Hurm... *Mammals ARE fish* hurm, hurm...
I am a layman in all respects and i am confused a little by certain evolutionary theories. We know that once there were mammals that devolved back into fish and that fossil records are based on skeletons and not necessarily biological processes.
As mentioned, the term 'devolve' is not very good. Evolution is a continuous phenomenon, the population acquire new genes and selective pressure make the individual carrying the most beneficial among these genes more prevalent.
Over time, these genes become the norm...
Depending of the situation, the 'winning solution' can be a more complex organism or, on the contrary, a simpler and/or more frugal ones... A population may even loose traits that its ancestors only recently acquired, but there is no 'devolution', it is the same evolutionary mechanisms, just selecting in two, somewhat opposed, direction.
To take your example, cetaceans (which, by the way, evolved from a full fledged mammal rather than a 'proto-mammal') did go back to the oceans and loose characteristics that their distant ancestors acquired when the conquered the land. Similarly, they were selected toward something that may appear superficially similar to their ancestral fish.
And yet, when you look at both, the differences are still unmistakable. The cetacean's tail, for example, move up and down rather than from left to right as the fish' do, a reminded of the mammalian's hip structure.
So i wanted to know what a clone was. Are clones built from DNA? And is it not true that DNA can be extracted from bones? Inside the cell is the DNA, and a piece of bone contains cellular properties, hence it must contain the DNA too? Is that right?
Pretty much.
Then shouldn't it be possible to clone any ancient species with skeletal tissue in a laboratory? I don't see why not.
Indeed, and it has been attempted. But cloning is still quite a difficult science and the process is still in need of improvement. I strongly believes that it's coming, though.
You could find the different species in the bones, the different bacteria, and date them, and then find the original DNA and repduce the bacteria or organism.
Ok... so...
Bacteria? Bacteria are microbes, germs... There are not part of the bones. They should not be present in a healthy bone.
Assuming you mean, 'finding the cells/nucleii' on the bones and extracting their DNA to clone them then, yes, it is probably possible, although there seems to be technical difficulties with that...
And you could build up a zoo of extinct organisms and animals and check their evolutionary trends very well in order to determine the exact lineage properly.
Yes... To an extent.
As people have mentioned, DNA is degraded in the decomposition process. It still is more stable than many molecules and hangs on longer, but it ends up being degraded nonetheless.
Even on younger samples, the genome will often be sheared, short sequences of incomplete DNA.
So, there would be a limit about how far we can go until there is no DNA left for us to extract and how ancient the species in our zoo could be.
As far as studying evolution, then, it would be of limited interest.
It's a bit like, if you want to study history be looking at videos. It probably works fine for the most recent events, but it only covers the last century or so of events, anything older, you simply won't have any records to go by...
And, our extracted DNA would be about the same, a very short tentalizing snapshot but not covering a big enough timespan to record much of the 4 billion years of evolution.
This could rule out or rule in the sudden appearance of mutations along the evolutionary lineage.
The implications for sudden mutations is quite important but not so important in the bigger scheme of things.
Mutations are all pretty sudden, but, I guess you mean, big, rapid evolutionary changes and, yes, these ones are difficult to pinpoints in the fossil records. Keep in mind, however, that the fossil record is much more complete than many people give it credit for...
There is yet one other aspect.
We, the organisms leaving today, are still carrying genes inherited from our ancestors. So, by comparing the genomes of two related species, one can discover the genes they have in common, inherited from their common ancestor. This is routinely performed in labs all over the world and gives us quite an insight in the evolution, beyond 'mere skeletons' and this technique allows us to look quite a bit further than any DNA that'd we could be extracting from bones...
