Ask me about evolution

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Re: Ask me about evolution

Postby Pedgerow » Wed Nov 21, 2018 12:08 am

One question I have always had about evolution, for about 15 years now: would it be possible for a non-monkey to evolve into a human, given the right circumstances and enough time? Like, if I had a laboratory with its own controlled ecosystem, and millions of years, is there anything stopping me from "naturally" selecting giraffes, or polar bears, or ducks, until they are indistinguishable from the humans we have now? Giraffes evolved long necks; they can evolve short necks too. Then they can evolve to walk on their back legs and not have tails and to develop opposable thumbs and so on, until they look just like people. I think it's called convergent evolution. So what I'm really asking is: is there a chance, however small, that I evolved from a bear instead of a monkey? What are the limits to evolution, if any?
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Re: Ask me about evolution

Postby SandTea » Wed Nov 21, 2018 3:02 am

Pedgerow wrote:...would it be possible for a non-monkey to evolve into a human, given the right circumstances and enough time?


Just first off, that is not really a coherent question. Humans and apes share a common ancestor. One didn't turn into the other. Also nothing is going to "become" human just because they look more like us. DNA alone would show that not to mention that we wouldn't be able to have half duck babies together no matter how hot and anthropomorphized they might be.

Pedgerow wrote:Like, if I had a laboratory with its own controlled ecosystem, and millions of years, is there anything stopping me from "naturally" selecting giraffes, or polar bears, or ducks, until they are indistinguishable from the humans we have now?


I have to point out that that would not be 'natural selection' by any definition, but yes hypothetically given enough time and resources you could potentially artificially breed a giraffe/bear/duck into something more homo sapiens shaped but it would still not be of the same species as ours and definitely distinguishable from humans. In fact, you would most likely see vast differences in biology between the giraffe that looks human and actual humans, for instance the organization of their veins or bone structure, especially among the non mammalians.

Pedgerow wrote:So what I'm really asking is: is there a chance, however small, that I evolved from a bear instead of a monkey?


No.

Pedgerow wrote:What are the limits to evolution, if any?


Quite a few actually but I'm thinking more like "physically impossible" than "could a bear be bipedal and have thumbs". More to what I assume is your point, the limits to evolution would be environmental. Your hypothetical removes that as an influence so there would be more possibilities but if you're asking about the world as it is currently there are many limits.
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Re: Ask me about evolution

Postby cmsellers » Wed Nov 21, 2018 6:00 am

Pedgerow wrote:One question I have always had about evolution, for about 15 years now: would it be possible for a non-monkey to evolve into a human, given the right circumstances and enough time? Like, if I had a laboratory with its own controlled ecosystem, and millions of years, is there anything stopping me from "naturally" selecting giraffes, or polar bears, or ducks, until they are indistinguishable from the humans we have now? Giraffes evolved long necks; they can evolve short necks too. Then they can evolve to walk on their back legs and not have tails and to develop opposable thumbs and so on, until they look just like people. I think it's called convergent evolution. So what I'm really asking is: is there a chance, however small, that I evolved from a bear instead of a monkey? What are the limits to evolution, if any?

I don't know all the limits of evolution, but I know some, and at least one is highly relevant to your question. You can only build on what's already present, both in terms of the structures you have and the genetic mutations which allow slow change. This is why evolution is for all intents and purposes irreversible, even with people trying to do things like deliberately backbreed aurochs from cows.

An animal similar to or ancestors absolutely could evolve to be similar to us after passing through similar ecological niches, that's what convergent evolution is. However it is impossible that even chimps could evolve to be physically identical to humans, because the chances of chimps undergoing all the same mutations we went through is infinitesimally small. I'll bring up backbreeding again, because with very closely-related species you can get animals which physically resemble their ancestors if you deliberately drive the process, but genetic drift means that they will still not be genetically identical.

The other limit that comes to mind is that natural selection does not have a goal, which means that if you reach a local maximum of fitness, you cannot decrease your fitness in order to reach a global maximum.

SandTea wrote:Just first off, that is not really a coherent question. Humans and apes share a common ancestor. One didn't turn into the other.

This is really a question of terminology. Cladistically, humans are a specialized kind of ape and apes are a specialized kind of monkeys. In terms of terminology, scientists generally recognize humans as apes but don't recognize apes as monkeys. But if you're being honest, humans are still funky monkeys.
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Re: Ask me about evolution

Postby CarrieVS » Wed Nov 21, 2018 10:14 am

cmsellers wrote:Cladistically, ... apes are ... monkeys.


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Re: Ask me about evolution

Postby Anglerphobe » Wed Nov 21, 2018 11:20 pm

Are implying the Sellers was assassinated by Ray Comfort?

Serious one, Sellers, if you survived: Is it possible for an organism to speciate as a result of human selection? Are there any examples of this happening?
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Re: Ask me about evolution

Postby CarrieVS » Wed Nov 21, 2018 11:52 pm

Anglerphobe wrote:Are implying the Sellers was assassinated by Ray Comfort?


Nope. I'd never heard of that guy until I googled him just now. You get two more guesses.
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Re: Ask me about evolution

Postby SandTea » Thu Nov 22, 2018 1:11 am

Anglerphobe wrote:Are implying the Sellers was assassinated by Ray Comfort?


:lol: Good one.

Anglerphobe wrote:Is it possible for an organism to speciate as a result of human selection? Are there any examples of this happening?


Yes, a few actually. The most well known would be something like monsanto corn but I assume most people would prefer a fauna example in which case the ones I am most familiar with are the fruit flies who were given different environments until they were no longer able to interbreed. I'm being lazy because pizza. sorry for not adding a link
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Re: Ask me about evolution

Postby cmsellers » Thu Nov 22, 2018 2:33 am

Speciation is not as well-defined as you might think. Speciation as it is relevant to evolution typically means reproductive isolation, which means that species cannot interbreed, will not interbreed, or cannot interbreed to create interfertile hybrids. But tigers and lions can produce fertile offspring and American black duck females preferentially interbreed with mallard males over the males of their own species. And taxonomists use all sorts of species concepts (I favor the ecological species concept myself, while the biological and phylogenetic species concepts seem to be most popular), most of which result in species that can and will interbreed easily if they come into contact.

So if you are asking if humans have created species that cannot interbreed to produce fertile offspring in the wild, I am pretty sure that the answer is "yes," but I cannot name a definite example. A good partial example is corn, which is dramatically different from wild teosintes. Corn and teotsintes can hybridize, and those hybrids can hybridize again with corn, but not, as I understand it, with teosintes, which indicates that there is a one-way genetic barrier between corn and teotsintes. My understanding of the fruit fly experiments is that they sometimes resulted in two populations that preferentially mated within the population, but not result in interinfertility.

However if you're asking if humans have created animals which are defined as species, the answer is absolutely yes. While most domesticated animals are now defined as subspecies of the wild ancestor, llamas, alpacas, guinea pigs, and society finches are still defined as different species from their wild progenitors, and that's off the top of my head. So are many plants. Most staple plant species are mutations and/or stable hybrids of multiple wild ancestors, including wheat, corn, soy, and potatoes. There are also varieties of several crops (bananas and seedless grapes) and one animal (turkey) which cannot reproduce without human help, which raises a number of issues for most species concepts, including the ecological species concept I tend to prefer.

SandTea wrote:The most well known would be something like monsanto corn

Trying to introduce a modification to prevent interfertility is something the scientists working on this stuff would absolutely do, and I agree that Monsanto would love such a patent-control mechanism and a way to allay "cross-contamination" paranoia. That said, I was not aware of any case where genetic modifications have resulted in organisms which are not interfertile with the parent organism. Was there a specific example you were thinking of?
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Re: Ask me about evolution

Postby Anglerphobe » Sat Nov 24, 2018 1:03 pm

Thanks for the answers, gang.

Another one: As far as I know, all the examples of animals switching from water breathing to air breathing are in that direction: ie an aquatic water breathing animal evolving the ability to get oxygen from the air. I can't think of any definite examples of the inverse: an animal which was already adapted to breathe air exclusively developing the ability to breathe underwater, which I'm guessing is because there is no selective pressure for this to happen. Land vertebrates at least have always retained an exclusive dependence on air breathing even when fully adapted to living their whole lives in the water (eg whales and ichthyosaurs).
The only one I can think of that might be an example of this is certain aquatic insects. Are they? Is it known whether any made the conversion from land dwelling and air breathing to water dwelling and breathing or did they all simply retain water adaptations from their ancestors and thus never fully adapt to life out of the water in the first place?
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Re: Ask me about evolution

Postby SandTea » Sun Nov 25, 2018 4:24 am

cmsellers wrote:Was there a specific example you were thinking of?

Not really. You probably are correct.

Anglerphobe wrote:Is it known whether any made the conversion from land dwelling and air breathing to water dwelling and breathing or did they all simply retain water adaptations from their ancestors and thus never fully adapt to life out of the water in the first place?


No idea but that question does bring to mind something like things I've seen with those external frond like gills. No idea of their evolutionary history though and now I'm curious about them. Might take a dive into that.
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Re: Ask me about evolution

Postby CarrieVS » Sun Nov 25, 2018 7:51 pm

SandTea wrote:No idea but that question does bring to mind something like things I've seen with those external frond like gills. No idea of their evolutionary history though and now I'm curious about them. Might take a dive into that.


Axolotls?
They're a kind of salamander that is neotenic - they retain traits as adults that would normally be juvenile traits. In this case, salamanders like other amphibians hatch as tadpoles which have gills, and most of them lose the gills as adults, but axolotls retain them.
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Re: Ask me about evolution

Postby cmsellers » Mon Nov 26, 2018 2:12 am

I don't know of an example. Carrie describes the situation with axolotls correctly: they never lost their gills, they were just reduced to one life stage and they then evolved to stay in that stage.

Lungs evolved from swim bladders in fish and gills in arachnids. The latter seems like it might be reversible, but I cannot find an example of it happening. Most animals get at least some oxygen through their skin. In frogs it's a majority, but I don't know how easily skin which extracts oxygen from the air could be adapted to do it in water.
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Re: Ask me about evolution

Postby blehblah » Fri Nov 30, 2018 5:09 pm

CarrieVS wrote:
Anglerphobe wrote:Are implying the Sellers was assassinated by Ray Comfort?


Nope. I'd never heard of that guy until I googled him just now. You get two more guesses.


Turtles, all the way down.

EDIT:

Was reading-back through this thread, and I have a bit of input on something CarrieVS was asking about.

Birds are dinosaurs which decided to not up and die. Something which Pterosaurs and modern birds have in common is very light bones. Though, it's not quite as straightforward as things like Pterosaurs evolved into yummy chickens.

http://palaeo.gly.bris.ac.uk/palaeofile ... atomy.html

The vertebrae and long bones of some pterosaurs were hollow. This would have made the animals considerably lighter and therefore more effective flyers. Even with this reduction in weight, some of the larger pterosaurs may have had difficulties taking off from the ground. It has been suggested that large taxa may have leapt off of trees or cliffs to take off, but some aerodynamic studies suggest that even the largest species could have taken off from a running or flapping start (though see below for a discussion of running abilities in pterosaurs).

Like modern birds, pterosaurs had an enlarged sternum for the attachment of flight muscles. Many pterosaurs were probably strong flyers, but questions remain regarding giant taxa, such as Pteranodon and Quetzalcoatlus. Some research suggests that large pterosaurs were obligate gliders, while some suggest that they were capable of powered flight.


I don't know how recent that is, but the "light bones" bit stands. Where it gets interesting is that these big flying thingies weren't actually dinosaurs.

https://www.livescience.com/24071-ptero ... saurs.html

Pterosaurs first appeared in the late Triassic Period and roamed the skies until the end of the Cretaceous Period (228 to 66 million years ago), according to an article published in 2008 in the German scientific journal Zitteliana. Pterosaurs lived among the dinosaurs and became extinct around the same time, but they were not dinosaurs. Rather, pterosaurs were flying reptiles.

[EDIT: snipped a bit of "more links" type stuff which I accidentally included via copy n' paste}

There are at least 130 valid pterosaur genera, according to David Hone, a paleontologist at Queen Mary University of London. They were widespread and lived in numerous locations across the globe, from China to Germany to the Americas.

Pterosaurs first appeared in the late Triassic Period and roamed the skies until the end of the Cretaceous Period (228 to 66 million years ago), according to an article published in 2008 in the German scientific journal Zitteliana. Pterosaurs lived among the dinosaurs and became extinct around the same time, but they were not dinosaurs. Rather, pterosaurs were flying reptiles.

Modern birds didn't descend from pterosaurs; birds' ancestors were small, feathered, terrestrial dinosaurs.


That article mentions that pterosaurs were likely warm-blooded, with some fuzz to help them stay warm. That, naturally, had me thinking about flying, skin-winged mammals, and what their bones are like.

https://www.quora.com/Do-bats-have-holl ... like-birds

Bats have normal mammalian bones, but they’re very slender and delicate to reduce weight. The wing bones in particular are quite flexible.


The trade-off between being able to fly versus lumbering about on the ground is crunchiness. Stepping on, say, something as dense and tough as a turtle produces very little crunch, while stepping on a bat produces much crunch. Pterosaurs were impressively large, but aerodynamics favour rather delicate structures. Minus impressive fire-breathing or venom-spewing, and the weight required for "invulnerable to pointy sticks except for that one tiny spot on the belly" defences, the idea of a dragon becomes a bit more like a very large, ornery, bat or eagle. While they may cast a dramatic shadow when circling above, and could perhaps deliver a nasty peck, clawing, or well-placed insult, a good swing of a baseball bat would be quite crunchy in an unfavourable way for the flying types.

"But, wait, Bleh - chemical reactions, armour on the outside, there are plenty of insects, like beetles and fireflies which check those boxes!", I hear a voice in my head, whom I call Blah, say.

The problem with insects is they have sacrificed some things to overcome what can be thought of as a weight:thrust problem. They don't really have hearts which pump oxygenated blood to muscles; instead, they have an open circulatory system (https://indianapublicmedia.org/amomento ... ave-heart/) which moves their version of blood around. They also don't have lungs; instead, they have a system of trachea (https://askabiologist.asu.edu/how-insects-breathe), meaning that they oxygenate passively.

By simplifying, insects reduce weight. The lack of an internal skeleton allows them have a hard exoskeleton, if they went down the beetle path. An open circulatory system makes swishing oxygenated blood around simple, and having no lungs saves a lot on the structures and muscles needed to keep those gas-bags operating. However, they suffer from the consequences of not having those systems, the greatest of which is a size limit.

As the last link above points-out, relying on passive oxygenation works over only small distances. Technically, a very long, and not very wide, insect would be fine. Even a very stubby insect is okay, so long as it flies for relatively short periods of time; Canada goose-type flying, at Canada goose size, isn't going to work because there is no effective way to deliver blood to a place to be oxygenated (lungs) and back to the muscles which are doing the flapping instead of the ones which do the pooping (which all birds are well-known to do only when over statues, cars, and hatless humans).

I think of it as the the difference between directing energy from an open fire versus an internal combustion engine. The engine has plenty of mechanisms which are demanding; deliver air to the combustion chamber to be fizzed with the fuel just-so, and so-on. It's demanding to build and maintain (which takes energy to do), but directs energy output of combustion in a structured fashion. An open fire is simple; throw logs (or gasoline, whatever floats your boat [not advised, especially on a boat]) into a hot pit, and enjoy the return. However, the return isn't directed, because it isn't contained by the system which is creating the combustion. It is inherently inefficient at a large scale, but ideal at a small scale. Scaling-up a campfire to create the energy produced by a nuclear reactor would be troublesome for forests everywhere, while firing-up a nuclear reactor to roast a few marshmallows would be equally inefficient.

Soooo, yeah... there be no dragons, here. Sorry.
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Last edited by blehblah on Fri Nov 30, 2018 8:24 pm, edited 1 time in total.
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Re: Ask me about evolution

Postby CarrieVS » Fri Nov 30, 2018 8:12 pm

*cries*

But the turtle moves.
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Re: Ask me about evolution

Postby blehblah » Fri Nov 30, 2018 8:48 pm

CarrieVS wrote:*cries*

But the turtle moves.


Did you step on it hard enough, for a spell?

One has to be very careful when comparing one's mass with any turtle. For one, you have to move a bit more wonderfully than the turtle, else the groovity of the turtle will overwhelm your stationary state, and possibly result in a grooved turtle eating a few of your most stationary plants. For C, turtles are well-known to absorb groove quite unlike any and all known elephants. Yielding a rock lobster is, at this time, considered the best way to groove a C-minor turtle, but that's just in the Western field of thinking.
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