You’re asking for examples of large-scale changes within a single generation.
Why would that be relevant to the question of evolution? No one (that I know of) proposes that large-scale changes occur on that time scale.
Do whales and other mammals have the “same” body plan, or different ones? No one thinks that change happened in a single event (and the fossil record shows it didn’t).
According to the serial endosymbiotic hypothesis for the origin of mitochondria, an unknown prokaryotic species engulfed an alphaproteobacterium, and instead of being digested or destroyed, the latter set up shop within the cytoplasm of its host (and you know the rest).
How many generations did that original event of engulfing take?
There are countless transitions within the macroevolutionary story that must occur within a very short time frame indeed.
Here’s one candidate for such a transition, from insect groups familiar to you. How long did it take for the holoblastic cleavage pattern exhibited by Aphidius ervi to arise? (I’m assuming, as most arthropod systematists do, that the syncytium pattern we see in Drosophila and honeybees, for instance, is ancestral within the Diptera and Hymenoptera.) See Figure 3b in this paper: http://www.pnas.org/content/pnas/95/3/1097.full.pdf
Divide this transition into as many, or as few, generations as one wishes. At some point, a major topological discontinuity must be bridged.
I have a meeting coming up and must leave this thread until tomorrow morning.
And engulfing is the whole transition?
One classic error you’re making here is that you’re taking present-day systems and structures and saying it would be difficult to transition between them. Well, those present-day systems have been built on for hundreds of millions of years, and they are not likely to be easily changed at this point.
But, evolution is not about transitioning between present-day structures and systems. Axe and Gauger make the same basic error in their experiments where they try to convert one enzyme to another. Here’s another YEC’s take on that (Todd Wood).
So, that means this actual laboratory result would be pretty persuasive to you, right?
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Protists that fed on algae cells swallowed some that would not be digested and did not die… and they were lucky they did! Those algae cells helped the Protists survive starvation - - and provide an exquisite parallel to the acquisition of proto-mitochondria by one celled life ages ago…
[Link to YouTube video: ](https://www.youtube.com/watch?v=VUfNEHl44hc
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Now you can say we don’t have any examples like the proposed Mitochondria scenario!
There are two general rebuffs:
If scientists want to make an impact in the scientific community then they publish scientific papers in peer reviewed journals, not books.
When people focus more on how they are treated instead of the actual science, it is usually because they don’t have the science to back them up.
Which would be expected if subsequent evolutionary adaptations built upon earlier developmental changes.
To use an analogy, if you take electric power away from a modern city like London it will screech to a halt and stop functioning. Does this mean that London could have only existed throughout history with electricity? Does this mean that electricity had to be introduced to London in one fell swoop, or could it have been slowly added to the city to the point where the city then became dependent on electric power at a later date?
Hi Paul,
Sorry I can’t get the quote feature to work but you said," Most evolutionary biologists who work on this puzzle say that the depth and type of variation required for macroevolution (e.g., as seen in the Cambrian Explosion) no longer occurs, as metazoan ontogenies have now “hardened” around their central control elements. This was the late Eric Davidson’s view, and that currently also of paleontologist Douglas Erwin at the Smithsonian."
Can you provide the references for this? I don’t doubt you, I’ve always thought this was pretty much every Evo bio’s view. I would just like to read their words.
Just so we are happily in sync with our terminology - - there is no such thing as devolution. There is no way for Evolution to go back in time. Evolution is cumulative and if a species adopts a form that looks like an earlier form, it has to do it the hard way… by mutating it’s way back to it.
There is no DEVOLUTION or DEVOLVING.
If we started trying to use that term, we would have to compare different mutations to arrive at some sort of NET EVOLUTION result.
For example, when fish evolved into tetrapods… is that evolution? Or did it become devolution when the tetrapod lost its gills and fins?
When a mammal evolved into a proto-whale… is that devolution? It could dive deeply … but eventually could no longer walk on land.
Is a snake a DEVOLVED reptile? Or a highly evolved reptile customized for its environment?
All things alive today are the living representatives of branches of life that have been evolving continuously for a billion years…
This 2011 paper by Douglas Erwin is open access: https://www.sciencedirect.com/science/article/pii/S0012160611000443
This 2009 paper by Eric Davidson (An integrated view of precambrian eumetazoan evolution - PubMed) is unfortunately not open access, but note the last sentence of the abstract: “A strong conclusion is that the evolutionary process generating the genomic programs responsible for developmental formulation of basic eumetazoan body plans was in many ways very different from the evolutionary changes that can be observed at the species level in modern animals.” If you email me (nelsonpa@alumni.uchicago.edu) I can send you the pdf under fair use rules.
“Evo-devo” is the nickname or shorthand for the research field of evolutionary developmental biology. Actually there is a very good open access journal with that name: https://evodevojournal.biomedcentral.com
Your cells engulf endosymbionts all of the time. Almost every human has had or does have a species of Chlamydia growing in one or many of their cells. BTW, it is just one of the Chlamydia species that causes the STD, the rest of the species usually don’t cause any symptoms. Endosymbiosis seems to be an ongoing process.
Yes indeed and thank goodness (actually, God) that they do – e.g., phagocytosis in the mammalian immune system.
But that wasn’t my point. Many events required by evolutionary pathways have an all-or-nothing character. These events don’t occur incrementally: they happen or they don’t. One prokaryote engulfing another would be one such event. Incidentally, the examples of phagocytosis provided above in this thread all involve eukaryotic, not prokaryotic, cellular processes. How a prokaryote successfully absorbed another prokaryote is as much a mystery today as it was when Lynn Margulis revived the endosymbiotic hypothesis in the late 1960s.
Clever name… not a big fan of its unintended appearance.
There seem to be many steps required to set the stage for endosymbiosis. There’s the initial interaction with bacteria that includes the steps for envelopment. There are probably a number of steps in the initial association (pre-permanent endosymbiosis) which affect whether the interactions are mutualistic or not. And there is prevention of lyosome fusion. So, there are probably a number of steps leading up to that transition.
As for plastid evolution, we see cases where secondary and tertiary acquisition seems to have occurred in several instances (endosymbiosis of eukaryotic cells containing chloroplasts) . There are also cases where photosynthetic bacteria are temporarily sequestered by hosts (see also, “non-obligate endosymbiosis”). And there are examples of kleptoplasty in which the plastids are removed and retained by the host.
So yes, there are distinct transitions that must occur in obligate endosymbiosis but there must also be stages leading up and supporting the transition.
That mitochondria are derived from an endosymbiotic event is largely a closed mystery (circa early 1990s’) for which evidence continues to accumulate.
There are examples of prokaryotes living inside other prokaryotes. Though we see a single lineage today, we’re not sure if the eukaryotes branched before or after acquisition of the mitochrondrion. Eukaryotes display a number of features that distinguish the group from the archaea and bacteria. However, it seems that the plastids became endosymbionts after eukaryotes emerged.
Additionally, we have evidence of a novel acquisition of a plastid via endosymbiosis with a cyanobacterium by an amoeba about 60 mya (Paulinella chromatophora).
Pleased but somewhat surprised that you would say this. I thought all Christianity engaged in human triumphalism to some degree. But then too I have been told on this site that an ape ancestor was not essential to being made in God’s image, that it was the suite of intellectual capacities which is the basis for that comparison. So a clever cephalopod or dolphin might have served His purposes just as well.
But don’t even evolutionary creationists assume there is a higher/lower polarity to evolution revolving around those qualities assumed to be most beloved by God - the capacity for reason, free will, self awareness and so on.
I believe Kenneth R Miller even cautions against viewing single cell creatures as less evolved than multi-celled animals since both have been evolving for an equally long time.
Paul,
Thank you for giving credit to the great scientist Lynn Margulis for endosymbiotic hypothesis which she rescued out of the garbage bin. Her discoveries have been used to reject ID, however they do not support Survival of the Fittest. It seems that there is politics in science as well as other aspects of life.
I’ve noted before that Nelson’s argument is pretty much in the same form as Behe’s irreducible complexity argument.
A few years ago I heard Loren Haarsma use a similar example of the trucking industry - which is completely dependent on trucks for supplying truck parts, fuel, and so on. The trucking industry is now completely dependent on trucks - so how on earth did the trucking industry come to be? It must have happened all at once, because if you take away any of the parts it won’t work.
A Christian can volunteer opinions about moral superiority… or spiritual superiority of humanity as a religioys claim.
But the science of evolutionary change makes no such claim on species. There is no way to net out the difference between traits lost vs traits gained to state objectively what is EVO-lution and what is allegedly DEVO-lution!
Yes, we’re as superior to a turnip when it comes to morality as they are to us in the photosynthesis event. 
Agreed.
Comparing undirected evolution to the electrification of cities, or trucking, would be meaningful if one could point to the designing intelligence at work in the evolutionary process. Creative intelligence enabled the first electrical generators and wiring systems, freight-carrying vehicles, and so forth, and thus solved the engineering hurdles entailed by the origin and development of both complex systems.
But, of course, evolution would then no longer be an undirected process.
Don’t appeal to intelligently-designed systems as epistemically relevant analogies, for a process (evolution) with no mind or foresight. Doing so entangles one in a contradiction.
“Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone.” -Colossians 4:6
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