Evolution, Evolution, Evolution

Hey guys, I've been wondering recently if there actually is any evidence for evolution, since I used to think that it may be true or there are some reasons for believing this theory, but now I'm not so sure.

What I would like to know is, what are the main points for believing in evolution, and what are the main points against it. Mainly on how each side explains transition fossils.

It would be good if it were just short points and explaination of the evidence, not like a massive essay that is a page long on each subject, and also to have points of theists, agnostics, and atheists.

Thanks,

Solarwave

Hey Solarware-

I'm glad to hear you've taken an interest in the subject of evolution. There are a lot of confusing facts and misinformation being fired around on boards like this, but I'll try my best to give a short primer on the underlying basics of evolutionary theory.

First, a little about myself:
I'm about to graduate from a university with an undergraduate degree in Cellular Biology and Molecular Genetics. For this reason most of the thoughts I'll share with you will have a little bit of a cell bio slant, as I don't want to get on a podium and talk at length about fossils when 1) my major isn't paleontology and 2) there is plenty of substantial evidence for evolution all around us that has nothing to do with old bones.

Evolution is astoundingly complex. Even most people who claim to understand it still have nothing but a rudimentary view of how it all works. I've been interested in biology for a long time, and intimate understanding and appreciation of evolution by natural selection is something that comes from keeping a critical mind open to new ideas.

Here we go:
To understand "natural" selection, maybe it will help to understand "artificial" selection. You already understand this as dog breeding. The species Canis familiaris is astoundingly diverse. Great Danes and Chihuahuas are both members of this family and are technically (though maybe not mechanically) able to reproduce and birth fertile offspring. There are dogs with gorgeous long fluffy hair and dogs with long powerful legs. It isn't hard for you to agree that these different dogs have been 'bred' this way. That is, a dog breeder decides which dogs will mate and pass on their desirable traits to the next generation. After hundreds (maybe thousands?) of years, we have the huge range of dogs that we see today, each prized for the traits that people have bred them for. The same has happened with other domestic animals (cows, sheep, pigs) and domestic crops (carrots, potatoes).

But what happens when the process is taken further? When a breed of dog becomes so different (maybe too big or too small) to mate with other breeds? Now it can only mate with those of its own breed and selection continues based on other traits until the 'breed' is so different as to be considered it's own species.

What is to say this process of 'artificial' selection cannot take place 'naturally'? What if it is not a breeder which selects traits that are passed to the next generation, but the environment? What if it is only the furriest and warmest animals that survive a cold winter to reproduce in the spring? Then the next year, there will be more animals around that are furrier and warmer than those that were around before the cold. Those offspring will be better suited to survive another cold winter, if it comes again like it did.

In order to keep this from getting too long, I'll stop here for now. I'll check back to see if I might expound or take the thought in a new direction, but in the mean time keep these thoughts on your mind that many forget:

In the natural world, the process of generating new species takes a long time-- when you're talking about big animals, this could mean tens of millions of years. Bacteria? Perhaps merely dozens of years if the conditions are such that things are being selected for and against at a fast rate. Exactly this is happening with bacteria which are quickly developing resistance to our antibiotics. Just as before, the few bacteria that are capable of mounting a response and surviving the drug pass on their traits to the next generation and now a whole population of cells are resistant.

Please let me know if you have any questions or would like me to talk about other examples. There are too many to name, and if you'd like I can help you sift through some of the data about the fossil record if that's what you're really interested in. Thanks!

~Chaoticeternal

Originally Posted by solarwave

Hey guys, I've been wondering recently if there actually is any evidence for evolution, since I used to think that it may be true or there are some reasons for believing this theory, but now I'm not so sure.

What I would like to know is, what are the main points for believing in evolution, and what are the main points against it. Mainly on how each side explains transition fossils.

It would be good if it were just short points and explaination of the evidence, not like a massive essay that is a page long on each subject, and also to have points of theists, agnostics, and atheists.

Thanks,

Solarwave

Given the general nature of your question, any proper answer would be a long post... I have stuff to do now, but hopefully I'll have time later on. I'll be sure to come back in the next few days if the thread is still empty. PM me if I don't I'm no palaeontologist either (I'm aiming for an evolutionary biology degree, though it's only my 2nd year ), but I should be able to explain some basic stuff.

Glad you are genuinely interested, BTW (if you are).

__________________
"There is much we do not understand about the history of life, and the same will be true of our grandchildren. But, then, if we knew all there was to know, scientific interest would cease. Textbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown." - A.H. Knoll, Life on a Young Planet

"Come on, put your bloody thinking caps on!" - Dr Tony Prave, geology lecture

Originally Posted by solarwave

Hey guys, I've been wondering recently if there actually is any evidence for evolution, since I used to think that it may be true or there are some reasons for believing this theory, but now I'm not so sure.

What I would like to know is, what are the main points for believing in evolution, and what are the main points against it. Mainly on how each side explains transition fossils.

It would be good if it were just short points and explaination of the evidence, not like a massive essay that is a page long on each subject, and also to have points of theists, agnostics, and atheists.

Thanks,

Solarwave

Ok, seems no one wants to take this up, so I'll try to bullet point some of the absolutely astronomical amount of evidence in favour of evolution. I can't promise to give transitional fossils more space than anything else. However, if you have specific questions about transitional forms I will try my best to answer them.

(1) The basic mechanisms of evolution, mutation (including duplications) and selection are alive and well. For some useful mutations have a look at nylon bugs and the other examples in this collection. Also, this historical overview of gene duplication research gives several examples of new useful genes likely arisen from duplication. As for selection, there were a number of selection experiment on maize, fruit flies and heaven knows what else; these experiments work amazingly well. Selection has also been observed in a completely natural setting, and shown to lead to change from generation to generation (for more info, look for material by the Grants and others on Darwin's finches).

(2) There are countless documented cases of speciation in the wild and in the lab. I'll be lazy and pull out the TalkOrigins FAQ on observed instances of speciation (with lots of references if you want to read more). Ring species such as the greenish warbler or Ensatina salamanders are rare cases where "transitional forms" between two species are present at the same moment in time.

Arriving at common descent, macroevolution and fossils...

(3) Life appears to fall into a single objective nested hierarchy. This is the only kind of hierarchy the process of splitting and diverging from a common ancestor can produce (i.e. if life followed any other pattern, common descent would be instantly falsified). Of the immense number of species discovered since Darwin's time, I don't know of a single one that violates this hierarchy*. (This is not proof of common descent, but considering that a designer would be free to reuse traits even between very dissimilar organisms, it is very strong evidence that no design was involved)

(3a) Classifications of life obtained from morphological and molecular data agree surprisingly well, even though in many cases the molecules in question are completely independent of morphology, excluding the possibility that organisms just have similar DNA because they look similar.

(4) Ontogeny. Human embryos have a tail, dolphins start to develop hindlimbs, only to be reabsorbed later, and sea squirt larvae have notochords. These and other examples all hint to ancestry and relationships.

(4a, a bit of an aside to my newest favourite topic. For a recent discovery that primitive bony fishes possess the developmental pathway that builds our hands, see the press release here and the paper here.)

(5) Vestigial structures and "design flaws" are "structures that have no other explanation than the shadow of their past" (see my sig ). In other words, why would a dolphin have a proper forelimb skeleton in its flippers, and why on earth would it have lungs, if it was created to live in water? An amazingly long list of other design flaws can be found here. (Please don't be offended by the site's title etc. Just look at the content, it's pure gold)

(6) The fossil record: general trends of increasing complexity. For anyone with the most superficial knowledge of the geologic record it's well known that bacteria appear earlier than eukaryotes, and multicellular things such as animals come even later. Over geologic time, fossils show an overall trend towards increasing complexity, and communities are made up of organisms increasingly similar to the ones alive today. Even the claims that the geologic column does not exist and it was just stitched together to look that way do not stand: firstly, the geologic column does exist, secondly, where multiple fossil communities are found on top of each other, for example in the South African Karoo Basin, the temporal pattern can be observed in a single area.

(7) The fossil record: transitionals. Let me note that one intermediate organism, though very suggestive, would not be overwhelming evidence for macroevolution. However, in several cases there is a whole series of progressive transitional forms, sometimes giving a very detailed account of a transition. My favourite example is the transition from reptilian to mammalian jaw, which is illustrated here. One great thing about this particular transition is that the stages were even preserved in the right chronological order (unlike, for example, the reptile-bird transition, which has excellent transitional forms, but the pre-Archaeopteryx record is extremely poor).

Hmm... that's all I could think of for a brief summary. Let me know if you want me to elaborate on anything (but please ask more specific questions if possible)

------

*this is not completely true, because there are organisms with genes acquired from two or more different lineages. However, in those cases (horizontal gene transfer, mainly in prokaryotes, and hybrid speciation, the phenomenon that gave us wheat, among others) the mechanisms are known and completely compatible with a genetics-enhanced ToE.

__________________
"There is much we do not understand about the history of life, and the same will be true of our grandchildren. But, then, if we knew all there was to know, scientific interest would cease. Textbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown." - A.H. Knoll, Life on a Young Planet

"Come on, put your bloody thinking caps on!" - Dr Tony Prave, geology lecture

Thanks both of you for the response. Interesting to know.

Ok, so evolution has to take a very long time for any big change in species. How would you explain the ''Cambrian explosion''? Just incase you havn't heard of this, it is in or at the begining of the Cambrian period when then is a ''sudden appearence of most of the major animal phyla that are still alive today, and some which are now extinct.''

The cambrian explosion doubtlessly was a special event, but it is quite well understood.

First off, it was not a sudden appearance of all those phyla "overnight". Even the shortest estimate for its duration is four million years, and it goes up to 40 million years and more.

The actual appearance of the phyla is not mysterious either. During the cambrian explosion hard body parts first evolved, such as shells. This resulted in a massive increase in fossilization rates, which in return results in many phyla making their first known appearance during this period.
And of course, many phyla are defined based on these hard body parts, so their emergence also marks the emergence of these new phyla.

Of course, there is a legitimate question: "Why did so many species evolve hard body parts at the same time?"
Evolution answers this as well though:
If your prey slowly develops hard shells, then you need something to crack that shell. So those predator species which developed hard tools to crack shells (teeth, claws, scissors) had access to a wider range of prey species and thus had an selective advantage.
The progress of evolution overall sped up during this time due to the increase of selective pressure based on such "innovations".

__________________
"One of the most basic laws in the universe is the Second Law of Thermodynamics. [...] Evolution argues differently against a law that is accepted EVERYWHERE BY EVERYONE. Evolution says that we started out simple, and over time became more complex. That just isn't possible: UNLESS there is a giant outside source of energy supplying the Earth with huge amounts of energy. If there were such a source, scientists would certainly know about it."

Originally Posted by jwu

The cambrian explosion doubtlessly was a special event, but it is quite well understood.

First off, it was not a sudden appearance of all those phyla "overnight". Even the shortest estimate for its duration is four million years, and it goes up to 40 million years and more.

Exactly.

And, for example, trilobites might have their ancestors right back in the Ediacara fauna (Parvancorina is a possible candidate; it's quite similar to trilobite larvae. Trilobites.info has a little page on this.)

The actual appearance of the phyla is not mysterious either. During the cambrian explosion hard body parts first evolved, such as shells. This resulted in a massive increase in fossilization rates, which in return results in many phyla making their first known appearance during this period.

*Nods*

And of course, many phyla are defined based on these hard body parts, so their emergence also marks the emergence of these new phyla.

Of course, there is a legitimate question: "Why did so many species evolve hard body parts at the same time?"
Evolution answers this as well though:
If your prey slowly develops hard shells, then you need something to crack that shell. So those predator species which developed hard tools to crack shells (teeth, claws, scissors) had access to a wider range of prey species and thus had an selective advantage.
The progress of evolution overall sped up during this time due to the increase of selective pressure based on such "innovations".

Hail arms races!

I've also heard somewhere that Hox genes might have had something to do with the explosion. I don't know if that hypothesis is still in the game.

__________________
"There is much we do not understand about the history of life, and the same will be true of our grandchildren. But, then, if we knew all there was to know, scientific interest would cease. Textbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown." - A.H. Knoll, Life on a Young Planet

"Come on, put your bloody thinking caps on!" - Dr Tony Prave, geology lecture

Thanks guys for the explanations

Solarwave

You're welcome! (where is the other side, though? In fact, where is this huge pro-evolution community that dominates the crevo forum?)

__________________
"There is much we do not understand about the history of life, and the same will be true of our grandchildren. But, then, if we knew all there was to know, scientific interest would cease. Textbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown." - A.H. Knoll, Life on a Young Planet

"Come on, put your bloody thinking caps on!" - Dr Tony Prave, geology lecture

I know, I was hoping from people like you, and also some from the other side who can give me some thoughts on that, but o well, it was helpful anyway.