If, in an instant, you could magically transport yourself to the ancient earth
4.5 billion years ago, and then in the next instant, you magically transported
yourself to now. you may say that only magic, or a supernatural force could have
transformed the earth to its present day from its humble beginnings. The diversity
of earth today can be explained largely through evolution by natural selection, a
process that occurred over billions of years. But this diversity must have had a
seed of some kind, the first semblance of life at some
point must have had a beginning, a start from the primordial soup. And it must
have started from nonliving matter. But how is it that the seemingly
unremarkable processes of geology, chemistry, and physics could have
combined in precisely the correct sequence to produce the first living
matter, from nonliving matter. This seems to many people utterly impossible.
There must have been a blueprint. There must have been an architect, they say. How
could such vastness of diversity, functionality, and beauty come from the
physical processes of the cosmos and nature? And how could it have happened on
its own? that's coming up right now...
The origin of living organisms from inorganic, or nonliving material is
called abiogenesis. It's important to distinguish this from
evolution. Abiogenesis is not evolution. Evolution is the process of development
or diversification of living things from earlier forms of living things. Evolution
does not say anything about how life first originated. So how did the first
life originate? Despite the incredible variations that we see today, at the
fundamental level all living things contain a trinity of elements. First,
nucleic acids, which make up the DNA or it's simpler form called RNA. These
contain the blueprints of life and are self-replicating molecules. Second, there
are proteins, which are the workhorses that perform the important functions of
your body. And third, are lipids which encapsulate the cells of your body.
Before any living things existed, before animals, plants and even bacteria existed,
these three things had to have been present in the primordial soup in order
for life to start. Some argue that the most important component of this Trinity
are the lipids, which make up the cell walls. Why would this be the most
important?...because without the wall, or a way to encapsulate certain elements
within the soup, there would just be a soup of material that would just be
disorderly and floating around in a sea of liquid. It would not be functioning
inside something that could potentially self-replicate. But because these lipid
membranes could potentially form around other elements, they could bring
disparate parts of various chemicals together, that could potentially interact,
combine, react and work together to perhaps eventually form a machinery for
self replication. So these fatty membranes composed of lipids were
critical components for abiogenesis. So any study of abiogenesis should
perhaps start with a closer examination of lipids. Lipid molecules have a unique
structure. There is a round part and a long tail part. It so happens that the
round part loves water. It's hydrophilic. The tail part however,
hates water. It's hydrophobic. So what tends to happen
is, when a bunch of lipids are floating around in water, they tend to gather
together and self assemble in spheres. Why does this happen?...because the
tail part of the molecule, since it wants to get away from water,
automatically faces other tails that also dislike water. And the round part
which likes water, exposes itself to the water outside and inside the sphere. It
is what these types of molecules do naturally. So it has a tendency to
self-assemble into natural spheres. But where do lipids come from? It was once
thought that they could only be produced by living cells. But experiments have
shown that when carbon monoxide and hydrogen is heated up with minerals
commonly found in Earth's crust, lipids can form. All components were available
in the early Earth and could have happened in underwater hydrothermal
vents. You might at this point say aha that's it! That's how the first cell must
have formed! Not so fast. It turns out that while lipids do have
this quality of self-assembly, when there are certain ions present, such as salts
or magnesium, it destroys the lipid structure they disintegrate. But the
problem is that RNA and other functions of a cell require these ions, and since
the early Earth was believed to have salty oceans, and since these spheres
can't form in these salty oceans, this theory always had a gaping hole.
However, just this year, in 2019 researchers at the University of
Washington showed that lipid spheres do not disassemble if they are in the
presence of amino acids, which are precursors to protein molecules. In
addition, the enclosing of amino acids within cell walls allows amino acids to
concentrate within the walls and interact with each other to form
proteins, which is part of the Trinity one of the essential components of life.
What is remarkable about this research is that it turns out that nonliving
lipid cell walls and non living proteins need each other to exist in an
ion rich or salty water. So now we see that lipids and proteins can potentially
form in the presence of each other. What about DNA and RNA? These are the key
self-replicating molecules, the blueprints of all living things.
Today, genetic information is stored in DNA. And RNA is created from DNA to put
that information into action. RNA can direct the creation of proteins and
perform other essential functions of life in a cell. The simplicity
of RNA compared to its cousin the DNA is the reason that most people
think RNA came first. This is part of the "RNA world hypothesis." which theorizes
that RNA, the molecule that today plays roles in expressing genes, was the
essential precursor which led to the first living matter. Only later did it's
more complex cousin, DNA, take over the task of storing and replicating genetic
information. This hypothesis has gained wide acceptance by scientists. So let's
look at RNA. How did the first RNA molecule form from nonliving chemicals?
Well, the answer to this is not as clear-cut. And this has been a major
stumbling block to any theory of abiogenesis. So here is what some of the
latest research points to regarding RNA. RNA is made up of three chemical
components - the sugar ribose the bases and phosphate. A ribose-base-phosphate
unit links together with other ribose-base-phosphate units to form RNA polymer.
Figuring out how a bond between the bases and ribose first formed has been
difficult to replicate in the lab. Attempts to show how ribose bonds can
form with the bases of RNA have been largely unsuccessful. This is because
cells in your body require complex enzymes to bring RNA building blocks
together before they combine to form polymers. But in a 2009 study,
researchers at Rensselaer Polytechnic Institute in Troy New York, showed that
current-day RNA could have formed on the surface of clays which act like catalyst
to bring RNA bases together, as shown in this animation. A 2017 paper by
scientists from McMaster University in Canada, and the Max Planck Institute in
Germany, showed that the building blocks of RNA could have polymerized in the
early Earth using organic molecules from meteorites and interplanetary dust in
shallow ponds. The wet/dry cycle of these ponds, they showed, are conducive to RNA
polymerization. They also theorized that such polymers were probably present
on earth shortly after its formation as early as 4.17 billion
years ago. So now we have ways that two of the Trinity could have formed - RNA and
lipids. But what about protein? How did they form? In the 1950s, several
experiments by Stanley Miller and Harold Urey verified that the natural formation
of amino acids, components of proteins, and other organic compounds, out of
organic materials, was possible under the atmospheric conditions of the primordial
earth. So the precursors of proteins were likely present in the very early Earth.
It turns out that it's pretty easy to form many kinds of organic molecules in
a wide range of environments. But so far, I have only presented ways that can
result in potential precursors needed for life. You might say, "Well, that's fine
and dandy," but having all the precursors get together inside a lipid cell wall
does not necessarily mean they will all come together to form a self-replicating
living cell. How do the complex molecules come together to self replicate and
become a living organisms? And if I'm being honest, this is currently not well
understood, and there's no experiment or smoking-gun evidence, right now, that
points to a precise mechanism of how this could have happened.
There are creationist arguments such as the one that says if I put all the parts
of a watch in a big vat, and keep stirring it for a million years, a
functioning, ticking watch is not going to magically form inside the VAT. And
some cite an estimate by scientists Fred Hoyle and Chandra Wickramasinghe
that the probability of all the chemicals in a simple bacterium arising
on their own by chance is something on the order of one in 10 to the 40,000
power, which is more than the Planck volume of the entire universe. So that is
a virtual impossibility. But this number and the clock-parts-in-a-vat argument
are oversimplifications. They ignore the fact that sophisticated life forms, like
current-day bacteria, almost certainly did not arise spontaneously, but arose in
much simpler incremental steps, that had a much higher chance of occurring. There
are stats such as the one that says the odds of creating a protein molecule by
chance is 1 in 10 to the 45 power. Odds such as these and others not only ignore
the idea of simpler precursors, but also ignore the fact that it
was not just one set of amino acids, at one place, at one time, but it was
trillions upon trillions of amino acids reacting in countless places, over
millions of years, that resulted in simple protein molecules. There are about
4x10^47 molecules of water in Earth's oceans.
Even if there was one amino acid among 1 million water molecules, that would be
10 to the power 41 molecules of amino acids that had the opportunity to interact with
each other, and to form proteins in numerous environments, in numerous places,
and in numerous trials, over millions of years, to produce proteins. The actual
probability is not how the hundreds of complex chemicals can come together to
form a modern-day bacterium, but the probability of a few chemicals, may be 10
or 20, forming and coming together to form the precursors of life, that can
chemically evolve over time to form the simplest kind of life form, that likely
looked nothing like any evolved life form we recognize today. But showing how
even this chemical evolution could have happened is problematic. Chemical
evolution is not the same as biological evolution, which is driven by favoring
organisms that have the best chance of survival and reproduction. Scientists have had
trouble figuring out what could have driven chemicals to evolve the
complexity needed for biological functioning. But in 2014
Jeremy England, physics professor at MIT, showed mathematically that the driving
force for chemical evolution may be hidden in physics, in Newton's second law
of thermodynamics. that's our old friend "entropy." From a physics point of view, the
one thing that distinguishes living things from nonliving things is its
ability to capture energy and convert it to heat. England argues that when exposed
to an external source of energy, such as the sun, any group of molecules will
restructure themselves to dissipate more and more energy. This, he says, is the
driving force for chemical evolution. And this can, over time, result in living
organisms, such as those we see today - organisms that are super efficient at
dissipating energy. This theory is further supported by a
2011 paper by Karo Michaelian, that showed that RNA and DNA are the most
efficient of all known molecules for absorbing the intense ultraviolet light
of the Sun. While there is no single generally accepted theory of the origin
of life, all credible proposals show that life under natural conditions by a slow
process of chemical and molecular evolution, could have plausibly resulted
in simple life forms over a long period of time, and that this evolution of
chemistry was probably the biggest hill to climb for life to have occurred on
earth. But once this happened, biological evolution took over and relatively
quickly, resulted in exceptional diversity of life forms. We see that in
the fossil record of early Earth, and of course, we see that on earth today. Do we
have proof that this is how life came about? No...at least not yet. Is it
plausible?...absolutely. Just like chemical and biological evolution, our knowledge
too is evolving in a slow process over hundreds and thousands of years, driven
by the pursuit of science, and hopefully, ever decreasing ignorance.
Hey guys, video is sponsored by the newly released sci-fi novel "New Eden" by Kishore Tipirneni.
New eden is a mind-boggling story of quantum entanglement and the origins of
life. Follow physicist Joshua Andrews and journalist Rachel Miller as they
discover that entangled particles were created the moment of the Big Bang,
creating a universe-wide communication network. So if you love sci-fi based on
some real science, I highly recommend New Eden. It's available now from Amazon. The
link is in the description below. And if you want to support us and see
more videos like this, then please subscribe, ring the bell icon, and give us
a like. Or support us on patreon. I'll see you in the next video.