Thank you very much for the wishes, Svinleshas, much appreciated. This is the first chance I’ve had to post since my last message, I tried to post this response yesterday about a dozen times but the board was refusing to cooperate. Anyway, I pick up as I may from your list of examples before (hopefully) proceeding as time allows. This follows from my previous post, which I had to cut short.
The example of poor/good adaptation in this case was the male peacock, but I submit that that is poor adaptation only as far as an individual male peacock’s life is concerned. In genetic terms, if sexual advantages outweigh survival advantages then very gaudy displays may be selected for, because they will be reproduced more than the inferior displays of less-endowed competitors who are less successful at attracting mates (even if they live longer). After all, it’s the transmission of genes that is relevant to the evolution of the peacock, not necessarily the long-term survival of individual males but how successfully they are able to reproduce and therefore spread their genes. Consider that a long, colourful tail and train signal not just beauty but also a peacock’s health: firstly, because bright, vibrant plumage in birds are signals of good health and relatively low parasitic activity; secondly, a male who manages to survive and thrive in spite of the impediment of a long, visible tail must be exceptionally fit for survival, and therefore good breeding material. Thus females’ attraction to these visually exorbitant characteristics would select for the characteristics, a situation that, overall, strikes me as quite advantageous for the peacock species.
But when you look at a morelet crocodile, it has adapted to deal with colder water than its relatives live in. You therefore wouldn’t expect to find a crocodile of the variety usually confined to warm waters in the relatively cold environment of morelets, and as far as I know you don’t (falsifiable prediction).
The above (including and especially the peacock) are examples of the levels of complexities involved in the study of organisms. Look superficially at just one or two features of a creature, and you could easily come to conclusions that are superficially contradicting. (or unfalsifiable).
No of course not, but the general observation is that organisms are well adapted to their environments and that those not well adapted either adapt or die off/fail to compete effectively; these assertions, I hope we have seen, are easily falsifiable. Specific observations, such as the cunning design and placement of the crocodile’s eyes and nostrils, or the thumblessness of certain primates, are subject to different and variable criteria because such adaptations necessarily serve different purposes and result from different, highly variable conditions (plus, they may not be immediately clear without a detailed look at the organism in question and its niche). In the case of the African and other colobus, the loss of the thumb actually seems to be an advantage to the creature: not only is there no misaligned digit to get snagged on a branch during the colobus’s regular high-speed acrobatics, not only is the hand grip on branches stronger as a result, but the monkey doesn’t seem to miss its thumb terribly much, manipulating objects by using fingers against palm instead of the more widespread primate manipulation strategy of the opposable thumb.
What’s interesting is that species of colobus are among the most arboreal of primates, seldom even setting foot on the ground, and are among the best adapted to arboreal life of all primates. It would seem that the colobo’s loss of thumbs allows it to move faster and more efficiently in the tree canopy – certainly in this case the logic is perfectly compatible with the observation - but the matter is difficult to falsify immediately without more data (it doesn’t mean it’s not possible, of course; I suppose an extensive study of the evolutionary advantages of thumb versus thumbless primate arboreal locomotion may help confirm that).
I discussed a number of the crocodile’s adaptations in the last thread, and noted how each feature we looked at (nictitating eye membrane, nostrils and eyes just above water level allow it to camouflage itself, etc.) is well suited to the crocodile’s preferred environment. The concept of natural selection is falsifiable in this case because we could (conceivably) find poorly adapted crocodiles competing with other well adapted crocodiles in the latter’s habitat (if we did, we would not observe them to last very long, but it’s conceivable they might and that should meet the falsification criterion). That is what my example of a crocodile with eyes and nostrils on the underside of its head was supposed to illustrate: such a poorly adapted croc could see and smell very little of its prey, and it couldn’t even breathe in water while lounging lazily around as crocs are wont to do waiting for meals. I consider this example a funny little thought experiment, certainly not the height of scientific inquiry but illustrative of the problem I named so clumsily.
Perhaps a biologist could help us out here. The short version is that the human genome should provide a record of our evolution. Common descent, a theory that goes hand-in-hand with evolution, postulates that the earth’s biota are all genealogically related, and differences are due to varying evolutionary paths. We can therefore predict the existence of substantial similarities in the genetic record across species that are taxonomically close, and somewhat less substantial similarities in more distant species. This brand new study is particularly interesting because it lends weight to a hypothesis some observers had regarding our shrew-like ancestors and our phylogenetic status quo:
A logical, evidence-supported, and falsifiable explanation to account for the numerous protein domains that humans share with other species is evolution from common descent. For a more hardcore biological approach and supporting data see W.H. Li et al., Evolutionary analyses of the human genome, Nature, February 15, 2001.
Now let’s look at the idea of common descent a bit more closely. From a link already provided:
That last paragraph ought to be of particular interest. I’ll let my betters in this camp discuss the probabilistic nature of evolutionary science. I think that may be an unnecessary refinement for the purposes of this conversation, however I recall it was brought up the first time a couple pages back.