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Butterfly Unlocks Evolution Secret
Anonymous Coward writes "The BBC has an article about a dramatic discovery in the quest for understanding evolution. From the article: 'Why one species branches into two is a question that has haunted evolutionary biologists since Darwin. Given our planet's rich biodiversity, "speciation" clearly happens regularly, but scientists cannot quite pinpoint the driving forces behind it. Now, researchers studying a family of butterflies think they have witnessed a subtle process, which could be forcing a wedge between newly formed species.'"
IANAEB (Evolutionary Biologist), so I'm just going by the article here, but it seems like the process itself was obvious (or at least pre-supposed) as you suggest, it's the chance to witness it in nature that's exciting here.
... that's all i got. IANAEntomologyst either.
I can't really answer your butterfly question, but I can point out that every insect has multiple stages of life. Flies start out as maggots,
While we're asking the tough questions, it seems like the one big gun the Divine Design people have left is in the differing number of genes between species. If all offspring have the same number of genes as their parents, and all species on earth are evolved from one original life form, shouldn't all creatures have the same number of genes? Are there any theories out there regarding how genes are added or subtracted over time?
While we're on the subject, I might as well reply to myself and point out a selective advantage to multi-stage lifecycles, namely that the different stages do not compete with each other: they eat different food, and fill different evolutionary niches. This means that in times of scarcity there is little advantage in adults behaving like those of some non-metamorphising species, who will kill youngsters, as they are in direct competition with them for resources.
It is also very unlikely that full-blown metamorphosis arrived on the scene ex nilho. There is apparently ample evidence in the historical record for incomplete metamorphosis, via a 'nymph' stage.
You may find the following page interesting: "How did the process of metamorphosis evolve?".
-- Help Digitise the Public Domain at DP.
I agree. The BBC report seems confusing and explains the after effect of speciation (distinct wing markings) as the cause of speciation and as being useful because it prevents hybridisation.
But prior to divergence it wouldn't be hybridisation.
I suspect it's just poor wording on the reporter's part and the full story is something like:
There are butterflies of different species present in the same area. In order to prevent hybridisation they select mates on the basis of wing pattern. Some members of a species develop an abnormal wing-pattern. Although they _could_ breed with other members of the species, the inbuilt preference for mating with similarly-striped partners means they only mate with each other. This isolation of their genetic pool leads to an accumulation of mutations which make it impossible to breed with their ex-species. Now they are a new species.
(Also, I though hybridisation could be useful when there wasn't enough genetic variability in the parent populations.)
This article from the BBC is misleading. I tracked down the original article in Nature.
The researchers didn't actually unlock any major secrets. It is no secret that two species who would not produce viable offspring together will try to avoid mating with each other. There are various mechanisms for doing that - having different wing colors so that species can distinguish their optimal mating partners is one method. If the two species are geographically separated, there is no need to develop other methods of separation, and thus their wing colors can look similar. There is nothing new about this.
Also, the BBC article never explains that the speciation of these butterflies occurred while they were geographically separated (this is called allopatric speciation, and the Nature article specifically states that the butterflies evolved this way). The species only developed different wing markings when they came back into contact with each other. This makes a lot of sense - they were now genetically very different, and offspring between members of different species would not be successful, so they needed ways of telling each other apart.
It's a nice finding, but certainly not the unlocking of a major secret.
Here is what I think about butterfly (and any creature that goes through a laval/pupation stage)
By being born with little more than the ability to eat and move to the next meal they save the parent a huge amount of energy. Usually a parent creature has to drop a lot of their energy and food into incubating or laying an egg that will feed the young until they reach a fully matured stage.
With butterflies, flies and most other insects it becomes more efficient to lay an egg with only enough energy to create a rudimentary creature that does little more than eat and move to its next meal. This allows the parent to lay many many more eggs that have a chance of survival than if their eggs hatched directly into adult forms.
Now comes the fun part. The insect larva can slowly continue to develop into its adult form. It can develop wings, shed the extra legs change form as it matures. This is very bad for the species as it will eventually reacha point where it is niether lavae nor adult. It will go through some rather awkward stages where it becomes quite vulnerable. The earliest insects would likely have gone through this transformation as a gradual process while they ate, and probably wouldn't have a cocoon stage at all.
The species that will survive the best are going to be the ones that can hold off this transformation until they have enough food stored in their bodies to go hide somewhere. By hiding and going through the transformation in one go they avoid any awkward vulnerable stages (like developing large wings but having a body too big to fly). The ones that have the ability to create some form of protective shell (silk, folded leaves, or burrowing into the earth or into wood) have an even better chance of survival.
Basically the whole larva>cocoon>adult thing is to minimise the amount of energy the parent needs to spend on each egg, allowing more eggs and thus a greater survivability of the species.
Just an idea.
First two minor points, then I'll get to the real subject, the math of evolution.
theory is a theory my friend
Every field of science is a theory, my friend. Everything from the theory of the atom to the theory of zymosis (that's fermentaion). You may as well try to attack relativity as being "just a theory".
sortof like the unprovable assumption of evolution?????
What unprovable assumption of evolution? Evolution fundamentally says that if if you have heritable variation and mutations and selection pressures on that variation then you will get evolution over generations. This is trivially observable fact. There is no genuine scientific dispute over biological evolution exacly because there is so much evidence that cross checks and cross validates across so many feilds, both current observations and study of prehistorical evidence left behind. Trying to even scratch the surface of this mountain of evidence in this post would be hopeless. If you are questioning the quantity and quality of the evidence, I suggest you either crack open a text book on the subject or at least browse the talkorigins website. It's all well documented if you actually question the issue. If you don't truely question the issue and you instead simply reject the entire subject on non-rational grounds, well obviously you're not going to be swayed by something silly like actual evidence and actual science.
Anyway, the real issue I wanted to address was this one:
the sheer numeric improbability of evolution
Correction, the sheer numeric CERTIANTY. There's powerful mathematics to evolution, powerful effects going on that you don't hear about in the common explanations of evolution. The common idea of evolution is as a sequence of individual beneficial mutations, like climbing a ladder. If that's how evolution actually worked then critics would be right, it would have been mathematically impossible for evolution to produce the incredible complexity we see today.
To show the true mathematical power of evolution I will first abandon that "ladder climbing" of beneficial mutaions. In fact lets assume that every single mutation that occurs is either neutral or harmful. I'll demonstrate that we still get the real and powerful mechanism of evolution, the math of evolution.
A good place to start is with the common complaint of creationists that mutation and evolution "cannot create information". Well in the initial mutation phase they are right. When a mutation occurs it introduces noise, it tends to degrade information. But look what happens the moment that mutation gets passed on to an offspring. That mutation is now no longer random noise, it now carries a small bit on information. It carries a little tag saying "this is a nonfatal mutation". The presence of this mutation in the offspring is new and created information, the discovery and living record of a new nonfatal mutation. Over time the population builds up a LIBRARY of nonfatal mutations. This library is a vast accumulation of new information.
That information actually undergoes even more processing and synthesis. Over generations beneficial mutations would obviously multiply, but we're assuming there are none of those here. However entirely neutral mutations will also tend to accumulate and multiply. Nearly harmless mutations would also accumulate and multiply to a lesser extent. Somewhat harmful mutations will even accumulate, and extremely harmful-but-nonfatal mutations will pop up and disappear at the rarest frequencies. So not only do we build up a library of nonfatal mutations, the mutations get tagged with a tagged with a frequency, the percentage of the population carrying that mutation. Each mutation is tagged with a measurement. Every mutation now carries a cost/benefit information tag at the population level. The best ones have a high percentage representation and the most harmful ones have a near
- - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
For your specific points, these are very common questions / issues from creationists and others (except the bone question), so the Index is useful:
It's actually even simpler than that: insects, because of their hard exoskeletons, usually moult (or shed their hard body) a couple of times throughout their lives: it's the only way they can grow.
Some insects (e.g. locusts and cockroaches) basically look more adult (bigger, better wings, etc) with each instar (period between moults.) This guys need to act like adults from the time they are hatched (although some species actually have the parents nurse until the offspring are developed enough.)
For insects laid on carrion, ripe fruit, edible plants, and other transient food sources, time is of the essence: hatch fast, be a sac with a mouth, eat all you can, then pupate and get to the complex, energy-expensive adult stage in one moult.
Note that simple cocoons are nothing more than hardened/dried outer skin - it's just a moult.
My favorite refutation of the bogus Second Law criticism is a seed in some soil in a terrarium. You add nothing but maximally-entropic hydrogen and oxygen in the form of water, maximally-entropic carbon and oxygen in the form of CO2, and sunlight. The seed will sprout and proceed to reduce the entropy of those raw materials in its own growth. The fundies who assert the 2nd Law don't realize that the system creates huge amounts of entropy; it's just leaving in the form of the ~300K waste heat that was once the 5700K solar blackbody spectrum.
Time is Nature's way of keeping everything from happening at once... the bitch.
Evolutionary Biologists have long known some of the mechanisms of speciation. And any freshman in any college intro to Population Biology class knows these quite well...
For instance, one of these mechanisms is spatial segregation, in which some members of a single population become physically separated from another group of that population, by some phenomenon (think changing tidal patterns/river flow paths). This physical separation causes reproductive segregation/separation that leads to speciation by non-shared mutation.
Another is behavioral segregation, which has been mentioned in this thread (orcas hunting fish vs hunting mammals), which leads to social exclusion and, again, reproductive segregation.
Finally, there is selective segregation, which refers to segregation of members of a population due to proficiency at some task necessary for survival. For instance, the Darwin Finches of the Galapagos Islands are under quite strong selective pressure surrounding the size and shape of their beaks. Some finches with long and thin beaks are able to feed on fruit that has small holes in the fruit body, while other members of the same species have larger and stronger beaks that they may use to crack open other kinds of seeds. When food is plentiful, both phenotypes are able to get along just fine on seeds and fruits that lie inbetween these extremes, but when selective pressure is applied (in the form of a famine, perhaps), this small phenotypic difference in beak size/shape results in survival for these two, now more genetically distinct, genotypes, while those finches that fall inbetween the two extremes tend to not survive. If such a selective pressure (famine) lasts for long enough, the two resultant populations may achieve speciation. All of these mechanisms have something in common, they all require reproductive segregation of some sort. This research is all at least 10 years old, and this article is just scientific fluff.
For an extremely interesting and pertinent read, try The Beak of the Finch: A Story of Evolution in Our Time by Jonathan Weiner.
I have to say that there clearly is a misunderstanding of evolution by either the reporter or the scientists; most likely the reporter. Species are not defined by their inability to reproduce. That is a creationist myth that somehow got accepted as being connected with evolution. Darwin saw it differently. First, start with variations in animals. Variations like long ears and short ears are defined as animals living today where "steps" linking the two animals can be found still living. Between the short ear and the long ear can be found not so short eared, medium length eared, and not so long eared, etc. That is variation. Species are linked not by "steps" living today but by "steps" in the fossil record. Today you would only find long eared and short eared and nothing in between. Only when you dig into the fossil records do have a hope of finding the lost "steps". Remember that only a small insignificant amount of creatures get fossilized and are found by us. The rest are lost to us. So once again variation is separated by space and species are separated by time. Whether the long eared and the short eared can mate together is also a matter of a gradient from full fertility to zero fertility of individual animals; not a cliff like separation. Every once in a while (every seventy years or so) you hear stories about a mule that gives birth. Can a giraffe and a fish mate? No, because the divergence of the two in time is so great that their reproductive systems are incompatible. Can a zebra and a horse mate? Yes, but with extreme difficulty and is dependent on finding two individual animals that can mate; i.e. less variations between the two in the reproductive area. Can coyotes and wolves mate? Yes, and it seems to be happening more and more to the point where the grey wolf will be replaced entirely by a new type of animal that is a mixture of wolf and coyote.