So life did start on land

[Berzerker]

https://phys.org/news/2017-09-primordial-soup-hearty-pre-protein-stew.html

For those not inclined to read it all, the precursor building blocks formed on land within pools or water sources that repeatedly dried up under very hot conditions. While they cite river banks and recurring pools, I imagine the heat required thermal sources other than just the sun which was weaker back then. They instead attribute the heat to a thicker atmosphere trapping more sunlight (ala Venus I guess).

Tides would have provided daily (how many hours in a day?) replenishment, but I presume coastal regions were cooler so thermal vents further inland but still within range of tides might have produced the best conditions. Course back then a closer moon would have produced tides on even small bodies of water like lakes, but heat was needed too. Maybe something like Yellowstone Lake, plenty of thermal activity with continual drying and watering of shorelines.

This research further limits the origin of life... Its unlikely the world had life soon after it formed, presumably heat was present and water appears very early on, but not what we'd call continents or land masses. Those start appearing with the introduction of plate tectonics during the late heavy bombardment - a period of impacts from asteroids (or something) around 4 bya.

The LHB is being credited with the influx of heavy materials found in the Earth's crust and upper mantle, possible why the Earth is still so hot and active. The gold in our bodies arrived around 4 billions years ago just before life appeared.

 

[Birdjaguar]

I'm surprised that Lehman Brothers Holding had anything to do with ancient life on earth. I always thought that they were all about getting rich at everyone else's expense. But if gold was involved, your claim may be true.

EDIT: Damn. I read your LHB as LBH. Oh well.

What's hard about the "how did life come about" scenario is that we don't know the conditions and can only speculate. So testing X criterion is mostly guess work. Lucky guesses will tell us circumstances when such proteins can be created, but won't tell us the conditions that existed when they were first created. there are lots of unknown unknowns going back 4 billion years.

 

[plarq]

Gold? Does it have biological purpose?

 

[Valka D'Ur]

Gold? Does it have biological purpose?

Like any element heavier than hydrogen or helium, it takes a supermassive star to blow up in a supernova explosion, to make the heavier elements. That's where metals like gold come from, and since Earth (and the rest of the solar system) were formed from clouds of interstellar gas and debris that used to be one (or more) of these ancient supernovae, that's why we have gold (and everything else).

Whether or not gold serves a biological purpose, that depends on which way evolution swings for whichever species you're talking about.

@Berzerker: The early Earth's rotation was quite a bit faster than its present-day rotation. Our planet is slowing down, so the days don't just seem longer, they really are.

 

[Hygro]

so tl;dr Life started in water on land?

 

[BvBPL]

I'm still a panspermist.

 

[Berzerker]

so tl;dr Life started in water on land?

sort of... imagine a lake like Yellowstone with thermals dotting the landscape and a moon nearby causing tides. The water continually coats hot shoreline rocks depositing the building blocks of life and then dry up. A layer builds up concentrating more and more of the material kinda like how sediments become sand and lime stone deposits. The process wouldn't work with standing water...or in the ocean. It was speculated ocean thermals might have been where life began.

 

[warpus]

I'm still a panspermist.

Panspermia still requires life to begin on a planet somewhere. Or moon I suppose.

 

[Bootstoots]

Gold? Does it have biological purpose?

Not on Earth it doesn't, to any currently-known organism. It's both way too rare and way too unreactive for Earth-based life to make any use of it. Except for the arsonist apes that got loose, who found it pretty. But it's definitely not an essential element.

Here's a pretty comprehensive Wiki article on which elements are trace elements in humans, including some of the ones that are speculated to be important in ultratrace doses but that the jury is still out on: Article

Surprisingly, arsenic is on the list. We get enough in any diet, so nobody go run out and buy arsenic pills. But if mammals are totally deprived of it in a lab environment with food designed to exclude it, they start losing hair and slowly wasting away, with very low successful reproductive rates. Nobody knows quite what it does, but a couple micrograms a day seem to be essential. Boron and silicon are also in the same category, although they're less surprising because they're not usually thought of as deadly poisons. And then there are things like lithium and fluoride that make certain things (brain chemistry and teeth) work better, but that where deprivation doesn't kill people outright.

But the "noble metals" like iridium, platinum, and gold just don't react readily and wouldn't likely be useful even if they were common, which they're very much not.

 

[plarq]

lithium calms you down.

Hey, I found one! Diamond (an allotrope of carbon) is related to human reproductivity! Those males who lack it may find it difficult to find mates!
So there is biological role for gold, and silver, and emeralds, and other gemstones.

 

[emzie]

Based on evidence, the oldest trace/chemical fossils are all from marine sediments. The oldest unambiguous ones are 3.5gya, and possible fossils go back beyond 4gya. The oldest unambiguous fossils in continental sediments are ~2.8gya, with possible fossils going back to 3.5 gya.

For both oldest known and oldest possible, marine fossils are older.