Specifically, what is the evidence for common descent?(Not quite) famously, Darwin mused about the similarities of taxonomic hierarchies in linguistics and biology and asserted that the hierarchies must ultimately point to common descent. (Chapter XIV, On the Origin of Species) That’s common descent as distinguished from microevolution.
The linguistic equivalent is the single origin of all languages (eminently unproven and deemed unprovable) as distinguished from a language family (with demonstrable relevant organic shared features).
Darwinists are welcome to present their evidence. From Rumraket, we have the observation that all organisms can reproduce, “Nesting hierarchies are evidence of common descent if you know that the entities sorted into hierarchies can reproduce themselves. And that particular fact is true of all living organisms.” Good start.
From Joe Felsenstein we have the doubt that the border between micro- and macroevolution can be determined, “OK, so for you the boundary between Macro/Micro is somewhere above the species level. How far above? Could all sparrows be the same “kind”? All birds?” Not very promising.
From Alan Fox, “Darwin predicted heritable traits. Later discoveries confirmed his prediction.” Questions: Which heritable traits specifically? Was there a principled improvement over Mendel? And how does this lend credence to common descent?
Thanks to all contributors.
It may be a while before I return to this thread. But I don’t know why you think that convergent evolution is evidence against common ancestry. I’d say there’s a pretty good chance I’m not the only one who doesn’t know. So you might want to spell it out.
It seems more likely that it is a confusion between process and history.
For language evolution, one builds a tree based on history. And then presumably one infers process of evolution from the history using that tree.
With biology, we have good knowledge of process. And then, using that known process and its production of one or more trees, we can build a history using relatively sparse historical data.
Tom English,
As an example convergent evolution is flight evolving in different animals that don’t share a near common ancestor like birds and bats. The evolution of flight is complex and hard to explain by blind processes. Having flight evolve more than once is quite a challenge. Other examples are sight and echo location.
What limits would those be? We’ve only been watching species for a few hundred years out of the 3.5+ billion years life has been on the Earth.
If you watched 10 seconds of a marathon would that indicate it’s impossible for a human to run more than 50 meters at a time?
Evolution isn’t a completely blind process. It has a feedback component in the form of selection provided by the environment.
Why do you think flight, sight, or echolocation are particularly hard to evolve? All provide great benefit in the environments of the creatures that possess them. Evidence shows all three have evolved independently multiple times too.
Adapa,
This is true but the advantage is not reached until a very complex system comes together. Selection needs the complex system to evolve before it can fix it in the population.
You need material that is aerodynamic (feathers) to evolve, a muscle system that matches with the aerodynamic material, navigational systems etc. Until all this comes together the advantage of flight cannot be selected for.
I invite you (for the nth time) to read my ratite paper I keep bringing up for you, or even the Theobald paper, for examples of how that’s done. Why won’t you just do that?
I can’t see why you need any more navigational system to evolve flight than you need to find your way around on foot. The muscle system and the feathers, as you really ought to know by now, evolved before flight. The old technical term is “pre-adaption”, and the newer one is “exaptation”. Of course bats don’t have that aerodynamic material and have to make do with flaps of skin, the sort seen in a host of mammalian gliders.
Further, even if flight can’t be explained by “blind processes”, that has nothing to do with common descent. Consider Michael Behe, for example, who accepts universal common descent but doesn’t think any natural processes can account for some unknown number of adaptations.
That is demonstrably false. A stubby proto-wing that allowed its possessor to jump a small bit farther between tree branches is enough evolutionary advantage to get selected for.
A light/dark sensing eyespot is better that zero light sensing capability and will be selected for.
Even a tiny bit of echolocation that gives its owners a 1% advantage in catching its dinner will be selected for.
The claim an entire modern flight system had to evolve before it could be of any use (the “what good is half an eye” argument) is one of the dumber claims out there. 1% functionality is better than 0%. 2% is better than 1%. You can figure it out from there.
Why convergent evolution? Because evolution doesn’t know anything about evolution that occurred in other lines of descent.
Why not homologous flight adaptations in separate lines, if there is a Designer responsible? Bats, birds, and pterosaurs all have homologies, but not in flight capabilities. Why? They all evolved from a common ancestor, but they all evolved flight after diverging from a common ancestor.
Evolution doesn’t know, the Designer should, but apparently didn’t. I always wondered why believers think they’re doing their God a service by making it no brighter than evolutionary processes are.
Glen Davidson
John Harshman,
John, I accept some level of common descent also as you have shown with some flightless birds in your paper. The evidence in your paper showed strong similarity among all flightless except for the ostrich. I would hold my final conclusion based on analysis of additional DNA segments but at this point I have no reason to doubt your claim.
I agree with Michael Behe and consider evolving flight once is beyond known natural process let alone several times.
As Eugene Koonan said in his paper supporting neutral theory as the current default hypothesis: ” Its time to get rid of the adaptionists just so stories” This includes all the transitional stories without transitional evidence.
I agree with Eric that Universal Common Descent is a monster claim with very little supporting evidence. It stumbles right out of the block with the evolution of the spliceosome, chromosome structure and the nuclear pore complex which lack evidence for precursors.
Behe has never opined flight is beyond known natural processes to evolve. Where did you get that turd?
More than a few people have shown you plenty of evidence to support evolution. Pretty much every dumb claim you’ve made has been beaten into the proverbial fine pink mist. That you choose to remain such a willfully ignorant knob on the subject is a sad reflection on your desire to educate yourself, a desire which seems nonexistent.
That’s so very open-minded of you. I bet you could google up a few additional segments if you tried just a little bit.
Are you agreeing with him on something he actually said? If so, where?
Ah, quote-mining. So much easier than making an actual argument.
Damn, and you were so very close before that last paragraph. You seemed to understand that the evidence for common descent doesn’t depend on the source of the changes, but I guess that was just me seeing what I wanted to see. And you’ve already completely forgotten Theobald 2010.
No. The evolution of language is observed, not assumed. A single generation is enough to effect a specific change and it’s usually irreversible, unless a norm is fixed by some authoritative diktat, but this only slows it down, instead of blocking it.
See, it’s precisely in biology where both the process and the history are assumed.
Linguists can build trees too (many places where you can draw trees, this by itself proves nothing about history), based on all sorts of linguistic data, but from the direct observation of the actual process it’s known that e.g. broad typological, syntactic and lexical phenomena are easily borrowed and thus deceptive, whereas core vocabulary, morphology and lawful phonetic correspondences demonstrate organic relatedness. These are conclusions made from observations, such as how things have gone from Latin to its modern descendants.
In biology you seem to have assumptions projected on the data, no observation of the process. I know it’s by necessity, and this is precisely the problem. With some imagination one can make all sorts of assumptions compatible with the data, even more parsimonious than evolution.
Such as no turtles come from rabbits. Breeding is consistently an intra-species thing.
This of course fails to impress you. Similarly, it should be understandable why your Very Long Time argument fails to impress me.
The way you prove a common ancestor to finches would illustrate your standard of evidence. The further conclusions you draw from it, baseless or otherwise, illustrate it further.
Which is why it’s lucky that I made the OP short.
You can fix the problem, I hope. Instead of arguments like “things breed with tiny changes over Very Long Time, therefore common descent” please bring all the relevant lines of evidence together.
However, from what I’ve seen, the distinct lines of evidence are in fact radically disconnected. For example, a few attested ancestors (which are conspicuously not there) would not prove universal common descent, but would be good for macroevolution, if it’s beyond species.
Erik,
That’s a fine summary of the arguments you have been presented on common descent there, Erik. You are quite the scholar.
Erik seems to be playing the role of an erudite Joe G but with the same underlying misconceptions.
Gordon Davisson,
Thanks, but your post does not explain anything. Given your peculiar definition of “explain”, this is all that I should say, but I will say more. I will really explain how your post does not explain anything.
First, you make the target small. Second, you make the claims minimal. Third, along with it, you make the definitions of “explain” and “predict” ridiculous.
Common descent, for you, is just the ability to build trees. Since there are two independent lines of data (morphological characters vs. cytochrome c) that yield a similar-looking tree, you take it that the tree represents history and there should be no objection. Moreover, you call the ability to build the tree a prediction, even though the human ability to connect similarities is ubiquitous, universal, not specific to Darwin’s theory of evolution and not a prediction in any relevant sense.
Unfortunately for you, the tree was there long before Darwin’s grandfather, even before Linnaeus. Linnaeus only systematized it successfully. So the tree was “predicted” long before Darwin. Darwin’s contribution was to project the “origin of species” on it. It is this projection that is at issue. The tree itself is not at issue. I never denied that the tree can be built. The issue is whether it represents the history of the species a la “ontogeny recapitulates the phylogeny” or if it is just the building blocks of natural life put together systematically.
Since living beings are made of the same building blocks, of course we can build a tree based on the building blocks. Instead of implying whether some or all of the species have a common ancestor, it could just as well imply a common maker and this is the more parsimonious explanation better in line with the observed evidence because
(1) Breeding is observed to be an intra-species thing
(2) Species gradually morphing into other species is not observed
(3) Ancestor species to modern species are not observed, i.e. the Darwinian theory even fails to project the past, not to mention the future
Thus the tree is not a prediction, certainly not specific to the Darwinian theory of evolution and it fails to explain anything relevant to what the theory actually claims. The actual claim of the theory is universal common descent – all species come from a single one. It’s not “we should be able to build a tree”. There are tons of non-evolutionary things we can build trees from. All this has already been covered in this thread many times. You have added nothing to the discussion.
Fourth, to mix things up and to answer your question, I actually agree with something like evolution. For balance, my theory involves devolution. Just like consciousness (souls) can climb up along the ladder of species, there must be descent also. This climbing occurs in the dark side, during death, which has its own laws of nature. On the physical side, which is the only side that the Darwinian theory considers, my theory would “predict”
(1) Fixity of species – some variation when the species settle new ecological niches, but not beyond the limit of species
(2) Hierarchy of species according to levels of consciousness
(3) Rough correspondence of expansion and extinction of species – when a species or group multiplies and commands many ecosystems, other species go extinct, because the number of souls should remain roughly the same
(4) The actual origin of the species lies beyond the material and the arrangement of the building blocks; the tree of life would illustrate something like the plan of creation, but the material does not arrange itself, it is being arranged according to the plan, a.k.a. laws of nature
Feel free to mock and criticize, but make it relevant to actual observations and human experience. Because actual observations and human experience are the points where your post was weak. It was even weak in terms of specific to Darwin’s theory of evolution.
OMagain,
It’s a syndrome. When you see such hopelessly off-the-mark paraphrases of concepts, time to get a new hobby.
colewd,
Drop everything, Bill Cole wants greater coverage of the ratites, in case the ostriches aren’t related at all. To the laboratory!
Erik’s obtuse, therefore evolution lacks evidence. Oh, and Bill Cole believes him, for the same reason.
Being without understanding is its own sort of freedom, I guess. Bliss, some say.
Glen Davidson
Rofl. He really doesn’t get it and it seems he never will.
Turtles and squirrels can’t interbreed. That’s the level he’s stuck at intellectually. All this stuff about why that pattern and not another? About explanatory power, prediction and retrodiction? Comparative hypothesis testing? No, fuck all that, because “it’s just the same species”.
That’s not describing any overall limit or barrier to change, just how much can be achieved in one generation. Try again.
What magic barrier prevents microevolutionary changes from accumulating over time into macroevolutionary ones?
It is easy to understand. You lack both the science background to understand even simple concepts and the intellectual honesty to want to learn. Bog standard Creationist in other words.
All of those “predictions” are known to be empirically false.
At least they resemble some sort of predictions, as opposed to “Darwin predicted a tree” that was there all along even before Linnaeus.
Anyway, can you link me to something that tells me that my predictions are known to be empirically false?
And species don’t have offspring either. Yet Allan Miller and Joe Felsenstein think they do.
When a species mates, who or what does it mate with, since species cannot interbreed?
Erik’s law of conservation of ectoplasm
I “brightness test” for evolutionary processes. Brilliant. When will you publish?
Yes they do. Literally.
So do I.
It doesn’t have to be “mating” to have offspring. Bacteria don’t mate, but have offspring. Literally, they split in two. Same for speciation. One species splits into two.
It doesn’t have to be EXACTLY alike in ALL aspects, to the process of cell-division, much less the process of sexual reproduction, for it to be literally true that a species can have descendants.
As usual, you can back up what you say, right? I’m particularly interested in the disproof of #2 and #4.
KN, he’s got you there. How can you say a prediction is empirically false if it’s meaningless word salad?
Mung,
Yeah, world authority, what does he know about it? Or Joe Felsenstein for that matter! 😀 Brrrrr – bish!
You think mating is the only way to get descendants or be ancestral? Allow me to introduce you to the concept of the asexual lineage.
I, Mentalo, predict a giraffe. Ooh look, a giraffe! It’s quite uncanny.
But it lacks both etheric forces and quantum affinity.
What good is word salad without either of those?
Glen Davidson
Maybe it would help if Erik had a dumbed-down response to some of his points. I’m sure I can be of help there! 🙂
Well, yes. In species that breed sexually, that’s effectively the definition. A species is then the group of individuals capable of sharing their genes with other individuals of that population. Obviously, this definition is problematic when looking at extinct species. Dead organisms are not capable of sharing their genes.
I wonder if it would help to point out that there are three basic processes going on. Extinction: when the contents of the gene pool are lost forever: adaptation, where the population gene pool as a whole shifts due to selection pressure (a change in the niche environment, mutations turning up that are beneficial in that niche, and speciation: where some individuals become isolated from the main gene pool so that there are now two gene pools. in separate niches. This allows the gene pools, when the separate niches differ (food sources, climate, etc., etc.,) to accumulate different alleles, possibly to the extent that the two populations can no longer interbreed, becoming two species.
Has the Grants’ work on Galapagos finches been mentioned to you?
Have you noticed that children resemble their parents, but not exactly?
Rumraket,
I see Rumraket has already covered this!
So? You have nothing better than “possibly to the extent that the two populations can no longer interbreed”?
How is all this specific to Darwinian macroevolution at least (because it isn’t to common descent)? Is there anything here that e.g. Mendel didn’t know and verify?
By what measure did they become distinct species? Did they stop interbreeding?
This has something to do with what, exactly? Can’t you think of any immediate counterexamples, such as currently extant species that emerged in Jurassic era (and we know they are the same species because they didn’t evolve a single bit meanwhile)?
Breeding is most definitely not just an intra-species thing. There are multitudes of examples of plants hybridizing across species boundaries. In some cases the plants need not even be extremely closely related. In fact, this is one way in which speciation happens.
Macroevolution is a term that really only useful to palaeontologists (and Creationists). As I said, all evolutionary processes are covered by adaptation speciation, and extinction. Macroevolution is just the accumulation of lots of adaptation and speciation events.
That’s a bit harsh. I’m trying to get some idea of how yuou understand the evolutionary process which may help to focus explanations, data and evidence that could improve your understanding (and mine). Yes, simply, speciation occurs when subsets of a population become isolated and develop separately. Sexual mixing otherwise prevents it.
Ah, so there really are no specific claims and no specific concepts in the theory of evolution. And that’s why it predicts things very well. Got it!
Maybe that’s a plants thing. Or maybe it’s just the way the concept of species is used in Darwinian theory. To quote Darwin, “I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms.” Species or variety, closely resembling individuals or fluctuating forms, all the same thing. That’s why it works!
The rate of evolutionary change is variable. Some modern species show less change from putative ancestral fossil species than others. The fossil evidence is far from complete but nothing new that has been found so far challenges the overarching nested hierarchy of common descent.
The Coelocanth
I understand the term just fine. If I didn’t, I would not be able to point out that the evidence is lacking. And if you understood it at least as well as I do, you would be able to point out the evidence.
You seem determined to be perverse, Erik. I was making the point that all you need for large changes is an accumulation of small changes and enough time.
ETA: Those that claim there is a macro-evolutionary barrier are mistaken.
The Very Long Time argument is still as bad as it was when it was presented the first time in this thread. Possibly the very worst.
And of course you have evidence at hand….
I don’t claim any great in-depth knowledge (a little out-of-date biochemistry) but so far, your ignorance is what has impressed me. That can be fixed if you want. You don’t even have to change your mind on the concept.
Alan Fox,
Not quite. It’s generally ‘evolution above the species level’. That does depend somewhat on the species concept in use, but it does provide an occasionally useful distinction between evolution inside a gene pool, and those processes that subdivide such a pool and diverge the components.
Alan Fox,
How would you support this claim?