Final Reflection

     I don't think overall my perspective of evolution has changed from this class, but most certainly my understanding of the mechanisms of evolution have grown considerably. Especially in understanding those mechanisms in an empirical and mathematical way e.g. how different starting frequencies affect fixation of alleles, visualizing mutation-selection balance, looking at genetic drift over generations, etc. Although I never saw evolution as an aimed track of nature, I now more better see how statistical probabilities play into how evolution unfolds. Sexual selection has been especially influential in helping see this more accidental, purely competitive side of evolution. I've grown into that idea that evolution serves to benefit individual after individual, not necessarily populations and definitely not necessarily communities. I still do not discount mutualism in nature, however. Even if evolution generally is a very selfish process, I still think there is an integrity in the way natural systems evolve together and generate a mostly self-sustaining balance.

    Most importantly from this course I have bettered my skill of data pondering and interpreting. In the past data has felt at times esoteric or otherwise confusing but working with R and seeing "raw" data that we then processed ourselves to generate communicative models...this helped develop the ability to see data as numerical realizations of hypotheses rather than just numbers collected. I've gotten a better sense at taking a question and brainstorming what data is needed to provide support/critique of that question. As a future wildlife biologist I feel that I can much more confidently walk out into a natural community and go through the process of developing answerable, mathematical hypotheses and addressing them accordingly. I do however need to learn how to not overthink data that I'm confronted with interpreting: in many of my self-assessments this was a common theme. I think this could be helped by seeking to fully understand the study before trying to understand the data, which I often neglected to do because of rushing through assignments. With R, I feel like I've just begun to understand it and to continue growing that skill I need to be more resourceful and practice varying tasks.

    I started off my blogs by giving a scientific and poetic definition to evolution, which I now would like to revise. With the technical side of the coin, I now see that evolution is more about the change of genetics of populations over generations through the survival and reproductive success of well-adapted individuals, rather than just species changing to fill the space of available niches (though I certainly would say this plays an important role, still). Poetically, I still see evolution as "Life" seeking to express itself in as many ways as possible, but within that ideology I'd like to add the notion of chance success and capitalizing upon it, rather than natural communities "working together" to develop that sustainable web of interconnectedness. I still think the beauty of that interconnectedness is a beautiful ~chance~ result of all those lucky breaks, of course. 

Speed of Speciation

     I'd like to start this out by saying that I think defining a speed at which speciation can occur may inevitably be futile. Not just in the fact that it most certainly depends on the context of each genus/ancestral species in question, but also in that our defining of species is arbitrary even in our most specific of definitions. Because, as always, nature doesn't give a flying hoot about what is a species and what isn't. But of course, our conceptualizations of species is important in the way that we as humans steward and manage populations and communities of organisms, so while it may be arbitrary it certainly can serve a pragmatic use.

   Anyways, this discussion on speciation speed will be something of a paper review, A paper by Hendry, Nosil, and Rieseberg from 2007 did a review seeking to understand an ecological perspective of evolution involving both contemporary evolution and ecological speciation. Most importantly, I think, they examine how adaptive divergence causes reproductive isolation (their definition of ecological evolution); this being a cornerstone to understanding species in a most objective way possible. An important note is that this study doesn't consider reproductive isolation to be zero gene flow between two populations but rather a significant reduction in gene flow. Just as a comment, I think this is very important because it goes back to how we as humans can't seem to solidly define reproductive isolation, at least most of the time.

    They first note how speciation seems to occur very first when their is a single locus or group of pleiotropic loci determining mating between individuals: a so called "magic trait." In these cases ecological separation can occur within well less than 100 generations. Dispersal rates of populations also seems to play a potentially important role: new populations colonizing new habitats are likely to experience bursts of adaptation. Selection against migrants in these newly colonized environment is also important as it significantly reduces inter-population gene flow.

    The next major thing looked at is mate choice. Disruptive selection can encourage assortative mating which can lead to reproductive isolation within a couple hundred generations. Likewise, adaptive speciation, where competition for limited resources forces evolutionary branching, can cause a similar mechanism of reproductive isolation. Reinforcement, where two divergent populations come into secondary contact, can also rapidly evolve mating preference to avoid maladaptive assortment of mating. Hybrids are looked at in this paper, although it seems that at the time the way they interacted with gene flow wasn't very well documented and didn't prove useful to this paper's goal, as the results don't seem very conclusive.  They do mention how hybrid species can quickly become reproductively isolated when they colonize new habitats and quickly adapt to it.

    Plants, especially, seem to have an immense capacity for speciation through dispersal of hybrids. A certain species of sunflower, Helianthus anomalus, based on genomic evidence, seems to have evolved within about 60 generations. Invertebrates, specifically insects, may also have a quick divergence due to hybrids as shown by a fly species, Rhagoletis sp. The authors claim that reproductive isolation may be almost immediate when a hybridization introduces a phenotype that automatically separates potential mates. In a certain species of salmon, Oncorhynchus nerka, after only 14 generations significantly reduced gene flow had occurred between two locally adapted populations.

    So, all in all, it seems that the rate of speciation can be quite rapid in the grand-scale of things, especially at a more microlevel and with certain softened qualifications for reproductive isolation. At the very least, within 100 or so generations seems to be somewhat of an "average" consistent across all the examples looked at in this review. I think it's also worth noting, that once reproductive isolation occurs (after 100 generations or what have you), then a more "recognizable" speciation is apt to take place as new selective pressures and lack of gene flow create ideal conditions to reproductively diverged populations to adapt and evolve different characteristics.

Resource:

(Hendry, Nosil, and Rieseberg, 2007): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2605086/

Antibiotics vs Disinfectants

 I personally think that antibiotics are an interesting case study of both modern ingenuity and, alternatively, hubris. Antibiotics are highly specific in the way that they kill bacteria, which is both their glory and their downfall. This specificity makes them very effective in deactivating whatever metabolic pathway they target but also places a selective pressure on the bacteria that allows them to quickly evolve a resistance. Thus, while antibiotics can be very effective in curing bacterial ailments, the medical community must be very careful about the prescription of antibiotics to patients to prevent the potential evolution and spread of hyper-resistant strains.

Disinfectants, on the other hand, do not pose this same threat. Heat, alcohol, ultraviolet light... these things do not target specific metabolic pathways that bacteria can evolve around. They produce environments that are highly intolerable to the bacteria to the point where they are simply obliterated, rather than just biochemically interfered with. This is extremely useful in the medical world for keeping pathogen exposure as minimal as possible without generating selective pressures on bacteria that allow for them to become something like MRSA, which is a considerable threat. A drawback to these things is that they are not so easily implemented upon the human body: you can't apply hundreds of degrees of heat to a human to rid them of bacterial infection nor use highly concentrated alcohol (although, has anyone with strep throat tried day-drinking absinthe?).

Hopefully we are able to find a way to use disinfectant-like techniques to internally fight bacterial infections so that antibiotic usage doesn't eventually create a superpowered bacteria monster that wipes out Western civilization! Marvel supervillain idea, maybe?

Mental Disorders as Diseases of Civilization

 For this blog post, I will be discussing how depression and anxiety are diseases of civilization.

In this modern day world, we live with a lot of stress. Our jobs, school, toxic family dynamics, social expectations, and so much more can all bring potentially daily stress-triggering moments. We evolved our stress response as wild animals, not civilized individuals; our stress response is meant to be activated, save us from danger, and end until needed the next time the mammoth you were trying to kill turns tries to stomp on you. With the advent of modern civilization, we began to be exposed to stressors that were drawn out in ways very contrary to how this biological stress-response system wishes to operate. 

The result of this? You name it. To my understanding, stress is linked to a myriad of problems: heart disease, IBS, hypertension, and what I will focusing on, depression and anxiety. 

Because of our disconnect from our evolutionary past, us moderners are deprived of the kind of exercise that keeps our bodies and brain stimulated, cut off from the diets that built our species, and exposed to exacerbated social pressures (in the workplace, and especially on social media). Miller and Raison (2016) point out a connection between stress-induced inflammation and molecular patterns from the gut microbiome with anxiety and depression. They also mention that depression is a sort of convalescent evolutionary response to fighting pathogens, and whether this is true or not, it certainly is an interesting idea to ponder. In our more sanitary and high-stress modern world, does that mean that depression is a self-defense mechanism of the body against pressures of civilized life? The long-term stress exposure that we experience can disrupt our sleep, damage our brains, and disrupt our immune systems, so potentially that makes depression our body trying to escape from stress and force ourselves to convalesce. 

Stephen Ilardi, a doctor of clinical psychology, recommends rewilding your life style as much as possible to try and combat the tension between the modern lifestyle and your brains ability to deal with stress. These include exercising (like walking and hiking), getting healthy sleep, sunlight, and social connection. 

I think by now because of self-wellness trends and such, we all know quite a bit of this information. However, I think this delve into depression from an evolutionary perspective rather than from a purely chance disease one is very helpful in thinking about how to reflect upon the way that the way we think we're "supposed" to live nowadays may hinder our wellbeing. 

Resources:

https://www.filmsforaction.org/articles/depression-is-a-disease-of-civilization-huntergatherers-hold-the-key-to-the-cure-return-to-now/

https://www.psychotherapynetworker.org/blog/details/456/anxiety-a-modern-phenomenon

https://www.nature.com/articles/nri.2015.5