Proving Evolution in the Age of Genetics

OK, chromosomes isn't the best way to put it, but fruit flies still 3-4 as many genes as a human. So you had to do something to add all those genes. So in order to make evolutionary changes, you would need to add DNA segments (bingo, there's a good enough term) that represent these proteins.I always knew I was better in physics than in biology, so excuse any mistakes

and Chimps have 48.It seems possible to me, that the human/chimp common ancestor had 48 chromosones (24 sex chromosomes) and the human lineage had a mutation event where 2 chromosones fused into 1.Here's some good stuff on humans and chimps and genetics.Page not found | Nature

Thanks for your reply.What do you mean by "not a closed loop?"

Er, wait now, more chromosomes doesn't mean more genes. And humans only have about 25,000 genes to the fruit fly's 13,000, so that's nowhere near the 3-4 times you suggested. Mutation and natural selection can do this. I'm pretty sure examples have been given, but there's literally thousands of examples in the literature.

And that's why chromosome isn't the best way to put it There's still an obvious difference in the number of genes between a fruit fly and human. On the subject of mutation, the following question is raised:
How many proteins must be added so that they give an organism an advantage that can allow it to thrive through natural selection.This message has been edited by commike37, 01-13-2005 22:57 AM

I thought that ring species form closed loops with each sub-species able to breed with it's neighbors but not with species across the ring. there are seagulls that fill this bill ... I believe there was a thread on ring species>...Ring species as evidence for speciation
EvC Forum: Ring species as evidence for speciation

Then I guess I don't understand what you're talking about. I have a suspicion you're trying to compare the "complexity" or "advancedness" of an organism and are trying to find a representation of that advancedness in that organisms DNA; in other words you'd like to say that humans are more complex than fruit flies, and so we must have more complexity in our DNA, and so how do you increase the complexity of DNA in order to turn a fruit fly into a human?Well, it doesn't seem to work like that. The DNA of all metazoans seems to be roughly of the same complexity, no matter how complex the organism might be. Yes there is, but we might as well say that a given species has a random number of genes. Number of genes has very little to do with speciation, and it actually changes over time as genes get knocked out or disabled through mutation, or new genes are activated. For instance I heard somewhere that humans are losing genes on the Y chromosome as it gradually shrinks throughout the population.By way of comparison, humans have 20k to 25k genes. C. elegans, a commonly researched worm, has 19.5k, and a flowering mustard plant of the family Arabidopsis has 27k. That's like asking "how fast do you have to run to win a race." The short answer is, it depends. It could be one. It could be many. Often just one new protein spells the difference beween life and death.

You started of by saying that what constitutes a dog is that it can only mate with other dogs. This is due to their genetics which also controls the size and hardware to even be able to mate in the first place. How different does a breed of dog have to be before it stops becoming a dog?What if a dog was "bred" by natural selection to be larger, have thicker fur, have much larger claws, and be able to stand on its hind legs. Would it still be a dog? Could it be a bear? The evidence in evolution says that bears and dogs have a fairly recent common ancestor. At what point did these two species of canine, who were at one time just different "breeds", change enough to the point that one became a "bear" and the other a "dog". What are "bear" and "dog" other then our own classification of things that look slightly different and do not interbreed.This is a real example. Now lets go back to my hypothetical example of the mole Chiuahuahs. At what point during the gradation of creating the Chiuahuah breed and its potential future outcomes does it stop becoming a dog?You seem to be thinking of genetic similarity as this discrete measure of a species. The only thing that prevents two animals from being able to produce a viable offspring is a blurry line of how different their genetic makeup is. Notice that this includes the situation where their genetic information might be compatable but, due to genetic differences that affect their physical characteristics, they are still unable to mate.You also seem to be inclined to use terms like "dog" as if it was some kind of definition that nature rather than men actually grouped a set of animals.

Indeed the answer could be 'none at all'. A minor change within a proteins structure or a slight change in its pattern and timing of expression during development could easily provide a substrate for natural selection.TTFN,WK

What you describe is often called "species idealism", the idea that all members of a species are variants of one essential "perfect" member of their species, and that they all share an innate essence that makes them (for instance) dogs and not cats, or whatever.It's an error of thinking that leads so naturally to the concept of animals being grouped into original "kinds".

Well that just made answering my question much much harder. If I can't precisely (or somewhat precisely) determine what kind of genetic steps need to be taken to make an evolutionary transition, then I don't have much to work with.But it doesn't bother me...not all questions can be answered.

to be even more blunt: the kind of difference you see in the DNA between very similar varieties of, say dogs, is the same kind of difference that you see in the DNA between much more divergent species, such as between bacteria and human.there is no genetic differentiation into classes or any other cladistic organization based on the kind of change in the DNA. all there is in the DNA is a pattern of divergence over time ... evolution, by definition.enjoy.

Transition from what to what? In order for there to be a transition, there has to be a period of no transition.But species are always in transition. We speak often of events that separate populations and eliminate gene flow in between them; these speciation events are the first step to a new species, but they do not themselves create new species.It would be better to ask "what allows a population of variant individuals to interbreed?" The answer to that will help illuminate you in regards to how populations differentiate into different species.

Just to poke my nose in here. This is actually inaccurate (at least as far as dogs go). Fertile hybrids of dogs and other species of canids are relatively common. Dog-wolf, dog-coyote, even dog-fox hybrids are known. The simplified explanation is that the divergence (speciation events) separating the various species were relatively (evolutionarily speaking) recent, and total genetic isolation has not been achieved. Often the F2 generation of these hybrids "breeds back" to the "wild type".NosyQ

Maybe I didn't do a good enough job of explaining it but I am pretty much in agreement with you. I was trying to say that his idea that species were discrete objects was wrong. Even among dogs some breeds cannot mate. Your point is also important in that some dogs can also mate with other non-dogs as we use the term in our vernacular. This is more evidence that the line is not so distinct which was the point.