[music playing]
NARRATOR: Sima de las palomas, Spain 2011.
Archaeologists unearth a prehistoric grave containing
three individuals buried side by side with their arms folded
in a ritualistic fashion.
Because of the manner of their burial,
the archaeologists assumed the remains are human, but are
surprised to discover that they are
actually our evolutionary cousin, Neanderthal.
It takes a good deal of imagination
to prepare the dead.
It suggests some kind of notion of an afterlife.
If there is that, there is usually a notion
of a deity of some kind.
That is fairly complicated religious thinking,
suggesting that the Neanderthals had
a capacity for symbolic reasoning
and the formation of culture.
This suggests a level of civilization, or at least
the protoculture, that is further
along than we used to think.
Neanderthals unfortunately, because of early discoveries
that made them look like a brutish
caveman, not intelligent, that they're
very, very different from us--
they were shorter and stockier.
But they had huge brains.
They clearly had clothing.
They cared for their sick and elderly.
They were very intelligent.
NARRATOR: In 2014, scientists analyzed materials
from 40 different archaeological sites
to determine a reliable extinction
date for Neanderthals.
The date they came up with is 40,000 years ago,
suggesting they coexisted with Homo sapiens
for at least 1,000 years.
But just why did they die off?
At this point, we don't know exactly why
these other species died off.
Certainly, it does broadly coincide
with the expansion of anatomically modern humans
to all parts of the globe.
But contrary to our notions from the past,
it doesn't look like it was a lack of intelligence that led
to the demise of Neanderthals.
NARRATOR: Although Neanderthals are long extinct, in 2013,
evolutionary geneticists discovered
select modern human populations carry genomes
from both Neanderthal and Denisovans,
suggesting that, at some point, interbreeding occurred.
Neanderthal genetic markers are concentrated
in populations in Europe and parts of the Middle East.
Denisovan markers can be found in the mainland Asian
populations, as well as Pacific Islanders, New Guineans,
and Australian Aborigines.
According to some ancient astronaut theorists,
this interbreeding may have led to the early demise
of an extraterrestrial experiment
with protohumans, leaving only Homo
sapiens as the sole survivors.
Consider the possibility that these different hominid strains
were meant to be kept geologically
separated from each other across tracts of land that were
considered to be too vast for them to ultimately come
into contact with one another.
Is it possible that interbreeding was frowned upon
and that once interbreeding with Neanderthals started
to take place, it was damaging the very essence
of the experiment.
And because of that, the Neanderthal strain
had to be terminated or removed from the planet
to stop this from happening?
When we look at ancient texts, particularly religious texts,
from millennia ago, what we find is the idea
of the gods, or a god, wanting to create
a human that was pure, sort of physically and morally.
What we also find are accounts where the wrath of God
or the wrath of the gods hammered
down on us for essentially going off the rails, so to speak.
And we could make a case that this was some example
of extraterrestrial intervention to essentially try
and purify again the species.
And that might have involved wiping
out significant portions of early humans and starting over.