Study Guide

Mechanisms of Evolution In the Real World

  • Health

    When the first antibiotic was developed in the 1940s, it was the solution to a huge health epidemic. Since then, dozens of new antibiotics have been made that are able to kill harmful bacteria. You've probably taken them a few times in your life. Antibiotics are generally pink bubble gum flavored goodness.

    Antibiotics were as revolutionary as the iPhone. Figuring out how to kill bacteria and stop infections and disease? A trip to the Genius Bar. We've been riding the antibiotic invention for a long time. What was once a brilliant move has now turned into a different kind of epidemic. Bacteria are quickly becoming resistant to our best way to stop them. These antibiotic-resistant bugs are being called superbacteria. Is there an app for that? We wish.

    The problem is that bacteria can evolve by natural selection just like the rest of life. Bacteria also have an upper hand on evolution. They are able to go through multiple generations in an hour, which means natural selection can happen quickly.

    When we pick up a prescription of antibiotics from the pharmacy, there is usually a label on it that tells us to take the entire bottle, even if we start to feel better. There's a good reason for that. When a population of bacteria is hit by antibiotics, most of them will die off. However, due to their fast generation time, they can also accumulate mutations fast. If one of them develops an adaptive mutation, it will start to multiply. It's important to kill all of them before this can happen. This also explains why it's important not to use antibiotics when you really don't need them. It gives these superbacteria a chance to develop resistance.

    Superbacteria are making their way around the world, passing their adaptive mutations on to other populations via gene flow. More than one species has antibiotic resistant strains using similar mechanisms of adaptation, including E. coli and Salmonella. These bugs are usually found in hospitals, where people with low immune systems are more likely to be affected. They have also been found in drinking water in India.

    We can't stop bacteria from evolving resistance to antibiotics. It's a scary international health crisis. While science is trying to find new ways to get rid of bacteria, there's a few things the rest of us can do to help out. Only take antibiotics when absolutely necessary. When you're prescribed antibiotics, take the full dose. And last but not least, wash your hands, yo.

  • History

    Throughout history, evolution has been challenged as unproven, false, and downright scandalous. Most of science can be seen by the naked eye or high-powered microscopes, or at least tested by a series of experiments with well-designed controls. For some people, seeing is believing. When it comes to understanding evolution, jumping in a time machine is pretty difficult to do. Until we get a flux capacitor and a working DeLorean, time travel probably isn't going to happen. Bummer.

    Evolution is a puzzle, and we don't have all the pieces. Since the events happened over millions of years, some pieces may be permanently lost underneath the couch, tossed out with yesterday's pizza boxes, or buried underground. But just like archaeologists can use ancient artifacts to piece together primitive cultures, science has been able to use fossils and carbon dating to gain clues about the world before we got here.

    In addition to studying history to learn about evolution, scientists have been going to their lab benches to recreate it.

    A famous experiment by Miller and Urey recreated an atmosphere similar to what Earth probably looked like when life began. By firing electricity into it, which mimicked lightening, they made amino acids from scratch.

    One of the current hypotheses about how the world began is the RNA World hypothesis, which states that life was made possible by RNA able to act as both the original genetic material and an enzyme. Can RNA make a functioning cell? Not yet, but recent studies have shown that RNA can chemically interact with itself in a cell-like compartment.

    Science has also done leapfrogs in genome sequencing, which tells us the exact order of every DNA nucleotide. We can use genome sequencing to see what genes organisms have in common, and to "watch" gene evolution progress through the tree of life.

    We can even use this technology to sequence the genomes of species that have gone extinct, including the wooly mammoth. Their genome was sequenced using DNA extracted from woolly mammoth hair and comparing it to a modern day African elephant. If only we could make Woolly Park a reality. Or can we?


    Watch out, we're bringing woolly back. Image from here.

    But there's more. Science keeps trying to push the envelope. Other experiments of historical note include a more recent ability for scientists to synthesize artificial DNA and use it to re-create self-functioning, replicating, brand-spanking new bacteria.

    Making the building blocks of life, sequencing our ancestors, and creating single-celled organisms are all pretty impressive feats. Is this recreating life from bare bones? Not exactly, but it helps scientists understand what is essential to life and how we might be able to prove our history.

  • Research

    No monkeying around—our DNA is 95% similar to that of chimpanzees. In fact, chimps are our closest living relatives, besides your second cousins of course. Humans and chimps parted ways approximately 4-6 million years ago.



    The chimpanzee is our closet living relative. Image from here.

    In trying to understand evolution, current research is focusing on the similarities and differences between our ears. Human brains tripled in size about 1.5 million years ago. Our brains today are three times the size of chimps', even though our body size isn't as different. Though humans and chimps display social interaction, communicate, and participate in tickle fights, we have developed sophisticated language skills and hair removal methods that set us apart from our ancestors.
    Recent experiments measuring the size of our brains, as well as their growth and activity have been done using ultrasound and MRI techniques. Human brains grow for a longer period of time in utero even though humans and chimps bake in the oven for a similar amount of time. Differences in brain growth could allow us to become bigger brainiacs. We can hold a dinner conversation, check out current events, and tweet at the same time. Take that, chimps.

    At the molecular level, studies are being done to see which genes are different between chimps and humans, and if these genes are expressed differently. Over 100 genes so far fit the bill. The challenge is sorting through them, and trying to figure out which ones were responsible for our speciation. One candidate is the gene FOXP2. Humans developed language around the time FOXP2 changed significantly. This gene has also been implicated in speech-related disorders and autism in humans, meaning these studies may also help us understand significant health problems.

    As you contemplate how current research aids in understanding human evolution, our common ancestors, and disease, we'll leave you with another video because we just can't help ourselves. It's time for adorable chimp babies. Aww.