Imagine Earth covered
in thick sheets of ice.
And sea levels so low
you could walk to a different continent.
This is what our planet would look like
during an ice age.
There have been five of them in
Earth’s history.
And they've had a huge impact
on our present world.
Now, try and imagine an Earth
where these ice ages never existed
in the first place.
Over a century ago,
Milutin Milankovitch hypothesized that
changes in the Earth’s orbit,
the angle of its axis,
and the direction of its axis
are what create long-term changes to the climate.
Known as Milankovitch cycles,
they create the seasons we know well,
and the ice ages that
we're glad to have skipped.
Without Milankovitch cycles,
Earth would look a lot different.
There would have been no ice ages.
None at all.
Which means no glaciers to carve out
beautiful inland lakes and valleys.
It also means Earth’s flora and fauna
would have evolved differently.
Grasses initially popped up on Earth
before the first ice age.
But they truly thrived as the Earth
became cooler and drier.
Grasslands,
tundras,
and savannas
grew all over the Earth,
replacing dense forests.
With no cooling period
leading up to the first ice age,
grasses would not have spread so easily.
There would be less variety,
and the animals that evolved to eat grass
would be less abundant.
Horses,
giraffes,
cows,
gazelles,
any animal you associate with dry grasslands,
would have had less habitat to flourish.
Instead, there would be more
rain forests left on Earth.
The climate in general would be warmer and wetter.
And what about the animals
that reigned during the ice ages?
Well, we wouldn't know of any.
Saber-toothed cats,
giant sloths,
mastodons,
woolly mammoths,
probably would never have graced our planet.
But what about us?
Homo erectus first emerged during the
last big ice age in the Pleistocene epoch.
This is the same time that
woolly mammoths roamed the world.
A general hypothesis is that the
extreme climate forced the evolution of Homo erectus.
They had to change their diets
from mostly plants to
half plants and half meat,
which increased their brain size.
They developed the use of tools.
And they had to migrate to seek
more hospitable land.
Without the ice age forcing the need
for adaptation and evolution,
humans would probably not exist.
Which also means our present Earth
wouldn't have any of the
human-induced climate changes
we're witnessing today.
Even if Homo erectus,
which preceded Homo sapiens,
evolved regardless of the ice age,
our progress as a species would change.
Many scientists attribute agriculture
to the rapid growth and global expansion of humans.
But without the ice age,
we could have developed the benefits
of agriculture sooner.
In the absence of dry,
arid grasslands,
we also might have advanced
different farming practices
which favored forest foods.
Our diet might consist of fewer plants
from the grass family,
like wheat and oats,
and more fruits and vegetables.
For evolution to occur,
it needs a catalyst.
like an ice age.
Earth as we know it today
exists because cycles and catalysts
have pushed living organisms to adapt.
It would be a very different planet
without Milankovitch cycles
and the ice ages they produce.
Even greater than this,
how different would Earth be if it
completely stopped its orbit around the Sun?
Well, that’s a story for another What IF.