so if we evolved from apes where are all the "missing links"?

[Bittercreek]

Just like similarity in form doesn't prove ancestry, neither does similarity in DNA. I'm not saying that they never can, but that they dont in this case. I think humans have 97% of DNA in common with mice, and like 75% in common with bananas so go figure. And regarding the similarities in non-coding sections there is great deal of scientific evidence suggesting that their may be a use to this "junk DNA" afterall. Having to do with the structural properties of DNA and theres other theories.

[AzurePhoenix]

Just like similarity in form doesn't prove ancestry, neither does similarity in DNA. I'm not saying that they never can, but that they dont in this case. I think humans have 97% of DNA in common with mice, and like 75% in common with bananas so go figure.

I think it's simply common sense to logically assume the closest and most similar group would in fact be the one to pinpoint as human ancestors. What else did we possibly arise from if not apes? Did an artichoke suddenly bloom one day and humans just sorta unfurled? If not apes or artichokes, what ancestral line do you propose makes most sense?

 

There is simply no logical reason to claim that similarity in DNA between morphologically related organisms (all morphologically related organisms in a comparative chain from one end of the evolutionary chain to the other, oh my! ) is just a monstrously freakish coincidence. And don't say "god made it that way," that abandons all logic for a mystical reason. You can say that of course and believe it if that's what you believe, but to be honest you'll have to acknowledge the paucity of logic and rationality in that line of thought from a scientific point of view.

 

Fine, go ahead and denounce the science, but if you're going to do so, can you try to provide a reason why it isn't so and provide an alternative explanation?

 

 

----edit----

 

Pah, this is all a non-issue because the thread-maker was asking a question about something specific in evolution he was wondering about, did not ask for the dispute between evolution and... whatever it is the other guys are clinging to at this moment. I apologise to Blackhole123 for letting myself carry this irrelevant sidetracking even further.

[scicop]

One reason to reconsile why DNA is similar (not really..i'll explain) among distant unrelated and related species is that when nature found something that worked, it kept it!!

 

Certain gene sequence motifs are so penatrant that if you were to do an "evoluntionary trace" of that sequence (a technique used by scientist of many diciplines), you would find it nearly unchanged accross multiple divergent species. For example, certain transcription factors and DNA binding motifs, or even receptor sequences. In fact in order to tell which part of a protein/receptor that may be ABSOLUTELY necessary for function, scientist turn to the "evoluntionary trace" analysis technique and assess what is unchanged. Chances are, once they find a conserved motif and do a mutagensis study, their change to that gene can render its product (protein) inactive.

 

So obviously nature "knew" that to change that motif would compromise survival of the protein, and ultimately the whole organism. As an example, take the "eyeless" gene. The gene is a transcription factor. A master regulatory gene as the geneticist call it. Without this ONE gene, NO EYES are formed. So one mutation (i.e. DNA binding domain maybe) to a region that is important to that gene, can mean the difference of life and death. Obviously this gene was important to one of our common ancestors and it survived through the ages. (you can take the fruit fly version of "eyeless", and express it in a frog..know what happens...ectopic eyes!!..NOT KIDDING).

 

So no, a banana didn't become a human one day. Rather in DNA motif similarites between us and other different unrelated species suggest that to our common ancestors, that gene was important and allowed for their propagation/survival. This story is similar to those genes that DO CHANGE. In that case a mutation provided an selective advantage and thus allowed a species to survive, in this case though I'm talking about conservation of sequences that nature deemed.."perfect".

 

As for similarities, yes we have similarites to APEs, but mostly with our coding sequences. There is alot of divergence with the non-coding sequences, which make sense given the non-coding sequences have regulatory elements for control of gene expression.

 

Did humans evolve from the fruit fly..no. There was a common ancestor, which, most likely was a single unicellular organism that lived at the bottom of the ocean.

[Mokele]

Oh, look, a pair of creationist trolls.

 

::Waves to them::

 

Bye! Have fun in Bansville!

[SkepticLance]

bjaminwood

Do you not know what a load of absolute codswallop you are selling?

 

I checked you 'rebuttal' on answersingenesis. What a load of idiocy.

Do you really think that a 'missing link' will magically be exactly half way between one organism and another? Of course not. The laws of chance will place it closer to one or the other. The fact that Livoniana was closer to ancestor than descendent does not stop it being a link.

 

Between fish and amphibians, we now have two more 'missing links'. In Scientific American; December 2005 page 80, we have a description of Acanthostega, which is dated 360 million years ago. A fish, with fish tail, and four clearly distinct legs. Since its legs were too weak to lift it out of water, it is suspected that they evolved to hold its head only above water. Since this was clearly a member of the lungfish family, the selective advantage is obvious.

 

In addition, we have fossils of Tiktaalik, named after the Inuit district where they were found. This is clearly a fish, with limbs less well developed than Acanthostega, but with a wrist-like joint showing it could do a 'push-up'. New Scientist : 8 April 2006, page 14

 

The relationship to later tetrapods that are full amphibians is clear.

 

I rechecked your earlier answer to a previous question, where you tried to discredit dendrochronology, by quoting answersingenesis where another total moron tried to say that trees can make two rings in one year, and this disproved dendrochronology dating. For your information, that is a rarity, covered by the fact that dendrochronologists test many trees, to eliminate such flukes. Tree rings have been counted back 20,000 years. Way beyond your ridiculous 'the world is no more than 10,000 years old.'

[Edtharan]

Rather in DNA motif similarites between us and other different unrelated species suggest that to our common ancestors, that gene was important and allowed for their propagation/survival.

Also gene sequances that can be in one of several stable motifs, but there is only one that can be found in organisms also evidence common ancestory. And where organisms have evolved the equivalent (but non identical) motifs it shows that the two species must have no common ancestor scince the motif evolved (thus proving a certain seperation).

[scicop]

Also gene sequances that can be in one of several stable motifs, but there is only one that can be found in organisms also evidence common ancestory. And where organisms have evolved the equivalent (but non identical) motifs it shows that the two species must have no common ancestor scince the motif evolved (thus proving a certain seperation).

 

totally didn't get what you're saying. clarify.

[Edtharan]

totally didn't get what you're saying. clarify.

err, sorry, I haden't had much sleep lately.

 

What scicop was saying was that there exist stable sequances of genetic code, that if changed much, stop a viable organism developing. There can be more than one viable, stable sequance tha tperforms the same function and the chance that a sequance can spontainiously mutate from one to the other is verry low.

 

If two similar organisms are found, one can use these sequances to trace their ancestery to see if they are genetically related. If the sequance is the same then the chances are that the two organisms are closely related. If the sequances are different, then the chances are that they not related (but could still be, but it would have to be before that sequance was evolved in them).

 

I hope this helps.

[Mokele]

We seem to be forgetting about non-coding regions of DNA, which can mutate freely. When examining species which changed recently, you can examine these sequences to see not only how similar they are, but the rate of change with time (molecular clock).

 

Also, most changes to proteins do nothing; they don't change the resultant amino acid, substitute it for one of similar properties, or affect a part of the protien which has no real function. Even functionally identical homologous protiens can have different genetic codes (and where they're *not* different can actually tell us where the important parts of the protien are).

 

Mokele

[Dr. Dalek]

.... most changes to proteins do nothing;

I thought when one part of a protein, or other complex hydrogen containing organic molicule, changes it alters the the shape of the molicule because of changing hydrogen bonds.

they don't change the resultant amino acid, substitute it for one of similar properties, or affect a part of the protien which has no real function.

 

Are you refurring to the vast number of redundancies in the Genetic Code => amino acid translation: IE the multiple ways of coding for the same amino acid?

[Mokele]

Well, think of a string of mRNA that's going to be translated into protiens, and where mutations could be and what the effects would be.

 

If the mutation is in an untranslated section of the gene that's snipped out before translation, the mutation will have no effect.

 

If it's in the translated portion, but the change doesn't alter which amino acid is coded for at that point (due to the redundancy), it won't matter.

 

If it does alter the amino-acid used, but it substitutes a polar AA for another polar AA, it'll have no effect on the final protien structure.

 

And last but not least, protien design is constrained by the fact that it's all in a line that's folded up, so, while it can be optimized by selection, some bits won't actually be useful, and are essentially just holding everything together (and thus, it doesn't actually matter what AA is there, only that there is one there).

 

So, in all of those ways you can see mutational differences between homologous protiens in different species. Hemoglobin's important, but you still see differences between fish, turtle and human hemoglobin, especially in the portions of the molecule that aren't particularly useful.

 

Mokele

[SkepticLance]

Dr Dalek.

You are absolutely correct. Quite small changes to a protein molecule can change its shape dramatically. And shape is all important with respect to function.

[Dr. Dalek]

Dr Dalek.

You are absolutely correct. Quite small changes to a protein molecule can change its shape dramatically. And shape is all important with respect to function.

So that being said probably a lot of genetic disorders arise from very small mutations. One change could screw up the whole protein.