do the double helix of DNA look different for different races? (cd, photobucket)

Originally Posted by green_mariner

I consider "Neanderthals" a subspecies. Everyone one this earth is of the same species, just different ethnicities.

Once again these terms need defining - ethnicity is more along the lines of culture not genetics. If you include common genetics then you are agreeing that there are different categories of human based on genetics. Neanderthal and human seemingly interbreed, even if it was miniscule, so that some of their genes are still present in modern humans. One of the crtieria for species is interbreeding.

[Konraden]

Originally Posted by Shiloh1

Once again these terms need defining - ethnicity is more along the lines of culture not genetics. If you include common genetics then you are agreeing that there are different categories of human based on genetics. Neanderthal and human seemingly interbreed, even if it was miniscule, so that some of their genes are still present in modern humans. One of the crtieria for species is interbreeding.

The term species attempts to classify a gradient. You can't look at one set of genetic code and say "this is one species," look at a slightly different set and say "this is another species." You can't reasonably make that determination either on any X amount of changes between gene-code A and gene-code B. I'm genetically different than everyone else on earth but I don't classify as my own subspecies.

[Chemistry_Guy]

The structure of the actual DNA molecule is the same for all multicelled organisms. The sequence is obviously different, as well as the size, but the secondary structure (right handed helix) is pretty much limited by steric constraints and thermodynamics.

You can't "see" something as small as DNA structure with visible light, but there are a variety of techniques, most popular of which is x-ray crystallography, that allow one to assign 3-dimensional coordinates to all of the atoms in the structure. Microscopy techniques such as TEM and AFM can image DNA but cannot resolve details such as bond distances and dihedral angles.

Originally Posted by Konraden

The term species attempts to classify a gradient. You can't look at one set of genetic code and say "this is one species," look at a slightly different set and say "this is another species." You can't reasonably make that determination either on any X amount of changes between gene-code A and gene-code B. I'm genetically different than everyone else on earth but I don't classify as my own subspecies.

I agree but taking into account a simple definition for subspecies:

'a category in biological classification that ranks immediately below a species and designates a population of a particular geographic region genetically distinguishable from other such populations of the same species and capable of interbreeding successfully with them where its range overlaps theirs'

According to this it would seem that the general, and historical, concepts of 4-5 'races' fits just fine.

[TheArchitect]

Originally Posted by Shiloh1

But are we a polytypic species? That is two or more subspecies.

Once upon a time long ago there existed more hominid diversity and there were likely other subspecies of Sapien or closely related hominids that were capable of interbreeding.

They are all extinct now and what currently exists is an unusually genetically homogenous species.

[Konraden]

Originally Posted by Shiloh1

I agree but taking into account a simple definition for subspecies:

'a category in biological classification that ranks immediately below a species and designates a population of a particular geographic region genetically distinguishable from other such populations of the same species and capable of interbreeding successfully with them where its range overlaps theirs'

According to this it would seem that the general, and historical, concepts of 4-5 'races' fits just fine.

There isn't significant genetic difference between geographies in the human population, which kind of shuts that idea down.

Originally Posted by Konraden

There isn't significant genetic difference between geographies in the human population, which kind of shuts that idea down.

What would constitute 'significant genetic difference between geographies' while maintaining the ability to interbreed, that would support that idea?

Would lactose tolerance, skin tone, eye color, medical issues strongly related to genes? I mean where is the line of demarcation?

[Konraden]

Originally Posted by Shiloh1

I agree but taking into account a simple definition for subspecies:

'a category in biological classification that ranks immediately below a species and designates a population of a particular geographic region genetically distinguishable from other such populations of the same species and capable of interbreeding successfully with them where its range overlaps theirs'

According to this it would seem that the general, and historical, concepts of 4-5 'races' fits just fine.

Originally Posted by Shiloh1

What would constitute 'significant genetic difference between geographies' while maintaining the ability to interbreed, that would support that idea?

Would lactose tolerance, skin tone, eye color, medical issues strongly related to genes? I mean where is the line of demarcation?

Therein lies the aforementioned problem. You're trying to categorize a gradient.

Originally Posted by Konraden

Therein lies the aforementioned problem. You're trying to categorize a gradient.

I am not trying to make the line - as such I think there is a case for subspecies of humans - particularly since the differences are not just outwardly noticable but also inwardly noticable given our understanding of genetics and history. I mean the fact that alleles for sickle cell are geographically relevant is just one gentetic case for a significant difference. But if you are going to say that there is none then it would seem that you have discerned where that line should and should not be and as such catergorized a gradient phenonmenon. Certainly saying that there are 4-5 subspecies is less catergorization than saying there are none and that we are all basically the same.

I am not sure how science defines all these terms so I don't see the problem with having a gradient that incorporates subspecies. I mean it seems pretty clear that until recently there were clear geographic distinctions between people groups. I am not sure why those factual differences are avoided in our discussion of genetics and anthropology (other than the obvious abuses that early 'science' engaged in with these differences).

If we are gonna say there are no differences (or significant ones) then that should be defined otherwise the differences that obviously exist seem to account for what are subspecies - what am I missing?

[Konraden]

Originally Posted by Shiloh1

I am not trying to make the line - as such I think there is a case for subspecies of humans - particually since the differences are not just outwardly noticable but also inwardly noticable given our understanding of genetics and history. I mean the fact that alleles for sickle cell are geographically relevant is just one gentetic case for a significant difference. But if you are going to say that there is none then it would seem that you have discerned where that line should and should not be and as such catergorized a gradient phenonmenon. Certainly saying that there are 4-5 subspecies is less catergorization than saying there are none and that we are all basically the same.

We are all basically the same. Predisposition to illness is hardly qualifying speciation material.

I am not sure how science defines all these terms so I don't see the problem with having a gradient that incorporates subspecies.

Imagine a line of color that goes gradually from yellow to red. Between yellow and red is orange, and at certain points along that line, you can say that the point is definitely yellow, definitely orange, or definitely red. as you move around between yellow to red, there are points where it might be yellow, or might be orange. But you'll call it Gold. So now you have a point called gold that sits between yellow and orange.

Rinse. Repeat. Classifying species based on genetic differences is akin to attempting to classify every possible color amongst this gradient. You can say that this group is a subspecies based on these genes, and this group is a sub species based on these genes, but what about the group between them? Is that another group? And the group between those? And between the new groups?

Evolutionarily, it's the same reason why there is no "missing link," because every form is a transitional form.

I mean it seems pretty clear that until recently there were clear geographic distinctions between people groups.

People definitely have different cultures and ethnicity, but these are socially constructed terms, not genetic or biological ones. Race itself is entirely socially constructed because it isn't genetically or biologically defined--for the reasons posted above.

I am not sure why those factual differences are avoided in our discussion of genetics and anthropology (other than the obvious abuses that early 'science' engaged in with these differences).

If we are gonna say there are no differences (or significant ones) then that should be defined otherwise the differences that obviously exist seem to account for what are subspecies - what am I missing?

There aren't significant genetic differences between humans any more than there are between breeds of animals. Breeds don't constitute a sub-species.

Geographic differences between people doesn't directly translate to genetic differences between those groups. Humans haven't had environmental pressure to force those kinds of genetic changes in 10,000 years. We're more or less the same.

The part you're missing is that gradient. We're incapable of taking these minute genetic differences between two groups of people and claiming each group a sub-species. You'll spend a lifetime breaking up further and further differences, increasingly insignificant, in order to continually classify subspecies.

Obviously skin-tone is the easiest one to start with. Let's say the dark guy who reflects light off his skin at X- wavelength less is considered subspecies 1. The guy who reflects light off his skin at wavelength X+ is subspecies 2.

What happens when two of subspecies 2 make a child whose skin reflects at X-? This kind of thing happens all the time.

Evolution 101: Cats don't turn into dogs.

You can expand your classification of subspecies if you want. Say, to include things like facial features, height, width, predisposition to illness, etc.

But what happens when someone only meets three out of six of those criterion?

We classify animals regularly on 'breed' based on such trivial markers as hair length and color, size, frame, and other genetically aesthetic but otherwise meaningless information.