Importance of Natural Resources

How Evolution Works (And How We Figured It Out)


Hey! Kallie here. Today’s episode was made in collaboration
with the Smithsonian National Museum of Natural History. Blake and I were lucky enough to visit the
museum’s Deep Time Hall during its renovation and that’s not all! On Friday June 15th, I will be back in the
Deep Time Hall, hosting a livestream We’ll be getting a behind-the-scenes tour
of the exhibit and an expert from the Smithsonian will be answering your questions. More information on where to watch the stream
will be in the description. Now let’s talk about evolution. The story of life on Earth is a story of change. Living things have changed the atmosphere
and the climate. They’ve endured the movements of the continents,
and the rise and fall of the seas. And they’ve responded to these changes,
over the long course of Earth’s history, through a process that still continues today:
evolution. This powerful force is, in the simplest terms,
just change over time. And it’s responsible for the shape of the
tree of life, and for generating the diversity that we see in the fossil record as well as
in modern ecosystems. It’s the very foundation of our understanding
of biology, and it continues to help us make sense of the world around us. As a scientific concept, evolution was revolutionary
when it was first introduced. Charles Darwin and Alfred Russell Wallace
were the first to put all of the pieces together into a unified explanation that would radically
alter our understanding of life on our planet. But our understanding of evolutionary theory
didn’t stop there. We’ve learned a lot — and we’re still
learning. In the last 160 years, we’ve learned what
Darwin and Wallace didn’t know, and we’ve figured out a lot about how evolution actually
works – like how it can produce the incredible array of animals you see here, and how we
know they’re all related. When the Smithsonian opened its first exhibit
of fossil animals in the early 1900s, it was called the Hall of Extinct Monsters. Today, Kallie and I are in a space that’s completely renovated and re-imagined: the David H. Koch Hall of Fossils: Deep Time,
also known as the Deep Time Hall. And it depicts, more vividly than ever, the
staggering variety of animal forms that have arisen and disappeared over time. A monument to the fact that, as Darwin himself
put it, “endless forms most beautiful and most wonderful have been, and are being, evolved.” Charles Darwin and Alfred Russell Wallace
were both British naturalists whose thinking about the natural world was deeply shaped
by long voyages of exploration. Darwin famously traveled to South America
and the Galapagos Islands, and Wallace went to South America and Southeast Asia. And together they observed an incredible diversity
of life. They saw first-hand how very similar organisms
seemed to be slightly modified in ways that made them ideally suited to their environments. For Darwin, he saw this in the different shapes
in the beaks of finches on the different islands of the Galapagos archipelago. For Wallace, it was the differences between
monkeys living on different riverbanks in the Amazon. And they both realized that the patterns they
observed meant that these species all probably arose from the same place – a common ancestor. The bodies of these animals, they realized,
had been shaped over time by the conditions in their environments, resulting in the different
forms they found on different islands and riverbanks. But, in addition to being well-traveled, Darwin
and Wallace were also well-read. And their ideas were deeply influenced by
other, earlier thinkers, in natural history, geology, and even economics. Scholars like Georges Cuvier, Charles Lyell,
Jean-Baptiste Lamarck, and Thomas Malthus helped establish the ideas that were critical
to evolutionary thinking — namely, that the Earth was very old, that species seemed to
change and go extinct over time, and that individuals competed over limited resources. Darwin and Wallace used these insights — along
with their own observations — to both arrive at the same mechanism by which species evolve:
natural selection. In a paper read to a meeting of scientists
in London in 1858, they presented their theory of natural selection based on a series of
principles: The first key idea was that, in a population
of living things, natural variations will occur, and as a result of those changes, some
members of the population will survive and reproduce more than others. Then, they posited that those that survive
and reproduce will pass on their traits to their offspring. And this meant that traits that give individuals
an advantage in a certain environment will get passed on more often. And as a result, more members of the population
will have that trait. Therefore, gradually and over time, this will
result in certain traits showing up more or less often in a population. Today, when this series of events happens
within a species, we call it microevolution. It’s how a single species responds to changes
in the environment. On a broader scale, we call it macroevolution. This is how these changes accumulate over
long periods of time to produce entirely new body plans, new species, and the grander patterns
of diversity in the tree of life. And one of the most incredible things about
the development of the theory of evolution by natural selection was that Darwin and Wallace
didn’t have a good explanation for how traits were passed from parent to offspring. Genetics as a field was still a long way off,
and neither of them were aware of the experiments that were being done on pea plants at the
time, by a Czech monk named Gregor Mendel. In the 1850s, while Darwin and Wallace were
putting all the puzzle pieces of natural selection together, Mendel was breeding peas at his
monastery to try to figure out how heredity worked. And he figured out that traits didn’t simply
blend together when living things reproduced. Instead, only some were inherited as discrete
traits by different numbers of offspring. Mendel’s results were rediscovered around
the turn of the 20th century, when a new generation of biologists was investigating genetics. And it was this new wave of researchers that
brought our understanding of evolution to the next level. One of these scientists was American biologist
Thomas Hunt Morgan. Instead of peas, he bred flies, and in 1910,
he bred a fly with an odd trait. It had eyes that were white, instead of red What’s more, he was able to breed that white-eyed
trait back into the parent population. Morgan had discovered another key driver of
evolution by natural selection: mutation. He realized that the fly had undergone a random
change in its genes that made it different from the rest. So Morgan theorized that mutations were a
source of variation in living things – and that it was the source of the variation that
natural selection acted on. Beneficial mutations would be passed on, he
thought, and detrimental ones would eventually disappear. So by the early 1900s, we’d already recognized
two of the four major forces of evolution: Darwin and Wallace gave us natural selection,
and Morgan brought mutation into the mix. It wasn’t until the 1920s that things would
really start to come together through the work of three of the founders of the field
of population genetics: Ronald Aylmer Fisher, John Burdon Sanderson Haldane, and Sewall
Wright. Fisher and Haldane both looked at natural
selection mathematically, especially in large populations, using Mendel’s ideas about
inheritance to figure out how often and how fast natural selection worked on variations. It was Haldane who did the math that explained
the transition of England’s famous peppered moths, in which a gene for dark color spread
quickly, as pollution darkened the bark of the trees they lived on. Studies like this led Fisher and Haldane to
conclude that natural selection acted slowly, but also uniformly, in large populations. Meanwhile, in the US, a geneticist named Sewall
Wright was thinking about how evolution worked in smaller, more isolated populations. He did some research breeding animals like
cattle and guinea pigs. But it was his mathematical studies of genetics
that led him to uncover another key idea: genetic drift. This is the idea that the frequency at which
certain genes appear will sometimes change, totally by chance, and randomly, and Sewell
found that this has a greater effect in smaller populations than in larger ones. Another, somewhat related, idea that came
up around this time, in the late 1930s, is gene flow – the movement of genes between
populations, by way of migration. So, when members of one population of a species
— say, panthers from Texas — breed with members of another population — like panthers
in Florida — that will change the makeup of the gene pool in the Florida population. And this, too, is a driving force of evolutionary
change. Together, the work of Fisher, Haldane, and
Wright showed that natural selection acting on genes was the most likely explanation for how evolution works And in 1937, another biologist brought together
all of the evidence from genetics and natural history to show how evolution by natural selection
could produce new species. And this enabled us to make the enormous conceptual
jump from microevolution to macroevolution. His name was Theodosius Dobzhansky, and he
had worked in Hunt’s fly lab. He’d found that fly populations from different
countries seemed to be genetically different, even though they were considered to be the
same species. But, these flies weren’t so good at reproducing
with each other. So he wondered if they were actually different
species. And this took the scientific conversation
all the way back to the 1800s, and the once-novel idea that evolution could eventually, gradually
produce new species. From his experiments, Dobzhansky produced
a theory about how new species originate. Mutations happen naturally in populations,
creating variations that can stick around if they’re beneficial or just neutral. And if populations are isolated, these variations
can remain within a single group, with new mutations popping up. But none of these would spread to the rest
of the species. Over time, this would make one group genetically
distinct from others, potentially causing problems if it tried to interbreed with others. And given enough time, it would lose the ability
to interbreed with other populations entirely. It would become a new species. This was the beginning of “the Modern Synthesis,”
a collaboration by many evolutionary biologists of the time to explain large-scale patterns
of evolution. And while the Modern Synthesis has changed
over time, it’s still the framework for our current understanding of how evolution
works. In 1953, we added a better understanding of
how genetics works, through the discovery of the structure of DNA and how it functions. So, now we know that mutations randomly happen
when DNA is copied incorrectly during replication – something Morgan didn’t know. Now we also know that natural selection
is only one of the mechanisms of evolution, along with mutation, genetic drift, and gene
flow. And it’s this knowledge that allows us to
witness — first hand! — microevolution taking place today — say, in studies of bacteria
that develop resistance to antibiotics. And it also helps us understand the story
that the specimens around us right now are trying to tell us, the story of macroevolution. With this understanding, we can see how the
aquatic mammal behind me, Pezosiren, is related to the more recent Metaxytherium. Separated by some 30 million years, these
mammals lost their hind limbs and acquired flippers instead of feet. And today, their closest living relatives
are the manatees and dugongs. Places like the Deep Time Hall show us evolution
at work, with specimens that take us from the most ancient fossil ancestors, to transitional
forms, all the way to the organisms we know today. In less than 200 years, scientific study has
completely revolutionized our understanding of the constantly changing nature of life. We’ve been able to see how organisms are
shaped by their environments to better survive and reproduce there. And we’ve learned that time is a key component
of evolution. This is why a deep look into the deep past
is critical for our understanding how life has changed over millions of years. And, it’s why we’re so excited about the
opening of the new Deep Time Hall in the Smithsonian National Museum
of Natural History in Washington, D.C. If you can make it in person, pay them a visit! And, if you can’t, follow them on social
media to see some of the amazing specimens now on display And be sure to watch a new special about the
evolutionary history of some of our planet’s most fascinating animals. When Whales Walked: Journeys in Deep Time
premieres on PBS and Smithsonian Channel June 19th at 9 PM Eastern. Check out the links in the description. Thanks for joining me today in the Konstantin
Haase studio. And an extra big thanks to our current Eontologists:
Jake Hart, Jon Ivy, John Davison Ng, and Steve


Reader Comments

  1. For future episodes could you do one on prehistoric pengiuns like Kairuku waitaki and Icadyptes salasi. Or an episode on how fossils were discovered in Antarctica and how they find them today?

  2. I am soooooo amazed!

    Btw, could you also make an investigation on Philippine Tarsiers and "Kapok" or Gigantic Fox Bats. Thaaaaaanks!

    I love you guys! Always watching you here from the Philippines.

    Mabuhay!

  3. Great vid. I was hoping you would have included the Hardy Weinberg assumptions, though. As a way to wrap up all of the known evolutionary influences to speciation and change. Without those assumptions, one can infer that there is not evolution occurring in a given population.

  4. I wonder who the wallace/darwin and mendels of today are.

    Both discovering things that will later turn out to explain eachother.

    So much studying going on right now. So many discoveries being made, and with today's technology… all this knowledge is more easily shared.

  5. Why did I take two classes on evolutionary biology an genetics in college when this video touched on most of the major topics? I guess learning all that math they talked about was pretty interesting too!

  6. it would be extraordinary cool if you do the presentation with the live streaming on June 30th, the exact date of 1:21. plus, that means you announced it a little further so more people(like me) could save the date.

  7. Errata corrige: errors don't produce new functions. Evolution is a beautiful explanation but it needs to be freed from the philosophical based belief that errors 'must' be the guiding invisible hand behind new functions arising.

  8. If molecule to man evolution were true then abiogenesis would necessarily have to be true as well. But since abiogenesis is not true it then follows that molecule to man evolution is not true either and has no foundation on which to stand.

  9. 4:52 hmmm notice that big leap in logic, macroevolution can not be understood by small changes as the in between stages would cripple the organism, making it die out. besides other problems.

  10. GUYS! I have a question! If all life on earth was killed by a plague and the only thing living was the bacteria, (Alot of them tho.)
    Would evolution start over? Assuming they were able to thrive could they evolve into new creatures and into another SUPER SMART animals like us?

    TLDR: If all life died but bacteria could bacteria evolve to start life again?

  11. This is THE BEST explanation of the history of thought of evolution EVER. You guys are so awesome. Also it's very cool to find out that some Americans played a role in the development of our knowledge of evolution.

  12. Please talk slower.
    I can't be the only one who want to be able to think through what you guys are saying.

  13. These 3 hosts rock! Tis one of the best ideas you have guys… Changing from Host to Host but still maintains spontaneity on the subject throughtout the video

  14. Really well scripted video and I would like to point out that her voice was like listening to clouds. It felt so soft when she started talking.

  15. You guys just made a great reference video to explain the general concept and how we came to the conclusions we did. Will be nice to have the next time I have to try and explain what Evolution is to a skeptic.

  16. Evolution is just another science, religion and is totally biased. There are major flaws and holes in this theory, and its never been witnessed or proven. I would go w life reduction more than evolution. I'm not coming at this from any religion perspective but some many brainwashed followers.

  17. Congrats for mentioning Wallace, that definitely sets you apart from the "science-loving" normies that we often find on Youtube or TV.

  18. Im sorry but this was just common sense. . . . did they even mention anything about epigenetics and how that might actually have a role in micro evolution? smh

  19. This is everything you learn in first year university biology! Wish I had this last year x)
    Great video! You explain everything so well and so easy for everyone to understand!

  20. 4:28 I'm confused here. I thought the Marco/mirco distinction was a strawman of actual evolution by evolution denyers since micro-evolution× time= macroevolution. So is micro-evolution a legit scientific term? Highly confused at the moment.

  21. that's all great and what not that our theories of new species creation came from 1953 before we knew about DNA… but what now since we know chromosome pairs cant mate. How do you evolve more or less chromosome pairs?? We left out the virus deposition of genes as an evolutionary thing right?

  22. Seems like whole evolution is like Machine Learning technology. This makes me think we might be inside the matrix.

  23. we learned about this first concept of evolution in my 2nd grade where we were given tongs, tweezers, cups, and other varying kitchen tools and we had to pick up beans from different surfaces – this showed my 8 year old brain that different ecosystems required species to adapt different tools (beaks/evolutions) in order to survive. really thankful i had a cool teacher like that and i love these videos for reteaching me and in more depth.

  24. I'd like to propose a new method of Evolution. Forced Evolution. Basically setting the environment a certain way and grooming a species to adapt to it over x amount of time. Would likely only work easily on species that have very short life cycles.

  25. Hello. First of, I have to thank all the people working on PBS Eons content, for they are downright spectacular! I would like to bring up a topic that PBS Eons might want to answer sometime in the future.

    How it is possible that only primates were able to evolve a species as intelligent as Homo Sapiens? How come no other order, or even class were able to evolve a species with comparable intelligence?

    In the videos in this very channel, we've been presented with most extreme evolutions and species nobody at a glance could guess are related, but indeed are. So how come genus Homo was alone in developing such intelligence as we have?

    If ability to make tools and use tools was the primary trigger in evolution of brains to this stage, why do we still have primates that are, well primitive? Shouldn't most of them have evolved higher intelligence by now? After all, they all do have hands to pick up those stones and to make tools with, and eventually discover you can spark a fire if you hit two stones together enough times.

    In a nutshell, why there are no lizard(wo)men around competing with humans for resources. Cue Doctor Who theme music.

  26. I would love to see a collaboration between Eons, Smarter Everyday, and It's Okay to Be Smart. Make it happen!!

  27. Mendel was not Czech but German Bohemian and would have considered himself a German-Austrian. Besides that minor error you guys did a great job. Thank you.

  28. Thank yoyu so much for yet another great video!
    But: mendel was a german speaking austrian from silesia, which only later became part of the chech republic.

  29. Can you guys do a video on how carnivorous plants evolved? In particular, how is it that plants managed to develop the ability to both capture insects as well as digest them?

  30. But.. why evolution? Why it helps to survive. Why life wants to survive? not seeking for a philosophical or religious answer. Is it to fight entropy with complexity? If so in what way? I don't think intelligence was planned, we are an accident . Why does survival of life matters?

  31. I have a QUESTION. DOes anyone know the answer to this or know a link where they disuss it? –So if all life originated from a very primitive organism. Did that organism, have the DNA of all living things that came after it? Or did tha information evolve?

  32. micro-macro that would involve DNA evolution the micro with macro making it more complicated along with climates and earths evolution

  33. EDICT = Evolution: Diversifying into Infinite Combinations (Theoretically). :o) Thank you! 𝓡𝓲𝓴𝓴𝓲 𝓣𝓲𝓴𝓴𝓲.

  34. I've been to see the new Smithsonian Exhibit! My son and I met friends their earlier this month. It was really cool! I'd like to go back after the school year starts when we have more time and it is less crowded.

  35. It's kinda funny now I think of it; this video is basically the evolution of evolution.
    I'm afraid that this wonderful hall of wondrous is located a few oceans too far for me, but maybe they'll make a 3D tour one day? I'm definitely interested. 🙂

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