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We find a lot of fossils today and I have heard
it is because there were different events that
caused animals and dinosaurs to die. Why didn't
the fallen bodies of the dead animals just rot?
Why did they turn into fossils if they just fell
down dead? If all of those dead animals that
are fossilized were buried rapidly with water,
etc., (which is needed for the fossilization
process) what caused that to happen with all of
the thousands upon thousands of fossilized
creatures? Was it thousands of small disasters
with water, etc? I'm just confused on that
subject because we find so many different fossils
in so many layers.
Why were bones of an iguanadon, mastadon,
hadrosaurus, monkey, bison, racoon, Indian jawbone
and teeth, all found together, and in the same
layer in the Ashly Beds in South Carolina if they
all were said to have lived at different time?
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Question Date: 2014-10-23 | | Answer 1:
The bodies don't necessarily rot because they
become buried quickly or covered. Sometimes they
did rot for a few days, and were eaten by
scavengers, and then buried in mudslides. This
stops the rot and results in fossils after a very
long time. You are exactly right: it was thousands
of random events like dust storms or floods or
mudslides that caused the fossils. It sounds like
a lot of random chance and it is, but over
millions of years there will be millions of little
burials like that. You've also figured out one of
the barriers to perfectly knowing every organism:
some by chance never were buried by those events.
When people criticize evolution and say we don't
have some missing links, which may be true. But
that doesn't mean they never existed, we just
haven't found them yet or they were never randomly
buried by chance. So it's a bad criticism of
science.
The Ashley Beds appear as a common criticism of
science in that they say dinosaurs and people
lived together. First, I want to explain how we
date bones from different animals. When an animal
is alive it eats from plants that take in a
certain amount of carbon 14 from the atmosphere
during photosynthesis. When the animals are alive
and continue to eat, they will have a constant
amount of carbon 14 in their bodies. When they
die, this carbon 14 stops being replaced. Because
the chemical is unstable, it degrades very slowly.
By measuring how much of the carbon is left, we
can get a very accurate date when the animal died.
So if we find a fossil that has half of its carbon
14 gone, we can see that it must have died many,
many years before an animal that still has all of
its carbon 14. Because we know exactly how fast it
degrades we can get accurate dates. So we can show
that all of these animals lived millions of years
apart, rather than just looking at how deep they
are.
Now, how could these things have ended up in
the same layer? Think of something like the Grand
Canyon. The flow of water over thousands of years
has eroded down and exposed deeper and older
layers of rocks. If you were to build a house in
the Grand Canyon now, you would be building on
older layers of rock. In the same way, sands can
shift in deserts exposing different rock ages to
animals many years apart. In changing
environments, dating based on fossil depth is not
always reliable. It is not possible that humans
and dinosaurs lived together, which seems to be
the suggestion by people who talk about this site.
If you aren't convinced of this though, please ask
what isn't clear! We know a massive amount about
how species came to be, and evolution/natural
selection is about as widely accepted as gravity
in the scientific community. In the public though,
evolution is less widely accepted than it was 50
years ago, which is not very good.
| | Answer 2:
These are interesting questions! You are right
that if organisms just rot after they die, they
will not be preserved in the fossil record. I
don’t have the data to quantify this, but I
suspect that a vast majority of dead organisms do
just rot and do not leave fossils. Keep in mind
that fossils usually do not usually contain any of
the original organic material (soft parts) that
made up the organism. More often, an imprint of
the organism is fossilized or minerals like quartz
or calcite replace body parts so that we don’t
usually find the original parts.
You are also right that certain special conditions
are required to preserve a fossil. If a dead
organism is left exposed in the atmosphere, it may
decay without leaving a trace. Rapid burial or
deposition in an anoxic (without oxygen)
environment may increase the likelihood of
fossilization. However, it does not require a
“disaster” to preserve a fossil. For a
hypothetical example, suppose that a vertebrate
animal dies on the edge of a riverbed. Normal
rates of sediment deposition could bury the animal
very quickly (in less than year).
Over geologic timescales (the earth is about
4.56 billion years old), many organisms have been
preserved, even through normal geologic processes
like the accumulation of sediment in basins.
Concerning the Ashley phosphate deposits in South
Carolina, I was unable to find an recent
peer-reviewed article (an article that has been
reviewed for accuracy by experts before being
published) that says anything about a hadrosaur
fossil being found in this location. It is
extremely unlikely that a (non-avian) dinosaur
fossil would be found in a Tertiary (the geologic
time period after the extinction of non-avian
dinosaurs) deposit. Without finding any
peer-reviewed articles from the last century that
report this, I cannot fully assess this statement,
but I think that it is probably a mistake. It is
unlikely, but possible, that a Mesozoic (the era
of the dinosaurs) sedimentary rock was “reworked”
in the Tertiary and that a Mesozoic fossil was
redeposited in the Tertiary sediment. Even if this
were the case (I suspect that it’s not), there are
an overwhelming number of observations that
non-avian dinosaur fossils occur in Mesozoic
sediments (~250–65
million years ago), indicating that they lived,
died, and were fossilized during the Mesozoic era.
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