"And in this paper, new genetic evidence shows that after two generations, there was complete reproductive isolation from the native birds. As a result, they are now reproductively - and genetically - isolated. So they have been breeding exclusively with each other over the years."
Remember, the land bridge was recent and humans with a long reproductive cycle still had very noticeable drift over ~1,000 generations. Which was not simply adaptation like reducing pigmentation when moving North.
Genetic incompatibility is actually rather difficult to understand in detail as in what specifically stops working and why that occurred, but easy to understand at a high level.
I have no problem with the theory of common ancestry. That has a lot of proof. But the idea that speciation happens EXCLUSIVELY by random mutation and "natural selection" is just handwaving theorizing. It's super hard to prove and we haven't even begun to get close to what constitutes as a proof. It's on the level of ancient people thinking the ONLY way to get fire is by rubbing some sticks together.
And yet I see the latter ("natural selection") being used by many in the scientific community to suppress other theories even though it is completely handwavy and vague. That is bullying.
Basically common descent can be rigorously defined and shown. The PROCESS by which speciation happens is poorly understood and has been a subject of much posturing by the scientific community (including popularizers like Dawkins) for decades.
(PS: if you're going to knee jerk downvote this because it criticizes "evolution", at least address it with substance.)
1. In both your comments on this thread you seem to want to relitigate some beef with 'random mutation and natural selection', even though that wasn't the point of, and isn't directly relevant to the article cited, Which is about the (predicted, but now for the first time observed) role of hybridisation in speciation.
2. You seem to have left your understanding of the mechanisms of evolution somewhere in the 1970s. I did my PhD in the 1990s, and I don't recognise "The idea that speciation happens EXCLUSIVELY by random mutation in natural selection" [caps yours], Except -- to be honest -- from historic papers and antievolution websites (though I'm very willing to believe it is a misunderstanding shared by journalists). Certainly the people I studied with had a much more nuanced view of evolutionary dynamics, not to mention one that didn't assume sexual reproduction or closed species.
3. Proof is for mathematicians. Obsession with proving evolution is again, something I only know from creationist rhetoric.
4. Citation needed for your bullying claim. There are certainly some who think natural selection is the most important mechanism in evolutionary change, there are those who would emphasise genetic drift, they go to the same conferences. Your image of the state of the science is fiction, in my experience. (Though I've been out of academia for 15yrs).
Their is plenty of examples where even short term separation results in population drift: EX: Skin tone among native Americans is unique even with only ~1,000 generations separating the land bridge from modern times.
In the short term this may be adaptation to a new envornment but eventually random mutation takes over.
Their is evidence that closely related members may have difficulty breading with anything from 1% reductions in fertility to 99%. Which arguably makes them the same species as they can still in theory breed.
However, adaptation can make it's own issues. Grizzly's + Polar bears is a solid example where offspring is fertile but poorly adapted to either of their parents environment.
So, now you have examples of drops in fertility and reductions in reproductive success as populations are separated. Nothing is going to stop this process from hitting zero net fertility and thus a new species.
We don't know how speciation happens, and many people including scientists use a lot of unscientific "just so" stories.
To claim we know that every instance of speciation happens through 1. random mutation and 2. "natural selection", a catch-all term which is not well-defined and signifies very little, is not very scientific. But worse than that, it is then conflated with the theory of common descent, and the emergent sociological result is that many scientists and non-scientists constantly co-opt the word "evolution" to say "evolution is true and creationism is therefore false" or whatever. There have been different theories such as punctuated equilibria but we don't actually KNOW how speciation happens. It's all posturing and catch-all terms.
The shocking thing is how many differences showed up not that we are still mostly though again not 100% comparable. Remember, fertility treatments among young people are a thing and incompatibility first shows up as an increase in the natural abortion (miscarriage) rate ~(30% to 50%). You can find set's of people such that A/B and C/D are more fertile than A/D or C/B.
In the former, you need to have some sort of event that separates the populations for millions of generations or they'd constantly be interbreeding. But allopatric speciation examples are few and far between. OR, you know, there could be ANOTHER mechanism besides random mutation and "natural selection" (handwavy term) that causes speciation.
In the latter, how a morphological feature came to evolve when the intermediate steps would have most likely been valleys in the fitness function is an interesting question. Proto-wings do not seem to confer any evolutionary advantage other than the speculative one trotted out by people who must have the development of morphological features proceed ONLY by random mutation and natural selection.
No one is disputing those two things take place. The question is whether they explain ALL SPECIATION.
Feathers for example provide great insulation.
Flying squirrels demonstrate another example. Important to note with flying squirrel vs bats is being even slightly better at flying is useful for squirrels. From their being slightly better at falling to flight is a steady improvement. Even normal squirrels splay their hips sideways to catch air and glide somewhat: http://feedingnature.com/how-high-can-a-squirrel-jump-off-th... Even their tails get into the act.
Flying fish similarly benefit from jumping out of the water, as part of a continuum of other fish that jump slightly further than normal out of the water etc.
Even seemingly useless stubby wings provide for threat displays like a Cobra's hood. Aka, I can make my self look bigger without needing to grow big.
Evolution is often just as much about removing things as adding. So, intermediate form may look clunky and then get cleaned up at a local optimum.
PS: Insects provide some great examples of wings with various amounts of utility.
What time-scales are we talking about here? If it's on the order of hundreds or thousands of years, then yeah, you don't necessarily expect speciation to occur. If your time-scales are on the order of hundreds of thousands or millions of years that's different - and hundreds of thousands of years may be too small. Are you trying to claim that genetic drift over geological time spans does not make speciation highly likely?
>They are still completely interfertile with Europeans after 1000 generstions!
A thousand generation is nothing.
Correct! Because in every generation it is far more likely that the mutant strains would be brought "back into the fold" through interbreeding, and you need the precise opposite effect to happen over many generations to produce a separate species or morphology. So the probability decreases exponentially with generations, not increases.
This very article shows that the male finch was not a different species since it's interfertile with viable offspring.
You are ignoring the need for the mutants to reproduce and outcompete the nonmutants eventually, while somehow simultaneously making a clean break with the other species. The process has not been understood at all.
Is that something you came up with yourself or is it something that mainstream biology acknowledges?
And if random-mutation+selective pressure (i.e. natural selection) is not the primary mechanism for speciation, then what is?
I am happy to say it's pretty evident we don't know.
If we do know, I want to hear the actual substance. What do we know, HOW do we come to know it and where's the proof that mathematically it makes any sense?
However without 2 copies of X, Y becomes harmful. So, it only spreads when the population A already has 2 copies of A.
Now, population B does not have any copies of X and pairs can only get one copy of X from a parent, but will also get 1 copy of Y from a parent resulting in offspring that have issues.
Critically, dependency between mutations is extremely common for example the shape of the bones in your foot are related causing an ever increasing number of incompatible issues. Thus, mathematically independent populations will become less compatible over time.
PS: Mules start to show up when only one copy of X is required so getting one X and one Y is enough. However, offspring are not going to always get a copy of X.
It's neither. I just asked you where you got your ideas from. And it sounds like you are dismissing an entire field of scholarship because you thought about this really really hard.
What alternative mechanisms are there?
While certainly interesting, I wouldn't say this is a great example of speciation. One might even argue that it's an invasive species.
Depending at what scale (in size and time) you observe, we are all one species.
Even in biology there are multiple definition of species. It shows how hard it is to pigeon-hole Life.
Is it more complex than that?
In fact even within sexual species there are a whole range of reproductive incompatabilities: from anatomical incompatibility, to impossible fertilisation, developmental dead-ends, through to live but infertile offspring, and seemingly viable offspring with dramatically lower environmental fitness. Species are an organising model, very useful in a lot of biological reasoning, but they are not a biological absolute.
In general, whenever you were taught something black-and-white with hard boundaries in high school science, they were probably oversimplifying.
The short version is that this definition only works for sexually reproducing species. The long version is that it doesn't work.
"Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression."
<bones>I'm a doctor, not a faith healer!</bones>
"Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers."
<kirk>You're a healer, there's a patient. That's an order.</kirk>
<scott>Now, you're an engineer!</scott>
Lastly when you realize not to worry about people with illogical beliefs, and instead focus on educating those who are either open to information, or already support your beliefs you'll focus your energy on the things that you can actually change. Yelling, worrying or typing "you're wrong" to dogmatic religious adherents, homeopathic healers or conspiracy theorists is not going to change their mind.
I thought it was autonomous mutation plus natural selection.
"We tend not to argue about what defines a species anymore, because that doesn't get you anywhere," said Prof Butlin. What he says is more interesting is understanding the role that hybridisation can have in the process of creating new species, which is why this observation of Galapagos finches is so important.
If you can't define what a species is, how can you talk about the process of creating new ones?
It seems they should be talking about the rate of gene flow between groups. "Genetically distinct" means very little because phenotypes can vary widely and still interbreed. Look at dogs, for example.
I would like to see more examples of allopatric speciation or other speciation. What they have here so far is reduced gene flow to a group of finches. Proving that none of them CAN interbreed with females is not so easy, as anecdotal evidence of females not recognizing songs of males doesn't cut it.
It's a bit like proving that an animal species has truly homosexual individuals. None of them do (except possibly for domesticated sheep) -- in fact the theory of evolution would predict that homosexuality would greatly reduce fitness, but there COULD be some members that are lifelong homosexuals, same as beta wolves etc. However to PROVE that an organism is exclusively homosexual they would need to carefuly watch it and all its pairings, however brief, its whole life.
Now, with species, you have to watch EVERY male with EVERY female around it, and vice versa. That is a huge undertaking and I doubt they did it here.
All they observed is phenotypical differences. And they haven't really explained how this is different from eg dogs, except to say that the females THEY SAW did not prefer the males' songs. Certainly this shows reduced gene flow due to preferences but not that they aren't interfertile. This is much different than a cat and a dog for example.
What I am ultimately trying to say is, I am quite skeptical that we have discovered ALL the means by which speciation occurs.
You can be a creationist or whatever else you'd like to be at this point. We barely understand how speciation really takes place, in the end we still only have theories.
I have read Lee Spetner's book "Not by Chance" which goes into the mathematics of speciation occurring exclusively by random mutation and natural selection. And it is astronomically improbable on its own terms.
This there HAVE to be forcing processes from the outside which we don't know about yet. We only guess into what they could be.
And on a related note, using evolution to explain behaviors and traits is like a religion, full of "just so" stories, in fields such as evolutionary psychology but also to explain pretty much ANY trait in a genetic fitness framework.
These "just so" stories are so pervasive yet smack of a notoriously unscientific practice and framework. All one has to do is concoct a possible way by which a trait (proto-wings, homosexuality, men becoming sleepy after an orgasm -- anything really) might confer some advantage. And the other way, such "just so" stories are used to "explain" the presence of certain traits as "the evolution of those traits" via totally untestable stories about the past.