So does this imply that we'll never know if the Cambrian Explosion is actually an explosion or just a continuation from a previously unrecoverable geological record? Is it even possible to have complex multicellular life under snowball earth conditions?<p>><i>Although it’s likely down to a number of factors, one possibility is that Snowball Earth’s erosion was so significant that there wasn’t much topography left to erode when all was said and done. The planet simply needed to forge more land first, and that takes time.</i><p>The balance of earth is so interesting. The process that forges new land (volcanism) is the same process that beats back snowball earth and re-balances the atmosphere with more CO2.<p>It's a bit old and cheesy, some of the info might be outdated, but this is a great episode on this topic: <a href="https://www.youtube.com/watch?v=XEiu611KsUo" rel="nofollow">https://www.youtube.com/watch?v=XEiu611KsUo</a>
Kudos to real scientists who bit by bit uncovers what happened in earths past, in ever-increasing resolution.<p>Whether "snowball earth" is accurate or not, what appears in outline is an earth that would have been uninhabitable for humans under most of, and even in relative recent, geological history.<p>It begs the question of how we might deal with the situation where the globe once again becomes uninhabitable (if we survive that long): terraforming or cocooning. The latter seems the best bet.
I find the use of zircons in this context very interesting. Starting with the Wikipedia article:
<a href="https://en.m.wikipedia.org/wiki/Zircon" rel="nofollow">https://en.m.wikipedia.org/wiki/Zircon</a><p>I went down the rabbit hole and learned a bit about Geochronology:
<a href="https://en.m.wikipedia.org/wiki/Geochronology" rel="nofollow">https://en.m.wikipedia.org/wiki/Geochronology</a><p>It is interesting how they “break up” dating depending on the time frame, for example some dating is only measured by “eon” (half a billion years), whereas the “finest” measurement seems to be “age” which corresponds to single digit millions of years.<p>A bit humbling to think that all of humanity can “fit” in the smallest geological measure of time.
Wow, I always assumed that complex life prior to our own was unlikely because it would have left a trace that we could detect. But if there is a plausible mechanism by which all such traces would have been erased, then who knows what might have happened deep in those billions of years when supposedly only single-celled life existed?<p>Perhaps Earth’s previous inhabitants triggered runaway global cooling, effectively hitting the reset switch back to single-celled life. Perhaps they escaped to Venus and vowed not to let the same thing happen there, but got it wrong in the other direction.
It's interesting how most comments here immediately see this gap in our history book of Earth as a potential time span during which another advanced civilization could have developed and gone extinct (my mind did the same). Meanwhile the article without much discussion jumps to this: "complex life first emerged when Snowball Earth’s monstrous mealtime came to an end."
TL;DR; Earth appears to have been covered by miles deep ice for many hundred millions of years during the last billion, and that caused normal geological leftovers of the period to be nonexistent. The best info for that period is stuff frozen into zircon crystals, which scientists think supports the ice hypothesis.