What Was the Ancestor of Everything? (feat. PBS Space Time and It’s Okay To Be Smart)
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What Was the Ancestor of Everything? (feat. PBS Space Time and It’s Okay To Be Smart)

Part of what draws us to the study of natural
history is our desire — our drive — to understand our origins. The more fossils that we can find and study,
the more branches and twigs we can add to the tree of life — that web of relationships
that connects all organisms, living and extinct. But fossils can only get us so far. As any astrophysicist will tell you, the story
goes back way farther than any fossil. The story of life actually begins with, well,
the beginning of everything. In the aftermath of the Big Bang the universe
was an energetic, structureless mess. But that mess pulled itself together into
atoms and stars and galaxies and planets and, finally, into life. How did these little eddies of order form
in a universe otherwise prone to increasing disorder and chaos? I’m Matt O’Dowd from PBS Space Time, and
you can learn all about the physics of the origin of life in a video over on our channel Just follow the links. But for us here on Eons, the search for our
origins go back to a single common ancestor — one that remains shrouded in mystery. If you trace all of the branches on the tree
of life backward, you realize they all come from the same trunk. That initial point, before anything branches,
is a single species. The first species. Darwin himself theorized that such a thing
once lived. He called it a “primordial form into which
life was first breathed.” Today, scientists call it the last universal
common ancestor, or LUCA. LUCA isn’t the first thing to have lived. Instead, it’s the common ancestor of everything
that’s alive today. It’s the ancestor of everything we know. Today, Eons is teaming up with our friends
at Space Time and It’s Okay to Be Smart to explore the origins of life. And our journey begins with LUCA. Even though Darwin suggested that there was
a universal common ancestor, we couldn’t even guess what it might have been — until
we started to master genomics, the science of mapping and studying the genetics of all
living things. Today we know that all life uses the same
molecules of RNA, DNA, and protein. And the genetic code that’s responsible
for making that stuff is basically universal, from bacteria to humans. That’s one of the best arguments to support
the notion that everything came from the same place. It’s also why most of the research that’s
gone into learning what LUCA was has involved comparing the genomes of all kinds of living
things, to see what else they have in common. One of the first to take this approach was
American biologist Carl Woese In 1977, he discovered the existence of organisms
that would make up a whole new domain of life, and a key to the search for LUCA. He discovered archaea. They’re a group of prokaryotes — simple,
single-celled organisms that are vaguely similar to bacteria. But they turned out to be so diverse, and
so different from any other living thing, that Woese proposed a new tree of life — one
that divided life into three domains: archaea, bacteria, and eukaryotes. And, he said, where those three main branches
converged, there was LUCA. But he saw the three domains arising not from
a single cell, but from a chaotic environment, more than 4 billion years ago, when cells
didn’t quite exist yet. In this scenario, he proposed, there were
extremely simple things that were even more basic than cells. He called them progenotes and envisioned them
as tiny scraps of genetic information, surrounded by a membrane. These progenotes wouldn’t have been complex
enough to create true offspring. They might have been able to copy their genetic
material, but not accurately. So instead, they may have just floated about
at random, constantly swapping little snippets of genetic code among themselves. Sometimes, that genetic info might have worked
well for a progenote, and could be copied. Other times, not. But out of this basically random transfer
of information, Woese thought, some of the key elements of life could have arisen. For instance, the genetic code that makes
up genes as we know them could have come about pretty early. But that information might have been stored
in RNA, not DNA as it is today. To explain how that might have worked, here’s
a biologist I know who specializes in RNA: Dr. Joe Hanson, host of It’s Okay to Be
Smart: Now, RNA, in addition to storing information,
can do stuff – biochemical reactions – like we see in the ribosome, where RNA is used
to not only code for, but also build, proteins. Early on, RNA machines like the ribosome would
have evolved alongside genetics version 0.1. So, it’s likely first life arose and evolved
in this so-called RNA world, and only began storing genetic information in DNA later on. For more on how this happened — and other theories
about how life first arose on Earth — check out our video over on It’s Okay to Be Smart. So, instead of being a specific organism,
or even a group of things. Woese thought that LUCA was the whole process
by which progenotes acquired the genes to make these essential molecules. And from them would have come three lineages
that evolved into modern bacteria, archaea, and us eukaryotes. Now, Woese’s view of LUCA hasn’t been
abandoned, but many scientists have moved away from it. That’s partly because, when Woese was publishing
these ideas, genetic sequencing was just coming of age. Back then, only a handful of genomes had been
sequenced. And now we’ve mapped the genes of
thousands of living things. And that means we can try looking for LUCA
in new ways — like, by lining up genomes from across all of the domains of life and
comparing them to see what they have in common. If a gene appears in basically every living
thing — so it’s considered universal — then it must have come from LUCA … or so the
thinking goes. So, many researchers who study LUCA are trying
to reconstruct its genome. One way to do that is by finding what they
call the minimal genome — the smallest amount of genes that a cell can have and still survive. Since these most basic, essential genes are
thought to have come from LUCA, if we could identify them, that could tell us how LUCA
looked and lived. This work has been spearheaded mainly by researchers
in Maryland who have studied the genomes of bacteria like Haemophilus and Mycoplasma. And based on what those organisms had in common,
the team proposed back in 2003 that LUCA probably had 5 or 6 hundred genes. Those genes would have provided for a simple
metabolism and a genome based on RNA — but not for making and copying DNA. Now, as genomes go, that is tiny. A few modern organisms do have about 500 genes,
but they are parasites that steal what they need from their hosts instead of using genes
to make stuff. Meanwhile, the bacterium E. coli has around
5 thousand genes, and we humans get about 25,000. Could LUCA survive on its own with so few
genes? Well, another study done in 2006 found that
LUCA would likely have had more like 1000 genes, maybe around 15 or 1600. According to this slightly more recent take,
our common ancestor might have been a little more complex and may have seemed more familiar
— to microbiologists at least. That means a genome based on DNA, ribosomes
to translate the genetic code, and a metabolism that could break down sugar for energy. So, the basics of biochemistry as we know
it. And Joe talks a lot more about that, too,
on It’s Okay to Be Smart. Now, a lot of this minimal-genome research
took place at the turn of the millennium — around the same time Woese was thinking about LUCA. But in the past 20 years, the genetic revolution
has redrawn the tree of life. Recently, many scientists have begun to argue
that the tree of life should have two main branches, with bacteria on one branch, and archaea plus
all of the eukaryotes on the other. That’s because, the more we learn about
genomics, the more it seems that all modern eukaryotes are genetically more similar to
archaea than to bacteria. In fact, many researchers now believe that
archaea are our ancestors. So of course, this has enormous implications
for what LUCA was, too. In this case, LUCA would sit just below where
those two main branches separate, before eukaryotes even formed. And based on this new line of thinking, a
surprisingly complete picture of LUCA was published in 2016, in the journal Nature Microbiology. Here, evolutionary biologists based in Germany
compared the genomes of more than 130 archaea and over 1800 bacteria in an attempt to reconstruct
LUCA’s genome. Keep in mind here, in the two-branch model, archaea
and bacteria are the most distantly related forms of life on Earth. So, if you can find any gene in both archaea
and bacteria, then there are two possibilities: Either the two groups traded genes at some
point, which prokaryotes sometimes do, or they both inherited that gene from LUCA. The researchers looked for genes that appear
in two different groups of archaea, and two different groups of bacteria, reasoning that
if a gene shows up in all four of those places, it must go back pretty far. Now, this is different from the minimal genome
approach, because it tries to identify the oldest genes, not the ones that everyone has. And the genes that were recovered in this
research suggest that LUCA lived in … hydrothermal vents. How do they know? Well for one thing, they recovered a set of
genes that we know are used by extremely ancient groups of archaea and bacteria that live in
oxygen-free environments, where they metabolize hydrogen gas and carbon dioxide into methane. Hydrogen gas is hard to find on Earth, but
it can come from deep sea vents; so that’s one clue. Other genes they found use metals like iron,
nickel, and molybdenum in order to function. And these are all found in the same kind of
environment as hydrothermal vents. Scalding-hot vents full of metals and sulfur
might seem pretty hostile. But our earliest ancestor might have called
these places home. Now, how could that be? Like, we don’t metabolize hydrogen and CO2
to methane. And neither do most of the organisms we know. So how could the ancestor of everything have
been so different from us? Well, it’s at least possible, because genes
are often lost over time. As creatures evolve and adapt to new environments,
lots of old genes aren’t always needed. That’s basically why cats have genes to
make fur, and not scales. So by the same token, long after molecular
oxygen became available on Earth, about 2.5 billion years ago, many of LUCA’s descendants
were able to lose the genes for metabolizing hydrogen and CO2, and still live comfortably. Now, as awesome as this picture of LUCA is,
it’s only one possible picture. It’ll be a long time before we know enough
to agree on one single model. Both the progenote model and the minimal genome
idea have proven useful to guide our thinking, but they probably don’t represent the true
LUCA. And not everyone agrees that LUCA lived in
hydrothermal vents either. There’s plenty more research to be done. Because the search for LUCA just might be
the one quest that defines the purpose of natural history — to reveal to us where we
came from. Now, to explore other facets about the origin
of life, I encourage you to check out the companion videos to this one, on PBS Space
Time and It’s Okay to Be Smart. Links are in the description. And as always, I want to know what you want
to learn more about! So leave me a comment below, and don’t forget
to go to youtube.com/eons and subscribe And also, tell people about us. Please. It’s so good, right?

100 thoughts on “What Was the Ancestor of Everything? (feat. PBS Space Time and It’s Okay To Be Smart)

  1. Sorry this is not true , because the DNA soup was far more diverse.
    The extremely many chemical reactions of abiogenies would have a diverse number of living simple starts to life.
    Although many would fail far more than just one would have survived and those that survived would blend into more resulting in a central core of living entities adaptable to the conditions of the time.

  2. Did not even venture the more important question of how did things go from Miller-Urey to LUCA. Without this step there is no tree of life. Without experimentally reproducing this step Evolution must be downgraded from a Theory to a Hypothesis.

  3. Take note how insects are needed to spread the seeds of plants. What would the plant do without them?
    Same apply to the way people spreads organisms across the world.

  4. We don't produce methane? "FARTS!" Or you're saying how it's produced?
    We breathe the most dangerous gases and drink it as water. I'm sure some break down to its elemental form. Hydrogen and Oxygen. Dangerous Gases That Blow up And Burns.

  5. No pure-breed Homo Sapiens exists today. But we gain a better understanding when we know what Sapiens was NOT. He was not a Neanderthal or Denisovan. Archaic hominids introgressed into African Sapiens groups but we have no idea who they were or what defined them. Please make a video that helps define just what a sapiens is.

  6. I read about the LUCA and how it was living and moving buy the protons movement in and out of the cell..I would like to see a video that demonstrates this act. And how did the LUCA look like..If there is a video already please send the link.

  7. Why does there have to be only one LUCA?
    Life could have emerged on different places to different times, then eventually merged …
    How would you know that such a process isn't still happening nowadays?

    One could ask the same about the "Big Bang"?
    Why only ONE?
    And why not again?

  8. Or, the Progenotes is the code (artificial?) that is functioning as Panspermia across the universe and ends in complex life on suitable planets.

    Those genetic codes in DNA and RNA are way too complex to have happened by chance and/or natural selections over time.

  9. Yes very clear and high quality…
    1. delve into Arcadia – Eukaryote nexus …
    2. Solitons and energetic landscapes of biological quantum phenomena like photosynthesis or smell sensation
    3. Comment on: Order and the energetic ledger in astrobiology such as it is in terrestrial life: ultimately particles from the sun: high energy, low entropy cosmic rays impinge earth and low energy, high entropy IR photons reirradiate into space… near neutral net energy balance but order capture as delivery of order continues to supply emergent phenomenon like life

  10. In some respects, the biological world is inverse to that of the material world. For example, vines crawl up the side of a house, contrary to what gravity would predict. The reason for the inverse nature of life is that the organic molecules in the cell nucleus have trapped cosmic or inverse atoms, which come from cosmic rays. These cosmic atoms then influence the DNA and RNA; periodically, the cosmic atoms cause DNA to replicate and RNA to open up certain sections. Study the Reciprocal System and prove it for yourself. www.reciprocalsystem.guru

  11. I want to know more about gene splicing. And if scientists have made any progress in Africa to genetically modify mosquitoes to only produce male offspring to eradicate mosquitoes and end Malaria.

  12. I have to believe there were competitors to the predecessors to RNA / DNA. RNA / DNA had to be significantly better, or we would have some life based on those competitor(s).

  13. Today I watched a man float a small steel trawler and an explanation of the common genes between life forms. Am I wasting time or what?

  14. advanced extraterrestrials come to earth eons ago and while they were here ate this and that and since there wasnt any port a potties just took a chit all over the place and thats how life started from the dna left over in the chit….. which is why most people are still full of chit

  15. If you have no evidence please don't present it as fact. All conjecture is NOT science. Scientist still can't explain molecular machines.

  16. Its OK to be smart? Evolution is smart? Nothing from nothing leaves nothing you got to have something to be wise DNA=DNA intelligent replication cell division sexual reproduction species perpetuation wake up Darwinism is dead dead dead!

  17. We start out with the big bang theory as if it is a fact. It's OK to be smart; surprise you are dumb theory's are not a fact so there you go and now think harder.

  18. I would suggest a fabulous book 'The Universe Story' by Brian Swimme . You will see this great story evolve as you read this work!

  19. Oh oh i know the answer to this one. The ancestor to life was actually a three celled organism called sophie’s tango. It was unique because one if the three cells was differentiated into a sex cell. Over time this sex cell split from the other two and developed into everything you see today.

  20. If life can occur it makes sense that it occured more than once, so i hypothesize that there was more than 1 Last common ancestor, so no universal

  21. If there is just one single common ancestor, that would suggest, either that life isn't as likely to form as we thougt, or that life under circumstances that are found on earth does require the specific carrier of information RNA/DNA. That would tell us, that there is no LUCA, but many LUCAs that are just very similar.

    So which of those two beloved ideas so you want to abandon?

  22. OK, now let me get this right, what you're saying is that we all descended from Luca Brasi, the bodyguard from The Godfather? Who am I to argue?

  23. Evidence for a common ancestor right here considering I barely noticed any change between PBS Eons host and It's Okay to be smart

  24. It's my understanding that all life forms today that exists came from that which no longer exists today, that being the case if we came from monkeys as to what Darwinism is about, why are there still monkeys 🤔

  25. My name is Luca, I live on the ocean floor. I live very far from you, you have never seen me before. Sorry, could not help it

  26. So what is the mechanism behind this? What is the driver telling these bits of 'matter' to self-assemble the way they have? The materialist paradigm is dead, none of this happens without mind, matter requires consciousness to exist, not the other way around.

  27. On a very local scale, life contradicts the Second Law of Thermodynamics – all systems maximize entropy. On the universal scale – the law prevails.

  28. Scientists had better try harder to find LUCA, because I really want to know who he is. Also, it would be fitting if someone at UCLA discovered LUCA, and especially fitting if the scientists were a member of the ACLU.

  29. Found this channel by total accident (hank wasn't on crash course like Im used to) and Ive now binge watched everything here. Not even sorry.

  30. If luca could metabolize hydrogen and carbon do you think there could have been other complex life that formed and retained that ability ?

  31. What i would like to know more about is how life got from nematode worms to cordates. I guess there are prescious few fossiles from that era, is there any other research on that subject?

  32. In my mental search for describing the evolution of the first "primordial lifeforms" a have come up with a theory called: Stable Strand Theory (SSt). Before life, these complex chemical reactions housed in lipid layers contain enzymatic RNAs. We can think of it in terms of natural selection selecting for those strands which were the most stable. In a chemical "soup" of lipids housing these enzymatic rnas, those strands that would be most stable will eventually lead to mass convergence to stable RNA strands. It this point in the stage to becoming life, we would see a state of hyper-evolution because there would be a very high state of mutation and cutting (reactions that cut strands into two pieces). However, as the evolutionary processes continued, it would again converge to those strands that would be less prone to cutting / mutation that would result in a branch that would be a dead end, selecting for those that cut in a way that can result in 2 stable strands that would eventually grow to larger ones. And hence the beginnings of replication.


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