[_ Old Earth _] One small question for evolutionists

[Ashua]

http://en.wikipedia.org/wiki/Living_fossil

Sorry I figured the feature article might mention the date. just control+F and type 100 million and you'll see it.

 

[Barbarian]

No. It says that lungfish are that old. I doesn't say the highly evolved ones we find today are that old.

 

[jwu]

Fossils almost identical to Neoceratodus forsteri have been uncovered in northern New South Wales, indicating that it has remained virtually unchanged for well over 100 million years.[2]

"Almost identical" implies at least some change. It's highly unlikely that those from 100 million years ago could have viable offspring with today*s, so they'd be different species.

"Almost identical" can mean as much difference as there is between homo erectus and homo sapiens.

 

[Barbarian]

J Exp Zool B Mol Dev Evol. 2007 Mar 15;308(2):163-71.
Is Palaeospondylus gunni a fossil larval lungfish? Insights from Neoceratodus forsteri development.

Joss J, Johanson Z.
As fossil lungfish cell sizes (and genomes) increased in the late Paleozoic, the diversity of lungfish morphologies decreased, so that taxa like Sagenodus and Conchopoma show morphological similarity to Neoceratodus, marking a point in phylogeny at which metamorphosis was potentially lost. Since ancestral larval characters are retained in neotenic adults, we predict that Devonian larvae should resemble these post-Devonian taxa,...
http://www.ncbi.nlm.nih.gov/pubmed/17068776

 

[Ashua]

Fossils almost identical to Neoceratodus forsteri have been uncovered in northern New South Wales, indicating that it has remained virtually unchanged for well over 100 million years.[2]

"Almost identical" implies at least some change. It's highly unlikely that those from 100 million years ago could have viable offspring with today*s, so they'd be different species.

"Almost identical" can mean as much difference as there is between homo erectus and homo sapiens.

That is quite a stretch there. "almost identical' would imply that micro changes occurred. Im pretty sure they would be able to mate. There is zero evidence for you to think they could not.

 

[Barbarian]

Wikipedia suggests that modern lungfish are in the same genera (not the same species) as some ancient ones. This can't be "almost identical", unless as jwu says, you think humans and human-like hominins are almost identical. In fact, as you see from the primary literature, modern lungfish may not even be of a genus known from the fossil record. All that we have is that the modern ones have some morphological similarities with ancient lungfish. Generally, organisms in the same genus but different species do not interbreed, although there are exceptions.

This is a good example of the dangers of popular media interpreting scientific papers.

 

[Pard]

Wikipedia suggests that modern lungfish are in the same genera (not the same species) as some ancient ones

Shoot, I better go fix that to say they are in the same species.

 

[Ashua]

Fossils almost identical to Neoceratodus forsteri have been uncovered in northern New South Wales, indicating that it has remained virtually unchanged for well over 100 million years.[2]

"Almost identical" implies at least some change. It's highly unlikely that those from 100 million years ago could have viable offspring with today*s, so they'd be different species.

"Almost identical" can mean as much difference as there is between homo erectus and homo sapiens.

Identical twins have "almost identical" DNA. Whats your point?

 

[Barbarian]

Actually, identical twins have identical DNA. Humans and Neandertals have almost identical DNA. Humans and chimps are a little farther apart, about 94% similar. So very different organisms can have very similar DNA, if they are in the same genus or family.

The fossil lungfish may be in the same genus as some modern ones, but they are not the same species. They've evolved a bit, even though they've lived in pretty much the same environment all that time.

 

[Ashua]

"Monozygotic twins have nearly identical DNA, but differing environmental influences throughout their lives affect which genes are switched on or off. This is called epigenetic modification. A study of 80 pairs of human twins ranging in age from three to 74 showed that the youngest twins have relatively few epigenetic differences."

-Wiki

 

[Barbarian]

"Monozygotic twins have nearly identical DNA, but differing environmental influences throughout their lives affect which genes are switched on or off. This is called epigenetic modification. A study of 80 pairs of human twins ranging in age from three to 74 showed that the youngest twins have relatively few epigenetic differences."

Identical. They are essentially like clones of each other, although technically, a clone is a new individual obtained by a tissue sample from another. One fertilized egg divides and instead of forming one individual, it splits and forms two or more.

Epigenetic modification doesn't add or delete any DNA, which remains the same. It only switches different genes on and off. The genome remains the same, which is why identical twins can donate tissue; the tissue is genetically identical to theirs.

Because identical twins often look almost exactly the same and share the same DNA, people often make the mistake of assuming that identical twins are actually "clones" of one another. In the strictest scientific sense, this is not true.

Identical twins originate from one egg that has been fertilized by one sperm. Sometime early in the cell division process, for reasons still unknown, this fertilized egg splits into two distinct embryos. Though these embryos are genetically identical (sharing the same DNA), they both originated from the fertilization of an ova.

Although identical twins have the same genotype, or DNA, they have different phenotypes, meaning that the same DNA is expressed in different ways.
http://ask.yahoo.com/20010213.html

What about mutations? These happen in the egg and sperm cells. So like all of us, they will have some mutations, but they will have identical mutations.

 

[abrown9]

Bear in mind that the fossils we see tell us very little about the fine details of the organism. Undoubtedly there has been genetic change but little phenotypic alteration.

I'm not sure whats so hard to understand about stabilizing selection. The environment that the lungfish inhabited did not produce selective pressure to favour a variation of the lungfish that would result in a phenotypic change in the organism. Instead, it produced selective pressure to have the lungfish remain exactly how they were. Why fix something thats not broken?

 

[Pebbles]

Punctuated equilibrium - Wikipedia, the free encyclopedia

Change in an organisms morphology through evolution is not a constant, It's related to selection pressures, If the selection pressure has not changed in a long time the species will real an "ideal" for that environment it's only a change in the environment that will induce further morphological changes.