did you know that approximately half of Americans think that Evolution isn't really a thing public acceptance of evolution has varied a little bit over the past couple decades but it's very rarely gone over 50 percent sometimes people are okay with the notion of plants or animals or bacteria evolving but it can be really hard for many people to wrestle with the idea of humans being part of the story of evolution this is a two-part video installment of Evo Ed where we'll take a look at Evolution figure out what it is and try to understand whether it's something that really applies to humans foreign before we get to humans the first thing we need to do is to figure out what exactly evolution is and this is actually harder than it may seem all right like if we start with the dictionary definition the dictionary defines Evolution as descent with modification from pre-existing species a process by which new species or populations of living things develop from pre-existing forms through successive Generations what does that tell us a paraphrase evolution is a process that results in new species that doesn't really tell us much about the process itself though how it actually happens it just tells us that it results in new species over successive Generations a definition of evolution that you often find in textbooks is something like the change of allele frequency within a population over time this one is focused on a pattern that one might expect to find if natural selection is occurring all else being equal to explain this I could use human blood types as an example humans can have one of four blood types a b a b and O if we had enough time and the Willing participants we could actually track the number of A's B's and O's that are present in a given population over time like over Generations if for some reason there was a benefit to having a blood type associated with an a a b or an O then the frequency of that particular allele in that population would increase over time why is this related to evolution well if a new species is to arise through a process of accumulated biological changes then we would have to see new alleles emerging in a population and we will have to see those alleles increase in frequency over time but a pattern of changing allele frequency alone doesn't really tell us any of the how and it's actually a pretty limited slice of The evolutionary process evolutionary biologist Douglas fatuma once famously offered this view of evolution biological evolution is change in the properties of populations of organisms that transcend the lifetime of a single individual the change in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next biological evolution may be slight or substantial it Embraces everything from slight changes in the proportion of different alleles within a population to the successive alterations that led from the earliest proto-organisms to snails bees giraffes and dandelions in a general sense this is a pretty comprehensive view of evolution once we start to drill down though again the question of how Evolution occurs becomes a little less clear but according to futema it occurs via genetic changes that happen from one generation to the next it can be as slight as changes in allele frequencies across generations and its impact is dramatic as it's responsible for the diversity of life that we see on Earth this definition offers some Clues as to how Evolution occurs but understandably it leaves much out and of course if you want to see what a leading creationist organization has to say on the matter this is what Answers in Genesis has on their website at the time of this recording Answers in Genesis is a creationist religious organization here's what they say biological evolution is the supposed process by which the first cell evolved into the diversity of life we see today they also say evolution is a word that's used a lot but is poorly defined evolutionists themselves frequently equivocate on the term using it to mean multiple things sometimes even within the same sentence I definitely agree with some of this evolution is supposedly the process by which the first cell evolved into the diversity of life that we see today that's what fatuma said it's the process that led from the earliest proto-organism to snails bees giraffes and dandelions and I think we can agree at least at this stage that evolution is at least somewhat poorly defined it's some huge process that led to the diversity of life on Earth but how exactly it works starts to get a little bit confusing is it the change of allele frequency in populations or descent with modification or something else entirely is it just a theory let's dig in what is evolution let's clear this up evolution is both a process and a pattern that makes it sound like two different things because in a way it is two different things there's the process of evolution and there's the pattern of evolution oh and yeah it's a theory too in this video we'll look at the process of evolution and in part two we'll look at the pattern of evolution to try to simplify I'll explain the process of evolution in four steps these four steps are DNA mutation protein production and new phenotypes natural selection and then drift or other considerations so let's go through these one at a time step one DNA mutations at the micro scale Evolution must involve a genetic change at the most fundamental level you can't have a heritable biological change without a genetic change when we get to the heart of it it involves the insertion the deletion or substitution of one or more nucleotides along a stretch of DNA and not just any stretch of DNA but a coding region what we would call a gene or it could be in the control region that's related to a gene Beyond this it can involve larger scale events like whole Gene duplication or whole Gene deletion or even chromosome deletion or fusing or copying and so on these larger events especially the ones that involve the deletion of genes or chromosomal changes those are most often deleterious or disadvantageous and they're actually extremely rare compared to single nucleotide changes in any case any change in DNA that happens during the process of meiosis that's as sex cells are being generated those are heritable those changes would be passed on to subsequent Generations those changes to the DNA in effect lead to the introduction of new genetic information into a species gene pool that's right errors in copying DNA during meiosis result in the introduction of new genetic information into a population step two proteins and phenotypes now these DNA mutations are only relevant to Evolution when they result in the manufacturing of a new type of protein or if they change the amount of a particular Protein that's already being made proteins are produced from DNA by processes called transcription and translation a new type of protein can result in new biochemical processes occurring within a particular cell type new biochemical processes can result in a new phenotype a phenotype pheno means observe so phenotype is an observable characteristic once a genetic change occurs during meiosis there's a chance that there's a change in phenotype or the observable characteristics in a new individual within a population sometimes a new phenotype can emerge when a single type of mutant protein is produced from a mutant Gene other times a new phenotype is the result of several different types of mutant proteins that accumulate over many generations and we actually have many examples of this where a nucleotide change leads to a protein change which results in a new phenotype this includes things like mutation in the melanocortin-1 receptor Gene leading to a change in the melanocortin-1 receptor which then impacts the amount of hair or skin pigmentation that an individual produces or mutations in the starch branching enzyme Gene which changes the starch branching enzyme itself in pea plants that can result in more sugar production in peas or there's a gene duplication and mutation from The Medium wave sensitive opsin Gene in primates which changes the types of proteins that are expressed in cone cells in the eye which then impacts color vision or even something like a mutation in a voltage-gated sodium Channel Gene in soft shell clams that results in a sodium channel protein that's resistant to the neurotoxins often found in algal blooms this can lead to toxin accumulation in clams and result in outbreaks of paralytic shellfish poisoning but I digress step 3 natural selection one of the most important drivers of evolution is not only the appearance of a new phenotype but the appearance of a new phenotype that results in a higher reproductive output for an individual in a particular environment if a new phenotype emerges that doesn't lead to a higher reproductive output than it typically isn't part of the evolutionary process there are many ways that a new phenotype can provide this kind of Advantage these can be Behavioral or physical changes which may provide an advantage when it comes to things like resource competition or resource acquisition Predator avoidance prey capture different reproduction parameters Offspring care and so on importantly these changes must at some level lead to an increase in the number of viable Offspring we would call this Fitness step 4 Drift and other considerations there are things like founder effects and bottlenecks which are alternate processes by which a particular phenotype can become more widespread in a population founder effects occur when a limited number of individuals from a species colonize a new region then become reproductively isolated the genetic and phenotypic diversity of that population will be limited to the genetic and phenotypic diversity of the founding colonizers and if by some chance certain traits from The ancestral population are not among the founders then they wouldn't become part of the new gene pool of that new population bottlenecks occur when the size of a reproductively isolated population is dramatically reduced for example by natural events or human-induced habitat change certain traits may become lost if they're not present in the relatively small remaining remnant of the population in both of these processes founder effects and bottlenecks the gene pool and phenotypic diversity of a population changes dramatically but it's not due to natural selection or artificial selection so that's an overview of the general process of evolution DNA mutations lead to new proteins which then lead to new phenotypes that are selectively advantageous in populations or become more widespread due to things like founder effects and bottlenecks and what does this have to do with speciation I mean just because a new trait or characteristic evolves in a population doesn't all of a sudden mean that we have new species popping out all over the place what I've outlined here is the engine of The evolutionary process this engine is factual all of the things that I've outlined here actually happen so you could imagine what would happen if you have two populations of a species and those two populations are reproductively isolated they would each experience random mutations and new different traits and characteristics would emerge in each as time goes on these changes start to stack up each population is experiencing different mutations so you would expect the changes to be different in each and if the environments where the two populations live are different than the selective pressures would be different as well different traits would be advantageous over time the differences between these two populations would be so great that we would then consider them different species and that's part of the theory of evolution it's a factual process that allows us to project what would happen as this process plays out over time and you don't even need two different populations for this to occur let's say that you have a species and over time that species experiences mutations that lead to Greater reproductive output over generations and generations and centuries and Millennia all of the changes would stack up until the species that you have at the end is different than the species where you started I teach introductory biology and when I talk about Evolution it isn't uncommon for a couple of students to privately share with me that they don't really believe that Evolution occurs or perhaps that it applies to humans my response to them is this I tell them I have no problem with you believing that Evolution doesn't occur or perhaps that it doesn't apply to humans my only request is that as you learn about all the sub components of the evolutionary process do some extra investigating and figure out what part of it doesn't actually happen or doesn't apply to humans do mutations happen in human DNA can these mutations lead to new proteins do new proteins in human cells lead to new cell functions can new phenotypes emerge in humans due to these processes is natural selection or artificial selection or bottlenecks or founder effects are these processes that happen to human populations whether that be historically or in modern times if the answer to any of these questions is no then the process of evolution wouldn't apply to humans but since we've observed these things in countless living organisms including in humans and we share the same basic biology as other living things then if we are to be intellectually honest then we must conclude that the evolutionary process does indeed apply to humans in part two of this installment of Evo Ed we'll look at the pattern and evidences of evolution and we'll explore an interesting angle that suggests that creationists actually agree with science more than they realize when it comes to speciation and evolution thanks for tuning in I'll see you next time [Music] foreign [Music]