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  • You may have an image in your head of how life came to be on Earth.

  • A bubbling primordial soup in which life forms evolved

  • over millions of years and eventually crawled from the oceans onto the land.

  • But new research suggests that instead... it might be the other way around!

  • We've had the idea that life began in the oceans since the 1920s, when it was first

  • put forward. This was cemented in our minds in the 1950s by the classic Miller-Urey experiment

  • from which scientists hypothesized that the ocean-atmospheric cycle of early earth could

  • have been the perfect conditions to instigate life... but there were many unanswered questions.

  • And since then, biogenesis researchersthose are the folks who study how life beganhave

  • been kind of obsessed with finding that key catalyst that would have brought chemical

  • components together for the very first time. And research from the past several years has shown

  • that in some situations, that special sauce could have been UV radiation.

  • And while some teams HAVE been able to recreate the building blocks of life using UV light,

  • no one has yet been able to successfully perform these transformations in experiments that

  • replicate seawater. Meaning that our whole 'life crawls onto land from the oceans' idea

  • could be wrong? And here's another problem: while water

  • is a definite requirement for life on earth...the chemical properties of straight up H2O actually

  • break down proteins. Including things that are made of proteinnucleic acids like DNA

  • and RNA, the genetic material that holds the blueprint for all of life.

  • Now these days, living cells tightly control their water balance to protect their insides from

  • water degradation, but... how are proteins supposed to have formed IN a substance that

  • actively attacks and degrades them? Scientists now call this 'the water paradox'.

  • And in 2009, we start to get some answers. John Sutherland and his team at Cambridge

  • performed a series of experiments that successfully produced two of the four nucleotides that

  • make up RNA, using just a really simple starting mix of basic chemicals that may have been

  • found on early earth. They exposed this mixture to UV radiation and presto change-o, nucleotides!

  • Now key in these experiments is that these chemicals were all dissolved in water...

  • but at very high concentrations. That means LOTS of the chemicals to just a little bit of water...

  • like, really strong Kool-aid. This indicates that even though water may have been involved at

  • the beginning of life, it couldn't have been in a giant body of water, like an ocean,

  • where the concentration of those chemicals wouldn't be as strong.

  • For the chemicals to be in high enough concentrations AND to be exposed to sunlight (for that

  • crucial UV component), some scientists believe that this life-giving reaction had to have occurred in

  • environments like small pools. And next, building on the work that produced the

  • nucleotides, in 2015 Sutherland and his team were also able to produce the building blocks of

  • proteins and fats. That's a big step, because now with nucleotides, and protein and fat

  • pre-cursors... we've got all the moving parts needed to get life goin'!

  • And in 2020, other teams have found even further answers to the water paradox.

  • Researchers created conditions where almost-proteins could form and survive during wet-dry cycling.

  • Which is exactly what it sounds like, the molecules are allowed to dry out for some

  • time before they're exposed to water again. The researchers discovered this process is

  • selectiveonly the molecules we would expect to see on an early earth withstood the cycling,

  • and are actually shaped by it. This wet-dry cycling has even shown to essentially

  • select for more complex combinations of nucleic acids inside little protective lipid bubbles

  • that help them make it through dry periods... and scientists are starting to think this may

  • be a precursor to something like a cell. All of this lends even more support to the idea that

  • the body of water from which life may have sprung would be shallow, and prone to drying

  • out from time to time. Imagine: all of life being descended from some stuff growing in

  • a puddle. It's also worth mentioning here that not

  • everyone is in agreement. Although there are commonly agreed on necessary original ingredients,

  • some teams are still looking into deep sea vents as a possibility for the birthplace

  • of life, while others think hot springs are a likely contender.

  • And why is any of this important, anyway? Aside from answering existential questions

  • about where the heck we come from, a better idea of how life originated here on Earth

  • gives us clues about what it might look like or where to look for it on other planets too.

  • For example, in February of 2021, the Perseverance Rover successfully landed in Mars' Jezero Crater... which

  • seems to have once been an ancient lake. And given all of this research, the crater is

  • now a prime suspect for signs of life on the red planet. Now it'll be years before the samples

  • return to Earth... but maybejust maybethey'll contain remnants of those proteins or lipids

  • that would tell us if we aren't only planet that's ever hosted life.

  • Check out this video here for more on what early life on Earth might have been like, and if you

  • have questions about this origin of life scenario, let us know down in the comments below. Let

  • us know if you have another experiment you want us to cover and make sure you subscribe

  • to Seeker for more on ideas about life on other planets. As always, thank you so much for watching,

  • and I'll see you in the next one.

You may have an image in your head of how life came to be on Earth.

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B1 life water earth cycling dry successfully

We May Have Been Wrong About the Origin of Life

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    林宜悉 posted on 2021/03/27
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