Actually, they do. They show descendancy and that species change over time. That *is* evolution.
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Does anyone believe in Evolution anymore?
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Actually, they do. They show descendancy and that species change over time. That *is* evolution.
LightofTruth
Well-Known Member
Considering all the life that this plant has known how is it that fossils are considerably rare to find?
Well, most living things decay. The fossilization process requires some pretty specific conditions to happen. Also, even the fossils tend to be broken up over time, so those that form can be lost.
TagliatelliMonster
Veteran Member
They do if the relations and nature thereof are consistent with the predictions of evolution.
And they are.
LightofTruth
Well-Known Member
What are those specific conditions for fossilization?
LightofTruth
Well-Known Member
What does it take for one species to be considered another species?
And how do different species come to be in the first place?
Were all species one species at the beginning?
That depends on the location. Generally, you need some sort of oxygen deprivation to make sure decay is slowed. But it is possible to have drying (mummification) as an alternative. I tis also possible to be encased in amber, for example, or an impression made instead of actual fossilization.
This is why most fossils are of species that are either in water or close to water. We have *very* few fossils from mountainous species. The conditions for fossil formation are much more rare in the mountains.
Now, ALL of this is easily found in a basic book. Maybe instead of trying to glean pieces of information from an internet forum, you might want to read an actual textbook about this material first?
Well, that is *precisely* what Darwin wrote about. The 'Origin of Species': how do new species come about.
And the answer is through mutation and natural selection, the variants that exist in a population can 'break off' (say via migration) and change independent of the original population.
Whether there was just one species (of bacteria) or several at the beginning is still somewhat of an open question. But 'at the beginning', only bacterial (simple single celled) life existed. Again, we have fossils of this.
LightofTruth
Well-Known Member
Are there any fossils that are of the same species we have today?
TagliatelliMonster
Veteran Member
Defining what is and is not a seperate species can be a bit hard at times. Ironically, this is so because of the gradual nature of evolution. So in some case, to a certain extent at least, drawing the line might be a bit arbitrary.
In general, the line is drawn on "no longer interbreeding". That doesn't mean that interbreeding has become physically impossible already. It just means that in nature, they don't interbreed when put together.
Vertically. Very simplisticly put, you can say that every new generation in a population is 0.001% different from the previous one due to genetic change / mutations.
These would be as good as invisible to the naked eye. These changes accumulate through generations.
If every new generation, is 0.001% different from the one immediatly preceeding it, then changes quickly accumulate.
Let's say generation 0 is the reference generation.
Gen 1 is then 0.001% different from gen 0.
Gen 2 is then 0.002% different from gen 0.
Gen 5 is then 0.005% different from gen 0.
Gen 10 is then 0.01% different from gen 0.
Gen 100 is then 0.1% different from gen 0.
Gen 1000 is then 1% different from gen 0.
This is off course a too simplistic representation. In reality it is a tiny wee bit more complex then that. But essentially it's the crux of the matter. Changes accumulate ever generation. Some achieve fixation, some done. Some branches die off, others thrive. etc.
So speciation is a vertical process. Species produce sub-species over time, through this accumulation.
When populations split up and become genetically isolated from one another (a group migrates away, or some geological event creates a geological barrier splitting a group in two, etc), then they no longer interbreed and the changes happening in one group, won't be crossing over to the other.
This is how multiple species evolve from one mother population.
Gen 10 is then 0.01% different from gen 0.
Gen 100 is then 0.1% different from gen 0.
Gen 1000 is then 1% different from gen 0.
This is off course a too simplistic representation. In reality it is a tiny wee bit more complex then that. But essentially it's the crux of the matter. Changes accumulate ever generation. Some achieve fixation, some done. Some branches die off, others thrive. etc.
So speciation is a vertical process. Species produce sub-species over time, through this accumulation.
When populations split up and become genetically isolated from one another (a group migrates away, or some geological event creates a geological barrier splitting a group in two, etc), then they no longer interbreed and the changes happening in one group, won't be crossing over to the other.
This is how multiple species evolve from one mother population.
That certainly seems to be what our collective DNA suggests.
The question is a bit ambiguous.
Many modern species do not appear in the fossil record until very recently. For example, the deer that existed even a million years ago were different than those that exist now.
On the other hand, there are species that have lasted fairly long periods of time, typically in stable environments without significant challenges.
There was a LOT of change in the range of species about 10,000 years ago (very, very recent) when humans invaded North America and killed off much of the megafauna (mammoths, giant sloths, etc). This was also about the end of the last ice age, so there was a lot of environmental stress too.
LightofTruth
Well-Known Member
I find it interesting that life existed as "only bacteria". Has bacteria life always existed?
The earliest life we have record of was bacterial. There was a time on Earth before life existed, though.
For about the first 2 billion years of life, it was *only* bacterial. For a bit over 1 billion years after *that* it was still only single celled (but more complex cells).
Audie
Veteran Member
If I may, rarity of fossils varies tremendously.
Clams for example, are to be found in vast abundance.
They live in the right places, and, they have a hard shell.
The "white Cliffs of Dover" are entirely composed of fossils!
OTOH, a small rare bird in the jungle? Next to no chance it
will leave any fossil behind.
LightofTruth
Well-Known Member
Doesn't the evidence show that those fossils were found after water has receded?
It is not at all clear what you mean here. There has *always* been some dry land, although initially it was volcanic and not suitable for life. This would have been in the first billion years or so of the Earth's existence.
The sea level has varied a lot over time, rising and falling based on the extent of the ice caps (and thereby temperature) and the movement of the continents. There wasn't a 'one time' of water receding. Nor was everything ever all under water.
And fossils have been found *throughout* the time periods we are talking about. Initially bacterial and then single celled, we get multicellular life about 800 million years ago. ALL life at that stage was in the water, but dry land did exist.
Modern humans have only been around about 300 thousand years with documented ancestors after the split with chimps going back a few million.
Audie
Veteran Member
I've had the unusual privilege of being out in the
badlands with a paleontologist, and did a little
"collecting" (pick up leaverights).
A common sight was turtles weathering out, and
scattered downslope.
He remarked that it is like a conveyor belt, fossils
being emerging and being washed away. This
turtle here was in the ground for 20 million years,
and when it reached the surface it practically
exploded. And every day,there are fewer and
fewer of the old fossils to be found... words like
that.
I would make a poor paleontologist, I did not like
being out in the bright sun and dry wind.
LightofTruth
Well-Known Member
Isn't there dry land under ice caps?
What do you mean by 'dry'? Ice is made of water, so that land is covered with water. Some of that water will be liquid, so that land will largely be wet.
Audie
Veteran Member
As with poly, I am not totally clear what you mean.
I am guessing a reference to "the flood".
There is no simple answer, unless it is to say, "Well,
you cant be looking for fossils underwater.
If you drill an oil well in Kansas, you will get little
pieces of seashells, from hundreds of feet underground.
Yeah, the water has long since receded from Kansas.
Those are marine fossils, of cretaceous age. There
was an inland sea, with giant sea turtles nesting on
the beach in Wyoming, 60 ft crocodiles lurking about.
That sea is long since gone, that which got
buried in sand or mud got fossilized, and
most of the life disappeared with no
trace. A typical setting for fossils to form would
be in a shallow bay,or in a river delta where
sediments will be brought in and sink to the
bottom.
Since our fossil of a sea dragon (Mososaur)
was buried 70 million years ago or so,
the rocky mountains started rising and eroding
so that a vast sediment plume spread out
across the prairie and buried the old seafloor.
Historical geology is actually pretty interesting.
The landscape really comes alive if you
have even a little understanding of what
you are looking at. The landscape can be
read, but you have to know how to read!