The Cambrian "explosion" really wasn't all that sudden--it took place over a period of ~70 to 80 million years. It appears to follow a growth curve similar to that seen in bacterial cultures: a "lag phase", where the number of multicellular organisms changes very little over time, while the conditions conducive to growth are being formed, a "log phase", where the number of multicellular organisms is increasing in a more-or-less linear manner, and a "stationary phase", where the number of species has approached the theoretical maximum possible in that system.
The rate of mutation *is* fairly constant over time; it is a function of the chemical nature of DNA. Various effects occur to reduce the effects of random mutation: a mutation that has an effect on survivability will be selected for or against, depending on the effect ("survival of the fittest"), and the ability of a neutral mutation to survive and propagate through a population over the course of generations is based purely on chance. This process of slow change over time is called "genetic drift" and occurs in every species--it can be observed to have acted on humans even within the span of recorded history. A change in environment, which can happen for any number of reasons, can cause previously neutral mutations to become advantageous or deleterious, and such mutations would then be propagated or eliminated within a few generations, changing the overall genetic characteristics of the population. There are many factors that affect the rate of evolutionary change.
2. Nobody on the planet can trace the evolutionary history of any animal on earth let alone a mammal. You look up evolution of the horse, and they start with a small horse. OK, what did the small horse evolve from. Nobody can tell you. Ditto the tiger. Small tiger to saber tooth tiger to modern tiger. Small wolf to Dire wolf to modern wolf.
Most of the illustrations of horse evolution only start at the point that the horse ancestor was already differentiated from the common ancestor of horses and bats. In theory, phylogenetic trees can be constructed to include every organism from single cells up to modern multicellular organisms, but in practice, such a tree would contain so much information and have so many branches that it would be unreadable. So, for the sake of simplicity and comprehensibility, horse evolution is only illustrated from the point where it is specific to horses. Most horse evolution illustrations also omit other equine species, but that doesn't mean they don't exist.
Big flipping deal. If evolution is real, then some genius should be able to show me some model tracing the horse back in it’s evolutionary genealogy back to it’s fish relative in the sea, right? As far as I know, nobody is ever able to connect the dots and go back more than a few million years for the horse or tiger or wolf, and identify its predecessors. Failing that, the theory stands on no legs at all.
You can find that information by googling "vertebrate evolution". There is so much knowledge about evolution that it is really impossible for any one person to know all the details, much less to present a comprehensive description to non-scientists within the context of a forum thread.
If you can’t identify the fossil ancestry of something as a horse, or if you can’t model that ancestry back to the fish from whence it supposedly came, then you haven’t got much of a theory, have you?
As I said above, the fossil ancestry of horses has been traced all the way back to the ancestor of all vertebrates. How would you know that a fish was the ancestor of all land vertebrates, if the ancestry had NOT been traced back that far?
As for the "legs" of evolutionary theory--it's based on many scientific disciplines. Paleontology, comparative anatomy, geology, physics, mathematics and statistics--molecular biology is the most recent addition to the tools used to study evolution, and, so far, everything we've learned using molecular biology dovetails quite nicely with the other approaches.
You say the Cambrian “explosion” took 70-80 million years, as if that is established fact. There is still massive debate over whether this took 10 million years or 100 million. And frankly, nobody knows. Did it take 80 millions years to develop eyes or develop skeletal systems? Call me skeptical, because the record doesn’t seem to show it.
Thanks for informing me that the experts can identify the entire line of horses back to the fish. Please do me a favor and just list 20 or so predecessor creatures down the chain of evolution for the horse, in the direction of fish. Just the names are fine. I can Google the pictures.
Since I keep getting stymied earlier than Hyracotherium, could you please start with that animal and go back 20 known species of creature before that. That would go a long way toward relieving my doubts about the theory of evolution. 55 million years ago is really recent history in evolutionary time so it would be nice if you could take the horse’s ancestry back 250 million years or so.
Thanks.
These people tried. It's a PDF, so you can zoom in and in and in--the fuzz you start to see around the edge after a few zooms is actually the names of species.