Human Evolution Overview

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Human Evolution Overview : From the extinction of the dinosaurs to humanity

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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 envelope the continents
for some period of time, then you would have 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 some place
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
you know, have all of their food nearby them
and maybe they could hibernate in some way
So you can imagine that once everything settled down
and now we're talking hundreds of years,
thousands of years,
even MILLIONS of years,
some of this guys' descendants start to poke their head out of the ground
and are 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 a get away from
some of the other predators
that have managed to survive this mass-extinction event.
And some of its ancestors, or some of its descendants I should say
that were good at climbing trees
decided, 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
So you could imagine, that some subset of this guys'
descendants evolved into something that might have looked
like this guy.
And all of the pictures I'm showing you
these are of modern animals, except for of course, the dinosaur
I'm sure it's just kind of photoshopped in, in some way
This is a modern Bush Baby, but I show this picture because
it could have been what some of the primitive primates look like.
Because a Bush Baby, it kinda climbs trees; it's able, it kinda looks like
it's able to get a hand here, to start climbing the trees
but it also has rodent-like qualities.
But this 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 that primitive primate
that was a descendant of rodents, that said "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; so you could imagine
a kind of primitive monkey.
And then, some of those primitive monkey's 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 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, maybe this was
actually if I'm talking about species,
maybe this was Tyrannosaurus Rex
because the dinosaurs involved a whole bunch of - -
so this might have been T. Rex,
and I mean there's a bunch of species we could list over here,
but after that mass-extinction event
that was an endpoint for a ton, for a ton of species
except for maybe this primitive rodent mole-like thing,
that was, you know, 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 in a mountain or someplace
who knows where they were?
And some of them were able to evolve into
primitive primates
And some of those primitive primates,
and this is once again 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 were able to find, even in today's world, a niche for themselves
they are able to find food and reproduce, and,
in ways, that, you know, don't get in the way of ther people
and other people don't get in the way of them
When I talk about primitive primates
I'm just talking about a kind of ancestral primates,
maybe something that's not there, uh, today
Although maybe some of it's descendants look very much like it.
But anyway, some of those primates evolve into primitive monkeys,
some of those primitive monkey's descendants become modern monkeys
so this is, 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 are like monkeys
but they don't have tails, and they are 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 a
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 7 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 Australopithecine Fossil of Lucy
that was discovered 3.2 mil --, 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 4 million to 2 million years ago
4 to 2, and we never know
you could always find a fossil that is older than this
maybe newer than this
I've read one account that said maybe 1 million years ago
but give or take, the Lucy Fossil,
which is the most well-established Australopithecine Fossil
is about 3 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 descendant from Lucy,
and it's actually not even clear that we are even descendant
directly from Australopithecine, we might be a cousin
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
2.3 to 1.4 million years ago
we see fossils that they are standing upright,
the brain size is bigger, because if you look at the
Australopithecine Fossils, they are standing upright, but their 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 are 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 this is, these are
one of the first, so 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 are starting to make primitive stone tools,
they stand upright like us,
and they have larger cranial capacities than the Australopithecine Fossils or modern Chimpanzees.
And once again, we never know if Homo Habilis, which
literally means, the Homo part means Man,
Habilis means Handy, because he liked to make tools or whatever else.
We don't if Homo Habilis is a descendant of Lucy's Species,
of Australopithecus, or maybe a cousin species
maybe they are both descendants from a common ancestor
we're not quite sure.
Then you fast-forward a little bit more
we're talking now about 1.8,
so now we're talking about 1.8 million to 1.3 million years ago
and we start seeing fossils where the cranial capacity larger than Homo Habilis,
getting closer in size to kind of what we know,
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 Hibilus,
maybe they have a common ancestor,
who knows?
It looks from the fossil evidence that there was,
especially when you look at this range here
that there was some overlap, where you had
both Homo Erectus and Homo Hibilus 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, you have the Neanderthals appear
And Neanderthals are in the same Genus as Humans,
so it's really Homo Neanderthalensis.
I always have trouble saying that,
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 are somehow cavemen and we are modern men
That's not the case.
The belief is that Neanderthals are either a cousin species, we have a common ancestor
or, that they're actually a sub-species of human beings
and there is some belief that they might have interbred with Homo Sapiens,
and maybe some, or a good number of us have Neanderthal genes.
It's nothing to be ashamed of, it's just something, you know, unfortunately that Neanderthals
just get a bad name, because of our popular culture.
If anything, so this is a drawing of Neanderthal brain, they actually had a
fairly large cranial capacity, although scientists say
they kind of make one reason or another why we think 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 this, 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, 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 have made a little sample here of Homo Sapiens
just in case, 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 of a sample of our species this really is.