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Human evolution overview | Life on earth and in the universe | Cosmology & Astronomy | Khan Academy


If we were to rewind the clock
back about 70 million years, you would see dinosaurs
roaming the Earth. And this is a very nice picture
here of a dinosaur enjoying a sunset at the beach. But unfortunately
for the dinosaurs, about 65 million years ago, we
believe that a huge meteorite struck the earth and essentially
wiped out the dinosaurs. And it probably wiped out a
bunch of other species with it. Because you can
imagine, the shock wave itself would just
exterminate tons of species. Then you would have the
tsunami of unimaginable size that would just
envelop the continents for some period of time. And then you would have
all of the soot that would go into the air and maybe
make it impossible for most of the plant species
to live, because it would be blocking out
all of the sunlight. And so in an
environment like that, we could imagine that
an animal like this would be well suited to survive. It’s sitting there underground. Maybe it can
hibernate in some way, so it doesn’t need food
for long periods of time. Maybe it has its own food
stash under there someplace. And so we believe that our
ancient, ancient, ancient, ancient, ancient ancestors,
after this mass extinction event, might have been
something like this– kind of a mole-looking, rodent animal
that was protected from all of this craziness that was
happening on the surface, because they like to hang
out underground and have all their food nearby them. And maybe they could
hibernate in some way. So you could imagine, once
everything settled down– and now we’re
talking, who knows, hundreds of years, thousands of
years, even millions of years– some of this guy’s descendants
start to poke their head out of the ground. And they’re like, you know what? There’s food in trees. And there’s no one
else in the trees. And trees are a good
place to maybe get away from some of the
other predators that have managed to survive
this mass extinction event. And some of its
descendants, I should say, that were good at climbing
trees decide, hey, let’s try this tree thing out. And so you started to have some
selection for the descendants of this rodent that
could climb trees well. They were able to find
food where their ancestors couldn’t . They could find protection in
the trees where their ancestors couldn’t. And so you could imagine that
some subset of this guy’s descendants evolved
into something that might have
looked like this guy. And all the pictures
I’m showing you, these are of modern
animals, except for, of course, the dinosaur. I’m sure this was kind of
Photoshopped in some way. This is a modern bush baby. But I show this
picture because it could have been what some
of these primitive primates looked like. Because a bush baby, it
kind of a climbs trees. It kind of looks like it’s
starting to get a hand here to start climbing the trees. But it also has
rodent-like qualities. But this is, of course,
a modern version of it. So this bush baby’s ancient,
ancient, ancient ancestor might have been that
primitive primate or that species of
primitive primate that was a descendant of rodents
that starts to say, hey, let’s see if we can climb these
trees and find some food. And then some of its
descendants might have had just the right
adaptations, found their own little niche
in the right ecosystems. And they would have
evolved into monkeys. Once again, this
is a modern monkey, but you could imagine some
type of primitive monkey. And then some of those
primitive monkeys’ descendants, they turn into these
modern monkeys eventually. But some of them, they
grow larger in size. They spend more time
outside of trees. They lose their tail. They don’t need it
as much for balance. Maybe it’s actually
a bad thing to have, because someone
else could grab it when you’re in a fight
or something like that. And they evolve into apes, and
in particular, the great apes. So one of the great apes. The great apes involve
gorillas and chimpanzees and the ancestor. Or really, the great apes
also include humanity. So let me just review
back on this timeline, just so that we
don’t get confused. I’ll review what we
just talked about. So before this mass
extinction event, 65 million years ago, you had
all these types of species here. Maybe this right up here. Actually, if I’m
talking about species, maybe this was
Tyrannosaurus Rex, because the dinosaurs
involve whole bunch of– so this might
have been T Rex. And there’s a bunch of species
that we could list over here. But after that mass
extinction event, that was an endpoint
for a ton of species, except for maybe this primitive
rodent mole-like thing. Maybe a lot of them
died in this event. But just enough of them survived
because they were underground or just in the
right place or they were in a mountain someplace. Who knows where they were? And some of them were able to
evolve into primitive primates. And once again, these are
pictures of primitive primates. And when I say primitive, these
are modern versions of them. So primitive doesn’t necessarily
mean worse, because obviously, these guys, even
in today’s world, they have a niche
for themselves. They’re able to find
food and reproduce in ways that don’t get in
the way of other people and the way people don’t
get in the way of them. When I talk about
primitive primate, I’m just talking about kind
of an ancestral primate, maybe something that’s
not there today. Although maybe some of those
descendents look very much like it. But anyway, some
of those primates evolve into primitive monkeys. Some of those primitive
monkeys’ descendants become modern monkeys. So I’ll call it M monkeys,
for Modern monkeys. And some of them evolve
into primitive apes. And apes, their
distinctive characteristic is that they’re like monkeys,
but they don’t have tails, and they’re larger
than most monkeys. And so these primitive apes,
some of their descendants are modern gorillas. At some point, they break off. Some of these descendants
are an ancestor of both modern chimpanzees
and of human beings. And we think, just looking
at the DNA evidence, we think that this
departure right here– and the
fossil evidence– was about seven million years ago. That’s our best guess for
when we, as human beings, had a common ancestor
with the chimpanzees. Now, you have that
common ancestor. Some of that common
ancestor’s descendants became modern chimpanzees. And some of them– maybe they
explored the right ecosystem, where it was more
advantageous to do so– started to walk on two legs. And the most famous
fossil of this is the australopithicine
fossil of Lucy that was discovered
3.2 million years– it was discovered more recently. It’s 3.2 million years old. So the whole
genus– and genus is kind of one level of
categorization above species. The whole genus of
australopithecine, these were four to two
million years ago. And we never know. You could always
find a fossil that’s older than this,
maybe newer than this. I read one account that says,
maybe one million years ago. But give or take,
the Lucy fossil, which is the most
well established australopithecine fossil, is
about three million years old. And this is a reconstruction
I have over here of Lucy. So this is probably
what Lucy looked like. And once again, there
were many Lucys. It wasn’t just
there was one Lucy. And we’re all
descended from Lucys. And it’s actually not
even clear that we’re even descended directly
from australopithecine. We might be a cousin species or
a cousin genus, I should say. Genus is the category
right above species. So if you fast forward
a little bit more– you go to about 2.3 to 1.4
million years ago– we see fossils that
they’re standing upright. The brain size is bigger. Because if you look at the
australopithecine fossils, they are standing upright. But they’re cranial
capacity isn’t that different than chimpanzees. You fast forward to 2.3 million
to 1.4 million years ago, we start to see fossils where
they’re standing upright still. And the cranial
capacity has grown. And you’re starting
to see primitive stone tools around the bone fossils. And so we believe that
these are one of the first. And this is really just
how we categorize it. But these are some of the first
fossils that we categorize as belonging to the
same genus as ours. And the genus is Homo. And Homo just means man. So it’s the group right
above species of man. And we call them similar
to man, because it looks like they’re starting
to make primitive stone tools. And they stand upright like us. And they have larger
cranial capacities than the australopithecine
fossils or modern chimpanzees. And once again, we don’t know
if Homo habilis, which literally means– so the Homo
part means man. Habilis means handy, because he
liked to, I guess, make tools or whatever else. We don’t know if Homo habilis is
a descendant of Lucy’s species of Australopithecus or
maybe a cousin species. Maybe they’re both descendents
from some common ancestor. We’re not quite sure. Then you fast forward
a little bit more. We’re talking now about 1.8
to 1.38 million years ago. And we start seeing fossils
where the cranial capacity larger than Homo habilis,
getting closer in size to what our notion is of
kind of a modern person’s cranial capacity, at least
relative to body size. And this is Homo erectus. And once again, we don’t
know if Homo erectus is the descendant
of Homo habilis. Maybe they have a
common ancestor. Who knows? And it looks from
the fossil evidence that there was, especially when
you look at this range here, some overlap where you had
both Homo erectus and Homo habilis living on the same
planet at the same time. Now, you fast forward even more. And we think about 600,000
to 300,000– once again, all of these are
constantly being modified, as we get better at
finding new fossils or interpreting
the fossils we have or we look at DNA
evidence or whatever. About 600,000 to 300,000 years
ago, the Neanderthals appear. And Neanderthals are in
the same genus as humans. So it’s really Homo
neanderthalensis. I always have
trouble saying this. So this is still part of Homo. And a common misconception
is that the Neanderthals are somehow a more primitive
version of humans, that they’re somehow cavemen,
and we’re modern men. That’s not the case. The belief is that
Neanderthals are either cousin species– we
have a common ancestor– or that they’re actually a
sub-species of human beings. And there’s some
belief that they might have interbred
with Homo sapiens. And maybe some or a good number
of us have a Neanderthal genes. And it’s nothing
to be ashamed of. It’s just something,
unfortunately, that Neanderthals just get a
bad name, because of, I guess, our popular culture. So this is a drawing
of a Neanderthal brain. They actually had a fairly
large cranial capacity. Although scientists, they kind
of make one reason or another why we think that
they might have been more primitive
than Homo sapiens. But who knows? We don’t know. We’re constantly learning
things every day. But of course, the
whole point of this is to talk about how humans
showed up on this planet. And the first
really human fossils we find about 200,000 years ago. And remember, we’re
in the genus Homo. And now, we’ve finally found
something that looks just like us, anatomically, at least. We can’t study its
behavior and all the rest. And now we get to Homo sapiens. The Homo part, once
again, means man. And the sapiens means thinking. So we can debate whether
it’s an appropriate title for our species, but
it’s “thinking man.” So once again, the
Neanderthals, they were either a cousin species
for a lot of this time, especially once Homo
sapiens showed up. And maybe Homo sapiens
showed up before this. We just haven’t found
the fossils yet. They were maybe both
inhabiting the same planet. Maybe there was
some interbreeding. But the Neanderthals disappeared
about 30,000 years ago. 30,000 years ago,
these guys disappeared. Maybe some of them
kind of got mixed in with the Homo
sapiens, started to interbreed with them. Or they might have
just been killed off, because they were fighting
over the same ecosystems. And I’ve made a little
sample here of Homo sapiens. Well, I’m assuming most of you
watching this video are one. But just in case,
here’s my little sample. We can debate how representative
a sample of our species this really is.

100
Comments
  • Lets stop fighting and agree to disagree, lets agree that we do disagree but evolution is a fact and atheism rules and religion sucks in a billion ways thats all =) PEACE ssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

  • @Mogley52 Congratulations, you are an idiot 🙂
    Here is a 4 step program for you to get cured of your idiocy.
    1. Remove your religion goggles.
    2. Learn what science is.
    3. Learn what evolution is. (You have no idea what it is or how it works)
    4. Go to a freaking museum.

  • @BigBagsForRent There is a reason it is called the "Theory of Evolution" is because it is just that, a theory, not a fact the basis of which is something called "Darwin's Theory of Natural selection based on his findings in the South Pacific. I hate ignorance ….now you know.

  • did any one ever thought that apes evolve from humans and not the other way around!!! i think that will solve the conflict. rate me if you think it might be tru -).

  • @malta1565p im afraid you dont know what scientists mean when they use the word "theory"

    if you actually care about the truth, open a dictionary and look at the definition of "theory". there the colloquial meaning that you are talking about, which means "estimation" "educated guess". scientists would say "hypothesis"

    when scientists say theory, they essentially mean fact.

    ill prove to you that you are wrong: i KNOW you are religious, and you have no scientific objections to evolution.

  • @annoloki so you intentionally stop being mean AFTER you made people mad with you. Congrats! You found a way to to make people that you do not like/agree with look bad by using reverse psychology. After you start insulting someone to get them made at you, instead of admitting that you were wrong you pretend to be nice than wonder why the people you angered are mad at you. You must be a god fearing "religious" conservative. I say religious loosely because I bet you do not practice what you preach

  • @GodDamnit7711 Why must you dose it really matters? It's none of your business if Khans believes in God or not. What matters is if you get a got damn education and care for humanity weather or not there is a god, weather or not if anyone believe in god? I must ask you thins are you a citizen of the United States of America? I ask this because the first amendment is separation of Church and state because the founding father felt it didn't matter if you were religious or not just an American.

  • @kentokae I'm actually only wondering what on earth you're talking about. I've no idea where you get your crazy ideas from. I have no interest in making other people "look" anything. I am not religious, I am not conservative, and the idea of "practice what you preach" when talking about evolution is so incredibly stupid I have no idea where to even start. Oh yeah, I'll just sit here and start to evolve.

  • @kentokae Why must you ask my citizenship? Does it really matter? It's none of your business if I'm an American or not.

    Haha, lighten up buddy. I know it's not my business but it's a valid question that lets me get to know about Khan as a human, or in a more negative sounding way, "get in his business". If you think asking a question is rude or doesn't make for legit conversation, please go learn how to be social in the real world instead of learning about sciences. Take it easy, really…

  • @AnthonyRF1996 Theory in sience is the highest form of sicencetific proof. Come up with the prosses that is able to demistrate how fully fromed animals can poop into existance. Ocorce magical explantions are easy to fully understand when things like evolation is more complicated however the magical explantion has always been proofen wrong and that includes things like creationism. Go to wiki and write ,,suppport for evolation,,

  • @biblesbooksmore do you even know what theory is in the science?
    In all honesty magic is not accepted in science.

    go to wiki and write ,,intellignt design,, and look on what is under the title ,,Peer review,,

  • My God scientists themselves agree that if genetic mutation occur it would be 99.99% chance that specie would die……that s all darvinism is all about .01% .. why dont u talk about 99.99%

  • @biblesbooksmore Really? You do know how the scientific process works right? In order for a hypothesis to even be considered for the title "theory" there must be a peer reviewed paper that was published in a SCIENTIFIC JOURNAL, not a creation science journal. I can not tell you how many creationists have told me that there was a paper but instead hand me a fox news report. Even after that, it takes years for the hypothesis to be accepted as a theory/law. Show me the paper first, then we'll talk.

  • @OneLeggedNinja I think you are the one looking at it from one angle. Casshyr actually looked at Evolution and Christianity and decided that it's not completely impossible that they can coexist. You're just looking at it from one viewpoint.

  • @OneLeggedNinja You sir are an idiot. Your god will disappear. The bible was written by nomadic people with no knowledge of the worlds we exist in.

  • @OneLeggedNinja christian science? whats that like, making iPhones that doesnt work, you just have faith that youre talking to people on the phone and when someone asks what the hell you are doing you throw a right strop?

  • Oversimplified to the point of almost being cartoonish. I am not confident this particular video has much merit beyond that of a mere talking point.

  • @joeiacovino cause some dirt lady ate an apple from a talking snake and they needed to twist that into something for something like your mind to over comprehend to believe it?

  • @cathysastupidslut First of all I am an atheist and be willing to bet that my knowledge and understanding of evolution far outweighs yours. What I was speaking to was not evolution itself, rather the presentation in this video which doesn't really offer more than a surface snapshot of the processes involved. Furthermore, because of that lack of detail, the video fails to be compelling or to give evolution the justice its body of evidence deserves.

  • @ProMajtas One: You misunderstand the meaning of theory. Did you want us to stop teaching the theory of gravitation also?

    Two: If there is no observable evidence it is only because you do not care to observe it. Granted we do not live long enough to witness many speciation events, though some have been recorded. We DO however have much evidence in the way of the fossil record and DNA evidence.

    In summation it would be better you learn a bit more before you make irresponsible statements.

  • @ProMajtas The same mechanisms that create change and variation within "kinds" (that term needs defining) allow one kind can become another. Observable evidence that this is so can be found in studies of phylogeny, the fossil record, genetics, developmental biology and the geographical distribution of species. This evidence requires some inference and interpretation, but it fits the theory of evolution perfectly, as no other theory (or theology) does.

  • If what you want is something like direct human observation of a housefly evolving into a spider over a few generations, there's two big problems with that.
    First, if we did make make such an observation, it wouldn't prove the theory of evolution; it'd actually contradict it, and the theory would have be scrapped or radically revised.
    Second, not all observable evidence is directly, visibly observable in real-time. If it was, we'd hardly need science–most knowledge would be obvious.

  • @Jestlow actually scientific evidence shows we have halted due to the lack of need to do so…madicine and such have made it easier for the less likely to survive, breeding with a stronger person maybe but the point is, your eating a drive-through meal and getting a flu shot……..so take the hand away fro your face and scratch your butt because your a ape-like evolved being.

  • One animal does not "turn into" another, just "snap" like that!
    It is a theory meaning that there is a set of working principals which are supported by mountains of facts. It is merely a theory, because it is not FULLY understood yet, not because we don't KNOW that it is supported by facts. We know there is MORE FACTS to learn, on top of the ones we already know. Give "The Selfish Gene" an honest read, instead of merely sampling quotes, and it will open up before your eyes.

  • You sir Are Stupid t Is True God Is Our King He Is Not An Idoint I Belive There Was SOme Evealution But I Doubt That We Came From A Rodent…..

  • I see you don't understand the meaning of "scientific theory".

    Since you haven't figured it out, I'll try and help. A "theory" is something that represents our understanding of FACTS (and you did seem keen on the importance of these) in a way that is accurate and consistent with observation. Fact and scientific theory are not separate entities.

    Please try to educate yourself a little more before you impress your ideas upon people.

  • We have found in the DNA that if you are not from Africa, then 1% to 3% of your DNA is from Neanderthals.

  • It never fails to see some creationist babble on these videos. They always say Atheists really know there is a god but are in denial, but I wonder if their constant opposition to anything that under cuts their belief system is really out of insecurity for the validity of their own faith. Kind of like the closet homosexual preacher who rants against the sin of being gay. In their case it may be subconscious, but nonetheless an existing insecurity they battle with.

  • What about earthquakes, tsunamis, or even strong wind…do they not move rocks? Yeah I think they do. Everything else you said is ridiculous enough but I had to just point out the fallacy in your example.

  • What I mean is that if your skin is not black, then you have 1% to 3% DNA attributed to another species. Namely the Neanderthals.

    That being said, black, white, red, yellow, we all ultimately come from Africa if you go far back enough. Just that Neanderthals bread with Homosapians after we re-entered Africa. (The couple thousand of us humans that were left on the planet completely left Africa, then some came back. Those that went back to Africa didn't interbreed with Neanderthals.)

  • I can't speak on whether there is any DNA in our veins attributed to Homo Floresiensis, though that would be pretty cool if we did! 😀

  • Because the Biblical God is the only God we're talking about here. Sure, let's exclude everyone over there in Asia. Those jerks, getting born without Christianity! Wow, how close-minded can you get?

  • The bible also says that the Earth was plane, that the sun was turning around the earth and that Jesus was some kind of super fast man as he could walk over water.

  • he is a fundi', dont group me with those idiots douche bag, if there is one thing that will disappear it will be you. so in the end, you sir are as much of an ass as the guy you are making fun of

  • chuck Norris isnt a human silly, he is deity that simply allows certain animals to live or kills the ones he doesn't like=evolution

  • Nothing to do with what I said, buddy. Shame on you! I was gone for 4 weeks, you had all that time to come up with something good, and all I find is something not even remotely related to my comment.
    Still, the CAPS-LOCK did make me tremble in my seat, as did the multiple question and exclamation marks and assertions that I was "FUCKING RETARDED". So you'd probably make a great bouncer. If, you know, you were only able to bounce people by typing messages to them.

  • Your point is stupid. Your logic itself is against you. Who created God, he doesn't just create himself does he now? PWNED

  • I am just curious, we all know that we have something call soul, thus we do think, create, and utilize things. By the same token if the great apes were our ancestors, why don't they have souls? Or did something happen during the "great" evolution process?

  • Thanks for the video. I just don't understand why scientific evidence is always immediately discredited by bible thumpers. Don't religious people go to doctors and hospitals to be treated or do they pray away the pain? It's the same science built from the same scientific theories.

  • What is a soul? How do you know it exists? If it exists, how do you know that it exists in humans? How do you know that it doesn't exist in apes?

  • By standard epistemology, most people claim that you are justyfied to claim knowledge if you have justification to do so.

    He does not have justification to claim that souls do not exists. But he can claim that people making claims about the existens of souls, are not justified in doing so.

    But you are right, he is not justified in claiming to know that souls do not exists. (From most philosophers view.)

    Just like no one can claim to know that santa exists. But he might see it as usefull.

  • I think that we should stop using the word "belief" for scientific theory. And the word "theory" as well, it's too confusing for theists.
    Believe – have evidence to support
    Theory – can build an assumption on available evidence

  • lol, is that chuck Norris in there, at the top right pic?….lol hahaha he da bomb sapien…the highest point of manvolution.

  • Can you tell me the significance of adaptive radiation!
    I know what is adaptatve radiation but to be exact i can't tell the significance. Did/does it help in natural selection?

  • If Im not mistaken humans didnt really come from monkeys, we the great apes share a common ancestor with old world monkeys, but that is not the same as coming from monkeys. Or at least that is what is normally taught.

  • And 65 million years into the future….we will have evolved into flying creatures capable of living in water where we believe we came from.

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