Species

Otto I · Jan 10, 2018

I wanted to discuss the concept of species. It has become clear that species doesn’t exist in reality. It is only a concept in the human mind (of course it is the best we have so far, so we have to continue working with it). Long gone are the days of the definition if organisms can produce (fertile) offspring, then they belong to the same species. Some interesting examples are:

Horses and donkeys
Horses and donkeys can have offspring. The offspring are not fertile.
One species or two?

Lions and tigers
Lions and tigers can have offspring. Male offspring are not fertile. Female offspring are fertile.
One species or two?

Brown bears and polar bears
Brown bears and polar bears can have fertile offspring. Some brown bears are genetically closer to polar bears than to the other brown bears (polar bears are inside brown bears).
One species or two?

Modern humans and neanderthals
Modern humans and neanderthals could have fertile offspring. Most genetic material from neanderthals is slowly squeezed out of modern humans, but there is a lot of genetic material which is favorable for survival, so it is increased and modern human genetic material is squeezed out.
One species or two?

Gulls/warblers
In europe you have the herring gull. If you follow it to the west to north america its wing colour gets darker and darker and somewhere in asia it is almost black. If you follow it to europe you have the lesser black-backed gull. In europe the herring gull and the lesser black-backed gull can’t have offspring, but nevertheless if you go into the other direction you end up with the other one.
Another example is the greenish warbler, where there are two "subspecies“ in the eastern tibetan plateau that can’t have offspring, but if you follow one around the himalaya (connected by other "subspecies“ which can have fertile offspring), you end up with the other one.
One species or two?

Edible frogs
The edible frog is a "hybrid“ between the pool frog and the marsh frog. Normal edible frogs can’t have offspring with other edible frogs, but they can if one parent is a marsh frog or a pool frog. So normally one would expect that edible frogs vanish, were there are no pool or marsh frogs. But this isn’t the case. There are some edible frogs which are triploid, which means they have the full genetic information of one of their "parent species" in them. An those frogs can reproduce with the other edible frogs.
One species or two or three?

Amazon mollys
Amazon mollys are sexual parasites. Only females are known. To produce offspring they need semen of male sailfin mollys, broadspotted mollys or atlantic mollys (maybe also common molly) to reproduce. But the offspring are amazon mollys, the genetic material of the males isn’t used. They only need the semen to start the development of the ovule.
One species or two or four or five?

Chronospecies
If a type of organism lives a long time, what if the first ones can’t have fertile offspring with the last ones, if they magically met each other?
One species or two?

Mitochondrions
Mitochondrions were organisms, that sometime went into symbiosis with another organism. Now they are just organelles of another organism. And this organism can't live without the mitochondrion. (See endosymbiontic theory)
One species or two?

Jake10 · Jan 10, 2018

Well, since horses, zebras and donkeys had a common ancestor, then it appears they have evolved to the point of no longer being compatible with one another. The same can be said for lions and tigers. So, the concept of species refers to the point at which organisms from the same background change to a point at which compatibility is no longer possible. This means that time will, eventually, result in mutations and adaptations which will introduce new species to the planet, which should apply to humans as well.

Naomasa298 · Jan 10, 2018

Otto I said:
I wanted to discuss the concept of species. It has become clear that species doesn’t exist in reality. It is only a concept in the human mind (of course it is the best we have so far, so we have to continue working with it). Long gone are the days of the definition if organisms can produce (fertile) offspring, then they belong to the same species. Some interesting examples are:

Horses and donkeys
Horses and donkeys can have offspring. The offspring are not fertile.
One species or two?

Lions and tigers
Lions and tigers can have offspring. Male offspring are not fertile. Female offspring are fertile.
One species or two?

Brown bears and polar bears
Brown bears and polar bears can have fertile offspring. Some brown bears are genetically closer to polar bears than to the other brown bears (polar bears are inside brown bears).
One species or two?

Modern humans and neanderthals
Modern humans and neanderthals could have fertile offspring. Most genetic material from neanderthals is slowly squeezed out of modern humans, but there is a lot of genetic material which is favorable for survival, so it is increased and modern human genetic material is squeezed out.
One species or two?

Gulls/warblers
In europe you have the herring gull. If you follow it to the west to north america its wing colour gets darker and darker and somewhere in asia it is almost black. If you follow it to europe you have the lesser black-backed gull. In europe the herring gull and the lesser black-backed gull can’t have offspring, but nevertheless if you go into the other direction you end up with the other one.
Another example is the greenish warbler, where there are two "subspecies“ in the eastern tibetan plateau that can’t have offspring, but if you follow one around the himalaya (connected by other "subspecies“ which can have fertile offspring), you end up with the other one.
One species or two?

Edible frogs
The edible frog is a "hybrid“ between the pool frog and the marsh frog. Normal edible frogs can’t have offspring with other edible frogs, but they can if one parent is a marsh frog or a pool frog. So normally one would expect that edible frogs vanish, were there are no pool or marsh frogs. But this isn’t the case. There are some edible frogs which are triploid, which means they have the full genetic information of one of their "parent species" in them. An those frogs can reproduce with the other edible frogs.
One species or two or three?

Amazon mollys
Amazon mollys are sexual parasites. Only females are known. To produce offspring they need semen of male sailfin mollys, broadspotted mollys or atlantic mollys (maybe also common molly) to reproduce. But the offspring are amazon mollys, the genetic material of the males isn’t used. They only need the semen to start the development of the ovule.
One species or two or four or five?

Chronospecies
If a type of organism lives a long time, what if the first ones can’t have fertile offspring with the last ones, if they magically met each other?
One species or two?

Mitochondrions
Mitochondrions were organisms, that sometime went into symbiosis with another organism. Now they are just organelles of another organism. And this organism can't live without the mitochondrion. (See endosymbiontic theory)
One species or two?

https://en.wikipedia.org/wiki/Genus

https://en.wikipedia.org/wiki/Species

fascinating · Jan 11, 2018

I wanted to discuss the concept of species. It has become clear that species doesn’t exist in reality. It is only a concept in the human mind (of course it is the best we have so far, so we have to continue working with it). Long gone are the days of the definition if organisms can produce (fertile) offspring, then they belong to the same species.

I don't know if I agree that the concept of species doesn't exist in reality. I thought that if two animals can mate and produce viable offspring, then they should be the same species. "Viable" means offspring that can themselves produce offspring. On that basis, horses and donkeys are separate species.

Otto I · Mar 21, 2018

fascinating said:
... I thought that if two animals can mate and produce viable offspring, then they should be the same species. "Viable" means offspring that can themselves produce offspring. On that basis, horses and donkeys are separate species.

It is not that easy. Polar bears and brown bears can produce viable offsprings. With your definition they are not different species, but polar bears are a subspecies of brown bears.

Also, how do you explain the greenish warblers with this definition of species:

Subspecies A - subspecies B - subspecies C - subscpecies D

B can have fertile offspring with A and C, C with B and D and so on, but D can't directly have viable offspring with A. Nevertheless they could have viable offspring over several generations via B and C.

Asherman · Mar 21, 2018

You may find more informed answers on sites where Biologists congregate, than in a room filled with Historians.

analysis17456 · Mar 21, 2018

Well, you can't mate an ant with a horse, so that is where we could draw our intuition for the traditional species definition. For, if the offspring is not fertile and thus there is no continuation, how could we even denote the existence of a new species? And, if it is (fertile), why should they be defined to be of a different species?

Definitions utilizing polypeptide combinations ("DNA", though calling it "DNA" is horrifically disrespectful of its first principles, doesn't jive with mathematical biology) will be much, much clearer in the future as more mathematicians enter biology. You'll love this OP, that the species definition is not going to be dropped anytime soon because there are very strong intuitive bases for it, it's just going to be refined.

analysis17456 · Mar 21, 2018

Otto I said:
Subspecies A - subspecies B - subspecies C - subscpecies D

B can have fertile offspring with A and C, C with B and D and so on, but D can't directly have viable offspring with A. Nevertheless they could have viable offspring over several generations via B and C.

How you describe it, they call this process evolution. Of course, it would be a tree instead of just A to B to C and whatever. And over time, the speciation becomes more concrete. .... Sapiens supposedly bred with Neanderthals, which is not a surprising claim, but they both have many common ancestors which they cannot breed with, including a multicellular "organism" that started everything, the number of species for which they cannot breed with continues up to the mammals and so on. Hence why the definition of a species won't be dropped so easily. Of course, modern definitions are being refined.

e.g.

etc.

You can obviously see the closeness of the Sapiens to the Neanderthals.

AlpinLuke · Mar 22, 2018

As usual, we follow conventions, since our mind needs “stable data” to reason. We need definitions to deal with “entities” of any kind and we love to categorize.

There are different conventions defining the species and this means that the word can indicate different things.

Generally it’s the biological meaning of the word to be the most used and diffused around.

The convention states that a species is based on common near ancestors and reproductive isolation. This means that:

* Going backwards through time a species exists until it’s recognizable;
* It’s not enough that a horse an a donkey have an offspring: such a offspring has to be fertile without generational limitation.
* Furthermore … the hybridization has to happen in nature [not planned or caused by humans]. So that if humans find a way to make horses and donkeys have a fertile offspring without generational limitation … horses and donkeys keep on being different species. Even If they are of the same genus [Equus].

Dreamhunter · Mar 22, 2018

Was Neanderthal a distinct species, i.e. .... neanderthalensis, or a sub-species of .... sapiens, i.e. .... sapiens neanderthalensis?

Dreamhunter · Mar 22, 2018

AlpinLuke said:
* Furthermore … the hybridization has to happen in nature [not planned or caused by humans]. So that if humans find a way to make horses and donkeys have a fertile offspring without generational limitation … horses and donkeys keep on being different species. Even If they are of the same genus [Equus].

Knowing the nature of horses & donkeys, and the nature of animals in general, it would be expected to happen every now & again in nature, even without human manipulation, if the two were living constantly in the same habitat.

Heck. If one has ever lived on a farm, with free range poultry, sheep, goats & all, one wud even be seeing the occasional randy cockerel chasing & mounting a hapless duck, and a rogue drake coupling with an unfortunate hen. No that frequent, but it does happen.

AlpinLuke · Mar 22, 2018

Dreamhunter said:
Knowing the nature of horses & donkeys, and the nature of animals in general, it would be expected to happen every now & again in nature, even without human manipulation, if the two were living constantly in the same habitat.

Heck. If one has ever lived on a farm, with free range poultry, sheep, goats & all, one wud even be seeing the occasional randy cockerel chasing & mounting a hapless duck, and a rogue drake coupling with an unfortunate hen. No that frequent, but it does happen.

A convention ...

Not occasionally. donkeys and horses, in nature, should normally generate an outspring. In nature this doesn't happen. Horses and donkeys tend not to look for interbreeding and they tend to preserve their reproductive isolation.

Otto I · Mar 22, 2018

Asherman said:
You may find more informed answers on sites where Biologists congregate, than in a room filled with Historians.

I wasn't looking for answers, but more for an interesting discussion. Also I noticed a lot of people in the natural environment subforum having very outdated knowledge, including how they use "species". I thought such a discussion would be useful to some people.

AlpinLuke said:
A convention ...

Not occasionally. donkeys and horses, in nature, should normally generate an outspring. In nature this doesn't happen. Horses and donkeys tend not to look for interbreeding and they tend to preserve their reproductive isolation.

analysis17456 said:
… And, if it is (fertile), why should they be defined to be of a different species?

Well, people do consider polar bears and brown bears seperate species, don't they? Even though they produce fertile offspring in the wild.

Dreamhunter said:
Was Neanderthal a distinct species, i.e. .... neanderthalensis, or a sub-species of .... sapiens, i.e. .... sapiens neanderthalensis?

They are considered a different species. But a few years ago, it was discovered, that they in fact mixed with modern humans and belong to the forebears of a part of todays humanity.

QUOTE=analysis17456;2916013]How you describe it, they call this process evolution. Of course, it would be a tree instead of just A to B to C and whatever. [/QUOTE]

That is essentially my point - because of evolution the concept of species doesn't exist in reality. But we just continue to use it, because we don't have anything better. The A, B, C and D thing was just a way to break down a more complicated example to give a point. You are right I shouldn't have used it in such a way. But you also shouldn't use such an outdated tree, but an example that follows phylogenetic systematics

.

AlpinLuke said:
As usual, we follow conventions, since our mind needs “stable data” to reason. We need definitions to deal with “entities” of any kind and we love to categorize.
.

This is exactly the reason why we still (need to) use the species-concept.

AlpinLuke said:
* Going backwards through time a species exists until it’s recognizable;
[Equus].

No. A species exists until either it dies out or it splits into two new species (or theoretically possible more than two new species).

analysis17456 · Mar 22, 2018

Otto I said:
That is essentially my point - because of evolution the concept of species doesn't exist in reality. But we just continue to use it, because we don't have anything better. The A, B, C and D thing was just a way to break down a more complicated example to give a point. You are right I shouldn't have used it in such a way. But you also shouldn't use such an outdated tree, but an example that follows phylogenetic systematics.

Alright, if species don't exist, then start your ant-horse hybrid colony, as apparently, the ants and horses are one and the same thing. If you didn't know, I'm also a dolphin.

By the way, it depends on who you're asking, I don't subscribe to the classical definition of species, for example, because I intend to improve it in the future if no one else has to sufficiency. All biologists know that classical biology is severely limited. But I don't understand how you can draw such an insane extension to the assumption that species, therefore, do not exist, doesn't make any sense.

MrKap · Mar 22, 2018

Jellyfish are an Androgyny species.

Dreamhunter · Mar 23, 2018

Otto I said:
They are considered a different species. But a few years ago, it was discovered, that they in fact mixed with modern humans and belong to the forebears of a part of todays humanity.

Well, since they did interbreed with the more mainstream .... sapiens, and indeed helped co-produce some fertile & viable hybrid ....-neanderthalis/....-sapiens humans as a result, then they could not hv been a different species. Simply becos two different species cannot produce fertile, viable hybrid offspring when they interbreed.

analysis17456 · Mar 23, 2018

Dreamhunter said:
Well, since they did interbreed with the more mainstream .... sapiens, and indeed helped co-produce some fertile & viable hybrid ....-neanderthalis/....-sapiens humans as a result, then they could not hv been a different species. Simply becos two different species cannot produce fertile, viable hybrid offspring when they interbreed.

That's an old and outdated definition, expect it to be gradually replaced in the future by more robust mathematical definitions concerning DNA with the awareness of statistical distributions within population samples.

sparky · Mar 23, 2018

.
the usual definition of a specie is that coupling would produce fertile grand children
a sub-specie is a race carrying an inherited distinct morphological difference
IE the Eastern European crow and the Western one
this is fluctuating quite a lot as to geographical extend and a fair bit of interbreeding on the margin

Otto I · Mar 24, 2018

Dreamhunter said:
Well, since they did interbreed with the more mainstream .... sapiens, and indeed helped co-produce some fertile & viable hybrid ....-neanderthalis/....-sapiens humans as a result, then they could not hv been a different species. Simply becos two different species cannot produce fertile, viable hybrid offspring when they interbreed.

Then how do you explain the amazon mollys or other sexual parasites, I mentioned in the first post?

analysis17456 said:
Alright, if species don't exist, then start your ant-horse hybrid colony, as apparently, the ants and horses are one and the same thing...

You equate no species = all the same (essentially one species). It doesn't mean that there are no barriers for reproduction. My opinion is just that reality is much more complicated than the species concept. For instance the endosymbiontic theory:
Two organisms you would describe as two species, which couldn't reproduce fertile or any offspring, "merged" and started reproducing a new type of organism.

stevev · Mar 24, 2018

Nature is stupid. We make rules and nature just can't seem to get it.

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