Evolutionists - In the course of evolution, when did a cold-blooded animal become warm-blooded?

'cold-blooded' and 'warm-blooded' are not well defined, distinctive categories, so it's impossible to say without first defining exactly what you mean by the terms.

There are also different degrees of warm-bloodedness and cold-bloodedness.

Some critters have behavioural and structural adaptations that assist them in maintaining a high body temperature. For example, a black insect will absorb heat more quickly and be better able to fly sooner on a cool day than a pale insect. Does this constitute warm-bloodedness?

Other critters have physiological feedback mechanisms that work to maintain a single, homeostatic internal body temperature. However, in some of those critters, the exact body temperature can vary over the course of the day, season or year. Is a hibernating bat cold-blooded? How about a frozen wood frog? A bluefin tuna that has bands of muscle that help generate body heat, but has no internal mechanism for cooling?

On top of the difficulty of defining those terms comes the fact that the vast majority of these adaptations leave absolutely no trace in the fossil record, so it can be impossible to even speculate as to what or when some of these adaptations first appeared. Looking at their skeletons, it would be impossible to tell that bluefin tuna have that muscle adaptation mentioned earlier, while the closely related (and skeletally nearly identical) yellowfin tuna do not.

So basically: no one knows.

Well, that mostly be mammals and birds. But some fish are warm blooded as well. It most likely developed after animals populated land.

Also, do some research on the definition of the term theory.

"Evolution is a theory. Not only that, but it's a theory that is missing many key components"

If it was missing key components, then it would be called a hypothesis, not a theory. theories are hypothesis's that have been supported and held up to scrutiny. For example, the theory of gravity. And it doesn't get any higher in science then a theory. A theory can only have two things happen to it, 1. it is disproven, and goes away, or 2. it remains proven, and remains a theory.

Simple. It gave birth to a cold blooded animal it named Kate then warmed her up in a microwave. When it got really warm the mother put Kate in a wet suit and so the baby retained her heat. Kate liked being warm. Soon she grew up and wanting to assert herself politically she made a lifestyle choice to remain warm blooded. She gave birth subsequently to a warm blooded creature and everyone lived happily ever. That is however until Kate was attacked one day by a pterodactyl who was in the mood for a hot snack and frankly didn't give a toss about tucking into the then famous evolutionary progenitor of all things warm blooded. Boy, is natural history weird!

We don't know (yet).

But you may have it backwards...fish are warm-blooded, and it's quite possible that warm-blooded aquatic life was the ancestor of everything else. Cold-blooded animals may have only evolved after complex life made the jump to land, where they could get heat energy from the sun to drive metabolism rather than generate it internally. It's quite likely that warm-blooded came before cold-blooded.

By the way, there's no such thing as an "evolutionist," which implies "belief" in evolution. There's no belief involved -- either the evidence shows its correct to a high degree of certainty, or it doesn't. Since it does, the only logical conclusion is that it's correct. No belief or faith involved.

Peace.

Sorry for the copy & paste but....

"Their immediate ancestors (archosaurs) were cold-blooded, and dinosaurs developed warm-bloodedness very early in their evolution." This would imply that dinosaurs developed warm-bloodedness in a very short time, less than 20M years and probably less than 10M years. But in mammals' therapsid ancestors the evolution of warm-bloodedness seems to have taken at least twice as long, starting with the beginnings of a secondary palate around the beginning of the mid-Permian (Kermack and Kermack 1980) and going on at least until the appearance of hair (the first known occurrence is possibly in the early-Triassic Thrinaxodon).

"Dinosaurs' immediate ancestors (archosaurs) were at least fairly warm-blooded, and dinosaurs evolved further in that direction." This answer raises 2 problems: (A) The early evolution of archosaurs is still very poorly understood - large numbers of individuals and species are found from the start of the Triassic but only 2 species are known from the very late Permian (Archosaurus rossicus and Protorosaurus speneri); (B) Crocodilians evolved shortly before dinosaurs and are closely related to them, but are cold-blooded (see below). "

and

"Modern crocodilians are cold-blooded but have several features associated with warm-bloodedness because they improve the animal's oxygen supply"

find more at:

http://en.wikipedia.org/wiki/Physiology_of_dinosau...

There's still more to learn and we don't have all the answers yet.

First of all it is not either/or. Different creatures exercise different levels of control over their metabolic rates so it is not a case of being warm-blooded or cold-blooded. Second, it was not a straight line evolution from cold-blooded to warm blooded. See the source listed below for an example of how complex this is.

Animals evolved endothermy, the ability to warm body temperature, as a random mutation that happened to be favorable for survival. Therefore, at some point in time, cold blooded animals mated and during the fertilization process, there was a mutation causing endothermy. As it turns out, the trait made it easier for the animal to survive and so it was able to reproduce and pass that trait on to offspring. That is the basic way all changes occur in the evolutionary process.

Over some fifteen-million year period or other.

It doesn't have to be either/or, any more than legs or wings do.

Multi-function and partial function can still convey advantages.

A swim bladder can additionally serve as an inefficient auxiliary lung without being a disadvantage, and being on the way to a better lung.

"Straw-man" arguments don't knock down evolutionary theory.

Out today: new gene analysis on how fish got legs...

It happened during the great flood when magical water appeared from the sky and disappeared down the drain.

The first warm-blooded creature was the crocoduck, who became extinct shortly after the flood when Noah's family ate it thinking its eggs would hatch.

It has happened several times independently

a) the reptiloid line that led to mammals

b) at least one dinosaur line, including the ancestors of birds

c) even some fish have partial homeothermy.