9 minutes
Published July 2014

Does the Theory of Evolution Really Matter?

Transcript

Does the Theory of Evolution Really Matter?

When Darwin published his theory of evolution in the mid 1800s, he presented us with two strange and interesting ideas:

First: living things are constantly evolving 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 fishers toss back the little ones.

The idea of course, is that small fish are young fish. If you toss them back they’ll have time to mature, hopefully have babies, and eventually grow large enough for fishers to catch them in the future.

This 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’s 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 the large adults are busy being dinner, only the traits for small body size are being passed onto future generations.

To test his hypothesis, Dr Conover and his team set up three aquariums, populated each one with 1000 atlantic silversides and fed them all the same diet until they were full grown.

Right before they had a chance to mate, he removed all the biggest fish from the first tank. In the second tank he removed fish at random (this was his control group), and in the third tank he removed all the smallest fish.

He let them breed and then repeated the entire process with the next generation. After just 4 generations, the adults from the first tank evolved to be half the size of the adults in the third tank. This experiment strongly suggests that throwing back the little ones, makes fish 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 lets look at a mystery from the world of medicine:

Where did HIV come from?

HIV is a deadly virus which seemed to have popped into existence in the 1980s.

The Center for Disease Control conducted a study which placed one man at the center of the HIV epidemic. This man, a French Canadian flight attendant, came to be known as ‘Patient Zero’.

The public began to blame patient zero for starting the disease but biologists suspected he was not actually the first person to get HIV. To confirm their suspicions and find the true origins of the virus, they turned to Charles Darwin, and his idea that all living things are related.

Scientists collected samples of HIV from multiple patients, and found that there were several slightly different versions being passed around. They analyzed the genetic code of each version and began to build a Darwinian evolutionary trees for the virus. They built their trees using the same methods that geneticists had been using to make evolutionary trees of plants and animals.

Examining the genetic differences between strains of HIV, and comparing those differences to HIV’s estimated mutation rates, they were able to get a rough idea of the year at which different strains split from each other. Their results suggested that HIV had been evolving inside of humans long 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 easily link branches together, there must be missing links. On a quest to find those missing links and the true origins of HIV, biologists traveled the globe searching for viruses inside of humans and animals.

Biologist Beatrice Hahn found viruses which were similar to HIV in populations of monkeys and apes. Her team began making family trees of these viruses.

Other groups continued collecting strains found in humans. They 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.

While studying wild Chimp feces in Africa, Dr Beatrice Hahn found a strain of Chimp virus which was almost identical to a human strain also found in the same region of Africa. She had discovered a missing link suggesting that HIV did not come from a French Canadian Flight attendant the early 1980s, but instead it came from chimpanzees, who we now believe passed it to humans as early as the year 1900.

The leading hypothesis is that HIV crossed over to people who hunted chimps for meat in South East Cameroon.

A handful of distant strains have since been linked to separate animal / human crossover events.

Understanding that HIV has crossed from animals to people, allows us to better understand how the virus works and is helping us prevent new diseases from crossing over to humans in the future.

In our final example, we’ll see how evolution applies to environmental protection, by looking at

the Mystery of Growing Deserts

All around the world, grasslands have been rapidly turning into deserts near human civilizations. Until recently, no one knew why.

The theory of evolution tells us that as living creatures slowly evolve to cope with the dangers of their environments, some will actually become dependent on those dangers in order to survive.

For example: Sea anemones are marine predators which can kill their prey with stinging tentacles. Sometime in the past, clownfish evolved an immunity to these stings which helped them survive and reproduce. Some clownfish went on to developed a dependency on anemones, using them as a safe place to hide from deadly predators. If you remove anemones from a region of the sea, in many cases, the local clownfish will perish.

Allan Savory, a Biologist from Zimbabwe, noticed that wild grazing animals often avoid human populations. He wondered if local plants had somehow evolved a dependency on those herds. With wild herds gone, the plants were dying.

To test his hypothesis, Allan 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 in the region. In less than one year, the grasslands began to recover, eventually being restored to their original health.

Our current understanding of the relationship between grasslands and grazers is currently very primative, but is appears that in most places of the world, grasslands have evolved a dependency on wild grazers to till the soil with their feet, fertilize with their dung and urine, and remove excess vegetation so that new shoots can grow when the rains return.

Knowing how this works, enables us to save these environments for future generations.

These three simple examples illustrate just a few of the many ways in which evolution is helping us overcome issues with food security, infectious disease, and environmental destruction.

The theory of evolution is extremely important. It tells us how biology works.

I’m Jon Perry, and those are a few of the many reasons evolution matters, Stated Clearly