Tré LaRosaComment

Science Sundays #5 – Evolution, Explained

Tré LaRosaComment
Science Sundays #5 – Evolution, Explained

Introduction

Evolution is one of my favorite topics in all of science. First and foremost, it’s just simply fascinating. Secondly, it’s one of the most researched topics in all of scientific history. Thirdly, and probably most importantly, it’s one of the best ways to demonstrate the power of induction, deduction, scientific reasoning, and science writ large. 

The terms “evolution” and “natural selection” are incorrectly used as synonyms. Evolution is the broader term to explain what happens due to natural selection. Personally, I also think natural selection is a somewhat misleading term because it implies that nature is actively selecting, when in reality, there is no end goal, and therefore, nothing to select towards. So, evolution is the general term I’ll use from here on out.

It’s unfortunate, but evolution, like some of my other pieces so far, has also been politicized. That’s part of the reason I’ve selected the topics I have so far, because I want to establish that these issues have relatively simple and well-documented underpinnings. If I’ve written about a topic that you may not have believed in beforehand, I hope that you can put in the effort to investigate for yourself, and I truly hope that you come out either seeing that the evidence is there, or for your own sake, can logically continue to believe in your own beliefs. This doesn’t have to be confrontational, but talking about scientific issues can get me worked up which can sometimes be misconstrued as confrontational or aggressive. I think we need to do our best to confront our own cognitive biases, and that may entail changing our own views. Part of being a scientist means taking a step back, recognizing our flawed thinking, re-evaluating, and changing our viewpoints as necessary. This makes us smarter, better, and more open-minded people.

I think this piece could be a bit more controversial than the last couple pieces due to the point I’m going to make in regards to religion. For the last couple of centuries, the most prominent resistors to acknowledging the science of evolution have been evangelicals and religious radicals. This has persisted into our culture for a long time. A sort of hero in academic circles, John T. Scopes of the famous Scopes Monkey Trial, is a fellow graduate of mine from the University of Kentucky. The basis of the trial was that, at the time, it was illegal to teach evolution in state-funded schools, even though evolution was already commonly accepted by scientists. He may have inadvertently broken the law, but he lost anyhow, and then the verdict was overturned on a technicality. The case itself wasn’t as big of a deal, as what it foreshadowed: the growing chasm between religion and science.

Something I’m fascinated with is the way religion affects our minds and the way we interact with others, but the truth is this: we are country founded on religious independence and tolerance. This means our country has no recognized national religion. While people of different religions have been mistreated here for centuries, it is of utmost importance that we never allow religious ideology to dictate how we run our public institutions, and schools may just be the most important to keep separate. In this way, we must continue to only teach the science behind evolution, and it is not necessary to teach competing theories like creationism, in public schools. 


Now that that’s off my chest, (drum roll please), it’s time for… some science, babyyyy.

Quick note: Since I don’t want to write these pieces with the assumption that you, the reader, have read every single piece of the project beforehand, it’s possible I’ll repeat asides and little personal points. I recognize that, if these pieces are read in succession, I’ll probably sound like a broken record, but I think for clarity’s sake, it’s necessary to repeat some things.

Quick note #2: With these pieces, I don’t intend to give somebody a dissertation’s worth of material to understand. If I were to do that, I would be forced to include sophisticated information that would reduce the understanding of the material. I think it would only clutter up my descriptions because it would require me to explain things that I think are more advanced than necessary. For this reason, I reserve the right to edit quotes from sources for clarity. Since I link to everything that I’m citing, if you’re interested in learning more about the material, I very much you encourage to explore my references! I would also love to chat with anybody interested in discussing these topics in more depth. So reach out to me!

The Science

Descent with Modification

Directly from Berkeley:

Biological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene… frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations). Evolution helps us to understand the history of life.

I think the central tenet of evolution is the hardest concept to grasp: all life on earth shares a common ancestor. As the definition above describes, evolution is not just change over time, it is descent with modification over long periods of time. What this means is that, over many generations (we’re talking hundreds of thousands of years in most cases), species change into something entirely new due to different gene frequencies over each subsequent generation. It’s due to these changing gene frequencies that such spectacular diversity is possible. 

People often mistake this as meaning that over the course of one generation, species become something entirely different. That isn’t the case at all. This takes lots and lots of time.

Evolutionary theory can encompass some elevated complicated formalisms, called phylogenies. An example of a phylogeny is shown below, showing species most closely related to humans. Since gorillas, humans, chimpanzees, and bonobos are all extant – meaning currently still in existence – it is not possible that any of these species ever evolved from one another. 

 (courtesy of  Berkeley )

(courtesy of Berkeley)

Regarding humans, people often incorrectly think that humans evolved from chimps. This is untrue. The forks in the phylogeny represent what are called “speciation events,” which is when there is a divergence in ancestors. The farther down the phylogeny shows the farther in the past. So based on the phylogeny above, chimps and bonobos share a more recent ancestor than humans and chimps. Based on this, humans are more closely related to chimps and bonobos than gorillas. 

Developing phylogenies is intricate work, involving statistics, algorithms and a ton more. If you click on that link, you can see just how intensive it is. I understand that this is sort of risky to say in science, but when it comes to trusting science, there is a teensy tiny bit of faith involved. To some degree, we have to trust that there are enough checkpoints before something becomes commonly accepted. That doesn’t mean we assume everything is true, but when talking about a broad-reaching topic like evolution, me taking the time to learn and then explain something niche like computational phylogenetics doesn’t seem to be a very smart use of time.

Mechanisms of Change

The mechanisms of change described by Berkeley are below:

  1. Mutation

  2. Migration

  3. Genetic drift

  4. Natural selection

Each of these topics have entire chapter’s worth of information in evolution classes. The important thing to understand is that all of these mechanisms change the frequencies of genes in a population, which leads to certain individuals to have a better chance of survival and reproduction. It then makes logical sense that the genes of the individuals that survive longer and reproduce more would persist for more generations. This is why species evolve: as frequencies of genes change, the species then change into something different. 

Not getting into the deeper minutiae of these issues hurts me as a scientist, but my writing integrity is winning by pushing me to try to be as concise and clear as possible. 

I personally believe evolution is difficult to understand because we can’t comprehend time scales longer than our lifetimes. Trying to understand how speciation can occur of millennia would require us to be able to fathom how long a millennium is. Our children look like us so the idea that hundreds of generations of our children into the future will likely not look anything like us and may be a totally different species is difficult, and quite honestly creepy, to imagine. 

Here’s a personal note that makes evolution interesting: cystic fibrosis is a result of a mutation in the CFTR gene. But the interesting thing about mutant CFTR is that it’s estimated to be about 52,000 years old. For people that carry even a single copy of a mutant CFTR are immune to typhoid fever and cholera; this is known as selective advantage. It’s possible that the reason mutated CFTR has persisted for so long is exactly because of that selective advantage; this would also possibly explain why it’s so much more common in Caucasian people. It’s probable that people that inherited two copies of mutant CFTR died before birth or shortly after, but carriers had a selective advantage that protected them against diseases that caused diarrhea. Over the course of time, mutant CFTR became more common in places where there were more diseases that mutant CFTR protected against. 

My Rundown of Evolution

It’s difficult to fathom the implications that every living thing on earth evolved from a common ancestor. It’s also a topic that requires us to try to think abstractly about something that seems like it should be concrete, and it also requires us to enter into some existential and philosophical territory. We’re forced to wonder about the existence of living things and where we came from; it all carriers a sort of religious level of thinking. I think when we start thinking about the existence of life, it also causes us to speculate on life itself and why we’re all here. Or maybe this is all just in my mind and I view science as poetry.


Anyhow, we typically think of evolution as “survival of the fittest,” which, is generally a pretty decent way of looking at it. When you think of “wild” populations of animals – as in not humans, not animals in captivity, and not domesticated animals – it makes sense that the strongest, or most appealing, or most “fit” individual in those particular conditions would succeed in surviving and reproducing. So, when you consider that genes are the cause behind those physical attributes, then that makes sense, based on inheritance, that those genes would be the ones that are passed on. For a specific example, there used to be different competing theories of how giraffes got their long necks. One theory was that giraffes would stretch their necks constantly, eventually lengthening them, and then their offspring would inherit that. However, that isn’t how genes or evolution work. Instead, the giraffe’s ancestor (that link shows what their ancestor was) had a shorter neck, but due to random mutations, different individuals were born with longer necks, which led to a competitive advantage; these individuals ate more, survived longer, and produced more offspring, basically filling the gene pool up with more of their genes. Over generations, eventually those genes became the norm, which led to a new species: the giraffe. (Two individuals are considered to be of the same species if they have the potential to interbreed in nature.)

Most simply: individuals don’t evolve, populations do.

Evolution is tough. It’s fascinating and I’m sure there are great explainers on YouTube and elsewhere on the internet. I hope this is a decent, clear explainer.

Misconceptions about Evolution

There are countless misconceptions about evolution. Naturally, that makes sense since it’s a topic that begs for controversy by touching on the origins of life and also by encompassing so many different aspects of biology.

Delving into the broad range of misconceptions of evolution is difficult, but I think the most pervasive of them all is that religion and evolution are incompatible. I don’t think there is any good for me to tell anybody that their religion and evolution are incompatible. I will say that I don’t think science and religion have to be incompatible, and there are plenty of people that reconcile their faith in religion with their beliefs in science.

This article about evolution and religion is very interesting: 5 Facts about Evolution and Religion.

(Also, for the record, Pope Francis does not believe evolution and Catholicism are incompatible, for you Catholics out there.)

In Conclusion

I consider the amount of Americans that don’t “believe” in evolution to be an alarming indictment of the way we treat science, politics, and religion in America. I explained last week that climate change is accepted by the vast majority of scientists; evolution is even more accepted in the scientific community. “While 98% of scientists connected to the American Association for the Advancement of Science say they believe humans evolved over time, only two-thirds (66%) of Americans overall perceive that scientists generally agree about evolution.” 

Evolution has an immense amount of evidence on its side. It’s a relatively complicated topic that overlaps genetics, population dynamics, and several other subsets of biology, but when you consider the overall idea, it isn’t that complicated. To sum up: there are genes that increase the chances that an individual will survive and reproduce, these genes are then inherited by the offspring continuing that increased chance of survival and reproduction, and then over a long period of time, enough of these gene differences give rise to different species.

Table of Contents

  1. My New Project: Science Sundays

  2. Science Sundays #1 – Vaccines

  3. Science Sundays #2 – Caffeine and Its Effects on The Body

  4. Science Sundays #3 – Genetically Modified Organisms (GMOs)

  5. Science Sundays #4 – Global Warming, Climate Change, or the Unnatural Heating of the Earth’s Climate Due to Human Activity & Negligence

  6. Science Sundays #5 – Evolution, Explained

  7. Science Sundays #6 – Tropical Cyclones: Hurricanes & Typhoons

TL