To really get a good grip on evolution without actually going to college and working in one of the fields associated with it, you have to go looking for facts, without preconceived notions.
You can start with carbon dating, it has been around for a while and this field actually tests it own parameters and of course this happens all the time. They take a specimen that they know the date down to the day and test it. This is how they know the accuracy, plus or minus how many years. Egyptian mummies make good test subjects and they can go back to 4500 BC. When testing for things that are millions of years old you start looking at triangulating the facts. Test using other carbon dating equipment. Testing other specimens that are at the same sedimentary level in the dirt or rock. Depending on the rocks, if they contain lead there is something that they call “clocks in rocks” lead isochrons are also a valuable radioactive dating process and one of the most accurate dating process is if the rock or sediment contains uranium-lead isotopes. Comparing the results of these tests can pin point the date more accurately.
Then you flip the coin….what can cause inaccuracies in carbon dating? It is good to know that to.
As far as billions of years, some of it is as simple as common sense. If you are sitting on the ground….you are sitting on a grave. The grave of millions of animals and plants. The planet started out as a rock. The dirt that carpeted it, are the remains of animals and plants that lived and died over billions of years.
As far as the evolution of Man, we not only have a large fossil record of that evolution, but now we are discovering variances that did not follow the common path. I am not saying that we have a fossil record that goes year by year and there are gaps….but the term missing link is a misnomer. By comparing the DNA in fossils before and after the gaps we can see the similarities, so it just means that we have not found that specimen yet. Over the last few decades those gaps are being filled in.
Then there is DNA comparisons between specimens on the evolutionary chart and comparisons between them and us.
And it is still all about God and some things only God knows. There are a lot of questions in the science of evolution and some things show intelligent design or influence. Proving evolution is one thing, understanding the evolution of Man is another. About 2.8 million years ago God choose the “great ape” for advancement. We can track this, but no one has the explanation for what happened next. If you look at the evolution of animals it can take millions of years for each stage of advancement to occur. But in humans after the great ape, humans not only evolved a hundred times faster than any of the animals, they got smart quick and after homo erectus the evolution of Man sprang forward like a jet. Maybe a thousand times faster than animals, no one has an explanation for this. It takes animals so long that right now it would seem they are standing still.
And there was a global disaster that occurred about 73,000 years ago. The largest super volcano on record erupted at Toba Caldera, Sumatra that darkened the skies for about ten years and more or less poisoned the planet, a lot of the water sources were poisoned and the darkened skies caused an extend volcanic winter. Some say that the human population on the planet was reduced to a few thousand, most agree that it killed a lot of humans. This should have at least slowed the evolution of Man, but instead it doubled the rate of advancement of Man. No feasible explanation for that.
By far the most abundant volcanic substance from eruptions is gas and water that is toxic. Also there is a significant amounts of carbonic acid, carbon dioxide, sulfur dioxide, hydrogen sulfide and hydrogen halides and radioactive radon can also can be emitted from volcanoes. Depending on their concentrations, these gases are all potentially hazardous to people, animals, agriculture, and property. In the case of super volcanoes tons of ash that obscure the sun worldwide for an extended time.