On the Origin of Feces

[tyrannosaurus vex]

So has the fossil record produced evidence for a complete transition from one species to another? Forgive my ridiculous questions, I'm just looking to fill in some gaps in my understanding of evolutionary theory.

Plus some bastard infected my brain with a bunch of this crap which is undoubtedly rooted in some kind of twisted Creationist plot to undermine my understanding of science.

But even after looking through wikipedia and other more reliable sources of information it would appear that the fossil record contains lots of evidence that there have been different species, but not as much evidence for those species evolving from one to another. Like a species exists in the fossil record and then died out, and another species that descended from the first shows up in the next epoch, but transitional species between the two are difficult to find for some reason.

Or is that just horse shit? I'd sleep better if I knew it was.

Edit: Or do I just have some fundamental misunderstanding of it? Using my own brain instead of repeating what I read on some website, I'd guess that every species is transitional in some lineage. Since the fossil record can hardly be expected to preserve every animal that ever lived, we have to use logic to infer that the species that showed up in the Jurassic didn't come out of nowhere spontaneously, and must therefore have ancestors in the Cretaceous, even though none of the animals in the Cretaceous belonged to that species.

[Requia ☣]

Homo Erectus to Homo Sapiens Sapiens is really really well documented.

[Kai]

So has the fossil record produced evidence for a complete transition from one species to another? Forgive my ridiculous questions, I'm just looking to fill in some gaps in my understanding of evolutionary theory.

Plus some bastard infected my brain with a bunch of this crap which is undoubtedly rooted in some kind of twisted Creationist plot to undermine my understanding of science.

But even after looking through wikipedia and other more reliable sources of information it would appear that the fossil record contains lots of evidence that there have been different species, but not as much evidence for those species evolving from one to another. Like a species exists in the fossil record and then died out, and another species that descended from the first shows up in the next epoch, but transitional species between the two are difficult to find for some reason.

Or is that just horse shit? I'd sleep better if I knew it was.

Edit: Or do I just have some fundamental misunderstanding of it? Using my own brain instead of repeating what I read on some website, I'd guess that every species is transitional in some lineage. Since the fossil record can hardly be expected to preserve every animal that ever lived, we have to use logic to infer that the species that showed up in the Jurassic didn't come out of nowhere spontaneously, and must therefore have ancestors in the Cretaceous, even though none of the animals in the Cretaceous belonged to that species.

Okay, so,

First of all, it is impossible to determine whether one species gave rise to another from the fossil record. It is untestable, unless you invent a time machine that can go back and watch the speciation.

In modern systematics and evolutionary biology, since incidence of one species turning into another within a single lineage (anagenesis) is untestable, we work only with testable hypotheses of relationship by branching or splitting of lineages (cladogenesis). We know that sister lineages must share a common ancestor, but whether one of those lineages is the ancestor of the other is untestable, so we just work with relationships.

We discover these relationships by homology, what I have referred to before as "the key to the heart of biology". Homology is not just similarity, but special similarity that is a hypothesis of a common origin. The forelegs of a mammal, a bird, and a salamander both in the sense of their location and constituant parts would be examples of a homology. By mapping homologies on different species and lineages, we arrive at a tree like diagram of hypothetical relationships. The most informative type of branching is dicotomous, since it has the least assumptions.

Here (http://en.wikipedia.org/wiki/Therapoda) there is a cladogram of the Therapoda, a tree diagram that maps the relationships between different Therapod lineages. Note the dicotomous branching, and that higher groups, like Eumaniraptors, are distinguished by nodes where all members of that group stem from the node, indicating a common ancestor.


Now, the media often talks about transitional fossils. In the true sense, all fossils are transitional, just like all species are transitional (unless they have become extinct). Usually what they mean is some sort of inbetweeness in form between two markedly different lineages. An example would be Archaeopterix, which has many characters shared by Deinonychosauria, the sister group to the group that contains the modern birds, but also has feathered wings, a uniquely shared character of all members of Avialae. Looking here (http://en.wikipedia.org/wiki/Avialae) you can see a cladogram of the Avialae. Since Archeopterix is related to the rest of the Aves clade, but not as closely related to the rest as they are to each other, it is put at a "basal" position on the cladogram. As I said above, it is transitional in the sense of morphology, but since we cannot test for ancestors and descendents, we use a branching pattern.

Clear as mud?

[Kai]

Homo Erectus to Homo Sapiens Sapiens is really really well documented.

How? Did you go back in time and show that the Homo erectus fossils we have gave birth to the ancestors of Homo sapiens? It's completely untestable. All we can say is there is some common ancestor to both; whether one is the ancestor of the other is unknowable.

[Telarus]

We actually have a little bit of recent evidence of current evolution happening:

http://news.nationalgeographic.com/news/2006/07/060714-evolution.html

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

This gets picked at by the creationists, due to it not being a 'radical' enough change.

[Requia ☣]

Homo Erectus to Homo Sapiens Sapiens is really really well documented.

How? Did you go back in time and show that the Homo erectus fossils we have gave birth to the ancestors of Homo sapiens? It's completely untestable. All we can say is there is some common ancestor to both; whether one is the ancestor of the other is unknowable.

I'd doubt that most of the fossils are our ancestors, given that they y'know, died horribly (if I remember right most of the fossils became fossils by way of being leopard food first), but we have representations of the gradual changes.

[Kai]

Homo Erectus to Homo Sapiens Sapiens is really really well documented.

How? Did you go back in time and show that the Homo erectus fossils we have gave birth to the ancestors of Homo sapiens? It's completely untestable. All we can say is there is some common ancestor to both; whether one is the ancestor of the other is unknowable.

I'd doubt that most of the fossils are our ancestors, given that they y'know, died horribly (if I remember right most of the fossils became fossils by way of being leopard food first), but we have representations of the gradual changes.

That is what we call a just so story.

"These fossils show that H. erectus is our ancestor!"

"How is that?"

"Well, because they look like they're somewhere in the middle!"


Yeah....doesn't work for scientists. The stories are colorful and fun but not the least bit scientific.

[Kai]

We actually have a little bit of recent evidence of current evolution happening:

http://news.nationalgeographic.com/news/2006/07/060714-evolution.html

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

This gets picked at by the creationists, due to it not being a 'radical' enough change.

That is the sort of thing you can judge ancestor-descendent relationships from, and very cool might I add.

Can't do that with fossils. Otherwise Darwin wouldn't have spent 500 pages trying to convince people.

[Requia ☣]

I'm not talking about proving decent.

[tyrannosaurus vex]

So has the fossil record produced evidence for a complete transition from one species to another? Forgive my ridiculous questions, I'm just looking to fill in some gaps in my understanding of evolutionary theory.

Plus some bastard infected my brain with a bunch of this crap which is undoubtedly rooted in some kind of twisted Creationist plot to undermine my understanding of science.

But even after looking through wikipedia and other more reliable sources of information it would appear that the fossil record contains lots of evidence that there have been different species, but not as much evidence for those species evolving from one to another. Like a species exists in the fossil record and then died out, and another species that descended from the first shows up in the next epoch, but transitional species between the two are difficult to find for some reason.

Or is that just horse shit? I'd sleep better if I knew it was.

Edit: Or do I just have some fundamental misunderstanding of it? Using my own brain instead of repeating what I read on some website, I'd guess that every species is transitional in some lineage. Since the fossil record can hardly be expected to preserve every animal that ever lived, we have to use logic to infer that the species that showed up in the Jurassic didn't come out of nowhere spontaneously, and must therefore have ancestors in the Cretaceous, even though none of the animals in the Cretaceous belonged to that species.

Okay, so,

First of all, it is impossible to determine whether one species gave rise to another from the fossil record. It is untestable, unless you invent a time machine that can go back and watch the speciation.

In modern systematics and evolutionary biology, since incidence of one species turning into another within a single lineage (anagenesis) is untestable, we work only with testable hypotheses of relationship by branching or splitting of lineages (cladogenesis). We know that sister lineages must share a common ancestor, but whether one of those lineages is the ancestor of the other is untestable, so we just work with relationships.

We discover these relationships by homology, what I have referred to before as "the key to the heart of biology". Homology is not just similarity, but special similarity that is a hypothesis of a common origin. The forelegs of a mammal, a bird, and a salamander both in the sense of their location and constituant parts would be examples of a homology. By mapping homologies on different species and lineages, we arrive at a tree like diagram of hypothetical relationships. The most informative type of branching is dicotomous, since it has the least assumptions.

Here (http://en.wikipedia.org/wiki/Therapoda) there is a cladogram of the Therapoda, a tree diagram that maps the relationships between different Therapod lineages. Note the dicotomous branching, and that higher groups, like Eumaniraptors, are distinguished by nodes where all members of that group stem from the node, indicating a common ancestor.


Now, the media often talks about transitional fossils. In the true sense, all fossils are transitional, just like all species are transitional (unless they have become extinct). Usually what they mean is some sort of inbetweeness in form between two markedly different lineages. An example would be Archaeopterix, which has many characters shared by Deinonychosauria, the sister group to the group that contains the modern birds, but also has feathered wings, a uniquely shared character of all members of Avialae. Looking here (http://en.wikipedia.org/wiki/Avialae) you can see a cladogram of the Avialae. Since Archeopterix is related to the rest of the Aves clade, but not as closely related to the rest as they are to each other, it is put at a "basal" position on the cladogram. As I said above, it is transitional in the sense of morphology, but since we cannot test for ancestors and descendents, we use a branching pattern.

Clear as mud?

Ok, I think I get it... species are identified, and then, according to their characteristics and their place in the geological record, they are said to be "somewhere on the path" of a given lineage, but no claims are made about whether or not specific species that are found are directly descended from other specific species.

Being the 21st century and all, though, is there still no way of finding enough prehistoric DNA to calculate actual descendants?

[Kai]

So has the fossil record produced evidence for a complete transition from one species to another? Forgive my ridiculous questions, I'm just looking to fill in some gaps in my understanding of evolutionary theory.

Plus some bastard infected my brain with a bunch of this crap which is undoubtedly rooted in some kind of twisted Creationist plot to undermine my understanding of science.

But even after looking through wikipedia and other more reliable sources of information it would appear that the fossil record contains lots of evidence that there have been different species, but not as much evidence for those species evolving from one to another. Like a species exists in the fossil record and then died out, and another species that descended from the first shows up in the next epoch, but transitional species between the two are difficult to find for some reason.

Or is that just horse shit? I'd sleep better if I knew it was.

Edit: Or do I just have some fundamental misunderstanding of it? Using my own brain instead of repeating what I read on some website, I'd guess that every species is transitional in some lineage. Since the fossil record can hardly be expected to preserve every animal that ever lived, we have to use logic to infer that the species that showed up in the Jurassic didn't come out of nowhere spontaneously, and must therefore have ancestors in the Cretaceous, even though none of the animals in the Cretaceous belonged to that species.

Okay, so,

First of all, it is impossible to determine whether one species gave rise to another from the fossil record. It is untestable, unless you invent a time machine that can go back and watch the speciation.

In modern systematics and evolutionary biology, since incidence of one species turning into another within a single lineage (anagenesis) is untestable, we work only with testable hypotheses of relationship by branching or splitting of lineages (cladogenesis). We know that sister lineages must share a common ancestor, but whether one of those lineages is the ancestor of the other is untestable, so we just work with relationships.

We discover these relationships by homology, what I have referred to before as "the key to the heart of biology". Homology is not just similarity, but special similarity that is a hypothesis of a common origin. The forelegs of a mammal, a bird, and a salamander both in the sense of their location and constituant parts would be examples of a homology. By mapping homologies on different species and lineages, we arrive at a tree like diagram of hypothetical relationships. The most informative type of branching is dicotomous, since it has the least assumptions.

Here (http://en.wikipedia.org/wiki/Therapoda) there is a cladogram of the Therapoda, a tree diagram that maps the relationships between different Therapod lineages. Note the dicotomous branching, and that higher groups, like Eumaniraptors, are distinguished by nodes where all members of that group stem from the node, indicating a common ancestor.


Now, the media often talks about transitional fossils. In the true sense, all fossils are transitional, just like all species are transitional (unless they have become extinct). Usually what they mean is some sort of inbetweeness in form between two markedly different lineages. An example would be Archaeopterix, which has many characters shared by Deinonychosauria, the sister group to the group that contains the modern birds, but also has feathered wings, a uniquely shared character of all members of Avialae. Looking here (http://en.wikipedia.org/wiki/Avialae) you can see a cladogram of the Avialae. Since Archeopterix is related to the rest of the Aves clade, but not as closely related to the rest as they are to each other, it is put at a "basal" position on the cladogram. As I said above, it is transitional in the sense of morphology, but since we cannot test for ancestors and descendents, we use a branching pattern.

Clear as mud?

Ok, I think I get it... species are identified, and then, according to their characteristics and their place in the geological record, they are said to be "somewhere on the path" of a given lineage, but no claims are made about whether or not specific species that are found are directly descended from other specific species.

Being the 21st century and all, though, is there still no way of finding enough prehistoric DNA to calculate actual descendants?

Even in the cases where you have DNA, like in the last 100,000 years, you can only show relationship. There are a number of genes, both nuclear and mitochondrial, that get used for systematic analysis on a regular basis. You compare the genes between specimens by lining their sequences up manually, and then running either a regular parsimony analysis to find homologies or (ugh) an overall similarity or model analysis like baetsian or maximum likelyhood, disrespectfully. This will show special or overal similarity, but theres no way you could calculate that this bone fragment comes from an organism that is the ancestor of humans, only that they are related to one another. Remember, these sequences aren't from species, they're from individuals, and individuals within species vary. You can calculate ancestor decendant relationships between generations in humans, but much more than that and you're showing similarity and not "who is spawn of who".

[Mesozoic Mister Nigel]

We actually have a little bit of recent evidence of current evolution happening:

http://news.nationalgeographic.com/news/2006/07/060714-evolution.html

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

This gets picked at by the creationists, due to it not being a 'radical' enough change.

That study is really interesting because it validates catastrophic evolution, where extreme pressures cause evolution to occur very rapidly. I've always thought there was a lot of potential in that theory.

[Kai]

We actually have a little bit of recent evidence of current evolution happening:

http://news.nationalgeographic.com/news/2006/07/060714-evolution.html

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

This gets picked at by the creationists, due to it not being a 'radical' enough change.

That study is really interesting because it validates catastrophic evolution, where extreme pressures cause evolution to occur very rapidly. I've always thought there was a lot of potential in that theory.

I tend to hold with Gould's ideas that evolution is neither completely gradual nor completely catastrophic; evolution is a punctuated equilibrium.

[Jasper]

I always assumed that was the consensus.  It makes the most intuitive sense to me.

[Mesozoic Mister Nigel]

We actually have a little bit of recent evidence of current evolution happening:

http://news.nationalgeographic.com/news/2006/07/060714-evolution.html

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

This gets picked at by the creationists, due to it not being a 'radical' enough change.

That study is really interesting because it validates catastrophic evolution, where extreme pressures cause evolution to occur very rapidly. I've always thought there was a lot of potential in that theory.

I tend to hold with Gould's ideas that evolution is neither completely gradual nor completely catastrophic; evolution is a punctuated equilibrium.

I like that phrase, and yes, it makes perfect sense that it would be. Gradual change punctuated by fits, starts, and dead-ends.