Mainly because they were all found lying in the right order, in the geologic ladder.
Unicellular organisms predate multicellular organisms.
Plants predate animals.
Exoskeletal predates endoskeletal.
Fish predate amphibians.
Reptiles predate mammal.
And so on.
And so on.
There's hundreds of such relationships. It just cant a coincidence.
And they always date the fossils by the layer. Never the other way around. So nothing circular there.
Then there's all the transitional fossils. Which is the really exciting part.
Did you know over the last 25 years, we have uncovered more than THIRTY different species of feathered dinosaurs?
We have pieced together an almost complete puzzle of how flight evolved, step- by-tiny-step.
And new species being found in other branches well all. Which makes it easy to miss what is happening, if you blink.
Sorry if I come off sounding over-enthusiastic. Like I said, is very exciting stuff.
"in the geologic ladder" This isn't a hard fact that connects the dots between lifeforms, is it? The fact you see them in the earth that suggests age doesn't mean one came from another; it only means they were found in the ground that indicates some period. What connects these dots beside the wants to say that they are connected through ancestry? If this is the strongest piece of evidence shouldn't it be more than a educated guess?
Because they always seem to date in the right order, to keep Evolution in the running.
All it would take is say, a rodent fossil dating back to the Cambrian, to turn Evolution on its head. And ID would be taught in schools today, by default.
But that fossil is never found.
Instead, species always pop up in the geologic ladder, in same order as they would in a world where Evolution did happen.
@wsswan fascinating background you have and thanks for discussing forams (my chair was a palynologist, also very useful for biostratigraphy). My own work is primarily in invertebrate paleontology (particularly trilobites) but not exclusively and I've done a variety of different field work from geologic mapping to biostratigraphy, sequence stratigraphy, paleosalvage for construction companies, invertebrate and vertebrate paleo (turtles, mammoths, whales, sharks, oreodonts, etc.--a little bit of everything), stromatolites, ichnology, taphonomy, etc., etc. Personal interests include studying large scale trends, coordinated stasis, faunal succession and turnover (especially benthic marine assemblages) and nothing imho beats the satisfaction of being able to go out and determine the paleoenvironmental context and history from the paleo, biostrat, sedimentology, vertical/lateral facies changes, etc.
It's great to have your contribution and I imagine your experience is similar to mine when it comes to the general public (and even many biologists) who have a very poor understanding of what the fossil record is really like (starting with the fact that it's not archaeology nor all about dinos as you mentioned!)