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So the advent in 1977
of molecular phylogeny
recast and restructured, fundamentally,
how we look at the emergence of life on planet Earth.
Now, an important context
for our modern-day understanding of the emergence of life
is to look at how different
and how drastically changing and evolving itself
the whole concept of evolution has been
over the last 150 years,
and in fact even deeper, um, into human history than that.
So what we wanna do is take a look at the changes
in evolutionary thought
and how people had tried to graphically structure
the tree of life, um,
and then see how fundamentally different from that, then,
that the departure is
for the results of Carl Woese and his colleagues here
at the University of Illinois.
So, we need to start all the way back actually in 1674
when Antonie van Leeuwenhoek,
who was a, um, a-a scientist in Holland,
uh, developed the first microscope,
and that first microscope was actually a-a brass plate
with a few very crude lenses,
um, and a-a setting screw that allows you to change,
um, uh, the angle and therefore the magnification
of the lenses.
Well, Leeuwenhoek, um,
is very famous because of that development of the microscope,
and he's the first one who actually published
an observation
that there was life on a very small scale,
and that microscope was strong enough for him to see,
uh, one-micron cells,
some of which were, uh, bacteria.
Uh, some of them were Eukarya, the more advanced, um, uh,
forms of cellular life on the planet,
and [clears throat] that publication
in the "Proceedings of the Royal s-Academy of Science,"
um, uh, was a-a benchmark.
It was the first time that-that- that human beings had seen life,
um, active at that kind of scale.
The next step in the process was about 100 years later,
and in 1735, Linnaeus,
who was a-a Swedish scientist,
um, decided to use primarily, um, the observations
of the diversity of life on planet Earth
for morphology, the size, the shape, the color,
some of the attributes of how the organisms lived,
try to use those
to break all of life into pieces and compartments,
uh, that can be used to look at the structure
and-and eventually the historical evolution of life.
And Linnaeus came up with two, uh, kingdoms he called them.
One was-one were the animals, and one were the plants.
And so, uh, Linnaeus was-was- was critically important
for developing the ability to describe
morphological differences, um, and-and-and, uh,
move forward with that kind of what we call taxonomy,
that descriptive taxonomy of what was living.
Well, and a-again, about another 100 years plus had passed,
and in 1866, um, Haeckel,
um, decided to start structuring
not only morphologies you could see with the eye,
but also some morphologies you could see
under the microscope.
Now remember, this is long, long before the genetic tools
were available,
so this was using whatever tools of observation,
uh, were-were-were possible at these times.
And what Haeckel put together was,
um, a very different kind of tree.
Um-um, again, Linnaeus had animals and plants.
Haeckel, as you can see from this,
also had plants and had animals,
but also had another small group of, uh, organisms
called the Protists,
and these Protists were single-cells
or sometimes multiple cells,
but they were small and they moved around
and he could see
they had these different morphological features;
they had some different colorations.
But then also
he broke things into another group called the Monera.
And the Monera were, what we call in the present day,
the single-celled microbes that
eventually were Bacteria and Archaea.
So the Monera was kind of a loose grouping
of-of single-celled organisms.
The Protists were the more complex
yet still small organisms,
and he-he kept with the plants and the animals.
Well, another 100 years plus passed,
and there was a benchmark work
by a scientist named Whittaker in 1969.
And you can see from the Whittaker tree of life,
um, there was this concept of having eukaryotes,
and that was the-one of the, uh, earlier times
that eukaryotes had been coined,
um, and then we had prokaryotes,
and those were all the single-celled, small organisms.
So going from prokaryotes to eukaryotes,
and you can see that tree makes it
a very linear progression of the two,
implying that eukaryotes
evolved directly from the prokaryotes
and all of the prokaryotes.
And you can see some of the same names were kept.
Uh, the Monera were part of that prokaryote group,
and the Protists,
um, again, these more complex, small single-cells.
So the Whittaker tree
is actually what is still used in a lot of applications,
uh, within science today,
and can still be found in some textbooks.
Well the advent of the 1977,
uh-uh, publication by Woese and Fox,
and then the ensuing publications,
especially Woese et al. 1990,
reset, fundamentally, the stage of how we
understand that the structure of the evolution of life
on this planet took place.
So all these came together to produce a drastically
different-looking tree of life,
and in this tree of life you can see that we're,
uh, hovering in a helicopter, if you will,
looking down at the uppermost branches of that tree of life,
and in the middle
we have an origin, we have a root or a stalk,
um, versus having these three branches,
uh, Bacteria, Archaea, and Eukarya,
uh, coming up and out.
The importance is that the context
of the history of the evolution
of the idea of a tree of life itself
really sets the stage for us,
because it compares and contrasts
what was thought of as being simpler life
and more complex life
and what came first and what came second.
Instead of some of those paradigms
and-and hypotheses that were put up,
and very reasonably, based on morphology,
the genetic tool, the molecular phylogeny
allows us to quantify these relationships
and look deep into time to see how diversity on this planet
is actually structured
in terms of its capabilities of- of lifestyles, ecology,
but, then even more importantly, its genetic composition.
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