Neither do evolutionists, if you mean what I think you mea by "spring full blown".
However, many "critters" have indeed arisen where they had not existed previously.
Quick, now, why do humans appear nowhere in the fossil record prior to a couple of million years ago?
Where are the horses prior to 40 million years ago?
Where are *any* large mammals prior to 65 million years ago?
Why are there *NO* mammals prior to 286 million years ago?
Where are the birds prior to 215 million years ago?
Where are the reptiles prior to 320 million years ago?
Where are the amphibians prior to 408 million years ago?
Where are the ray-finned fish before 438 million years ago?
Where are the fish of any type prior to 590 million years ago?
All these animals types were absent from the fossil record for a long, long time, and then later appeared -- and appeared after the pre-existence of different, more "primitive" types which could reasonably have given rise to them via evolution.
The conclusion is entirely obvious. And it has never been stated any more clearly than:
It is time for students of the evolutionary process, especially those who have been misquoted and used by the creationists, to state clearly that evolution is a fact, not theory, and that what is at issue within biology are questions of details of the process and the relative importance of different mechanisms of evolution. It is a fact that the earth with liquid water, is more than 3.6 billion years old. It is a fact that cellular life has been around for at least half of that period and that organized multicellular life is at least 800 million years old. It is a fact that major life forms now on earth were not at all represented in the past. There were no birds or mammals 250 million years ago. It is a fact that major life forms of the past are no longer living. There used to be dinosaurs and Pithecanthropus, and there are none now. It is a fact that all living forms come from previous living forms. Therefore, all present forms of life arose from ancestral forms that were different. Birds arose from nonbirds and humans from nonhumans. No person who pretends to any understanding of the natural world can deny these facts any more than she or he can deny that the earth is round, rotates on its axis, and revolves around the sun.Deal with it.- R. C. Lewontin "Evolution/Creation Debate: A Time for Truth" Bioscience 31, 559 (1981) reprinted in Evolution versus Creationism, op cit.
It's been just varieties of them (like your weed) since then.
See above.
That's all we've ever observed.
Only if you adopt an artificially restrictive definition of the word "observed". We have *observed* fossil sequences which, chronologically, map out the rise of new forms of life from earlier, different forms of life.
That's all that can be determined by SCIENCE.
You clearly don't understand science. Science is not simply sitting around watching stuff happen in front of your face.
A sea-horse will not become a race-horse, no matter how many million years you wait.
And yet, a fish became a race-horse in 400 million years. The fossil record is entirely clear, as is the DNA record.
Be a flat-earther if you wish, the rest of us prefer to learn what the evidence tells us.
You just don't get it, Mr. Smart-guy evil-u-sham-ist. All them big numbers was invented by a buncha evil people, probably athiests or commies, who hate God and want to destroy him. How else can you explain away the fact that Stegosaurus died for man's sins? Huh? Huh?