Discussion of everything related to the Theory of Evolution.
Alright, I want to start off by saying that I am NOT a creationist with a bone to pick with evolution ... rather I was raised to be open-minded and to question things around me.
So, that being said, I have posed many questions to biology professors and received round about answers directing me back toward the basic theory of evolution. My questions are always of a specific nature - I want to know how scientists believe certain things happened. You don't need to be able to show me exact evidence, but at least forward an opinion. For example:
Why do I never hear anything about how complete systems evolved? An organ, for example, is a system - it is a complete hardware device with all the necessary components with which to function. A form of "software" must also be present within an organism to regulate proper use of that organ and integrate it into an organisms infrastructure.
Now, say there's an increase in genetic materials out there through all the usual pathways (mutation, speciation, etc.) and you've got all the pieces you need. Let's use a snake - did the organism compile all the necessary genes to create lets say it's venom glands and then boom ... there it is? I mean that whole deal is a system - you need the venom gland, the right musculature, the hollow fangs, etc., etc., etc. On top of that, let's say that you get a snake now that has this complete package - what are the odds that this combination will be bred out of the species within a few generations?
On the PBS special on evolution there was an example used of a fish that has a special protein which protects its blood from being frozen. Ok, well, we know that evolution is not a "need" based process so if the water suddenly got really cold these fish aren't going to spontaneously evolve this defense. At the same time we've seen animals move out of areas where the environment moves towards an extreme. Having your blood freeze is pretty extreme. Now, can anyone follow this through to a conclusion? How did they get there?
Again and again we see species that are perfectly attuned to their environments. Flamingo's in Africa have thick leather on their legs which protects them from an acidic lake where they lay their eggs. Other birds would be disabled by these liquids. Ok, well talk to me about how you think that happened ...
In all these cases I'm not looking for THE answer but at least approach the question in some detail that gives me a better understanding of how biologists think these creatures evolved. When you look back at the fossil record or you look at how species can adapt to their environs - yes, evolution looks pretty juicy. But evolution has a lot of questions to answer when it comes to the specifics and, I'm sorry, but someone is going to have to address them because they're present in just about every species on earth.
One last note - the reaction I've received upon asking these questions from a lot of scientists is often a frustrated/defensive one ... which is not very helpful. You want to teach my kids that this is the way the world works - that this is what life is about. Those are very important messages so either pony up and tackle the issues or stop whining about the criticisms.
So ... fire away.
The main problem for specific questions, is that we can make hypotheses, but it is rather hard to have complete answers because of the historical nature of evolution.
But as a manner of fact organs or completely formed objects do not appear just like that after insertion of a bit of code. life is not a computer you have something rather gradual. for poison, things probably started as a salivary gland producing an enzyme probably helping digestion (decayed meat is easier to digest). The fangs were quite common, the canal could have evolved from a deepening slit on the fang that progressively helped reduce loss of the poison (this would be favoured because less poison needed to kill the prey makes a healthier snake). Not everything need to arrive at the same moment and indeed not all snakes have the complete system with ariculated fangs and canals. But by trial (and error) a better overall structure can arise that is the idea.
Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
Nice post. In the case of the flamingos, perhaps the thickness of feathers and resistance to acid gradually increased as the individuals with greater resistance to the acid had increased ability to use the food sources in these areas. The population would evolve these feathers.
As for organs, perhaps they evolve gradually, for example, the first 'eye' may have been a singular cell with the ability to tell dark from light. This could become more advanced through evolution eg multicellular, ability to see colour, lenses etc as these are evolutionary beneficial.
The fish with the anti freeze protein could have come about as the water may become very cold due to some freak event numerous times. Those with a mutation to make such a protein would be much more likely to survive, others would die, evolution follows its course. Perhaps an antifreeze protein allowed individuals to gain access to more food and thus they were more likely to survive.
Of course its hard to tell the specific way things evolved, thats obvious it happened millions of year ago. Its a poor arguement against evolution to criticise because we dont know the specifics. We can almost always have a go at trying to guess how evoution occured. The process is passive and makes a whole lot of sense. Just thinking about how the ability to survive and go onto reproduce is affected can often lead to a more specific guess. But criticising evolution because we dont know the specifics about specifics is not really fair.
Last edited by James on Mon Aug 21, 2006 1:29 am, edited 1 time in total.
The antifreeze protein thingy is probably even easier because the blood is already full of proteins. If a fish have, for any reason, a protein that helps it survive in water 2 C below the other, or slow down the freezing it will be able to reproduce in waters were its offspring will be the only one to survive, they willl get more food, and thrive. Among them, any modification that will increase this advantage will definitely put them at a bigger advantage, and so on generation after generation. The base protein function is now lost or replaced, but the fish can survive where no other is.
Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
you could also ask about how clotting evolved. It was recently featured in a court case for ID vs science
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Thank's everyone for your posts ... this is all fascinating to me …
I just want to clarify, James, that I'm not criticizing evolution for its lack of specifics. I am trying to get people to talk about specific cases to see how evolution can possibly explain specialization in a species. This is by no means an attack.
I also understand that we would need a lot of genes to constitute the creation of a new organ … what I’m trying to understand is process -
So - a particular gene set will create the venom glands + musculature + delivery system. At every stage in this animal’s evolution it would be housing an incomplete system, the parts of which fit into the proper blueprint.
What I find interesting in this trying to look at evolution as anything other than a means to an end. In this example we’re talking about the creation or co-optation of a lot of genetic material to create a very complex system. It feels like we're taking a huge whisk to a junkyard and coming out with a complete 65 Impala.
One last note – it seems that if you have a these multitude of genes milling about in a group of entities, you’d see a growing number of partials before the emergence of a complete system. Is that right?
Yes, however evidence is difficult, ie the fossil record is obviously usually very incomplete and limited.
Whoow hang on you're all talking like you've been asleep the last twenty years of biology research. Replying to James's post above will allow me to start explaining some of the original poster's questions.
First of, the idea that the fossil record is incomplete. This actually and very interestingly was one of the great gaps that plagued Darwin and his reasoning for slow adaptation 'How is it possible that through small changes over many generations species adapt to their environment if we never see these transitional forms in our fossil record?'. Darwin was right in that the fossil record does appear incomplete if you're looking for these rare transitional forms. Gould and Eldridge in the 80's offered a way out of this conundrum by postulating their theory of punctuated equilibrium. This theory posits that genetic pressures for change build up but lie dormant within a population until BHAMM! a species changes which appears to occur almost overnight if you consider the timeframe of the fossil record. Punctuated equilibrium therefore means long periods of no change/stasis/equilibrium punctuated by periods of rapid change. This impt realization means that the fossil record is not I repeat NOT incomplete, our understanding as always was incomplete. Many examples for Gould's theory have now been found.
One of these examples relates to your first question. 'How can an organ evolve slowly if most of the steps along the path would have been detrimental to the specific individual involved or function without the software?'. This process may occur through a process of co-option where one of the functions of the organ in another environment is co-opted for a totally different function; you dont need to evolve a completely new organ and in the fossil record it will look as if suddenly (because of the major advantage this new use of an organ affords) allows for quick species radiation. Example? Well consider the swim bladder in fish which was coopted by the ancestors of the frogs to swim in swallow waters with little oxygen. This bladder was now used as a lung. The bladder was already but by giving it a new function in the mature individual it allowed for a complete different approach and fast-track evolution.
This fish w/anti-freeze is actually simpler. Gould calls this the wheel of fortune which interacts which Darwin's 'wedge'. Species compete for space in an overcrowded environment by wedging out others. However during periods of mass-extinction due to changes in the environment wedging continues but the rules of the game change and those individuals that might have been wedged out luckily survive during this process where nature's wheel of fortune calls forth these bizarre and unpredictable adaptations.
Very good thread. You're questions are very relevant and I'm sorry to hear that your professors couldnt help you with these questions. Hang on to asking these types of questions, the only we can make advances in science is for people to challenge and question the paradigm. Read up on Stephen Jay Gould, read his essays or download his stuff onto your iPod from a P2P server (for example evolution and extinction).
Appreciate the reply - I'm relatively familiar with punctuated equilibrium however I was under the assumption that it remains a contested topic. Punctuated equilibrium would seem to coincide with paleontologists findings ... how does it work with regards to accumulation of genetic materials? You mentioned "genetic pressures for change build up" ... by this do you mean that we have gene accumulation up to a critical point and then we see a species wide transformation?
You're co-optation point is very interesting ...
I'll also check out Gould ...
This may be a little off-topic - but does anyone have any reccomended reading regarding the evolution of inter-species dependence?
I would be interested to see whether you have any material to show that it is a contested topic since most of the stuff that I read acknowledges it as 'true' (always dangerous when that happens). Not to flame you, but I would just be interested in a different take on this.
The idea of the build-up of genetic pressures is difficul but relates to population biology.
Do check out Gould. Have no idea on your recommended reading.
According to anthropologic principle, you see something, because that is the only thing that is there to see. Many things that may have been there have been lost in the ruthless process of evolution. The things that were halfway through, are gone. Only those which are perfectly attuned have survived. Millions of organisms develop mutations everyday (even human, cancers for example). Mutations by their very nature, are only rarely additive of better functions, and so, that particular organism never appears on our radar screen. Well, I am just starting. So, will have to wait for better responses.
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