Bechly is the most frustrating member of the DI. He used to be a good paleoentomologist. Not sure why he is making a big fuss about the lack of anagenesis in the fossil record. Anagenesis should be rare. And he gets the history of punk-eek wrong as well. He also is confusing as heck. I thought he accepted some form of common ancestry but now he seems to be denying it. I read on his Facebook that he holds to a hopeful monster type scenario where the descendent species is placed in the ancestral womb (huge problems with that scenario). Stick to odonates Günter. Also, stop fighting with Bill Needle. Yes, he is rude, but he does not know his stuff. But stop getting in internet fights like a teenage girl and get out in the freaking field. I know you’re reading this Günter.
My big issues:
He isn’t defining gradualism. To me The term “gradual” can mean different things. For some writers, it means “very smooth”, but another meaning is “stepwise”. We can see this in e.g. the terms graduation, graduated cylinder, etc. – these are referring to discrete steps. Similarly “gradations”. Considering that the raw material of evolution is mutations, at some level, everyone should agree that evolution is fundamentally a stepwise process, not perfectly smooth. The interesting argument, then, is more about how big are the steps.
Darwin was not a phyletic gradualist
Punk eek was based on positive evidence from Gastropods and trilobites. It wasn’t created to explain things away as Bechly implies.
Anagenesis should be very rare in the fossil record. If he didn’t selectively read Gould, he would know why. So he is complaining about something missing that we don’t really expect to see much.
Why? And really, how do we distinguish anagenesis from cladogenesis in the fossil record; I mean, how do we tell whether morphological change is or is not coincident with the splitting of populations?
Because it doesn’t add diversity. If most evolutionary change was due to anagenesis life would’ve gone extinct a long time ago. Trying to track down the Gould quote.
It’s hard and controversial
I think Gould confused evolutionary change with speciation. Since morphological change is the only way for paleontologists to see speciation, I suppose it’s understandable, but he extended this into a general principle. To a neontologist, speciation is the evolution of reproductive isolation between two populations. It may have little or nothing to do with morphological change, even more so if we restrict ourselves to changes visible in fossils.
I don’t think there is much evidence that morphological change is associated with speciation (in the neontological sense; in the paleontological sense they may be synonymous). To a neontologist, anagenesis isn’t speciation at all.
In order for increased diversity, all that’s necessary is that the speciation rate (the rate of splitting) exceed the extinction rate for some period of time. The rate of anagenesis compared to the rate of cladogenesis (again, splitting, a neontological definition of speciation) is irrelevant. Even if most morphological change is anagenetic, it doesn’t matter to diversification; just speciation rate vs. extinction rate. And speciation may be unaccompanied by any preservable, or even observable, morphological change.
My opinion is that you can’t actually distinguish cladogenesis from anagenesis in the fossil record. If you see a punctuation event that leaves two sympatric morphospecies, all you know is that at some unknown time in the past there was speciation. You can’t distinguish punctuated speciation from punctuated anagenesis in previously existing cryptic species. Further, you can’t reliably recognize biological species in the fossil record, just morphospecies, and the two are not well correlated. Add in problems of stratigraphic and geographic sampling and it becomes even harder.
Of one isn’t a paleontologist. Please explain to observers the difference?
Paleontologists recognize species based on morphological differences, the only things that are preserved. Neontologists recognize species based on reproductive isolation, for which morphological difference is a very imperfect clue. Cladogenesis, the splitting of lineages, is speciation as neontologists understand it. Anagenesis, change within lineages, is not. Paleontologists can see only change. There’s no way to know if that change is anagenetic — unaccompanied by splitting of lineages — or cladogenetic, coincident with splitting.
Heres a good resource I just found by Theobold. Covers a lot of the stuff we are discussing and that Bechly mentioned in his blog post
Is there recognition of species based on genomes?
There are attempts at it. But genomes are just another clue. It can take a long time after speciation for the genomes to settle out (you may have heard the term “lineage sorting”), and long-term geographic separation can result in genome divergence without speciation.
In fact, Darwin embraced Punctuated Equilibria:
That isn’t punctuated equilibria. If anything, it’s just standard allopatric speciation, though in fact it isn’t even speciation. He could as easily be talking about the spread of variation within a single population as anything else. Darwin was never very clear on what species might be or how variation might arise or be spread about, whether by replacement of populations or by what we now call gene flow. But at least he understands the problem of geographic sampling in the fossil record.
The Darwin quotes do show that Bechly is wrong about what “ Darwinian Gradualism” predicts though. Darwin never argued for slow continuous fossil sequences as being vital for his theory. And I don’t see how “Darwinian Gradualism” predicts anagenesis. Sure it might, but it also predicts other types of speciation as well. So I don’t see the point of Bechly’s argument .Also, isn’t punk eek just allopatric speciation applied to the fossil record?
No, it’s Ernst Mayr’s ideas of peripatric speciation and “genetic revolution” applied to the fossil record. Don’t confuse that with standard allopatric speciation. But Darwin doesn’t seem to have had any clear concept of what speciation was, nor did he seem to share a modern concept of what species are.
It doesn’t really predict anything. It’s a strawman that has nothing to do with Darwin: the notion that all populations must be changing at the same rate all the time.
Yeah after reading his post again I’m seeing he is equating gradualism with phyletic gradualism. A position not held by Darwin. Gould also got that wrong.
Gould, I believe, actually made up that term. To be fair, it may have been the model assumed by some paleontologists at the time, but you can’t blame it on Darwin.
Which makes things like this:
“Therefore, Darwin’s appeal to an undersampling of the fossil record to explain away the absence of evidence for phyletic gradualism is no longer tenable.”
“ Gingerich (1983) acknowledged that the little fossil evidence that has been used to support the Darwinian hypothesis of phyletic gradualism “
Even more wrong and confused.