delboy

OK The commercial aspects of being controversial did cross my mind, but I don't think that's the whole story. This from his foundation website: So it does seems like a crusade against religion.

This is what I was thinking, whether a David Attenborough type of approach is more effective. I wanted the views of evolutionary biologists really, I don't know how many of them look in here. If it was rephrased - 'Does Richard Dawkin's style of promoting evolution work' could that stay in the evolution section?

Do you think that Richard Dawkin's style of crusade against religion works?

I don't quite understand the question, but a crow is a crow because 3.5 billion years and however many billion generations of evolution got it there. Every trait it has, has been selected. That's the beauty and the wonder of it surely, that it's so complex, and that the reason it reached this point is only because of the immense amount of time that it's had to get here. Selection is like binary, it's either for or against. I think what you're asking is how can one unit of selection work on so many traits. The answer is the number of generations and the number of individuals selected for or against over many years. Eventually the favourable traits (sorry, don't know what else to call them) will spread throughout the population and the less favourable ones will cease to exist. One individual crow with a poorly deformed beak might survive and reproduce (ie be selected) if food is plentiful. But no way is the trait going to survive long term.

Surely not a problem with the theory, just the language. How about: What do organisms have? Traits. What happens? Some get selected. Those could then be defined as favourable traits. Anything within the phenotype.

Yes, all very subjective. Atlantic Krill could be top of the pile in an objective sense - the single species with the largest biomass.

The fossil record is one of the best observations. A species that exists now, but didn't exist 10 million years ago proves speciation. There are so many 'transitional' fossils in the human evolution line that no one can agree on which are the same species and which are different. Which is the way it should be really, because evolution is a gradual process - there are no sudden jumps from one species to another.

I've been thinking of starting a thread along similar lines, but have held back because I thought it was potentially a bit depressing! My thinking was that life started by certain inevitable chemical reactions. Once natural selection took over these reactions gradually became more and more complex. But have they remained as inevitable chemical reactions ever since, just very complex ones. So is every decision made by every living thing just due to chemical happenstance? If so, it's not a thought I want to dwell on too much I don't think!

So after the lemur/rest of primates split, the rest of primates have produced things as varied as humans, chimpanzees, gorillas, tarsiers, marmosets, baboons, gibbons, etc. You're suggesting that extinct species branching from the lemur line were just as varied. Can you link me to the evidence please.

I still think you don't see what I'm getting at. Delta1212 seems to. I do understand about extinctions. I suppose I'm really asking if there's a link between diversification and evolutionary change. Or looking at it the other way, that lack of diversification tends to lead to less change. I seem to see this within primates. Unless you are suggesting that the extinct forms derived from the lemur ancestor were once as diverse as the rest of the primates. Which I doubt very much.

I'm not making myself clear. Just consider apes. c18 million years ago there was a split in the early apes. One branch didn't diversify much and led to gibbons. The other group diversified more (presumably due to greater geographical movements) and led to all other apes. I believe that gibbons look more like the 18 million year old common ancestor than any ape on the other branch. Same goes for all primates. 65/70 million years ago they split. The side that didn't diversify led to lemurs and they look more like the common ancestor than any other extant primate I think. I think I'm seeking a better way of explaining the old phrase that might have said that lemurs are primitive primates. They are not but they have the more primitive features. I'm also wondering why isn't there a primate on the other branch with primitive features. I assume it's because evolutionary branching leads to change. The lemur has had exactly the same amount of time to evolve but has changed much less - presumably due to less branching (or fewer pressures that cause branching).

I was actually citing platypus and echidna as an exception to the trend. My assertion (if strict) would be that, since monotremes have diversified far less than the rest of mammals, they should relatively closely resemble the first mammal. I'm saying this clearly isn't true, so I would consider it a trend rather than a strict rule. Though they are certainly closer than whales or bats. I think the examples amongst primates were better ones. I'm only suggesting it's a trend, which is perhaps not very scientific

Plus a few others The common feature to every living thing is the structure of DNA.

Yes, I was a bit uncomfortable using the word primitive. My thought is that when a lineage shows little branching and diversity there seems to be a trend that the species in that particular branch tend to resemble fairly closely the ancestor. That's a very early synapsid. I was thinking of the early mammals, possibly http://en.wikipedia.org/wiki/Morganucodon The platypus and echidna are very unlike it in appearance. Though perhaps not so much given the 180 million years between them. If we're considering Dimetrodon, we'd have to consider it with other synapsids at the time compared to their common ancestor. I'm not saying it's a rule, it just seems to be a trend. It would seem logical to me. Geographical movements and ecological pressures would cause diversification and change, whereas geographical isolation, for whatever reason, would mean a group wouldn't diversify but also that evolutionary pressure to change would be minimal. Such as lemurs in Madagascar.

I have a perception of diversification which I'm not sure is correct. Or it might be just partly true. There is often talk of a more primitive type within a group and this is the one that branches off first in a particular tree. I'm a little uneasy about why this should be because they have had an equal amount of time to evolve to the present day. For example, amongst apes, the gibbons branched off first, and they resemble the ancestral ape more than other modern apes. OK, I'm thinking aloud here, I've just realised that if gibbons branched off 18 million years ago, so did 'the rest off' apes, on the other branch. But the other branch so happened to diversify more, I assume due to geographical movements and separations. I guess I'm puzzled that when a group has a lot of diversification they tend to become less like the ancestor (I might expect one of the lines could remain ancestor-like). But when a line doesn't diversify it stays closer to the ancestor in appearance whereas it could become completely different. Is this not coincidence, but the same lack of need or pressure to diversify means there is also no pressure to change? The same seems to happen in primates as a whole. Lemurs have not diversified since branching off, and they more closely resemble the primate ancestor. I can think of an exception to this. The platypus and echidna are considered 'primitive' mammals, but are very unlike the mammal ancestor. Am I looking for a trend where there isn't one, or is there a trend but not a strict rule?

The exoskeleton covers the entire body of insects. The pronotum is just a thickened area of exoskeleton covering part of the thorax.

You seem to be suggesting that evolution happens as a result of the recombination of genes in sexual reproduction. True this does create differences in the offspring but it limited to the variation within the gene pool of that species, and this would not be enough to create a new species. This requires greater variation which can only happen by genetic mutation. What is the source(s) for your theory. You mentioned Dawkin's books in another thread. I have read The Selfish Gene and nowhere in there did it suggest what you seem to be suggesting.

The huge variety of evidence supporting evolution puts it virtually beyond any doubt. I'm not going to waste my time quoting any because your mind seems completely closed. But I'll quote one piece of evidence unconnected with evolution science. I don't know much about young earth creation, but radioactive dating puts the age of the earth at billions of years. But maybe you don't believe in radioactivity either.

I read somewhere that attraction and sexuality develops at about 4 years old, and a male will tend to be attracted to those that look how his mother looked then. In a book by Oliver James I believe.

I can't top delta's brilliant answer, but you could just tell him not to be silly and go and look at a seal or a penguin.

If two species can definitely not produce fertile offspring they are certainly considered as different species under the current definition. But very similar species have definitely diverged from a single species some relatively short (in evolutionary terms) time ago. It's not possible to quantify a cut off point because change is always gradual - fertility will slowly diminish with divergence. Nature doesn't really recognise species definition. To try and put things into sharply defined boxes is going against nature to a strong degree, it's better not to try and define so sharply.

The basic definition of a species is a population that can interbreed and produce fertile offspring (so, could the birds breed and produce fertile young?). But the definition has blurry boundaries, partly because of the gradual nature of evolution - things change very gradually and two populations will not suddenly be unable to interbreed, it will diminish very slowly. Ring species illustrate the idea very well... http://en.wikipedia.org/wiki/Ring_species Wider classifications are even more arbitrary than the species definition.

Thanks, I'll have a read. I didn't know that about amphibians/reptiles.

I'm not sure what you're saying there. I didn't phrase it very well - I'm asking if there is a name for a group before synapsids/anapsids/diapsids?

My understanding is that mammals are now not to be considered as evolved from within reptiles. So synapsids must have branched off the amniote line before the reptile common ancestor. What does the group they branched from lack (or have) that means they are not considered reptile? And does the group have a name? I think reptiliomorphs date back a bit further and are more amphibian like. EDIT - I may have partly answered my question - just found a reference to reptiles/birds having beta-keratin and mammals having alpha-keratin. If alpha-keratin is softer than beta, maybe that means mammal-like reptiles didn't have such a rigid skin as reptiles?