NARRATOR: Houston, Texas, 2010.
Doctors at the Texas Heart Institute
examine a 59-year-old man complaining of chest pains
and make an astounding discovery.
The patient has a three-chambered heart,
similar to that of a reptile.
Researchers attributed the rare condition
to an evolutionary phenomenon called atavism,
when a lost trait of a distant ancestor
reemerges in a modern organism.
GAGE CRUMP: So the idea is if you look at where we evolved
from, we were first fish.
Fish have a two-chambered heart.
And then we came on land.
We're more like a reptile.
That has a three-chambered heart.
And then, eventually, we have a four-chambered heart as we
became mammals and then humans.
So interestingly, during development,
that same sequence of evolution is played out again as embryos.
So if there's any sort of defect in the embryo along the way,
it could get stalled out at that earlier state.
And now this man has a heart that's
more typical of our distant ancestors, the reptiles.
NARRATOR: While the discovery of a human with a reptilian heart
is incredibly rare, other genetic conditions
have been found that suggest a link with reptiles.
Since the 1800s, over 100 cases of human tails
have been reported in medical journals.
People with the disease ichthyosis
have dry, scaly skin.
And people with the diseases called
syndactyly and ectrodactyly have fused
fingers and claw-like hands.
But if such anatomical irregularities
are a link to our ancient ancestors,
as some scientists suggest, could it
be that they are not the remnants of a reptilian stage
in human development but, instead,
reveal that humans once commingled
with reptilian aliens?
Ancient astronaut theorists say yes
and believe that further clues can be found in the stories
of China's first emperor, Fuxi.
Fuxi is one of the mythical rulers of China.
And he is considered to be the original or prototypical man.
He was created along with his sister, Nuwa.
They were humanoid in form in the sense
that their upper bodies were that of humans,
but their lower bodies were that of snakes.
And they're often represented with snake
tails intertwined together.
NARRATOR: Similar stories of reptilian humanoid beings
exist in cultures around the ancient world,
including Japan, Greece, and South America.
DAVID CHILDRESS: We even have good drawings
and reliefs of many of these fantastic creatures.
And so is it possible that some of these creatures
really are aliens that look like that?
And it seems like in some cases that is probably the case.
NARRATOR: Other unusual anomalies also
appear to mirror the descriptions of divine beings
from ancient texts.
Millions of infants are born with blue patches of skin
called Mongolian spots, evoking the blue-skin gods
common to India and Egypt.
There have also been many cases of gigantism
throughout history, bringing to mind biblical stories
of the Nephilim, giants that were said
to be the hybrid offspring of humans
and divine beings called "the watchers."
Within us is the whole evolutionary development
of humankind, as well as the other species
that humans developed from--
reptiles, fish, and so forth.
Extrapolating this idea, if extraterrestrials had a hand
in retooling our DNA, then do we also carry their genetic makeup
within us, as we would?
JASON MARTELL: We know today that our DNA
contains a lot of junk DNA that we still don't understand.
So when we see these genetic anomalies surface
in physical form in children, it could be that it's not anomaly.
It's actually a lost extraterrestrial gene,
a marker that's now resurfacing at the right time.