Well, of course he would elaborate more. There's hardly any alternative, is there?
But homology is a concept initially defined for morphology, and which works perfectly well if you consider only morphological data, and which
still makes Davison's paper look like the
scientific equivalent of the result of a Goodenough-Harris test.
Consider the following, for instance. Following what passes for his logic, the wings of a hummingbird and those of a bumblebee are similar, and thus they are expressions of the same preserved genes that were present in their last common ancestor. However, penguins don't have wings, they have fins, so these would have to originate in another part of the DNA that codes for fins. This would be the same region that codes for fins in seals, perches, thecosomates, plesiosaurs, and shrimp. But wait! There are several groups of birds -- like the Diving-petrels -- that use their front extremities both for flying
and for diving, so by Davison's logic, we only have two choices: either wings and fins are expressed in the same way in all animals, or these birds have a mixture of both of them; put in another way, either the genes that make things that function as a wing and those that make things that function as a fin are the same, or both are expressed in the Diving-petrels, without that resulting in them having two pairs of front appendages.
This is pure insanity, but
this is exactly what Davison proposes in this paper. He argues that if some part of an animal has the same function as a part of another animal, this is evidence that the genetic information for making these two parts are the same, and have been fed into the ancestral animal by God in long-lost days and remained there unmutated until they were needed several million years later. If you do not see that this is the same thing, then it is
you who do not understand the implications of his paper.
The words "horse", "genera", and "genus" do not occur in Davison's paper, and the word "variation" occurs only in his quote of Grassé. "Fossil" occurs only once, in an unsubstantiated assertion that there is an "absence of intermediates both in contemporary and in fossil species." I must therefore assume that you are discussing something entirely else here.
Nevertheless, lack of variation within a genus
is not surprising, as a genus is per definition a construct which collects organisms that show a great deal of morphological similarity.
Against my better judgment, I will download and read those other papers (I have access to the J. Theor. Biol. ones as well, including a response that was published in that journal by M. P. Maguire). This will likely take some time, as his manifesto alone is 56 pages, so I will simply stop looking into the other threads we have both participated in recently. If there is anything there you wish to continue discussing, please transfer it here instead.
You don't know what analogous organs are in biology? And you lecture other people on their need to learn evolutionary theory? Really, Randman, you could at least have read up and concealed your ignorance.
Then you will have to elaborate. Are you suggesting that the fact that it never happens that taxon X evolves into taxon Y which evolves into taxon Z which evolves back into taxon X?
If so, the fact that this never happens
is precisely what evolutionary theory predicts and is as such not evidence against it. You can imagine a lineage as a train going through a landscape with a virtually unlimited amount of dimensions. At every stop (generation), the train changes direction. Its present location determines which options are available to it at that stop, but the options are still, for all practical purposes, unlimited. The probability that it will return to a previous stop is proportional to the amount of stops it has passed in between, as well as on entirely unpredictable circumstances.
If Davison is correct, then we
would see lineages revert to ancestral taxa all the time, because the descendant taxon would still contain all the genetic data needed to make the ancestral taxon. All it would take would be a small change in what genes were expressed during development, and my kids would turn into monkeys. And their kids, if randomness struck again, could turn out to be frogs, or cats, or fruit flies, or velvet worms, or acorns, or bacteria, because they would all contain all the genes needed to develop all these organisms, and all it would take is a change in what genes are expressed and when.
Evolutionary theory suggests no origin of the genome in the first place. Evolutionary scientists may speculate, but the theory is silent on it, in the same way that it is silent on gravity or politics. It is a separate field which is, by definition, outside the scope of evolutionary theory.'
Subgroup isolation, as Dinwar has told you, is not in any way correlated to statements of the genetic variation in this subgroup. A subgroup that is isolated from the mother population may have higher relative genetic variation than the mother population, it may have lower relative genetic variation, or it may have exactly the same relative genetic variation.
Random mutations do increase genetic variation in any given population that is subject to the same genetic processes as a standard population. Over time, these will give rise to genetic variation (supposing the population survives) regardless of the initial genetic variation at the isolation event.
This question makes no biological sense. When a population splits,
both subpopulations by definition are daughter populations. This does not work like a family, where the mother is still there after having given birth to the daughter. Phylogenetics is more or less per definition asexual, and each division gives rise to two daughter populations, one or both of which is initially largely identical to the mother population, but both of which due to known evolutionary processes over time will typically diverge.
You seriously need to sort out your terminology.
