[music playing]
NARRATOR: Guanghan City, China, 1986.
Construction workers unearth two sacrificial pits
that contain the relics of a long-lost civilization.
The cache contains hundreds of bronze and gold masks, statues,
and figurines, in addition to numerous marble and jade
artifacts.
Chinese historians consider the discovery one
of the most important finds of the 20th century
and date the site back between 3,000 and 5,000 years,
to the very start of Chinese civilization.
Before the Sanxingdui discovery,
Chinese civilization was understood
to have arisen from the Yellow River Basin,
basically one spot in China.
This discovery showed that there were other very advanced
cultures on the periphery of the Yellow River Basin
that also heavily contributed to the formation
of Chinese civilization.
JULIE LEE: Nobody wrote about the culture at Sanxingdui.
There's nothing that comes up in Chinese texts,
and the Chinese are very good at documenting their history.
So one of the most surprising things
is how a culture that was so sophisticated
could slide under the radar of history.
NARRATOR: The Sanxingdui culture left no written record.
No human remains have been found.
And according to their artifacts,
they appear to have only existed for 350 years.
JULIE LEE: For some unknown reason,
the artifacts were broken, burned,
and placed into two pits and covered
up, rendering them useless.
So it's very curious as to why that happened.
NARRATOR: Adding to the intrigue of the vanished civilization,
they left behind dozens of bronze heads with odd features.
On November 1, 2007, the official press agency of China
asked the question whether or not what we're looking at here
are ancestors or, in fact, extraterrestrials.
And my question is, what if what we have here is both?
If you check out this one right here, look at the eyes.
Now, why would any artisan carve or create something like this?
Because our eyes don't look like this.
The whole thing is very bizarre looking.
It is not necessarily human.
It is something else.
The masks look very unusual.
They have big ears, big eyes.
They don't look like normal human beings of today.
NARRATOR: Could it be that the masks found at the Sanxingdui
site are depicting ancient astronauts who visited
our planet in the remote past?
And if so, could this help explain
the abrupt disappearance of a seemingly
advanced civilization?
Ultimately, they vanish, and we don't
know what happened to them.
So were they some kind of extraterrestrial civilization
or human hybrid civilization?