I think it's more that they're trying to point out the difference between evolution and genetic mutations. Evolution is what occurs on a macroscopic level over a long period of time to organisms. Genetic mutations are what happens on the microscopic level that could play part in the evolution of an organism. That doesn't mean that a genetic mutation implies that the animal has evolved.
I'm an evolutionary biologist and this is incorrect. By definition, evolution occurs any time the frequency of alleles changes in a population. Microevolution is still evolution. That means that a single novel mutation is still evolution, even if it doesn't spread to fixation in the population.
That means that a single novel mutation is still evolution, even if it doesn't spread to fixation in the population.
Then conjoined twins, of varying degrees, would be considered evolution? Evolution, by academic definition, is successful mutations, surely? It's not known if this chick could even even successfully reproduce given the chance.
By definition, evolution occurs any time the frequency of alleles changes in a population.
This isn't a population though? Once there's enough four-legged chickens for their own taxonomic classification, then sure.
Nope, the academic definition of evolution has nothing to do with whether or not a change is "successful"
The mechanisms of evolution are mutation, genetic drift, natural selection, sexual selection, and gene flow. That means if you have 1000 brown cows and 100 white cows migrate in and now you've got a population of 1100 cows with a different distribution of alleles for coat color than the original 1000 brown cows had, that's evolution.
In evolutionary biology a population is just a group of organisms of the same species that are in an ecosystem together, so the mutant chick would be part of the population of whatever group of chickens it's in. But if the four legged chicks did become more common and started mostly only breeding with other four legged chicks, then yes, they might just get their own taxonomic classification. But they don't need their own taxonomic classification for their presence to count as evolution.
As far as conjoined twins go, that depends on whether it's a result of a genetic mutation or something weird that happened in utero, and whether the population is in a mutation-selection balance (where the rate of mutations that cause a deleterious trait is balanced by the negative effect of natural selection, so the frequency of the allele remains the same from generation to generation). If it's genetic and the frequency of the trait increases, then yes, that's evolution!
As another example, if the prevalence of autism in society is increasing due to an increase in the frequency of autism- related genes, that's evolution-- even if autism doesn't spread throughout the entire human population and become universal. If it's increasing due to environmental factors, then it's not evolution. If it decreases due to autism-related genes becoming rarer, that's also evolution.
It drives me a bit crazy to see how badly pop science butchers evolution. Macroevolution is extremely cool and probably my favorite field of evolution, but it's not the only field.
/u/discordagitatedpeach is right. But I can provide some additional context. What you're describing is what I was taught in highschool. So I understand the misconception. In college and beyond, any change in the population is considered evolution even if its fleeting.
I really wish they'd find a better strategy for teaching high school students that doesn't involve "lies you'll have to unlearn when you get to college"
Why not just say "the complexities of [issue] are beyond the scope of this class, but if you think it's cool, here are some resources you can look up to learn more about it." That way it would encourage students to take charge of their learning instead of making them think they know something that's not actually true
Yeahhhhh that one annoyed me too, especially when they made us use these tragic thesis statements like "World War 2 had social, political, and economic causes"
It has its purposes for practicing certain skills but they should've let students branch out and do more than just one thing.
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u/SousVideDiaper 29d ago
You just gave context for what they said, tho