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We've looked at the building blocks of the
origin of life and thought about some of

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the processes by which early life might
have come to be, but another question is

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where did this occur? Where did these
early reactions occur and where are

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plausible environments where the origin of
life Might have happened. Well, in order

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to answer that question or think about
answering it, we first of all have to

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understand what we need for an origin of
life. Quite apart from those building

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blocks, there are three other things that
are necessary in order to get an origin of

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life. First of all, we need an energy
source. We need energy to do those

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chemical reactions, to create those
building blocks. And, eventually, to

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assemble those building blocks Into more
complex structures and eventually cells.

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We also need a means of concentrating
molecules. In an absence of membranes

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those early molecules that we need to
assemble early membranes and other

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chemical reactions have to be able to be
concentrated otherwise they'll just

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dissipate in the environment. They'll
become diluted in the oceans. So we need

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environments where. Complex chemicals can
begin to concentrate. And finally we need

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an environment that's conducive to these
complex molecules and their assembly once

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they've been made. It's no good having an
environment for example that's so hot that

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when we assemble membranes they simply
fall apart because of the intense heat. So

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we need to find environments where the
physical and chemical conditions. Might be

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conducive to these molecules once we've
made them. One of the earliest

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speculations about the origin of life was
made by Charles Darwin. Who in an 1871

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letter to his friend Joseph Hooker, wrote
the following, and it's worth reading it

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out, it's rather a remarkable speculation.
But if, and oh, what a big if, we could

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conceive in some warm little pond, with
all sorts of ammonia and phosphoric sorts,

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light, heat, electricity, etcetera,
present. That a protein compound is

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chemically formed, ready to undergo still
more complex change s.

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At the present day such matter would be
instantly devoured or absorbed, which

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would not be in the case of Before living
creatures were formed. Darwin's warm

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little pond has become rather an iconic
image of where the origin of life might

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have occurred. It's certainly a good idea.
But based on what we know about

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environments today on the earth can we
come up with perhaps some more concrete

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speculations about what that warm little
pond and about what those environments

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might have looked Look like. Let's have a
look at some of the environments where

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people think the origin of life could have
occurred. One possible environment is deep

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sea vents. These are vents at the bottom
of the ocean where reducing fluids, hot

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fluids by gushing up from the crust of the
earth into the oceans. These fluids

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contain iron and sulfur, which is very
interesting because In some of the energy

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transfer proteins in life we find chemical
compounds that contain iron and sulfur.

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Some people have speculated that these are
in self a complexes, maybe a remnant of

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early life on the earth. Alkaline deep sea
vents are thought to be particularly

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favorable places. The formation of
chemical compounds. The source of energy

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in this environment comes from the hot
fluids coming up from inside the crust.

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The concentration of organic compounds
could potentially occur in the chimneys

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around these vents where they're gushing
up into the oceans, in the rocks that are

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formed around the edges of these plumes of
materials. That's, are being produced in

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the oceans. They may be conducive to
formation of complex compounds because the

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compounds could be dissipated into the
oceans or collect around the vent where

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temperatures are cooler and where they
wouldn't break apart so easily. So we can

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see that many Of the requirements for the
production of chemical compounds needed in

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the origin of life might have been, might
have been met in these deep sea vents.

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Another possible location are impact
craters. An asteroid or comet impacts onto

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the early Earth were much more c ommon
than impact events today and in these

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environments. There may have been places
where early chemical compounds required

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for the origin of life could have formed.
When an asteroid or comet slams into the

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surface of the Earth several things
happen, first of all it heats up the rock

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providing a source of energy for chemical
reactions. Secondly, that heat can create

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hydrothermal cells, in other words,
circulating water through the impact

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crater. That circulated water could've
provided environments for early chemical

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reactions to occur to produce complex
compounds. And, the water that collects

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inside that impact crater Might be an
almost literal interpretation of Darwin's

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warm little pond. A body of water heated
by that, by the energy created that came

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from the impact and creating an
environment where early chemical compounds

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could farm. Inside the impact crater. As
the impact crater cools down so conditions

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will become more conducive to complex
chemical compounds to assemble and form

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inside the crater as temperatures became
less extreme. So asteroid craters At yet

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another possible location for the
formation of early compounds and their

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assembly into early lifeforms. Yet another
environment that people thought about are

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beaches. Beaches are interesting because
of course as the tide comes and goes.

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Water flows over the surface of rocks. And
as the tide goes back out again, the water

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inside the rocks begins to evaporate,
concentrating chemical compounds inside

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those rocks. So perhaps rocks on the edges
of beaches were also places where early

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chemical compounds could have concentrated
and. And early chemical reactions could

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have occurred to form the building blocks
of life and ultimately more complex

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chemical compounds. A bit like the
hydrothermal vents, yet another location

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could be volcanic hot spring on the early
continental land masses instead of in the

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deep oceans now on the continents, and the
Advantages of these early volcanic hot

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springs would have been much like the deep
sea hydro thermal events. The sourc e of

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energy would've been hot fluids coming
from volcanic regions in the crust,

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flowing onto the surface of the earth.
Chemical compounds would have collected in

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these early volcanic hot springs and as
some of these hot springs began to cool

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down and circulate into regions of.
Cooler. There would have been conducive

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conditions for complex organic compounds
ultimately cellular material to have

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formed in these hot springs. Here's
another very interesting idea for how the

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early building blocks of life might have
formed in bubbles. And the idea is the

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volcanoes erupted onto the sea releasing
gases enclosed in bubbles. And these gases

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might have included hydrogen. Methane come
outside other types of reactive gases. The

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gases concentrated inside the bubbles then
reacted to produce simple organic

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compounds. These bubbles rise to the
surface of the ocean and burst releasing

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their contents into the air. These simple
chemical compounds, these simple organic

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compounds would then drift through the
atmosphere and react even further, perhaps

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with ultraviolet radiation in the
atmosphere from the sunlight, creating

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more complex organic compounds. And
eventually, these complex organic

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compounds will rain back into the ocean as
raindrops, and rejoin that process. Again,

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forming bubbles and being recirculated to
the surface of the ocean, and back out

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into the atmosphere. There's no direct
evidence for this process as a way to form

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the early compounds required for life, but
it's a very interesting alternative

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possibility for the production of early
organic compounds. Of course, we've also

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seen that organize compounds could have
been delivered from outer space in

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meteorites. So there are other
possibilitirs other than some of the

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environments we've looked at on the early
Earth. Yet, another possibility is that

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all of these environments Were reactors
producing the early compounds required for

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life. Many scientists get very focused on
one particular environment. It's not

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surprising people do research on volcanic
environments, or impac t craters, or for

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example production of organics in early
sea water. But it's quite possible

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everyone of these environments is
generating organic compounds, perhaps the

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whole of the early Earth was a giant
prebiotic reactor producing chemical

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compounds in different environments, that
came together in one particular

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environment to produce early cells, an
environment. That we don't know the

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identity of yet, but early environments
would have all been producing, these early

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chemical reactions. Can we find any
evidence in life for the environment in

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which it evolved? Is there anything about
the biology of life that tells us where it

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might have evolved? What's very
interesting is that some of the most

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primitive microorganisms at least some of
the most. Deep branching as we call them,

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micro-organinizms that seem to be the most
ancient, are heat loving micro-organizms.

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Thermophiles, literally heat lovers. And
these micro-organizms grow in vulcanic

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vents, and also in deep sea vents And they
may be some indication that the earliest

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life forms on Earth, were actually
heat-loving microbes that lived in hot

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environments. We have to be careful
though, because the early Earth was

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bombarded by astroid and comet impacts.
And because of volcanic activity, it was

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much hotter than it is today. So it might
be that these. Ancient microorganisms that

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love heat represents some sort of
bottleneck in evolution, microorganisms

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that were capable of surviving hot
conditions on the early Earth but not

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necessarily the earliest organisms that
represents the earliest stages of life

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when it first evolved. But nevertheless
the fact that some of the most primitive

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organisms on the Earth seem to be heat
loving is rather intriguing. There are

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other more intriguing environments that
are quite counter-intuitive, where early

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reactions for life on earth might have
occurred, and one possibility is in ice

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sheets. Water has an interesting property
that when you freeze it, it tends to

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exclude salts that collect in boundaries
between ice grains. Here you can s ee an

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image of some ice crystals and between
them, the boundaries where salts might

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collect and in those boundary lines we
might find concentrated chemical compounds

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where earlier reactions could have
ocurred. Of course at low temperatures,

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chemical reactions occur much more slowly
than at higher temperatures but with many

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millions of years for these reactions to
occur Maybe ice sheets on the early Earth

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where, were the places where early life
could have evolved. Now, we have no

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evidence, of course, that early life
evolved in ice sheets or the possibility

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that early chemical compounds would have
formed in ice sheets. But it reminds us

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that we need to keep an open kind about
the possibilities for the early origin of

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life. There maybe some quite, quite
unusual environments that we think are not

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plausible locations for early chemistry,
but might turn out To be important as

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places for early chemical reactions. So
what have we learned in this lecture? Well

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hopefully we've learned that numerous
environments could have provided plausible

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locations for the production of the
building blocks of life and we've looked

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at some examples of those possible
environments. We've learned that these

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environments need not be mutually
exclusive and different molecules might

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have been produced in different places.
Indeed the whole of the early earth might

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have been a giant Prebiotic reactor. And
finally, we don't know how quickly this

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happened. Did the origin of life occur
within a matter of days, or weeks, or did

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it take hundreds of millions of years?
This is one of the unsolved questions in

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the origin of life and a question that
astrobiologists still have to address.