the hypothesis in question.
Because evolution isn’t arithmetic. If selection is the factor limiting change, then increasing variation will have little or no effect on the overall evolutionary trajectory, while it will have a large effect if lack of variation has been the rate-limiting factor. These are empirical questions that cannot be answered by thinking about them, and the answers are likely to be very different in different cases.
If you pour jelly beans through a filter that eliminates everything but red beans, you’re always going to have a bowl full of red beans. Increase the number of purple and black beans, and even add new colors to the stream – you’ll still have a bowl full of red beans. If you have a red bowl this week and come back next week and find a rainbow of colors, is that because your jelly bean stream has become more varied in the meantime, or because your filter has changed? Logic can’t tell you the answer.
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Do you have a source for this claim? Have any tried? On the face of it, I don’t see why they couldn’t.
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By showing that there is more evolutionary variation when you do have such sources of genetic variation.
Your example is contrived. Of course if you arrange that the only variations are ones that get filtered out then there will be no change. But take this contrived aspect out of it and yes you will always get a bowl of red jelly beans but you will still have ones of all different sizes and shapes.
I disagree. Math really is the essence of all the sciences and evolution is no exception. It always comes down to arithmetic in the end.
But lets get down to the heart of the matter here why don’t we… Variation drives evolution because without that evolution is a non-starter. That is indisputable. However changes in the filter of natural selection certainly can create an increase in end result. This is what I have called an opportunistic source of variation. So going back to the original question… What about predation? Is this an example of going to a more restrictive filter or to a less restrictive one?
Well, not sure if jellybeans reproduce by fission or sexually. Fission I hope. But if only the tasty jellybeans get eaten, soon we will only have the yucky flavors left which will take over the candy jar.
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I don’t see how you could get a branching tree through variation alone. In order for any twig to diverge from its branch, selection is required to eliminate the middle creatures capable of interbreeding with either population. If you tried to map a ‘tree’ which had only variation and no selection, your trunk would just get wider and blurrier as it expanded in all directions simultaneously. Discrete branches would never occur without selection.
That is not correct for either evolution or the tree. The twig simply grows, there is no elimination process involved. And so what if you have middle creatures all over the place capable of interbreeding with either? You seem to be overly concerned about speciation and separating organisms into separate species but is the lack of such a thing really such a big deal? Though you know… that breaks down for pragmatic reasons like a Saint Bernard and a Chihuahua who despite being the same species cannot interbreed without artificial insemination. So even without natural selection you are eventually going to get speciation.
Incorrect. Variation is never a continuous process but a production of discrete individuals.
The example is yours, not mine. I gave you a less contrived version – one more relevant to evolutionary biology – than the version you gave.
Well, yeah, if you eliminate selection, then the amount of variation will be critical for the rate of evolution. But since eliminating selection means removing the case from the realm of real biology, what’s the point in talking about it?
This is profoundly wrong. Physical reality is the essence of science; math is what we use to model that reality. If your math doesn’t match reality, then you’re using the wrong math.
Of course.
Great – we’re in agreement.
Your terminology seems guaranteed to confuse people, then. If variation is the input and selection is the filter on the variation, why on earth would you call a change to the filter a source of variation?
It’s an example of going to a different filter, which makes an increased rate of evolution likely. It is also a filter that introduces a new feedback loop into an already complex dynamic system. Arithmetic is not the right math for modeling that kind of system.
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Yes, the twig would simply grow. It would never branch. Perhaps you’re fine with that, and the unspeciated mass of diverse organisms that would result, but my point is it wouldn’t be a branching tree.
I need to brush up on plants, but I am pretty sure the process of branching involves orchestrated, deliberate cell death at key points. So yes, the process is very comparable.
It’s still selection even if it’s artificial selection. But the reason they’re not considered different species is that they can both breed with a poodle. Without any selection, natural, sexual, artificial, whatever, all the living things in the world would be able to breed with something that could breed with something that could breed with…it would be like playing “Six degrees of Kevin Bacon.”
Yes, that is certainly true.
Because opportunistic sources of variation represent a decrease of natural selection. It is important because it shows the flaw in the old idea that protecting the weaker members of the species puts an end to evolution, which is wrong.
Yes but it IS more restrictive not less restrictive. The immediate result is to terminate those which are more vulnerable. Compare that to my example of a community protecting the weaker members which is a change to a less restrictive filter. And predation itself a product of variation not natural selection.
First of all natural selection is not really a filter.
@glipsnort
Then the reason that organisms change is because the ecology changes. The direction that the ecology has been changing is that it has become more varied and diverse, which means that there are more and varied ecological niches which produce more and varied species.
Nope, and it is not difficult to look up. Apparently branching is caused by a reservoir of stem cells at the base of each leaf which remains dormant until activated. It is known that removing the leaf can stimulate such an activation so one hypothesis might be that a greater amount of light received over time will activate these reservoirs.
I think you mean it is still selection even if it is reproductive selection. And this is true… but somewhat question begging. The point is that even in imaginary conditions where survival is not an issue you are still going to have evolution and even speciation because the driving force of evolution is variation. My point is not to say that natural selection is not important only that this importance is sometimes exaggerated out of all proportions to support this whole “survival of the fittest” mentality.
https://en.wikipedia.org/wiki/Programmed_Cell_Death Whether or not it’s important to branching, it is extremely common at all levels of life.
No, I meant what I said.
You will still have evolution, although of a mushier, less effective sort, but you would not have speciation, since all variations will be equally able to survive and propagate and therefore no population will be much different from its neighboring populations.
I am glad you are not trying to say that. I have have found it does not work to try to discount either variation or selection. Both are indispensable.