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The term "evolved" has really evolved over time.. it used to mean genetic changes that were carried forward through natural selection, even if it's actually pre

The term "evolved" has really evolved over time.. it used to mean genetic changes that were carried forward through natural selection, even if it's actually pretty hard to find any positive genetic changes at all in modern history, let alone those that are passed down to progeny. However, now the term simply seems to be a catch-all for any change at all, including just "adaptation", or natural selection without genetic changes.

JellyBeanThief 2y ago
...and now it means https://en.wikipedia.org/wiki/Semantic_change https://en.wikipedia.org/wiki/Semantic_change too
solardev 2y ago
In this case, they were measuring the differing responses to lethal doses of salt between groups of tadpoles. Those that came from the salted parking lot pond survived longer. What leads you to believe this adaptation isn't genetic? Do you have an alternative, non-genetic explanation as to why these certain tadpoles are better able to tolerate otherwise lethal doses of salt?
tasty_freeze 2y ago
"...it used to mean ..." When did it not mean that? The mechanism of natural selection was Darwin's main contribution to explain how evolution worked, even if they didn't understand genetics at the time. Darwin's famous finch example is a great demonstration of that. Finches with shorter, stouter beaks were able to take advantage of harder berries that were available on one island that other birds couldn't as easily eat. And once there was some geographic separation, birds with that same feature tended to breed more birds with that same trait. It wasn't some wild stroke of genetic luck where bird was born with a short beak -- it simply selected an existing trait that had previously been neutral (or close to it). Evolution happens to populations, not individuals. Selection pressure is exactly what shapes population genetics. During times of stability, genetic diversity is introduced through gene drift, but it is selective pressure that leads to population-level shifts. (Please don't nitpick -- everything is statistical a neutral change can spread through a population even without pressure, but that isn't the main vector). The article was about frogs, so my comment is in that context. In the case of bacteria, which are asexual and which exist in much greater numbers and have much shorter generation times, the "eureka" model of evolution you seem to be thinking of is more defensible, where one lucky bacterium out of a trillion gets a mutation that gives it some significant new ability (say, like being able to metabolize plastic or something) that allows its descendants to out-compete the rest of the population and take over.
dumbo-octopus 2y ago
In large part because speciation by natural selection is so incredibly rare as to be observationally non-existent. The only justification for it is that many species exist now, and this is the only way we can explain it to have happened, so this must be the way it happened. This is hardly "scientific" in the sense we like to think of the term, but it's the best one can do when trying to answer unobservable untestable hypotheses without resorting to the supernatural.
- Retric 2y ago
  We’ve seen a few examples of new species coming about. HeLa cell line being a rather gruesome but still interesting example. Also, science tests models not history. There’s quite a bit you can predict via evolution that turned out to be verified from new discoveries. Consider you look at the local geology and then make predictions about what fossils will be discovered where and then check the actual rocks, that’s an experiment.
  - dumbo-octopus 2y ago
    Did HeLa ever demonstrate speciation via sexual reproduction and natural selection or just the simpler mutations-passed-on mode? The vanishingly rare trick with speciation by natural selection in sexually reproducing creatures is that you have to have find a compatible partner.
    - Retric 2y ago
      The first, but speciation via sexual reproduction is much easier as non sexual reproduction blurs the lines of what counts as a species. For sexual reproduction simply isolate populations and they drift apart genetically. This is why you can get ring species and populations that can’t get in touch naturally are considered separate species even if when artificially reintroduced they could interbreed. Thus many invasive species technically count if they could naturally get in touch the species would already be in that location. Anyway that’s based on the current definition used by zoologists though some people find this definition unsatisfying but in both directions. Grizzlies and polar bears can interbreed and therefore count as the same species in that definition even though they are developing different traits not just hair color but body weight is diverging. In the end biology doesn’t give a fuck about our definitions so things are messy.
Terr_ 2y ago
Are you trying to draw a distinction between base-pair mutations in DNA sequences versus changes in the mixes and combinations of those sequences in a population? The latter is still evolution. For example, imagine a population with a current mutation-rate of zero, but there's a dominant allele that makes individuals instantly die to new highly-contagious disease. Later on, the (surviving) individuals are all safe from the disease because that allele is gone. Did they evolve? Yes, even if on a chemical level it was purely subtractive.
seeknotfind 2y ago
Yup. The funny thing is, it could even be a reduction in biodiversity. An important part of evolution, but only as advantageous as the previous environment is ephemeral.

JellyBeanThief 2y ago

...and now it means https://en.wikipedia.org/wiki/Semantic_change https://en.wikipedia.org/wiki/Semantic_change too

solardev 2y ago

In this case, they were measuring the differing responses to lethal doses of salt between groups of tadpoles. Those that came from the salted parking lot pond survived longer. What leads you to believe this adaptation isn't genetic? Do you have an alternative, non-genetic explanation as to why these certain tadpoles are better able to tolerate otherwise lethal doses of salt?

tasty_freeze 2y ago

"...it used to mean ..." When did it not mean that? The mechanism of natural selection was Darwin's main contribution to explain how evolution worked, even if they didn't understand genetics at the time. Darwin's famous finch example is a great demonstration of that. Finches with shorter, stouter beaks were able to take advantage of harder berries that were available on one island that other birds couldn't as easily eat. And once there was some geographic separation, birds with that same feature tended to breed more birds with that same trait. It wasn't some wild stroke of genetic luck where bird was born with a short beak -- it simply selected an existing trait that had previously been neutral (or close to it). Evolution happens to populations, not individuals. Selection pressure is exactly what shapes population genetics. During times of stability, genetic diversity is introduced through gene drift, but it is selective pressure that leads to population-level shifts. (Please don't nitpick -- everything is statistical a neutral change can spread through a population even without pressure, but that isn't the main vector). The article was about frogs, so my comment is in that context. In the case of bacteria, which are asexual and which exist in much greater numbers and have much shorter generation times, the "eureka" model of evolution you seem to be thinking of is more defensible, where one lucky bacterium out of a trillion gets a mutation that gives it some significant new ability (say, like being able to metabolize plastic or something) that allows its descendants to out-compete the rest of the population and take over.

dumbo-octopus 2y ago

In large part because speciation by natural selection is so incredibly rare as to be observationally non-existent. The only justification for it is that many species exist now, and this is the only way we can explain it to have happened, so this must be the way it happened. This is hardly "scientific" in the sense we like to think of the term, but it's the best one can do when trying to answer unobservable untestable hypotheses without resorting to the supernatural.

Retric 2y ago
We’ve seen a few examples of new species coming about. HeLa cell line being a rather gruesome but still interesting example. Also, science tests models not history. There’s quite a bit you can predict via evolution that turned out to be verified from new discoveries. Consider you look at the local geology and then make predictions about what fossils will be discovered where and then check the actual rocks, that’s an experiment.
- dumbo-octopus 2y ago
  Did HeLa ever demonstrate speciation via sexual reproduction and natural selection or just the simpler mutations-passed-on mode? The vanishingly rare trick with speciation by natural selection in sexually reproducing creatures is that you have to have find a compatible partner.
  - Retric 2y ago
    The first, but speciation via sexual reproduction is much easier as non sexual reproduction blurs the lines of what counts as a species. For sexual reproduction simply isolate populations and they drift apart genetically. This is why you can get ring species and populations that can’t get in touch naturally are considered separate species even if when artificially reintroduced they could interbreed. Thus many invasive species technically count if they could naturally get in touch the species would already be in that location. Anyway that’s based on the current definition used by zoologists though some people find this definition unsatisfying but in both directions. Grizzlies and polar bears can interbreed and therefore count as the same species in that definition even though they are developing different traits not just hair color but body weight is diverging. In the end biology doesn’t give a fuck about our definitions so things are messy.

Terr_ 2y ago

Are you trying to draw a distinction between base-pair mutations in DNA sequences versus changes in the mixes and combinations of those sequences in a population? The latter is still evolution. For example, imagine a population with a current mutation-rate of zero, but there's a dominant allele that makes individuals instantly die to new highly-contagious disease. Later on, the (surviving) individuals are all safe from the disease because that allele is gone. Did they evolve? Yes, even if on a chemical level it was purely subtractive.

seeknotfind 2y ago

Yup. The funny thing is, it could even be a reduction in biodiversity. An important part of evolution, but only as advantageous as the previous environment is ephemeral.