Proving Evolution in the Age of Genetics

One of the key components of evolutions is the changing of species. A man is not the same species as an ape. In the age of genetics, we have discovered that the code for each species is contained in the DNA. Man and ape are not the same species because their DNA is different. Now although evolutionists claim that certain species exhibit characteristics of natural selection, do any of these examples involve the modification of the actual DNA structure? Natural selection can occur if the alleles of the genes change, but has the actual composure of the DNA and its genes changed so that a different species has evolved? I think this issue raises three main questions:1. Is there evidence for natural selection through changing DNA (to the point where the DNA evolves into that of a different species)?
2. Darwin says that evolution occurs in small, successive steps. What sort of change in DNA would qualify as one of these steps?
3. What two species have DNA that have the closest relation to each other?

Thread moved here from the Proposed New Topics forum.

Well, now, the structure is the same in every single species we've ever encountered; a double helix comprised of four different complimentary nucleotide bases.It's the sequence of those bases that is the difference between species, and it's established beyond a doubt that the mechanisms of evolution can change those sequences, without limit as far as we know.I mean this was one of the first things to be tested when we discovered the structure of DNA and the mechanisms of inheritance, and it was fairly trivial to do so. If you care to search at pubmed.org you can see thousands of papers getting right into the specifics of how a given selection pressure on a population caused an effect in the DNA of the individuals of the population. Yes, much. Not least of which is the observation of new species arising. When we check we find distinct genetic differences between the new species and its parent species. Well, the smallest possible change to a DNA sequence would be the substitution of one base pair with another. That's pretty common. That's impossible to answer at this point; we've only sequenced the genomes of very few species, so we have no basis to determine which are the most similar out of all possible combinations.

I think there is a misunderstanding here. He things that selection directly changes the DNA??? That is the way I read it.

I think he's just fast and loose with his terminology. Of course, natural selection doesn't actually influence the genes of an individual. Only mutation does that. Natural selection selects among individuals, which causes changes the the frequency of alleles (alternate genetic sequences) in a population, which is what evolution is - changing allele frequencies.In other words, mutation causes changes in the genetics of an individual; selection causes changes in the genetics of a population.

Also man and ape aren't the same species because "ape" isn't a species. There are 4 genera and 3 species in what we call apes.
Gorilla gorilla
Pongo pygmaeus
Pan troglodytes
Pan paniscusit may seem like nitpicking but it really helps the discussion when you're specific.This message has been edited by DrJones*, 01-13-2005 02:00 AM

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*not an actual doctor

But changing alleles doesn't change the species. Dogs come in many different varieties, but a dog can only still mate with a dog. Has natural selection changed the DNA of a dog to the point where it can't mate with another dog because they're two different species. In order to make the jump from the earliest single-celled life forms to the species we have today, the DNA would have to change to describe a different species.

OK, we can nitpick, but all of those species are still not the same as the species of a man.

A Chihuahua and a Great Dane are both dogs that cannot interbreed. Different species?What if Chihuahuas adapted to living in burrows to escape predators, then adapt better eyesight for seeing in the dark, then adapt better claws for digging? Did Chihuahua's just become moles? After how many adaptations does it stop becoming a dog?

Right now, you're looking at the external features of the animals. I'm looking internally, at the DNA. A dog and man can't mate. Why can't they mate? They are different species with different DNA. We're not talking about alleles changing, we're talking about the compostion of genes changing (ie: a different number of chromosomes [excepting genetic defects], adding the DNA for another leg, etc).

It does, and it can. Not all dogs can mate with all other dogs. For instance good luck getting a St. Bernard and a bichon frisse to mate - they're physically incompatible. If it weren't for the existence of intermediate varieties of dogs, there'd be no gene flow between large dogs and small dogs, and they would be different species of dog. All it takes to do that is a change in the sequence of the nucleotides, which is what mutation and selection do.

So are we. How did it get that way?By the cessation of gene flow between two populations. That's how new species are formed. All dogs might be the same species now, but if you eliminated the intermediate dogs, you'd wind up with two populations of dogs that could not interbreed physically; after a few generations they'd no longer be genetically compatible, either.

But the alleles of these dogs don't change (or to clarify, the genotypes of these alleles change, but the alleles don't). How about the quantum leap where the DNA changes in this way to a different species?This message has been edited by commike37, 01-13-2005 20:02 AM

How accurate is it to describe the different varieties of dogs as a ring species? Is it at least a similar concept?A personal anecdote, I had Miniature Schnauzer (small dog) that got impregnated by a Newfoundland (very big dog). My dog had to have an abortion or the pup would have killed it.

Which I think qualifies it as a different species based on the biological species concept. That, IIRC, deferentiates based on usual successful production of fertile offspring in the wild.If the situation you describe is the general case (and I would think it is) then those two varieties are separate species are they not?This message has been edited by NosyNed, 01-13-2005 20:16 AM