Meh.
Piltdown man. Fifty years and more that crap was in the science books.
They were messin with it all the way back to Galileo and Isaac Newton's days. The power writes the law and dissent is not tolerated... The whole damn show started out in alchemy and such - The seven liberal arts ARE the seven sacred sciences of the occult. If the foundation is no good, and the metering is no good, there ain't no reason the believe any of it.
Different lanes. Piltdown man was a biological fraud, presented as a fossil, likely for fame and pecuniary exploitation (Come see the home of Piltdown Man, stay at the Cave Inn, and eat at the Fire Pit...). It played on the Darwinian fad of the times, and met a cadre hungry for confirmation of theories that made them feel superior, intellectually (AKA, 'ripe' marks). They wanted to believe.
I met Jesus in '02 when I had pneumonia, I don't
need to
believe, I'm convinced. I know there is a there, there. What He wanted of us is pretty basic. He spelled it out, all we have to do is practice it. The rest is just a fascinating puzzle to me, and some day, I'll get the answers as to how it all happened, not that it will really matter.
If you want to see fraud in science books, consider it is likely that neither of us will outlive all the references to Anthropognic Global Warming (rebranded "Climate Change") which was a scam foisted to sell Carbon Credits on the Midwest Carbon Exchange, said Carbon Credits purchased from farmers for a small fraction of what they would have sold for on the Exchange to virtually any industry that wanted to stay in business, had putting cap and trade policies in effect become law. IIRC, the chief profiteers would have made trillions, and included AlGore, Morris Strong and George Soros, but it has been a while since that was going on.
Like I said, for fun and profit.
But one way to get a guesstimate of the thickness of the old ice sheets, is isostatic rebound. The ice that's gone weighed a bit over 57 lbs/cubic foot. Since the continental crust more or less floats on the Mantle, stacking an ice sheet one mile thick on that crust will cause it to sink lower in the mantle, just like loading a boat makes it displace more water. It sounds strange, but by studying river channels and deposits, you can get a handle on whether the crust was sinking or rising (due to the ice to the north--South down under, or even perhaps where you are) The leading edge of continental glaciation is relatively easy to pick out, the deposits are diagnostic. As the ice iceward melted, it relieved that weight on the continent, and the continent which was riding lower on the mantle rebounded (and still is rebounding in places) just like removing the cargo from a ship causes it to displace less water and ride higher. That rise causes streams to cut deeper and leave terraces behind. The guys who do this sort of calculation get a rough idea of how much weight was there, by figuring out how much weight has melted off and how much the continent has rebounded from that relief. I'll be the first to admit, it isn't precise to the inch, but within a few hundred feet or so, I think they have something.
In the meantime, there were serious geochemists out there long before Erf Day, who were taking a different approach, along with Oceanographers who had noted apparent river channels (and submarine canyons) on the Continental Shelves, which appeared to be the product of terrestrial erosion, as opposed to scouring channels from debris flows. Yet another angle would work with the boundaries of glaciation on land, pencil in those same limits on water. Knowing the area under the ice, and how much sea levels dropped, lets you make a rough calculation of how much water would have to be trapped in the ice sheets to get that much sea level drop, and with that, a thickness.
I'd wager there is something that could be done with trapped water in sediments, too, comparing salinity which may or may not produce an estimate of how much water was removed from the oceans by evaporation and deposited as ice and snow on land, leaving water in the ocean basins that was more saline than usual.
There really isn't much motive I can see to game the numbers there. It's just trying to get an idea of what was.
What I wonder, as long as we are on the topic of Glaciation (Continental, more than Alpine), is what the land surface looked like before the last round of regolith vs God's Own Bulldozer.
The Missouri was believed to have flown north, not south, and now follows what was the edge of the ice sheet. The Red River of the North did (and still does) flow north, but got dammed up to form Glacial Lake Agassiz, and the sediments from that make Eastern North Dakota and the Westernmost part of Minnesota (the Red River Valley) one of the flattest places on Earth. It turns out that that old lake bottom is some incredibly fertile farmland, too. But as those lake levels changed, the beaches along the lake edge moved, sometimes miles for just a few feet of elevation. Those have been mapped, too, but it's difficult to tell whether the changes are due to more ice to the North or the Lake draining episodically.
Anyway, people like living on the beach, and where rivers come together (since water is a great way to transport most anything) and where the earlier river channels went and met, there should have been settlements in warmer times before the last (Laurentide) Glaciation. A friend who was up by Tioga ND was drilling water wells for a living, and pulled a piece of brass our of a new hole from about 50 ft. down. For some reason, it didn't dawn on him at the time that there just should not have been any brass at that depth, and that it does not occur anywhere naturally, and it got tossed on the truck and lost. Who knows? Did something near the surface get kicked downhole? Hard to say otherwise without being able to examine it, but it invites thought. Glaciation would have either wiped away or buried any signs of previous occupation.
In the interglacials before the laurentide sheet, my archaeology professor back in college pointed out that there were times when the corridor from Asia was open, just much earlier than the presumed peri-Clovis migration event. He postulated (like a good heretic, one of the reasons I liked him) that humans came here in waves, as climate and geography allowed, and the first wave was likely somewhere close to 32,000 years before present.
He also noted that the facial features of the southern South Americans were notably different from the MesoAmerican tribes (Aztec, Olmec, for instance), who differed from the Natives of our Northern Plains, and elsewhere in what became the US and Canada.
Sure, that might be an artifact based on cultural tastes for what constitutes attractiveness, or tribal constraints on subsequent procreation, but it also raises the possibility of distinct populations coming over and just sticking more or less together, and getting pushed further south by new arrivals. Immigration only came pretty much from one direction--unless the seas had been conquered long before Columbus, Henry the Navigator, Vespucci, and Magellan came along.
All fun to speculate about.
