Stated Clearly presents
Does the theory of evolution really matter?
When Darwin published his Theory of Evolution
in the mid eighteen hundreds,
he presented us with two very strange and interesting ideas.
First, through completely natural processes living things evolve
to better survive and reproduce within their environments.
Second, all living things on earth are related in a single evolutionary tree.
These concepts are interesting to think about,
But, do they have any practical use?
To find out,
Let's take a quick look at a few examples of
how evolution is being applied to real life problems …
... starting with the mystery of the shrinking fish.
In order to maintain healthy fish populations,
governments often make fisher's toss back the little ones.
If you toss them back, they'll have time to mature,
hopefully have babies,
and eventually grow large enough for fisher's to catch them in the future.
This method worked great at first,
but something strange is happening.
All around the globe, people are reporting that adult fish
full-grown specimens of many different species are shrinking in size as time goes on.
What could be the cause of this?
Biologist Dr. David O. Conover wondered, "If maybe
our fishing policies were causing fish to evolve smaller body sizes?"
It is true that small fish are usually young fish.
But adults can come in small sizes too.
If the small adults are busy making babies.
while many of the large adults are busy being dinner,
the traits for small body size are much more likely to be passed on to future generations.
To test his hypothesis,
Dr. Conover and his team set up three sets of aquariums,
populated each set with a thousand Atlantic silversides
and fed them all the same diet until they were fully grown.
Right before they had a chance to mate,
he removed all the biggest fish from the first set of tanks.
And the second set, he removed fish at random.
This was his control group.
And in the third set, he removed all the smallest fish.
He let them breed and then repeated the entire process a year later
with the next generation.
After just four years, (four generations of selection) the adults
from the first set of tanks evolved to be half the size of the adults from the
third set of tanks.
This experiment strongly suggest that throwing back the little ones
does indeed cause Fish to evolve smaller body sizes.
Understanding how this works allows governments to make wiser fishing policies.
Which will ensure a healthy fish population long into the future.
Now let's take a look at another mystery…
This time from the world of Medicine.
Where did HIV come from?
HIV is a deadly virus which seemed to have
popped into existence in the early nineteen eighties.
The Center for Disease Control conducted a study
which placed one man at the center of the epidemic.
This man, a french-canadian flight attendant came to be known as patient zero
and was quickly blamed by the public for starting the disease.
Biologists however suspected the patient zero was not actually the first person to get HIV.
To confirm their suspicions and find the true origins of the virus,
they turn to Charles Darwin's idea that all living things are related.
Scientists collected samples of HIV from multiple patients in the US
and found that there were several slightly different versions being passed around.
They analyzed the genetic code of each version
and began to build Darwinian evolutionary trees for the virus.
They built their trees using the same methods
that other geneticists use, to make evolutionary trees of plants and animals.
In addition to simply creating these trees, they were also able to examine the
genetic differences between strains of HIV
and compare those differences to HIV's estimated mutation rate.
Doing this, they got a rough idea of the year
at which different strains evolved away from each other.
The results suggest that HIV had been evolving in America
before patient zero could have ever been infected.
Early on,
scientists came up with multiple trees which could not be easily linked together.
Evolutionary theory tells us there should only be one tree.
If we can't link branches together, there must be missing links.
On a quest to find those missing links and the true origins of HIV,
biologist traveled the globe searching for viruses inside of humans and animals.
Different strains of HIV were found in people all around the world.
Scientists even looked at tissue samples from the past,
which doctors had collected and preserved from patients who died strange deaths.
Primitive versions of HIV were found in several human samples
and added to the tree, connecting many loose branches.
Viruses which was similar to HIV were also found in populations of monkeys and apes.
For the most part, these viruses could not infect humans.
But researchers began making family trees for these viruses as well
hoping they might eventually find a connection.
Dr. Beatrice Hahn
while studying stool samples from wild chimps in central Africa,
found a strain of chimps virus which was almost identical to a human strain also found in Africa.
She had discovered a missing link.
It told us that HIV did not come from a
French Canadian flight attendant in the early nineteen eighties.
But instead, came from chimpanzees possibly as early as the year 1900.
The leading hypothesis is
that a hunter, in southeast cameroon first got the disease by accidentally cutting himself
while preparing the meat of an infected chimp.
Understanding the HIV spilled over from animals to people
allows us to better understand how the virus works.
and is helping us prevent new diseases from spilling over in the future.
In our final example,
we'll see how evolution applies to environmental protection
by looking at the mystery of the growing deserts.
All around the world grasslands are steadily turning into deserts.
Until recently, no one knew why?
Allan savory, a biologist from Zimbabwe
have been trained to study the health of different plant and animal species one at a time.
His understanding of evolution however, inspired him to step back
and look at the health of entire communities of species at once.
After all if Darwin was correct when teaching that living things evolve
to better survive and reproduce within their environments.
They must be adapting not just to the climate and terrain
but also to the other creatures evolving alongside them.
Different species can evolve to cooperate
and eventually depend on one another for survival.
For example, sea anemones are marine predators which kill their prey with stinging tentacles.
Sometime in the past, clown fish evolved an immunity to these stings
which helped them survive and reproduce.
Some clown fish even went on to develop a dependency on anemones
using them as a safe place to hide from other deadly predators.
If you remove anemones from a region of the sea,
in many cases, the local clown fish will perish.
Back in Africa,
Alan notice that as human populations expand wild grazing animals often disappear
due to hunting and loss of habitat.
Inspired by Charles Darwin and the grazing research done by André Voisin,
Allan wondered if local plants had somehow evolved a dependency on grazing animals.
With wild herds gone the plants were also dying.
To test his hypothesis,
Allen and his team brought large groups of cattle to a region of dying grassland.
They moved the cattle in special herd formations
designed to mimic the behavior of wild grazers which once lived in the area.
In less than one year the grasslands began to recover.
After three years, they were thriving.
Our understanding of the evolutionary relationships between grasslands and
grazing animals is still fairly primitive.
But it appears that in most seasonally dry places of the world
plants depend on wild grazers to till the soil with their feet,
fertilized with their dung and urine,
and remove excess vegetation
so that new shoots can grow when the rains return.
Understanding how these evolutionary relationships work
is enabling us to save these environments for future generations.
So, to answer our question: Does the theory of evolution really matter?
Absolutely YES!!!
Besides just being interesting,
The Theory of Evolution is continually
guiding us to new sometimes life-changing discoveries.
I'm John Perry and these were just a few of the many reasons evolution matters
stated clearly.
This animation was funded by a grant from the Howard Hughes Medical Institute
to Emory University Center for Science Education in atlanta georgia.
To learn more about evolution and the examples presented in this animation,
visit our website at statedclearly.com
To learn more about the Center for Science Education,
visit cse.emory.edu
until next time, stay curious.