- Despite lack of observational basis, Darwin proposed Universal Common Descent (UCD) saying: “Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed“. He also said elsewhere (referring to UCD): “…the littlest creature (or four or five of them)…” With his remarks, Darwin left the door open to creation (“life was first breathed”), but since then, Neo-Darwinists have rejected creation and replaced it with belief in undirected abiogenesis while maintaining belief in UCD.
- UCD is incompatible with the current view of Earth as just an ordinary planet circling an ordinary star located nowhere special inside an ordinary galaxy. If Earth is “nothing special” and abiogenesis is an ordinary “arising” of life from non-living matter, spontaneous abiogenesis would be a trivial common occurrence here on Earth as well as throughout the Universe, and we would have many “trees of life” instead of one. However, until now, all abiogenesis experiments have failed to produce life, spontaneous generation has been rejected, and the Fermi paradox stands, all these keeping the single “tree of life” and UCD hypothesis still alive and still inexplicable.
- Conditions for starting life should be similar to those required for sustaining it. The Big Bang model mandates a beginning of life. Furthermore, once started life must be sustained by the same or very similar environment. And since life is being sustained now on Earth, abiogenesis should be ongoing contrary to all observations to date. Tidal pools, deep sea hydrothermal vents, and the undersurface of ice caps have been hypothesized to originate abiogenesis due to their persistent energy gradients, but no abiogenesis or its intermediate phases have been observed around these sites. Given these, the only methodological naturalistic alternative is ‘limited window of opportunity for abiogenesis which suggests primordial life substantially different than all known forms of life, and perhaps originating on another planet followed by panspermia. However, this alternative defies Occam’s razor and the absence of supporting evidence including the earliest ever known fossils (stromatolites) that are of commonly occurring cyanobacteria rather than of alien origin.
- Universal Common Descent requires an inexplicable biologic singularity. All known forms of life are based on the same fundamental biochemical organization, so either abiogenesis happened only once or it happened freely for a while but then it stopped when the ‘window of opportunity’ closed and only one organism survived to become the Last Universal Common Ancestor (LUCA) of all existing life on Earth. However, these two biologic singularities should be unacceptable given the lack of evidence and the assumption of continuity in nature. Furthermore, the second scenario requires two discontinuities: one for the cessation of abiogenesis and the second one for the bottleneck leading to LUCA.
- In conclusion, UCD hypothesis leads to a number of bad and very bad scenarios: a) Earth is “nothing special” should lead to a “forest of life” rather than a single “tree of life” and to ubiquitous abiogenesis (unobserved); b) Alien life plus panspermia is refuted by the Fermi paradox and oldest known stromatolites fossils; c) Single event abiogenesis is an unsupported and therefore unacceptable singularity; d) ‘Window of opportunity’ abiogenesis followed by LUCA bottleneck is even less acceptable double-singularity. And this brings us back to Darwin’s “open door” to creation, perhaps the most rational alternative that fits all biologic observations.
Con: Maybe abiogenesis is happening a lot. I think the already existing life would dispose of it quickly though.
Pro: if so, 1. We should be able to duplicate abiogenesis in the lab; 2. We should see at least some of the intermediate abiogenesis steps in nature; 3. Existing life can only process what looks like food. Cellulose is a well known organic material that cannot be broken down by a lot of organisms and is known to last as very long time in dry conditions.
I was comparing animals in general with plants in general. If sponges are not “plantlike” then why did Linnaeus do the following?
If I asked you if you thought sponges were more plantlike than zebras, would you be able to give me an answer? I would hope you could. On the other hand I would not expect an answer from a sponge or even a zebra.
Well enough to suspect that they are closely related, but you cannot infer linear descent from this.
So you agree that linear descent cannot be inferred?
Here is some interesting research
I have included an image of just one of the protein complexes involved in photosynthesis. I would like to know the Darwinian path by which this process evolved in this very early organism?
Also if the evolution of the photosystem was found to be non-linear, how accurate are other molecular clocks?
Look, I can see that, in order to argue that humans contain the “essence” of all other life forms, you try to reduce the essence of all other living things to something trivial. Hence the essence of plants, bacteria and animals that do not appear in “My First Book of Animals” is reduced to growth. But most organisms sport a substantial collection of characters and abilities that humans do not (like photosynthesis). You dismiss that stuff as “not essential”, but that just goes to show that you don’t care about anything but cognitive abilities. People who actually give a damn about biology (like me) know better than to ignore the tremendous diversity of life and trust Charlie to distill the “essence” of all-plant-like-organisms for them.
That is because cell organelles have clearly become part of the organism, whereas most bacteria can survive as independent individuals. If you are already having problems wrapping your head around that basic stuff , then you are well advised to stay away from the more fuzzy cases, like the Wolbachia that Allan mentioned.
Do you smell burnt rubber? That is from you making a 180 degree turn:
The point is that groups of bacteria exist that have certain characteristics that are decidedly not-plant-like, arguing contra you shoveling them unto the pile of “plant-like thingies”. Bacteria have greater diversity than animals or plants, as evidenced by the larger phylogenetic distances between them and by them having a greater repertoire of metabolic pathways. I believe we discussed this previously.
Does it look plant-like? Ah, so this is an example of you studying life in “intimate details”?
I can see where the sentiment comes from; Sponges do not have active movement, and some of them may even harbour photosynthesizing symbionts. As far as I am concerned, neither of those things establishes sponges as being plants.
You look at the little word “growth” and then your thinking stops there because you do not see all that it entails. The word, “growth” is only trivial if we do not seriously think of the meaning behind it. Concentrate on plant growth and all that it entails: Mitosis, intake of nuitriants, differentiation of cells and organs, photosynthesis, rising up against the force of gravity, and much more. All that is contained in the understanding of plant growth. It is nothing like a reduction to a single, trivial concept. I’m sorry but if anyone is making light of concepts it is you.
The little word “growth” encompasses phototropism, gravitropism, and apical dominance, all of which are seen in huma…
Personally, I do NOT think that sponges are more “plant-like” than zebras. But then I’m a biochemist by training, so I focus on the xylans.
You have obviously forgotten or have not read my earlier post where I wrote the following:
Yes growth even applies to humans.
Probably because of your specialist training you are so focused on the detail that you have forgotten to consider the whole.
Sponges can move, you know. Some of them move considerable distances, though slowly. Others are fixed to a substrate, but their cilia still move and pump water. Plants, on the other hand, don’t have cilia, though some of them can move certain parts; think of sensitive mimosa and Venus fly traps.
Now what is this sentience? If it’s mere ability to sense and respond to stimuli, don’t the plants I just mentioned have that? If it’s something else, what exactly is it that a sponge has or lacks that make it sentient or non-sentient, whichever you’re going for? What about a jellyfish?
Charlie, as usual, makes it up as he goes along and has little idea of biology.
Sorry Charlie if I was being too subtle for you.
In the post that I was responding to, you quoted Corneel thus
and you condescended thus
You are ever so carefully defining “growth” to mean those characteristics that you think that humans and plants have in common. Remember: the thing that Corneel is challenging is your baroque claim that all non-human life is just devolved versions of the acme that is man.
To maintain this Goethean archetype woo, you listed the aspects of plant growth that could be analogized to humans. I particularly enjoyed “rising up against the force of gravity.”
To counter this, I listed three rather essential aspects of plant growth that cannot be analogized to humans, although I’m sure you’ll give it the good ol’ college try…
All his talk of purity of essence reminds me of that movie with Slim Pickens…
Remind me which planet they come from?
Yes I hadn’t forgotten that a sponge is different to a mimosa or a venus fly trap in that it is an animal and they are plants.
From Marc Bekoff, emeritus professor at the University of Colorado, Boulder:
After 2,500 Studies, It’s Time to Declare Animal Sentience Proven
Can you see any difference between a Venus fly trap snapping shut on an insect and a cat scratching its ear?
The kind of sentience I am talking about requires a nervous system. More advanced animals can outwardly express their inner feelings to some degree.
From National Geographic
So one of the most primitive of animals has the makings of a nervous system but this animal is like the plants in that it doesn’t possess any nerve cells. Higher animals incorporate a central nervous system culminating in the most complex structure in the known universe.
Not in any important way.
Do cnidarians have inner feelings? You really are making it up as yo go along, aren’t you? You have no coherent view based on anything like observation.
Sorry, you’ve lost me.
I still think you might be pursuing the ‘why are there still monkeys?’ fallacy. If the closest relatives of mitochondria are alpha proteobacteria, this is not a claim that mitochondria are ‘linearly descended’ from modern alpha proteobacteria. No-one is trying to infer that peculiar thing.
What would you prefer to call the common ancestor of modern mitochondria and alpha proteobacteria, if not bacteria? Mitoteria? Bacchondria?
Or perhaps he has been studying the intimate details in order to make the necessary connections.
They’re plant … like-ish.
They tend to be a little prickly,
I have not defined growth. I assumed everyone would have known what I meant by it. Can we agree to call it expansion of material substance? I was certainly not defining “growth” above, I was specifying some entailments of plant growth in which I included photosynthesis (not something that accompanies human growth).
Do you deny that if we compare three entities, mitochondria, prokayotes and humans; the first and second are much more alike than either is to the third? If so how do you see the relationship? Also we contain prokaryotes within ourselves in the form of gut bacteria.
Which of these statements do you disagree with?
1. Plants grow, decay and reproduce.
2. Animals grow, decay, reproduce and are sentient.
3. Humans grow, decay, reproduce, are sentient, are capable of self conscious rational thought and with their thinking are capable of exploring vast areas of space and time.
No I didn’t, see above.
You are giving examples of the means by which specific creatures achieve growth. This does not alter the fact that all creatures have this in common, that they increase their material content, they grow.
Here are typical examples:
Grasses use their energy to grow and maintain viability.
Zebras use their energy to grow up to a point, then they use it to move around satisfying their desire for food, mating and such like.
We humans use our energy to grow up to a point. Some of it is used on moving about in order to satisfy our desires and our brains use up a considerable amount of energy which increases when we are concentrating.
So we progress from growth to sentience to rational thought.
And I have spent far too much time and energy composing this reply 🙂
Okay, then how about the difference between a Venus fly trap snapping shut on an insect and you typing replies on a keypad?
They have inner feelings in the proportion that they have a central nervous system. In other words virtually non existent.
Basically I said that when it comes to mitochondria and prokaryotes experts infer that one evolved from the other, mainly that (ancient) mitochondria evolved from (ancient) alpha proteobacteria. You said that this is not the case. They suggest common ancestry, not that one evolved from the other.
I had previously given the example of the series of leaves on the stem of a buttercup. They can be placed in a hierarchical series due to similarity of form, but none in the series has developed from the one nearest to it. In other words we cannot infer linear progression of descent from their similarity.
So when you wrote:
you were saying that they did not suggest that mitochondroa evolved from alpha proteobacteria, only that they shared a common ancestry. In other words they both evolved from the same presumably unknown source, not one from the other.
Is that what you are saying?
No I’m not.
Yes I already know that.
I am saying that common ancestry is not the only scenario. As in the buttercup leaves they could have originated from the same plan and not be linear descended.
You should get to know one. You might be shocked by their affection.
So, in other words, inner feelings are not a characteristic of animals, only of some animals. What about flatworms? Do they have inner feelings? How would you know?
All animals either have sentience or have the potential to be sentient. Don’t forget everything is in the process of evolving. You would not say that because a 3 week old baby does not have rational thought then humans can not be said to have rational thought. The stage of development of the nervous system will determine their level of sentience.
Plants capture light in order to produce energy and carbohydrates. It plays a vital part in their growth. Humans and higher animals capture light in order to sense the visual world. It plays a large part in their sentience.
Contrary to what you may think I do not consider the divide between plants, animals and humans to be unbridgeable. There is graduation with forms in transitional positions. When I say that animals are sentient etc., I am talking about average, well developed animals, plants and humans.
Do you have any reason to suppose that the leaf cells in a given buttercup are not commonly descended?
Of course. It’s all magical woo.
You must realize that to most people this all sounds like nonsensical blather. And you say it with such confidence!
Nope. Not after the extensive discussion with gpuccio at UD.
Do you have a link?
Very persuasive! 😉
Yes, Allan. Even geologists and the astrophysicists must show experimental evidence.
What does that even mean: “descent with modification”? Modification of what? …considering that not even monozygotic twins are identical.
Note that this OP does not ask for proof of the OOL mega-singularity. It merely explores the implications of the UCD hypothesis.
Did you read all relevant comments? Or just the last one?
What are you talking about? Looks like a passage from a conversation I was not part of.
Does anyone else here know what this is about? Can you provide a link?
Descent with modification from a common ancestor assumes the prior existence of the common ancestor. (Well, I say assumes but the almost universal genetic code is a strong indicator of shared ancestry.)
The consilient evidence of the branching relatedness of all extant and extinct life on Earth is not the least dented by your musings.
Depends who’s deciding what’s relevant. I scroll over comments by BA77, Kairosfocus, ET etc. Are there some gems there you’d like to draw attention to?
I’d add comments by Nonlin to that list, for obvious reasons.
And reading gpuccio’s responses to nonlin’s comments there, I suspect nonlin is on gpuccio’s list too! 🙂
Too bad you can’t ban them, huh Admin Alan?
URL as synopsis!
A link? What would that achieve? There was a side discussion about ‘information’, which you saw because you mentioned it. I saw a connection between information (the Shannon variety) and sequence divergence (part of the argument on common descent) and so constructed a post on that connection. You suggested I take it elsewhere, while admitting at the same time you don’t understand it well enough to know where it belongs.
Kairosfocus was invited by Lizzie more than once to join discussions here. He’d have the same opportunity to comment within the rules as anyone else.
BA77 regularly calls for dissenting voices to be silenced at UD and I suspect he’s better off staying there. Nothing stopping him registering and posting here (subject to TSZ rules) should he wish.
ET/Frankie/JoeG is suspended from posting here. Should he wish to give an undertaking regarding future conduct, we could reconsider his suspension.
So, you are talking nonsense, basically.
And moderation issues belong in the moderation issues thread. I may have pointed this out before.
Good question. No I don’t.
From Goethe quoted in “Thinking Beyond Darwin”, by Ernst Michael Kranich:
Whether we are looking at the multiplicity in the plant growing from seed by cell division or the changing forms of the leaves along the stem, we must not lose site of the fact that the entity we are studying is a unified, viable whole. The cells or the leaves are just aspects of this whole.
Goethe made a comparative study of plants in Italy with those of his native homeland. Steiner referring to this writes the following:,
Whether it be a plant, a zebra, a human or earthly life as a whole, at all stages from its birth to its death it remains a unified, viable whole. And it is this whole that is the reality. Individual cells and leaves may come and go but it is the unified plant that is the overarching reality that the cells and leaves are just a part of.
Cantonese sounds like nonsensical blather to me. But I realise this is just because I don’t understand it. The fault lies with me and not the language.
I agree that the fault lies with you, but in both your analogy and the present case. Your arrogance is not helpful. Some kind of coherent argument would work better, if you are capable of such a thing.
Nonlin wants to know what descent with modification means, then points out a case of it. Lulz.