HBV 1

Mutation is a change in the structure of DNA that creates genetic variation. It can be passed on and may be neutral, harmful, or beneficial. An example is the Milano mutation, which reduces the risk of cardiovascular disease. Gene flow is the transfer of genetic material between populations, often through migration. It increases variability in the receiving population. An example is the interbreeding of early humans with Neanderthals, which contributed beneficial traits. Genetic drift is the random change in gene frequencies due to events like natural disasters or small populations founding new colonies. It decreases genetic diversity. genetic risk, and natural selection. Starting at the top, with mutations, we're not going to get completely back into the ministry of, you know, how DNA is replicated and has all the different types of mutations it might be. But, broadly, a mutation is basically a change in something about the structure of DNA, of a gene, that is caused by usually the alteration of single base units of the gene's DNA double helix structure. So, to remember back to our biology class that covered double helix structures, DNA is sort of like twisted wires. The neurons are made up of those base pairs paired together, and they match up, you know, adenine, cytosine, cytosine, selenium. If you get an error in the replication of those copies of those DNA strands, then you have a mutation. So, the mutation and mutation is the only source of actual new genetic variation within individuals in the population. So natural selection might act upon the results of the mutation, but mutation is the way that that different trait or, you know, really minor differentiation of the wheel comes to be. It may be passed on, thereby allowing a natural selection to act upon it, but it must occur within the right parts of the body. So, for example, a mutation that causes stem cancer melanoma, that is not going to be something that is passed on if someone has melanoma and they have a child, and that child is not going to be born with melanoma. But, if there are mutations in the gamete or in that cell within the body that are passed on, when you do, it may be passed on. Of course, the same rule still applies where all of your genes are not passed on, so it's sort of all of the sites have the likelihood of it being passed on. But, if it is passed on, it might be neutral, deleterious, or advantageous. So, that's basically the use. Neutral, bad, or good, depending upon, you know, the specific context of the patient. So, a cool example of the mutation that we see in a very specific human population. I'm going to do my best not to confuse any of these. So, this is a mutation in what is called APOA1, alpha-protein A1, and the mutation is called Milano. So, basically, this mutation is the result of a substitution for Rd5-C, and it creates a variation of lipoprotein or lipoprotein within the body that is removing plaque from the various vessels in the body. So, if you think about cholesterol, I don't know if you guys, how many of you are old enough to have ever had your cholesterol checked and told that it's positive. Raise your good cholesterol, lower your bad cholesterol. Always a little confusing, but basically, when this mutation was discovered by a researcher at the University of Milan in Milan in 1974, it was shown to reduce HDL levels and increase triglyceride levels in the blood. So, HDL is good cholesterol. Triglycerides are the bad cholesterol. So, on the surface, it seems like this mutation should be a bad thing based off of just the levels themselves, but the researchers that discovered this were actually able to prove that the levels being sort of different than what you would expect is the result of this mutation, and it's actually the cause. It is removing that plaque, that, you know, blockage and stuff from the vessels within the body, and thereby the blood levels might be just higher, but in fact, the mutation reduces the actual risk of cardiovascular disease in individuals that have this mutation. So, it is a mutation that's present in 2.5% of the population of New Romanesco, Giardia, a small village that is located in northern Italy, again, an example of why it was discovered by researchers at Milan. And it can actually be traced back to a single individual, Giovanni Romarelli, who was born in that village in 1780. Giovanni Romarelli. So, it has been perpetuated since then, it was identified in the 70s, and we're able to sort of track its expression back through a pedigree card or, you know, the family tree to figure out where it originally is. So, two mutations that we see in the population. And certainly, just more in the community. All right. So, we talked about mutation, now we're going to talk about gene flow. Gene flow is sometimes equated with migration, because most instances of gene flow are migration, but not all migration is gene flow. And I'll explain why. So, for gene flow to occur, you need to have two populations. So, it's the flowing of genetic materials from one population into another. So, they need to fit as two big populations. And migration into places where, for example, if you think about human migration, migrating into North America and South America, when that first happened, there were no other humans in North and South America, and so that was not gene flow, that was migration on its own. Now, when you've got a population moving into places where there were already dead humans established, and having their genetic materials in that overall constructed pool, that is very beneficial. So, when this happens, usually, although not always, it changes the overall composition of the gene pool of the secondary population that results from this flowing. And it's especially noticeable in smaller populations, because it's magnified. For instance, if you have a very, very large population, and you can think about the population size diluting, your fraction should be 12, and then you add two new people to a population of 10,000, you're not going to see really a significant change, you won't see any sort of change at all. But, if you add two new people to a population of five, that is going to make, perhaps, a very significant difference. So, what this means is, usually when gene flow is happening, it increases the variability within that seeding population, and decreases the variability within the parent population population. An example of gene flow is an event that occurred within human history. Every single person alive today with European ancestry, many parts of Asia ancestry as well, but some could either have DNA. Because modern beings, anatomically modern humans, evolved in Africa and then spread out. They moved out, and when they arrived in the range in which Neanderthals were living, they interbred with Neanderthals, for example, even though they are already two different species. And, Neanderthals have been shown to have contributed several key characteristics. There's still some debate as to whether some things that we can trace back to Neanderthals are good or bad, but with certainty, we know that when our early modern arrived in northern Europe, there were a number of species already present and endemic in that area that we were not resistant to. So, the addition of that Neanderthal DNA and community and genetic predisposition to the species that already existed in those Neanderthals, who had been there for thousands of years, was a beneficial influence to support community and ultimate survival of largely the human modern population within those same areas. We also know that Neanderthals had pre-cultivated. Many of them had red hair, which is not what we've seen since discovery, but we know most predictions of them are really not red hair, but they have a very high percentage of the gene that causes red hair. So, they contributed a couple of more rapid spread and variations in terms of light skin versus dark skin. So, when those early modern species moved out of Africa, moved away from the equator, and moved into more northern areas, having lighter skin was beneficial for vitamin C absorption, and there was no longer darker skin protected from UV radiation. We'll be talking about that in the next few minutes or weeks when we reevaluate if we want to work. But basically, that was a benefit. It helped vitamin C absorption was a necessary function for our early modern ancestors. Probably, thanks to Neanderthals, there is a greater predisposition to certain allergies, and there's a number of complex factors. It's a very different type of allergy, but, again. Now, the question about a possible influence on the predisposition or likelihood of having diabetes is something that is still debated and somewhat unclear, but these are all things that are related and can be directly traced back and be influenced by the G-12 that occurred when our modern ancestors flowed out and interbred with Neanderthals. Now, Neanderthals obviously look at the weight, so we can't really look at 0.1 or 0.2. I would change that for you guys. So, a very interesting example. This is the link that has much greater detail about all these Neanderthal things that probably are present in the human population because of that influence of Neanderthals, which most of the European populations have 2%. Some Asian and Southeast Asian populations have as much as, what, 4 or 5% of Neanderthals and then there's a combination of the genetic solvent gene as well. All right. Genetic drift is our next source of evolution. So, basically, genetic drift is drifting away from the original. I was trying to come up with the best way to help you remember G-12 versus genetic drift and every year I revisit it and try to come up with a better way. But, we can think about genetic drift in particular in relation to these very specific criteria for situations that are types of genetic drift. So, bottleneck effect. You basically want something like a natural disaster, wipe out a lot of the population and then you have a much smaller remnant population, which is, it might be fully representative of the original larger parent population, but usually it's not. So, this is usually due to random chance, a random event of some kind. Generally, predict how genetic drift is going to occur with, like, a bottleneck effect with a natural disaster. If you talk about the disaster effect, where a small group is sort of raced away from the original history, usually where they have small population leaves and found a new colony or something like that. It's very common on islands. It's human population on islands or in really isolated areas. But, if you're supposed to reduce genetic variation from the larger population, you can think of it as sort of, you know, it's always going to be a little different. But, with so much genetic diversity, especially when that founding population is not representative of the entire population, but even if it is, over time, you're going to have other things that are going to alter the genetic structure and enjoyment of the population, I would say. And then we have natural selection, which is certainly the one that really equates to evolution. When we say evolution, we think of Darwin, and we think of evolution by means of natural selection, which was one of the most famous public agents. Now, these are not identical, obviously, but natural selection is certainly the most significant evolutionary force at play. It is the force that results in education, i.e. the emergence of a limbic tissue. So, when we get to the side of genetic representation, usually natural selection is not going to serve as an actual influence upon the changes that result from those sources, and that is where we are going to get a lot of that evolutionary power from natural selection. So, I know we've already talked a little bit about natural selection, but the logic underpinning natural selection, now, natural selection does not act in a totally logical way that makes sense to us. It is a force driven by nature and policy in which man and his own social issues live. But, within natural selection, there are components that there is some biological variation. If every single individual were identical, then natural selection is not going to act because there's going to be no sort of ranking in terms of population, age, trade card, and so on. All organisms can produce more offspring than the resources of the environment can support. So, it is possible for populations to outstrip the resources, the food, the space available, things like that, whereby there is going to be some sort of competition for survival, competition for resources. Within that, individuals with charitable traits, so remember these traits have to be passed on, because an asymptotic trait that is not charitable or not passed on will not ultimately be acted upon by natural selection, that are best suited to acquire resources, lead to those individuals getting the resources, and reproducing successfully, passing on those genes, and creating more offspring that carry that as an agent of the trait. So, because of that, it's very context dependent. When Darwin, well, not when Darwin went, when the Rands, who are the other famous biologists who study the rockfish, there are a huge number of them, but they are very, very famous for studying the rockfish, which is the Darwin study. When they went in and studied the finches during the period of drought, they were able to observe that the larger-leafed finches that had sort of tougher beaks and were able to eat really dried-out feed, that was the allele that was selected for within finch populations during the period of drought, whereby by the time the drought ended, nearly every single finch individual in that area had larger beaks. Then the drought ended, and things sort of went back to the morms, where food resources were more abundant, there were many more non-tough resources available, and they were able to observe and document how beak size over multiple generations sort of oscillated back towards the cavern size, instead of being very, very strong and beaky, like, for example, this finch. So it's very much context-dependent. When the context changes, natural selection will then act in turn, and probably it will result in an evolutionary change or change in the traits that are present or most prevalent within a population. So within natural selection, you reproduce because you have survived long enough to reproduce. You pass on those seeds, and you are fit, and you have sort of won the, you know, jeopardy round of natural selection. If you don't survive, then... We can talk about natural selection in a little bit more of a drawn-to-define way. This is a vast implication of sort of how complex things can be, but if we conceptualize the types of things that are selected for within populations, we can think about directional selection, which usually means selection against one stream. So normally a population, say, in each of the rams is stable, you will see a distribution of the traits across a bell curve. So in this example, we are looking at lizard tails. So the extremes for our tailed lizards is the really long tails that look like snakes. And so selection, for example, if the long-tailed lizards aren't selected, you only have their tail eaten by predators, and the tail falls off and the lizard gets to go on living, versus the short-tailed lizards are eaten completely by predators. That is going to be an extreme that is going to be selected for through natural selection, one extreme over the other. Stabilizing selection is selection towards the middle of this bell curve, and usually it amplifies the expression of that trait in the middle, and the number of individuals that express that trait is well beyond what is seen in the norm. So away from both extremes. And then we have constructive selection, which is the opposite of the hood. So selection from both extremes against that middle. You can also talk about selection in relation to negative selection, meaning selection that sort of weeds out bad mutations that prevent them from having a negative impact on possible good characteristics of the population, versus positive selection, whereby natural selection is sort of favoring positive or additive mutations. And then, sorry, balancing selection is sort of maintaining genetic variation for longer than you would expect. So, this is only if you guys remember, we talked a lot about psychokinemia, and how it stops with autism, because that heterozygous expression where you have one allele per single cell, one allele per mole, is so advantageous, that it essentially perpetuates the existence of both of these homozygous expressions, because they are not raised. So you either have malaria or you have a single cell, but if you have a little bit of both, you are so supercharged and superpowered that those alleles persist in the population. So that's a great example of balancing selection. All right. Let's look at some more DNA samples. This is a famous phenomenon, a real thing. I tried to find many photos, pictures of this family, and all I could find was this chafing of them, because they were really isolated in this really small sample action. This video is pretty good at indicating all of these things. So they have a mutation in the methemoglobinemia, so that's HG, which basically means that there's something different in terms of the ions in their blood that produces the oxygenation capabilities of their blood. Now, Marsha and Elizabeth, a few dates, only a few dates, have this mutation, and so this is a great example of balancing that. Now, there was also another nearby group that had this mutation as well. Part of this is, you know, which I'm not sure if it's in the documentation, because I was super concerned with the details of who the variant 2 was in the population, because people thought it was homozygous, but it wasn't. Having this mutation that expresses itself as blue skin was not really selective against, because it didn't really have enough of an impact on how soon these individuals died. There were still antigens we could use before it became problematic enough or before it contributed to the death that it would have done. So it didn't really have an effect on selective pressures within this group. And between these two isolated clans that both have this mutation increases the frequency of the trait within both populations. The population was drifting away from sort of the original form of all the other selection. So this is a great example of contact annuity or inbreeding, which we have known for a very long time, and it's not a good thing. Obviously, artificial selection, raising of livestock, and less human animals has proven that to be true. It's also been proven in a number of humans, and Darwin himself knew that this probably wasn't a good idea, even though he married it off for his cousin. He talked about it in one of his writings that he was concerned about and talked to him in the back of his very small group. And so we see, predictably, a number of things, like overall reduced fertility levels, so reduction in birth rates, how many offspring individuals are able to have enough support for the lifetime to maximize life span, higher interest in child mortality, so children become less likely to survive in this way, reductions in immune function, immune response to all the other diseases that you might be exposed to or the risk of, and things like increased risk of cardiovascular disease, and, of course, genetic disorders. So the royal families of anywhere are really prime examples of this. This would be Spanish Hatsfords, many of which the Hatsfords, at one point, were sort of the equivalent of what I think those in Victoria have now, in terms of our more modern chronology or family history of European royalties. But the Hatsfords were, at one point, a very robust and prominent family. So by the time you get down to your very first cousins and uncles and nieces and multiple uncles and nieces and second cousins and more first cousins, you get the last Hatsford, all of the second are the same. And he had what we call the Hatsford gene, which is sort of this gene that doesn't really articulate directly with the Maxwell upper key, so it sort of has really big ponder bites to the point where, you know, he was one of the first documentarians that were living in a coffee shop and talked about how he was an evil robot and was hard to see incorrectly. He had a huge number of genetic issues, and he didn't live with people. So people have Hatsfords somehow. The Hatsfords are a great example of the folly of this identity issue or inbreeding issue in royalties. Of course, we can think about Queen Victoria and the presence of hemophilia in her children and grandchildren and all the problems that that causes with the European Revolution, but there's just a multitude of examples to look at, so it's really not anything new. We've talked about some specific examples in the population, but in a broader sense, what does this have to do with homo sapiens and the evolution of homo sapiens. So we know that evolutionary forces have shaped modern humans for at least 200,000 years, based off of the molecular clock and our knowledge of mitochondrial DNA and the shared common ancestor in Africa at least 200,000 years ago. It's very likely that it's more than 200,000 years, possibly 500,000 years if you think about the continued gene flow that existed between the archaic species outside of Africa, heterobergensis, homoherbergensis, and certainly when we look at the connection and the evidence that we have on modern homo sapiens post-migration out of Africa. So we can think about migration of humans as sort of a fusion phenomenon, a relationship whereby migration happens, populations split apart, they divide, and then they oftentimes come together again, split apart again, and it's sort of this recurrent pattern and trend that we see happening over and over again, not exclusively, there are certainly some populations that make it over and remain pretty isolated, although we now do think that there was some Columbian influence on parts of America. But regardless, it's a very complex relationship. This is sort of another depiction. I don't know if you can see it, but this is showing how many thousands of years, so 200,000 years ago, 70,000 years ago, 65,000 years ago in Australia, around 25,000 in the New World, and so on. Again, these are just sort of ballpark ranges. They change a lot depending on the evidence that we get. But we can see the course of evolution at play throughout these myriad migrations and fusion-fusion relationships. As humans leave Africa and encounter these archaic species like Neanderthals and Bramstowans, they are, of course, contributing to the ultimate genetic genome of modern human populations, depending on which ancestors you're looking at. So that is why sub-Saharan African populations do not have a Neanderthal or Bramstowan gene because they do not migrate up and begin to change genes with archaic and sub-Saharan species. So, we can think about this as adaptive introgression, which is when this material transform species moves into the gene pool for another and is collectible. So, I've already talked about some of these when we looked at those Neanderthal traits. Some of the good things that came from the connections with Neanderthals that are archaic species, and I described Neanderthals there. Immunity, that ability to repair from sunburn. Blood clots is another one that we're going to talk about in relation to the ability for blood to coagulate. Neanderthals were perhaps more predisposed to blood clotting, but that is something that was not that great. That perhaps was exacerbated by those Neanderthal genes. So, all of this is really going back to this idea that we are not perfect. We are not the pinnacle of evolution. Everything alive today is completely evolved. Humans have just as much time to evolve as every other living species. But that gene flow that just existed, that fission-fusion relationship, is why we cannot neatly categorize genes. Why we cannot subdivide their boundaries for races, for definite ancestry groups, and why there is so much overlap. We've already talked about this, but again, it doesn't seem sometimes that fun. So, migration gene flow, it can create greater variety within the population, reduce differences between them, reduce those boundaries, or in the case of humans, really prevent those boundaries from coming to be in many categories of our genetic lineages. And so, this gene flow prevents us from continuing to evolve into a new species. We are Homo sapiens. We have been Homo sapiens for hundreds of thousands of years. We are a single-competent species. I've already talked about that. Our C-value is 57. We have actually less diversity in our entire species than might come here, in the top 200 states. But, we can measure some differences in variation within the population. For example, Africa, sub-Saharan Africa, has the most variability, and diversity decreases with distance away from Africa. So, this is where we get applying. So, applying is what we talk about when we are referring to a radiation in one or more, because oftentimes there are multiple final radiations in traits within species, and also between populations. So, usually this means the lack of well-defined boundaries. It was proposed by Julian Hochschild. But, he proposed this idea of clines within human populations. There was thereby no way to clearly separate out human populations. Unfortunately, he was an outspoken geneticist, so not the greatest contribution overall. But, this was an idea of clines. This is why we talk about symptoms. We want to have a particularly great network understanding of clines. This is how we think about, or want to think about, traits and populations. But, then, how is it related? When we think about clines, yes, there might be these discrete colors that exist within the broader range, but we can't separate them from the broader range. We have to take that into account, because in reality, it's all about radiation. It's all a matter of, usually, relation to some sort of geographic or environmental feature or factor that is resulting in this evolutionary pattern. So, in the case of skin tone, it is the equator. We can think about darker skin as being more equatorial, versus lighter skin as a whole. That has to do with, actually, from the UV ray, it's the equator versus the nature of what it would be. I know I've already discussed this on some level, but it's good to revisit, because this is, by far, the most demonstrative visual representation of clines across the entire world in human populations. We can also look at it in terms of blood typing, which is perhaps not as adaptive, but they do distribute based off of migration patterns of populations that have a higher representation of certain blood types, thereby resulting in the descendant populations having higher frequencies of certain blood types. So, this is just a visual depiction showing you why the intensity of UV radiation is so different, and how it's not very nicely responsive to that situation. There are some exceptions, which we will talk about in greater detail later. So, the assumption of grouping traits together, you know, skin tone, say, and hair texture, or skin tone and eye color, or whatever it may be, no, this sort of has to do with general development. But, we can also think about it in relation to, people want to think about variation as concordance. So, concordance variation makes the assumption that certain specific physical traits are always packaged up together. So, skin tone, eye color, the shape of your face, specific DNA markers, whatever, everything in the inheritance wants to have one of those, and you're going to have all the others as well. And that continues and endures over time from one generation to another. So, this is why we have this idea that people from a certain place should look a certain way. So, for example, all really supportive people, long hair, blue eyes, tall, you know, super model-esque, whatever it may be. This is, of course, not the case, right? People, humans, as we believe, exhibit a lot of non-concordance variation. Things like hair color, eye color, skin color, facial features, as well as general morphology and physiology, are all non-concordance in human communities. This is a diagram that shows the frequency of long hair in Indigenous Australian individuals and communities. So, typically, Indigenous Australians are thought of or conceptualized as being more transparent, being closer to the equator, but having a little darker brown hair as well. So, this distribution of long hair does map onto a natural decline as well, but doesn't necessarily map onto an identical marker of skin tone. So, this certainly goes against the preconceived assumption about the link between the intolerance of long hair in Indigenous Australians. This is lactate persistence, or lack of tolerance, showing the distribution of how many people, or how many adults, I should say, digest lactose in the Indigenous populations of various areas. So, we're not talking about a localized society where people eat adults or girls, and so plenty of people in various places, or some people in various places, will digest lactose. Similarly, this maps onto a decline. So, this is a decline that is not driven by an environmental factor like the equator and human degradation, but rather maps onto, or only maps onto, the biocultural or cultural factor of a history, or an early history, of being pastoral herders and raising domesticated animals that produce milk, and the significant selective favorable pressure that was dictated by the continued ability to digest lactose, to drink milk, and utilize milk as a food and energy resource into adulthood, not having to slaughter the animal to get the meat to get that as a food source, and to get a much longer available food resource than if you had to kill every animal. So, that served as a selective force that led to the increased frequency of the mutation for lactase-induced or lactose tolerance in these communities, where we know that historically there was an apparent frequency of pastoralism and herding practices. So, all of this is just to say that the evolutionary trajectory of humans is that there is not an end. There are a number of mutations that come into play. There are a number of mutations that come into play, and when that happens, does that result in us not being passed on to changing flow, genetic drift, genetic selection? There are a multitude of traits that have allowed us to become so successful, and so prolific in terms of our occupation of the world, occupation of all these different nations across these areas. So, the lack of speciation in humans has been disrupted by, you know, that maintenance of connection between human populations, but technology as well, as part of culture, has ameliorated or has sort of amended many of the natural selection cultures that might act upon our actual biology. So, this is why any anthropology class that's involved in this, we've been talking a lot about the concept of bioessential forces, the concept of biocultural imposition, anthropology, thinking about it in that biocultural balance. So, we'll be talking more about all of this, but we should know that when you look at that, when you refresh your memory about these different evolutionary forces, the things you can be aware of, if you didn't, you know, take advantage of some of those additional resources, those videos, you know, talk to me, whatever it may be. It's important to have a good grasp of this, it's important to have a good grasp of this basic stuff, again, to make sure that with the second half of the semester, really on to connecting onward, that we understand what we're talking about, understand where humans came from evolutionarily, and what that means and how the world can move forward. Thank you.