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What has evolution done for me lately?

“I have a dream…”

Zach Weiner. SMBC.

Zach Weiner. SMBC.

Almost everyone will have heard this most famous line by Martin Luther King, Jr. in the past few days. In honor of the holiday, rather than introduce another fossil, review a book, or some such thing, I thought I would do something a little different. I have a dream too, one in which teachers are not afraid to talk about evolution within the classroom, one in which people don’t recoil from the word because they think it goes against their religion, a dream in which everyone embraces the concepts, not because some scientist or teacher tells them they have to, not because they think it is part of a body of education they need to sound smart, but because they see the logic of evolutionary theory and the application of it in their everyday lives, because they understand how it affects them every day in ways they normally never even think about. In this essay, I am going to discuss a few of the many ways evolutionary theory helps us in practical applications. Next post I will discuss why I think most people deny evolution (it’s not what most people say, what people say and really think are often entirely different things), and why that denial is something we need to get past.

Cancer is an inescapable fact of life. All of us with either die from it or know someone who will. Cancer is so prevalent because it isn’t a disease in the way a flu or a cold is. No outside force or germ is needed to cause cancer (although it can). It arises from the very way we are put together.  Most of the genes that are needed for multicellular life have been found to be associated with cancer. Cancer is a result of our natural genetic machinery that has been built up over billions of years breaking down over time.

Cancer is not only a result of evolutionary processes, cancer itself follows evolutionary theory as it grows. The immune system places a selective pressure on cancer cells, keeping it in check until the cancer evolves a way to avoid it and surpass it in a process known as immunoediting. Cancers face selective pressures in the microenvironments in which they grow. Due to the fast growth of cancer cells, they suck up oxygen in the tissues, causing wildly fluctuating oxygen levels as the body tries to get oxygen to the tissues. This sort of situation is bad for normal tissues and so it is for cancer, at least until they evolve and adapt. At some point, some cancer cells will develop the ability to use what is called aerobic glycolysis to make the ATP we use for energy. Ordinarily, our cells only use glycolysis when they run out of oxygen because aerobic respiration (aka oxidative phosphorylation) is far more efficient. Cancer cells, on the other hand, learn to use glycolysis all the time, even in the presence of abundant oxygen. They may not grow as quickly when there is plenty of oxygen, but they are far better than normal cells at hypoxic, or low oxygen, conditions, which they create by virtue of their metabolism. Moreover, they are better at taking up nutrients because many of the metabolic pathways for aerobic respiration also influence nutrient uptake, so shifting those pathways to nutrient uptake rather than metabolism ensures cancer cells get first pick of any nutrients in the area. The Warburg Effect, as this is called, works by selective pressures hindering those cells that can’t do so and favoring those that can. Because cancer cells have loose genetic controls and they are constantly dividing, the cancer population can evolve, whereas the normal cells cannot.

Evolutionary theory can also be used to track cancer as it metastasizes. If a person has several tumors, it is possible to take biopsies of each one and use standard cladistic programs that are normally used to determine evolutionary relationships between organisms to find which tumor is the original tumor. If the original tumor is not one of those biopsied, it will tell you where the cancer originated within the body. You can thus track the progression of cancer throughout a person’s body. Expanding on this, one can even track the effect of cancer through its effects on how organisms interact within ecosystems, creating its own evolutionary stamp on the environment as its effects radiate throughout the ecosystem.

I’ve talked about cancer at decent length (although I could easily go one for many more pages) because it is less well publicly known than some of the other ways that evolutionary theory helps us out in medicine. The increasing resistance of bacteria and viruses to antibiotics is well known. Antibiotic resistance follows standard evolutionary processes, with the result that antibiotic resistant bacteria are expected to kill 10 million people a year by 2050.  People have to get a new flu shot every year because the flu viruses are legion and they evolve rapidly to bypass old vaccinations.  If we are to accurately predict how the viruses may adapt and properly prepare vaccines for the coming year, evolutionary theory must be taken into account. Without it, the vaccines are much less likely to be effective. Evolutionary studies have pointed out important changes in the Ebola virus and how those changes are affecting its lethality, which will need to be taken into account for effective treatments. Tracking the origins of viruses, like the avian flu or swine flu, gives us information that will be useful in combating them or even stopping them at their source before they become a problem.

Another place that evolutionary theory comes into play is genetically modified organisms. I won’t get into the arguments about whether or not they are safe to eat, other than to say that there is very little evidence to indicate GMO food is any more dangerous than normal food (i.e., yes, there are certain dangers, but nothing that you won’t find in regular, non-GMO food). There are two things about GMOs that I do want to discuss here. First is the belief that GMOs are somehow altogether different from natural organisms. In truth, DNA is swapped between unrelated organisms all the time. Horizontal gene transfer, such as this DNA swapping is known, has been well known in bacteria for over a hundred years. In the past few decades, it has also been found throughout the plant kingdom and even (what people like to call) higher order animals. It has been estimated that as much as 8% of human DNA comes originally from viruses that made their way into our cells, some of which allowed the evolution of the placenta. We even have bacterial DNA in us.

(a) Red aphids get their color from red carotenoid pigment. Genes necessary to make this pigment are present in certain fungi. Scientists speculate that aphids acquired these genes through HGT after consuming fungi for food. If genes for making carotenoids are inactivated by mutation, the aphids revert back to (b) their green color. Source: Boundless. “Horizontal Gene Transfer.” Boundless Biology. Boundless, 02 Jan. 2015. Retrieved 22 Jan. 2015 from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/phylogenies-and-the-history-of-life-20/perspectives-on-the-phylogenetic-tree-135/horizontal-gene-transfer-545-11754/

(a) Red aphids get their color from red carotenoid pigment. Genes necessary to make this pigment are present in certain fungi. Scientists speculate that aphids acquired these genes through HGT after consuming fungi for food. If genes for making carotenoids are inactivated by mutation, the aphids revert back to (b) their green color.
http://www.boundless.com/biology/textbooks/boundless-biology-textbook/phylogenies-and-the-history-of-life-20/perspectives-on-the-phylogenetic-tree-135/horizontal-gene-transfer-545-11754/

GMOs also may have an effect on natural ecosystems. They can and do occasionally escape into the wild. Genes from the GMO oilseed rape plant that provide herbicide resistance has spread into wild mustard plants. These plants have spread quite far. Herbicide resistant weeds are springing up all over the world, to the detriment of our farmers and food supply. What was once only a concern for agriculturists is now a concern for anyone concerned about conservation of natural ecosystems. How much of an effect? Unless you understand how evolutionary changes can spread through an ecosystem and what ramifications that may have, you are simply guessing, which is of no use to anyone. People often think of this as a genetics problem or an ecology problem, but this is the effects of evolution at the ecosystem level.

The problems we see in GMOs are not really related to the fact that they are GMO, as evidenced by the natural horizontal gene transfer we see. We see similar problems with no GMOs involved. Pests becoming resistant to pesticides after generations (of the pest) of exposure  is a common issue farmers need to address. Weeds will become resistant to herbicides on their own, with no help from GMOs needed. Evolutionary theory will help deal with this problem, guiding us to solutions we may never have reached otherwise.

Another highly controversial topic these days is climate change. Whether we caused it or not is really beside the point and is not a topic we will discuss here. It is undeniable by a quick glance at the evidence that the earth is getting warmer. We will have to deal with it, and so will every other living thing on the planet. Organisms respond to climate change in one of three ways: adapt, move, or die. There are numerous accounts of animals and plants shifting ranges in response to climate change. This is most easily seen in highly mobile organisms. Plants are not generally considered mobile, but pollen and many seeds have huge dispersal potential, so some plants can spread surprisingly quickly. The difference in dispersal ability is a big factor in how the plant communities adapt to climate change. This is not biological evolution in the strict sense of the word. However, over time, these shifts will cause evolutionary change as the population spatial patterns are disrupted.

Unfortunately for many animals and plants, humans have so sliced up the land that mobility is limited (for others, it is greatly expanded, but that is chiefly for things we don’t want to expand, like fire ants or zebra mussels and numerous other invasive species).  For these organisms, they have the options of adapt or die. Obviously, this isn’t a conscious choice they make, but conscious or not, these are the options available to them. For these, if we want to know how they will respond to climate change, we need to know their evolutionary potential, what is their ability to adapt and how fast can they adapt. This will depend (assuming similar selective pressures based on climate change) in large part on the genetic variation within the species, their generation rate (the shorter the time between birth and reproduction, the faster evolution can function), and population size. As a result, their conservation depends on our understanding of their evolutionary potential.

Not a good candidate for evolutionary adaptation to climate change. http://inhabitat.com/evolution-cant-keep-pace-with-climate-change/

Not a good candidate for evolutionary adaptation to climate change. http://inhabitat.com/evolution-cant-keep-pace-with-climate-change/

A critical component here is time. It can be hard to tell whether or not evolution is occurring or more simple phenotypic plasticity (the ability of an organism to respond to changes via changes in gene expression rather than actual genetic change) without substantial genetic study. If an organism has a high phenotypic plasticity, they will be able to adapt quickly. However, if it requires real evolution in the strict sense, that takes time, meaning they will be less likely to adapt in time to prevent extinction. Again, this is a question that can only be answered by proper application of evolutionary principles.

These are just a few examples of how scientists are using evolutionary theory to save lives by improving medical treatments and protect our food supply and environment. I did not provide much in the way of specific examples of these processes, as that would expand this essay far beyond comfortable reading times. However, the links throughout the essay will lead to you several specific examples. Some people may argue that these examples are all microevolution and adaptation, not true macroevolution. In truth, there is no significant difference between the two. Microevolution and adaptation are simply subsets of a larger concept, processes that cause macroevolution over longer time frames.

More importantly, the argument doesn’t matter anyway. It is not important that doctors and farmers know the evolutionary history of earth. The application of evolutionary theory is the same whether one is looking at the present or eons in the past. One can incorporate evolutionary thinking and utilize the theory without ever having to deal with things that are millions of years old, but only if one understands the theory in the first place. Evolutionary theory touches on so many aspects of our lives that if we want to be able to make good decisions on many of the most pressing issues of our time, we need to have some basic understanding of how evolution works. If we do not teach evolutionary theory to our kids, we are crippling our future doctors, farmers, conservationists, fish and game managers, coastal development planners, lawmakers,…

 

 


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