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 researchers—those are the folks who study how life began—have
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 protein—nucleic 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
selective—only 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 maybe—just maybe—they’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.