the "point" is that there are 2 hypothesis that explains this.
the "slow gradual change" was first introduced, the other couldn't reconcile how "sexual relations" could occur.
That's incorrect. Sexual reproduction is a trait that evolved from more primitive asexual forms. And it was gradual. The intermediate stage is a spore producing one. The spores produced by colonies of cells, and some later forms (true metazoans with cells integrated into primitive tissues), had been through another intermediate evolutionary stage in which they developed the ability we call
signaling which is the ability of one cell nucleus to chemically interact with another cell nucleus by sending a chemical message which penetrates the receiving cell's membrane. Spores capable of chemical signaling are what we call sperm and egg; thus the lateral exchange of DNA was born out of gradual accumuilated change. This is roughly in the late pre-Cambrian, and it's the cause of the "punctuated equilibrium" called
the Cambrian explosion, since the development of sexual reproduction drastically altered that timeline you're worried about, the one that Gould call the period of
stasis. Now the cuffs came off and stability is subject to a multivariate function, insofar as rates of change are concerned.
the "point" in ALL of this aqueous is that we will NEVER figure this out by believing assumptions.
That's just how it seems to you because you're not aware of the evidence that screams at you to pick it up and study it. Also, for some reason you're choosing to rely on creationist propaganda to replace the science you could be digesting. For the rest of folks, anyone who remembers high school biology, those who took it in college, and those who study it now, either as a vocation or avocation--all of them will tell you that they are not informed by assumptions, but knowledge. In all cases I know of, all the assumptions are stated as such. No scientist's "assumptions" are taken as a done deal. What happens instead is that people adopt theories based on the weight of the evidence. And that's where you get off the bus. You're not particularly interested in the evidence nor the ways we weigh it. And I don't blame you. It's very tedious, difficult and time consuming. Presumably it bores you. But that's where the true disconnect is. Is not a lack of evidence among scientists, it's a rejection or disinterest in the evidence by all the folks who have a chip on their shoulder about science, particularly the creationists, who feel threatened by it. And you're relying on them instead of the technical information you need to make an informed decision.
I think a lot of science seems like assumptions to you because you either don't remember high school biology or perhaps you never took it, and it's obvious you haven't been
for example, it's assumed that "slow gradual changes" is the driver for macro evolution.
As I mentioned above, the mere development of sexual reproduction toward the end of the pre-Cambrian drastically altered the pace of evolution, and the process itself. For example, it opened the door to something other than natural selection: sexual selection. That's not to say natural selection went away, but that sexual selection began operating in parallel with natural selection, or in tandem. And this is the era you want to study if you're concerned about macroevolution. But it's a silly concern. Who cares? Do you question the "macro" changes between some icky looking caterpillars that morph into spectacular butterflies? Not to mention the way a cute baby morphs from a monstrous looking embryo. So what up with that? What's the big deal?
i doubt if this is the case.
i honestly feel the article in "science" was fair reporting.
Ok but it's no big deal. It's people talking. Get back to the evidence, get back to the triviality of "macro" changes which you don't worry about when you observe insect metamorphosis, and the whole issues collapses into a nothing burger. It's a non-issue. It's of huge importance to science, to properly interpret data, but not to arrive at the creationist concern you've aligned yourself with ("OMG the cow and the whale are related!". Yeah but so are the maggot and the fly, so who cares?)
in my opinion, these "regulatory genes" are directly responsible for macro evolution.
Any evidence? Before you propose an explanation, be sure to reference what it explains. Otherwise it's just another wild idea. That doesn't mean you're necessarily wrong, it just means if you're right it would be because of happenstance rather than anything based in reality. I doubt it though. Go count all the periods in geologic history where you think "macroevolution" occurred (in quotes because I think you're confusing it with speciation events that produced large phyletic changes) and compare those events to what the geologists are telling us was happening to the geosphere (volcanism, subduction, river deposition, you name it). Then you're on the road to formulating the question. You need to properly frame the question before you jump to the answer.
Write4U said:
And how do these regulatory genes work? Slow gradual changes by many individuals, yielding a variety of subtle changes, some which are beneficial to the species, some which are detrimental and do not survive to breed and continue that particular DNA line. The mechanism and function of natural selection is so crystal clear that I cannot imagine another possible method.
There are of course some other contributors (genetic drift, sexual selection and so on) but the pressures from the niche to adapt or die are inescapable. I think the in vitro demonstrations of bacteria developing antimicrobial drug resistance are a perfect example of how natural selection works, although Darwin was happy enough to acknowledge the fundamentals of plant and animal breeding. That's really where the fundies need to cut their teeth as far as I'm concerned. Before worrying about "a whale from a dog" (or however jan used to put it) they need to worry about a wiener dog vs. a St Bernard, from a wolf (or pick your favorite candidates).
As examples of the subtle changes you're talking about (given in the educational material from 9th grade or so) are the shifts in coloration between in insects that enter a new niche where the background color changes and they adapt. The remarkable English moth that became darker during the Industrial Age where their habitat was under a cloud of soot, and then got lighter again when environmental controls came into use (to match the lighter bark), is a great example. Another (anyone here from California?) are the salamanders of California which adapted all kinds of crazy camouflage to blend into the many different niches they inhabit in that very ecologically diverse part of the world. And there are a lot more subtle changes (invisible) like the adaptation in humans to form the red blood cells in "sickles" which serves as a resistance to malaria--at the expense of reducing the individual's ability to survive other pressures. And the other topic that often comes up is the adaptation for improving Vitamin D production in the skin which accounts for the change in human skin pigmentation between the high latitudes and the tropics.
Can you give me an example of an evolutionary process which is not governed by the earth's ecosystem? .
Indeed. We can talk about sexual selection, but never out of the context of the ecosystem. Same-same with genetic drift. In every case the species will either fit into the niche or stick out like a sore thumb and get eaten or fail to eat, or whatever else happens to it. Either it will crash or barely hang on with a marginal kind of adaptation, or adapt well and thrive. And for examples of this we can list the thousands of species vanishing from the Earth under the pressure of human impact.
Fraggle Rocker said:
When you look at it that way, it's obvious that it is an absolute miracle that we have any fossils at all! It's not uncommon for a species of animal that lived tens of millions of years ago to be represented by a single bone.
Trippy made a good point, which you amplify, that the most likely parts to make it to the point of fossilizing are the hard parts. And it's amazing how some small fragment of a skeleton or shell or whatever will often reveal some detail that folks like leopold are overlooking.
People will immediately shove Arizona's impressive Petrified Forest at us,
That's a Creationist talking point? I must have missed it. Sounds pretty absurd even without hearing the propaganda.
without realizing that this will backfire on them as a teaching moment. It's absolutely true that when trees died in the past, their trunks simply lay there on the ground, as they slowly fossilized by the action of water coursing through their capillaries. (Although many of them were eventually buried by tectonic activity, to be compressed into petroleum or natural gas.)
But then evolution kicked in to fix this "problem." Trees could not decay because decay is the action of scavenging organisms, but no organism had an enzyme that could metabolize lignin, a complex of sturdy polymers that allow trees to grow to astounding heights without collapsing under their own weight.
What was the solution to his problem? The emergence of mushrooms. Mushrooms contain lignase, an enzyme which, for all intents and purposes, was "invented" for the specific job of digesting lignin.
I see you spent a lot of your formative years experimenting with mushrooms.
That would certainly explain you switching between Fraggle the Erudite and Fraggle the Wild n Crazy with such finesse. But I digress. Fungi are way older than trees, so I see your point. You're saying (I think) the fundies missed the lecture on co-evolution, otherwise they wouldn't try to manufacture lies about the origins of petrified wood. That, and of course they just never took the class and/or never got that far in school.
Bad, bad fundies. :spank:
Co-evolution is huge piece of the puzzle leo is overlooking. The craziest cases (and I wouldn't want to have to try to think thru this after mistaking my portabello for the magic kind) are the ones that show multiple stages--like: the worm's eggs that pass through the host's feces (hope no one’s eating now), a snail eats the feces, ingesting the encysted egg which it vomits, then an ant, which likes to eat snail vomit, ingests the still-encysted egg, but in the ant's crop the egg emits a chemical message to the ant's brain, causing it to go stand on the top of a blade of grass (that's a thread in itself), a cow eats it, and the egg hatches in the cow's dung, producing microscopic worms . . . the next host goes traipsing barefoot through the cow paddies and a microscopic worm enters his (the females would have sense to wear shoes) bloodstream directly through a pore in the foot where it finds its way to the alveoli, climbs through a capillary into the trachea and enters the esophagus, makes its way to the small intestine where it attaches, gets big and healthy on the endless supply of fresh blood, and releases eggs which pass back to the soil through the host's feces, to restart the cycle.
All of these stages evolved in succession. It's a good way for leo to understand how much abundance of evidence there is for "gradual accumulated change", depending, I guess, on whether he thinks critters like hookworms are examples of "macroevolution". More important, I think, is for the creationists (the ones who would be rehabilitated) to begin treating science more holistically, in this case taking a moment to recognize that there are system effects going on at various levels of nesting. (Another critical level of analysis leopold & the creationists have yet to consider is the coupling between the biosphere and the geosphere).
BTW another teaching moment for the creationists in regard to shrooms has to do with their role in the development of sexual reproduction leo is concerned about. Here I'm referring to forms that undergo meiosis although reproduction is asexual (another “missing link”). And of course that has to be considered in regard to the geologic era of their appearance, which is close to the time Adam actually hooked up with Eve (probably as red algae--
Bangiomorpha pubescens--also the name of my Jr High garage band). And a related topic for them is to discover why so much of human DNA matches yeast. (Somewhere in there I would have them go through the PBS series "Our Inner Fish". Over a plate of grilled salmon-portabello if they still want to pacify their fears about their place in the food chain.) (While we remind them that fungus and bacteria will of course still win in the end.) (Too bad LG isn’t here to remind us something about mouldering.)
I now return control of your mind to you. :smilie of guy in hypno-glasses staring at "snow" on TV screen: (inside joke for people old enough to remember analog TVs).
