Lol, look at this guy, trying to use science and facts to disprove my fairytale. What a joke!

I had a dude come up to me at the reference desk and tell me that the earth can’t be billions (he said trillions, lol) of years old because erosion from the Mississippi River would make it wider and deeper than it is. I pulled up some info including the idea that the Mississippi was something that came about more recently because of plate shifting, etc and he just said, "Nah."

The correct answer would have been: "Why should I? You're an idiot."

Lead 204 is entirely primordial and the other isotopes found on earth would be found at roughly the same concentration were all of the lead on earth primordial. It's the excess ratios of the other isotopes of lead that can be attributed to radioactive decay. That is a substantial proportion of the lead on earth, but to say the "existence of lead" is proof of the age of the earth is entirely incorrect.

https://en.wikipedia.org/wiki/Isotopes_of_lead

I mean, the existence of lead doesn't necessarily prove the age of the earth so much as that those elements have existed for that long.

HOWEVER -- you're basically guaranteed to find lead in uranium deposits found around the earth, and the ratio of lead/uranium is how we calculated the 4.6 billion years.

Uranium is formed in Neutron stars or Supernova, so at the very least - the uranium found on earth itself is 4.6 billion years old. Whether "Earth" was "Earth" back then, who knows. This could be pre-moon? Could be before the earth even cooled down to have a solid outer layer? So the estimate is bound to be off by a little...

Just not by 4.5 billion years.

I'm pretty sure just soap has been around for more than 4.5k years and that means civilization too. So even if you do some backflips in justification here, there's no way you get 4k.

There’s bread from 14,000 years ago

There's evidence of human civilization and agriculture going back at least 10,000 years. You have to be extremely willfully ignorant to think the earth is only 4,000 years old. Hell the pyramid of Giza is older than that.

This proof is partial though. This assumes there is only 1 way of obtaining lead. What if lead appeared from fusion in stars younger than that.