Man made climate change vs meteor question...

The darkness caused a shift in plants, which led to less food and different places to hide. This leads to the advantage for being smaller or able to fly. The eruptions, dust, change in oxygen, made it harder for everything to breath. I would look here for why small mammals did better than small crawling dinosaurs, but I don't know that much about small dyno breathing. Did the small mammals and flying dynos find and eat the eggs of the small non-flying dynos? I don't really know.

Here is one theory, and it should say direct, as the astoroid would have caused these changes indirectly.
Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere

 

Definitely a fun subject. The one dramatic shift was the appearance of placental mammals well after the impact. I don't know of any reason why reptiles or dinos could not have developed placental abilities, but if they could have, it was too late. What may be interesting with placental animals, is the multitude of secondary effects. For example, being able to figure out how to get food for the offspring even after they wean may have put a new premium on thinking ahead. Something whose "side effect" is to unintentionally outwit the competition. (Wild speculation-that's what makes it fun.)

 

Lamarckian evolution has been discredited, sorry, too much biology for me in school. We don't just develop abilities as needed. Evolutionary biology - descent through modification - happens with random mutations in dna that survive because they give the organism a survival or reproductive advantage. Placental birth gives a survival disadvantage to the mother, but a reproductive advantage. If the mutation occurred at an earlier time the disadvantage of higher chance of death of the mother could have killed the mutation, and the modification would end. We don't really know when mammals first appeared, we may just not have found the fossil evidence.
Face-to-face with the earliest ancestor of all placental mammals : Nature News & Comment

Say that the first mammals happened 100 million years ago, and there were those with folded brains and others with simpler brains. The folded brains would have helped them survive the world after the asteroid, while the simpler brained mammals may have gone extinct even before the fossil record.

 

I don't think I implied Lamarckian evolution anywhere. That's why I explicitly said "secondary effects". My point more specifically, was that placental development could not have evolved as just an isolated feature. Other mammal aspects (milk glands, parenting behavior, etc.) had to be affected greatly down the line. All of which Darwinian evolution would have amplified or attenuated. What is clear from the original Science article was a big placental mammal "explosion" occurred in the following millions of years after the dino era ended. We can justifiable infer that something in the placental arsenal made a big difference. My (semi-random) guess was possible brain changes.

 

No we can't. Given that every species larger than a cat had just become extinct, we can expect there to be an explosion of new species to fill all those now empty ecological niches. Whatever group happens to be around is likely to have the best chance to fill them. It is not clear that mammals were anything more than lucky. On the other hand, non-specialization might be considered advantageous for situations like this. Having a number of small, non-specialized species in your phylum could help that phylum be more dominant after a near complete ecosystem collapse. But this wouldn't point to an advantage in the phylum itself, just in having the right species at the right time.

 

The thing lamarkian about your description was the idea that organisms have a choice in developing features adapted to their environment. Did they have time to develop placental birth, versus the current idea that mutations occur, then if they aid survivability, reproduction, or mating they are kept, other wise they disappear. There is no stretching of the neck of the giraffe to cause the adaptation, but if a mutation occurs with a longer neck, and it helps the organism survive droughts by getting to leaves other shorter neck giraffes can not, then the genes will be passed on, either because other giraffes think the long neck is sexy and want to mate with it, or because it lives long enough to mate. We do have some epigenic inheritance through gene expression that is lamarkian - acquired traits during the life time passed on to one or two generations, but the creature does not choose these. Gene expression from starvation can be passed on, but the theory is this is not like the stretching of a giraffe neck No insult was meant. Lamarkian evolution is evolution and helped push back the idea of a static created environment, where creatures did not mutate and pass on new traits.

Insects seemed to survive fairly well, but the large creatures disappeared. Bird dinosaurs and the newer mammals were both small and ate insects. Both likely had most of their natural predators disappear. Both fed their babies, birds by regurgitating food, mammals by lactation. Remember some small brained birds also seem to be able to innovate for environmental changes, perhaps better than the first mammals.

The Life of Birds | Bird Brains

+1

Mammals had certain traits that helped in the environment. These traits might have been disadvantageous in the previous environment. As food became more plentiful, mutation that conferred larger sizes did well in mammals. Perhaps the genes that cause midgets survived in human dna because they gave advantages with low food supply. Just as two sickle sell genes can cause death, but also one gene helps survive malaria.

 

Somehow my position is getting twisted to claim the opposite of the point I'm trying to make. Under no condition am I inferring or stating that any organism "chooses" features for evolutionary advantage. Nature makes that selection. Now that we agree that Darwin is in charge here, I'll make one last attempt to restate Darwin's general point to this specific situation. Survival of the fittest usually results in more of the fittest and less of the competition. Since placental mammal far outnumber non-placental mammals, I thought it was fair to say they had a Darwinian advantage. All I was doing was speculating on what that advantage could have been.

 

Nor did I claim anywhere that you did.

That isn't what Darwin's point is. Generally he was only talking about populations within species. Placental mammals far outnumber non-placental mammals mostly because of the relative sizes of their respective habitats. If body count was the metric, bacteria and viruses would 'win' hands scillia down.

 

Like I said, I was not really trying to judge your position.

My position is we are well beyond Darwin. Darwin's origin of species also included some of the now mostly rejected purposeful adaptation to the environment. We now have Mendel and Watson and Crick, with genetics and gene expression explaining genotypes and phenotypes. Similar looking creatures (similar phenotypes) often are quite far apart genetically. The mechanism for modification is genetic mutation, and we can see in the dna if these mutations are linked. As for the various types of mammals -placental versus marsupials versus monotremes, we can easily see why placental won out. The monotremes - egg laying lactating mammals are the oldest line both genetically and in fossils, but only platypus and echidna remain to present day. Infant mortality in the harsh conditions likely kept the numbers down. I don't know why placentals out competed marsupials, but with a few exceptions like the opossum, only where marsupials have been separated from placentals in their ecological niche do we still have marsupials.

 

Ultimately, one has to have faith - right? - that certain 'givens' such as the speed of light, and uranium decay are in fact absolutes. But if (like every other phenomena) light used to travel 1,000's of times faster (and is slowing down) and if uranium used to decay 1,000's of times faster, then yes ... the 33,000 year number may be way over stated.
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Nope, faith not required. Supernova SN1987A can be used to calibrate the speed of light 167,000 years ago.

 

lol, hill. Light if you look at the scientific evidence follows einstein's theory and is a physical constant in any given medium. Although this theory does include time, c does not change. We have no theory where the speed of light varies that is supported by experimental evidence.

On the time of extinction for dinosaurs we have some other problems. Some dinosaurs are still with us, so not all went extinct that fast. We are left with the fossil record, and many disappeared in a very rapid time period, but there are some fossils in other strata of earth. Some have theorized these were displaced, moved up to higher layers of the earth, but a few have been dated directly to be past the asteroid impact. Not finding fossils is different than them not existing. We do know that drastic climate change happened quickly after the asteroid impact - colder temperatures, darker skies, less oxygen and carbon dioxide. Did some spiecies survive for tens of thousands of years after these changes - almost definitely from the fossil evidence. Did many species die out within years of the impact, that also seems very likely from the fossil evidence and current theories. The deccan traps of millions of years to extinction seems fairly well contradicted by the fossil record, but again, maybe we just haven't found the fossils.

 

I duno. I've read there is contoversey. Some disagree.

Utah Space Association - Special Topics - A Plan for Exceeding the Light Barrier

What intrigues me is how adversarial the very thought is to those on the 'light must be a constant' belief. I do get a mental 'knee-jerk' reaction that only one thing ... light speed ... is permitted to violate the physics law of entropy.
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Hill the speed of light does not violate any physical laws that are real. How could it?

So from our link - can some objects theoretically travel ftl (faster than light), yes absolutely.

Could special conditions quite different than those on earth make the speed of light variable? A good scientist would leave open that possibility, but I have not seen a viable theory or experiment that has supported it. Now Einstein's theory of relativity showed that newton's theory of gravitation was wrong, and we have experimental evidence - data - that supports Einstein over newton. But, here is the important thing about this light constant thing, when reduced to the situations that most were using newton's gravitation theory, low speeds compared to light, newton's gravitation Gm1m2/r^2 is a great approximation for relativity warped space time. In such a way, if there is a theory where conditions of light speed is variable we would expect on earth it would stay having little variation and could correctly be thought of as a constant.

The main advocates for a slowing down speed of light are biblical fundamentalists that want to say that the big bang was not so vary long ago only thousands of years. A slow down in calculation of the speed of light from 250 years ago is much more likely measurement errors than a real exponential decline that would show the earth is less than 10,000 years old. It is that argument that gets emotionally angry responses from physicists.

I don't think there are angry reactions to things like this
Has Speed Of Light Slowed Down? - CBS News

 

I duno. I've read there is contoversey. Some disagree.

Utah Space Association - Special Topics - A Plan for Exceeding the Light Barrier

What intrigues me is how adversarial the very thought is to those on the 'light must be a constant' belief. I do get a mental 'knee-jerk' reaction at the idea of only one thing ... light speed ... is permitted to violate the physics law of entropy.

Certainly some of the 'slowing light speed' advocates coincide with bible/faith - but some are not of that ilk. Whether the advocates motive is based is research is what's interesting to me. One recent read I found (in reference to time slowing as much as 10 to the 10th power) made the following comment:

Mental gymnastics ... wow.

 

OK.

Darwin wrote about a huge number of points. One of the main ones was how natural selection enabled new niches to be filled with organisms not originally suited or equipped to do so. Knowing that, I'm not sure what you mean by "populations within species". No criticism implied, just confused by what you meant.

(Scillia? ....Oh Cilia...got it! You're right.)

 

The uncertainty I was referring was how as dating techniques continuously get better, the "error bars" get smaller. Many times the "time" it took for something to die out changes due to improved dating techniques, not new theories.

Here is an example. Let's say some powerful disease killed off all the dinosaurs in one year. However due to fossil dating variations being only good to around 33,000 years, the common consensus is that it took that long for the dinos to die off. That is NOT what happened. It's just a made up example of how dating accuracy variations can obscure a much quicker event. What is true is that as dating accuracies of fossils and fossil sites have improved, the demise of the dino's has continued to become quicker in the wider literature over the past decades.

 

"I do get a mental 'knee-jerk' reaction at the idea of only one thing ... light speed ... is permitted to violate the physics law of entropy."

I have tried, and can't get this sentence to make any sense. What is 'the physics law of entropy'? Do you mean the second law of thermodynamics? What does it have to do with the speed of light? Why do you think light speed is 'violating' it? Please use equations in your explanation.

 

The main item on variable speed of light there was Montgomery, but when googled this, it mainly was those fundamentalists trying to explain how the earth might be much younger than the rest of us believe. What is really going on? Likely experimental error. In 1911 einstein proposed a variable speed of light based on frequency. In 1912 he found some experiments with different numbers that worked out to a constant. If light had slowed significantly in the last 250 years as Montgomery calculated, why has it stopped slowing down in the last 50 when we can take accurate measurements? No one has proposed a good explanation, but many have said god I guess in Kansas it still is controversial teaching evolution.

On other topics though, feynman has stated virtual photons can go faster or slower than the speed of light for short periods of time, but..... when we measure it over meaningful distances the real photons seem to go at a constant speed.

Now general relativity does have a term that allows for variable speed of light. Some have looked at some quasars billions of light years away and frequencies appear to either violate a constant speed of light or quantum mechanics, and some have theorized that we need to look at that term in general relativity. Other astrophysics measurements either violate the big bang theory or constant speed of light. In both instances the change would have happened over a billion years ago, leaving us with a constant speed of light in the last 100 million years when most of the dinosaurs went extinct. Jesus is unlikely to have buried dinosaur bones to test our faith, the other part of the short earth variable speed of light theory.

 

I didn't mean for my lack of precision to stumble anyone from grasping my thoughts - disjointed as they get. To abbreviate and distinguish entropy from the idea that systems or societies deteriorate I (wrongly) made reference to the 'physics' type of entropy ... which I understand (in my abbreviated way of thinking about such concepts) as matter / energy evolving towards a uniform/non-reactive state. The notion that light (a wave) goes on and on - constantly maintaining its speed (or not) rather than diminishing is/was a topic I'd stumbled on, and I hope to be able to look at the issue more. The speed of gravity intrigues me too. The idea that if I had the planet Pluto on a string ... whipping it around on its orbit (in stead of the sun) ... then I let go ... would Pluto continue to orbit? ... for days? ... weeks? I'm reading about it because it's intriguing. I read Stephen Hawking critiques ... too ... it doesn't mean I rise or fall by either sides beliefs. No I can't draw out formulas. I'd have to use the big words.
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