- [Instructor] In our journey, studying evolution
and natural selection, we often index on
individual organisms.
If we look at a species or population of a certain species,
we've talked about how there could be variation
in that population, which I will depict
by these colors and these shapes over here.
And sometimes the variation really doesn't confer
any advantage or disadvantage for reproduction,
but sometimes it might.
And if a certain variation
maybe because the environment changed
or maybe this population finds themselves
in a new ecosystem confers an advantage,
well, that variant will be more likely to multiply.
And the genes which produce that phenotype
are more likely to become a larger and larger
part of the gene pool.
Similarly, if there's some disadvantage,
maybe because the environment has changed some way,
well, that might select out certain variants
and the underlying genetics that cause it.
But this is when we're thinking about traits
that primarily affect an individual's chances of survival
and reproduction.
But what we're going to do in this video
as this title implies, is focus on...
it's not just about individual traits.
There is also evolution of group behavior,
and we see that right over here in a school of fish.
Why does it make sense for these fish to ball up
into this huge school?
It might seem like it makes it very easy
for a predator to just go right into the middle of that
and open its mouth and get as much as it wants,
an all you can eat buffet, so to speak.
Well, it turns out that this type of behavior
does confer a benefit.
The benefit is yes, this shark that I just drew
might be able to get a mouth full of fish,
but the great majority of the fish
are going to be protected.
And by being in a big ball like this,
instead of just having your own eyes,
looking for a predator,
as soon as any one of these tens of thousands,
or maybe hundreds of thousands of fish spot a predator,
well, the whole school will know it.
So they're able to share information.
Also, even though some fish might get eaten up,
the probability that any one will be eaten by this shark
is actually lower versus
if there was just one of these fish,
just swimming by itself,
that one is much more likely to be picked off.
And we see this type of behavior in
many, many, many types of animals.
This right over here is a herd of wildebeest.
And once again, if you have an individual wildebeest,
it would be easy to be surrounded by say,
hyenas, by predators, that could be caught by surprise.
The younger of the wildebeest would be easy to pick off
if they were by themselves.
But if they're in a herd,
maybe they can be in the middle of the herd.
Here's an example of adult elephants protecting their young
when they see a threat approaching.
And notice, more than just the parents
are protecting the young.
These elephants are probably related to each other.
And so even though one elephant might sacrifice themselves,
maybe from some type of a threat,
if they're able to protect the young,
even though it might not be their child,
it might be their nephew, it might be their cousin,
their shared genetics are more likely to be passed on.
You've sometimes heard people say things like
I'd be willing to die for two brothers or eight cousins.
And that would actually make sense
from a genetic point of view,
but it's not just about protection,
where we see the evolution of group behavior.
We could also see it in terms of predation.
So this right over here as a pack of wolves
that are attacking this bison here, and first of all,
you can see how much more vulnerable this bison is
when it's alone than if it were part of a herd.
If it was part of a herd,
it would be much harder to surround it.
You'd have a ton of these other bison all around
that could run and chase individual wolves.
But when this bison is surrounded like this,
when it's outnumbered, it is more vulnerable.
And these wolves, which are
much, much smaller individually than this bison
have a decent chance of taking it down.
So once again, this group behavior of these wolves
to not hunt by themselves, but to hunt together,
to surround animals, to coordinate with each other,
that allows them to prey on animals
much, much larger than themselves.
So I encourage you to think about this idea
because it's happening all around us,
including in human beings.
We are social animals.
This is occurring through out the animal kingdom.
And it's a really fascinating thing to observe
all around you.