(gentle music)
- [Narrator] Like buried treasure,
they lie hidden from sight.
Echoes of an ancient past, they whisper secrets
and tell tales once lost to time.
Fossils are remnants or impressions of ancient organisms
that are naturally preserved in stone.
While there are hundreds of fossil types,
they are often grouped into two major categories,
body fossils, which are the preserved remains
of plants and animals, and trace fossils,
which are records of an animal's behavior,
such as footprints.
Together, they form the fossil record,
a primary account that tells the story
of life on Earth through stone.
Fossilization or the process of preserving
organisms in stone, can occur in countless ways.
These methods are largely grouped
depending on whether the organisms
are altered during the fossilization process.
Fossilization that does not alter a specimen
can help to preserve its original form and texture.
Among many methods, this group includes organisms
that have been frozen,
preserved in tar pits, and mummified.
One special case involves trapping organisms,
oftentimes insects, in amber.
This process begins when an organism is covered
in tree sap.
The sap or resin forms a protective seal
around the entrapped organism.
Over time, the soft resin hardens
and turns into amber
with the organism suspended within.
This process creates a biologically inert tomb
for the organism, allowing its soft tissues
to be remarkably preserved.
Other fossilization methods change the specimen
as it is being preserved.
For instance, carbonization transforms soft tissues
into thin black films of carbon.
In fact, countless layers of carbonized plant material
create a well known fossil fuel, coal.
But one of the most common types of fossilization
that changes a specimen is called permineralization.
Permineralization begins when minerals from water
or the ground enter the pores of dead plant
or animal material.
Over time, the minerals attach themselves,
clinging onto cellular walls
and building a crystalline network in the empty cavities.
This mineralization hardens the bone
and turns it into stone,
thereby preserving its original structure in fossil form.
When conditions are right,
fossilization can preserve crucial information
about an organism.
Permineralized wood often contains enough information
to identify its tree genus
and sometimes its species.
Insects encased in amber have been so well preserved
that their genetic material was extracted
and partially sequenced.
And footprints left behind by ancient hominids
help paint a picture of what life was like
for early human ancestors millions of years ago.
With every fossil uncovered,
the planet's ancient past becomes clearer,
helping shape our understanding of our world today.
(gentle music)