- [Instructor] Most of us are familiar with dogs,
often times known as man's best friend.
And what's fascinating about them is that
they are one species, even though different types
of dogs, different breeds could look very, very different.
And the fact that they're one species says that
if you have a male and a female dog,
any two, that in theory they could reproduce
and produce viable offspring.
Although in, for example, the case of this character
and this character, the mechanics could get quite difficult.
But an interesting question is, is where do dogs come from
and why do we have these seemingly
specialized breeds amongst dogs?
You might have things like a Rottweiler that's better
for protection, you might have things like terriers
that have been specialized to maybe go after rodents.
You have things like border collies that are good at
herding other types of animals.
The simple answer is,
through artificial selection and domestication.
Remember, in any population of a species
there's variation in that species.
And when we talked about natural selection,
that's where the environment might select
for certain of those variants.
Certain of those variants might make it a little bit easier
to survive or reproduce, and then those would predominate
and that's how evolution happens.
Artificial selection and domestication is where
humans take matters into their own hands.
And instead of waiting for nature to do things,
they are the selection factor.
They pick which of the species get to reproduce
and which ones don't.
And when you have that type of artificial selection,
the change can happen much, much faster.
Breeding is essentially artificial selection.
So dogs like this, and all the dogs we know of
had ancestors that looked like this,
that looked like a wolf, that were a wolf.
And what we theorize is that the early stages
of some wolf eventually evolving into dogs
might have been more traditional natural selection
where tens of thousands of years ago
our hunter gatherer ancestors as they hunted and gathering
they might have left over food here or there,
and some of the wolves that just happened to be the variants
that were a little bit more comfortable getting close
to humans might have benefited from being able
to get some of that left over food,
being able to get some of the remains
that the human beings left behind.
But then over time, human beings probably realized
that hey, these wolves are useful to have around.
Maybe they provide some form of protection,
maybe over time they started breeding the wolves
so the wolves that were especially friendly,
the wolves that were especially good at a certain task,
say protection, or going after some type of an animal
or retrieving things, they allowed those
to reproduce together and over time,
over tens of thousands of years,
we went from wolves to dogs.
And even once we had dogs,
the breeding got even more specialized.
As I mentioned, things like border collies,
this was many years, many generations of breeding
where sheep herders might have selected dogs
that were good at herding sheep.
That terriers came from dogs that were good
at going after rodents, things like rottweilers
or dogs breeding the dogs that were especially good
at providing protection or defense.
And it isn't just dogs that are products
of artificial selection and domestication.
Pretty much any animal that you might see
on say a farm would be the product
of artificial selection and domestication.
A wild pig looks like this, while the ones
that you would see on a farm look like that.
And once again, they would have selected for things like
docility, things where they're less aggressive
and they're easier to take care of.
And artificial selection and domestication
does not apply just to animals.
Pretty much anything you might see in the produce section
of your supermarket is the product
of artificial selection and domestication.
There might be wild variants of these different
vegetables or these different fruits,
but over roughly 10 or 15,000 years
of human agriculture, every generation of crop
they would have selected for the crops
that are more robust, that tasted better,
that were able to grow in different climates
and by allowing those variants to reproduce,
we eventually ended up with the domesticated crops
we see today.