Wortfish wrote:

NineBerry wrote:You still don't get that the definition of species that is used is not useful when looking at beings that do not live at the same time. The concept of species is a tool used in biology in certain contexts. It is not useful when talking about beings living in different time periods except when for that purpose you use different criteria to decide which beings belong to the same species.

The basic point is this: If members of a species can only give rise to members of the same species, how can new species emerge?

Let's say that humans (species B) and chimps (species C) are descended from species A.How did our ancestors, and those of chimps, stop being species A and become some other species if species A can only produce offspring that are the same species?

I get what you mean about different time periods, but the argument only makes sense if - as you say - the definition of a species is just a case of arbitrary biological nomenclature and only reflects the accumulation of change within the same group over a period of time. I thought it meant the distinction made between a group of organisms that can interbreed among themselves only.

That's one common definition, yes. Let's try another way of explaining it:

Consider a line of descent such as this:

A -> B -> C -> D -> E -> F

Genetic differences accumulate thru each generation such that, by the end of the lineage, F would no longer be able to interbreed with A.

However, at each step along the way, each ancestor would be interfertile with its descendent. So A could interbreed with B, B with C and so on.

So if we use the definition of "species" you suggest, then you should be able to see that each of the following groupings belong to the same species:

A,B,C,D,E

B,C,D,E,F

IOW, B,C,D, and E belong to the same species as A and to the same species as F. However, A and F do not belong to the same species as each other.

B,C,D,and E are transitional forms between A and F.

This is how speciation occurs. A new species, F, has arisen from A. However, at no point in the process did an organism give birth to one of a different species from itself.

The point that you seem to be misunderstanding, and which seems to be causing your confusion: The members of a species do not necessarily form an exclusive group, with no members overlapping with another species. It just usually is appears this way, because the transitional organisms who would have belonged to more than one species group have gone extinct. Ring species are the rare examples (and, if I understand correctly, it is not certain that any true examples exist) in which this is not the case.

I hope that clears things up.

Well presented, Shrunk.


Just to muddy the waters there is the documented instances of whole genome duplication arising in one generation and both the ancestral and descendants coexisting. The entire genome of the parental species doubles in this one generation. This genetic landscape seems to allow for selective filtering and experimentation overhead, and more than one new species may arise from an ancestral stock/population that is coextant. From a morphological cladistic prospective it could be impossible to detect a species line which could be drawn between them. Testing of the genome would show the similarities and forensic evidence of the position of the test subject(s) within the nested hierarchy. This is yet another way speciation events take place. The fusion of our chromosomes is just another form of this completely natural, and random, event wherein DNA undergoes radical shifts.

RS

So, crocoducks are a transitional species then, because crocodiles can mate with crocoducks, and crocoducks can mate with ducks, but crocodiles can't mate with ducks.

laklak wrote:So, crocoducks are a transitional species then, because crocodiles can mate with crocoducks, and crocoducks can mate with ducks, but crocodiles can't mate with ducks.

I should have mentioned that.

Shrunk wrote:

That's one common definition, yes. Let's try another way of explaining it:

Consider a line of descent such as this:

A -> B -> C -> D -> E -> F

Genetic differences accumulate thru each generation such that, by the end of the lineage, F would no longer be able to interbreed with A.

Ok. I get you.

However, at each step along the way, each ancestor would be interfertile with its descendent. So A could interbreed with B, B with C and so on.

OK.

So if we use the definition of "species" you suggest, then you should be able to see that each of the following groupings belong to the same species:

A,B,C,D,E

B,C,D,E,F

IOW, B,C,D, and E belong to the same species as A and to the same species as F. However, A and F do not belong to the same species as each other.

B,C,D,and E are transitional forms between A and F.

This is how speciation occurs. A new species, F, has arisen from A. However, at no point in the process did an organism give birth to one of a different species from itself.

The steps you have carefully made are all perfectly logical except that if F does not belong to the same species as A, then it must be a new species even if it can interbreed with its parental generation. So generation F does mark the onset of a new species different to that of its parents. So E actually can be said to belong to both the species of generation A and of generation F. It is, thus,transitional between both species as you correctly point out.

The point that you seem to be misunderstanding, and which seems to be causing your confusion: The members of a species do not necessarily form an exclusive group, with no members overlapping with another species. It just usually is appears this way, because the transitional organisms who would have belonged to more than one species group have gone extinct. Ring species are the rare examples (and, if I understand correctly, it is not certain that any true examples exist) in which this is not the case.

I agree that there is a "grey area", with generations in transition, but at some point a new species must be allowed to arise whereby the parents of one generation give birth to offspring that are of a different species with respect to prior generations.

I hope that clears things up.

Well, I think we have identified the issue.

Wortfish wrote: So generation F does mark the onset of a new species different to that of its parents. So E actually can be said to belong to both the species of generation A and of generation F.

Here lies the law of non-contradiction. RIP.

Well, I think we have identified the issue.

Yes, we have. The issue being: Creationists are too stupid to understand facts no matter how clearly they are presented.

The issue was that previously you had identified your version of "species through time" with an additional factor - that the parents could never breed with the children.

Wortfish wrote:... then speciation can only happen if parents give birth to offspring who are of a different species and cannot (hypothetically) interbreed with them...

Thommo wrote:The issue was that previously you had identified your version of "species through time" with an additional factor - that the parents could never breed with the children.

Wortfish wrote:... then speciation can only happen if parents give birth to offspring who are of a different species and cannot (hypothetically) interbreed with them...

Well, in the model used above the parents - from a scientific point of view - are members of the old species and also of the new. However, I still think that there may be a tipping point where the offspring cannot interbreed with the parents because of some phenotypic or genetic difference that may have been building up over the generations but now acts as a barrier.

Wortfish wrote:

Thommo wrote:The issue was that previously you had identified your version of "species through time" with an additional factor - that the parents could never breed with the children.

Wortfish wrote:... then speciation can only happen if parents give birth to offspring who are of a different species and cannot (hypothetically) interbreed with them...

Well, in the model used above the parents - from a scientific point of view - are members of the old species and also of the new. However, I still think that there may be a tipping point where the offspring cannot interbreed with the parents because of some phenotypic or genetic difference that may have been building up over the generations but now acts as a barrier.

No.

Shrunk wrote:

Wortfish wrote:

Thommo wrote:The issue was that previously you had identified your version of "species through time" with an additional factor - that the parents could never breed with the children.

Wortfish wrote:... then speciation can only happen if parents give birth to offspring who are of a different species and cannot (hypothetically) interbreed with them...

Well, in the model used above the parents - from a scientific point of view - are members of the old species and also of the new. However, I still think that there may be a tipping point where the offspring cannot interbreed with the parents because of some phenotypic or genetic difference that may have been building up over the generations but now acts as a barrier.

No.

Well, let's look at two scenarios:

1. Loss of the penile bone.
2. Increase in cranial size.

The first case may have happened gradually, but the final and complete loss of the baculum no doubt happened in one generation within the human lineage. The offpsring may have not been able to mate successfully with their parents or the parental generation if the absence of the baculum caused problems and prevented reproduction.

The second case involves the problem of larger brain size set against the limited capacity to give birth to larger heads. Although the fact that the female parent gave birth to the offspring proves it could cope with the larger head size, any male offspring may not be able to interbreed with females of the parental generation that have narrow pelvises and birth canals.

No.

NineBerry wrote:No.

How can you be so certain?

Because the baculum is greatly reduced in the other apes for a start. So it certainly wasn't lost in one generation in the human lineage. It was already on its way out a long time before that.

And why should the absence of a baculum mean impossibility to procreate with animals that have genes for a baculum.

This is interesting: https://www.nature.com/articles/ncomms9432

Fig. 3: There is clear separation between African apes and H. sapiens. Dinaledi, along with Au. afarensis (A.L. 333-8) and Au. sediba (MH2) fall outside the human range of variation.

Wortfish wrote:This is interesting: https://www.nature.com/articles/ncomms9432

Fig. 3: There is clear separation between African apes and H. sapiens. Dinaledi, along with Au. afarensis (A.L. 333-8) and Au. sediba (MH2) fall outside the human range of variation.

There’s also a clear separation between reality and your cognitive abilities, so what of it?

felltoearth wrote:

Wortfish wrote:This is interesting: https://www.nature.com/articles/ncomms9432

Fig. 3: There is clear separation between African apes and H. sapiens. Dinaledi, along with Au. afarensis (A.L. 333-8) and Au. sediba (MH2) fall outside the human range of variation.

There’s also a clear separation between reality and your cognitive abilities, so what of it?

Explain. I don't see how an ape with so many arboreal features can be called a member of the Homo genus.

Wortfish wrote:This is interesting: https://www.nature.com/articles/ncomms9432

Fig. 3: There is clear separation between African apes and H. sapiens. Dinaledi, along with Au. afarensis (A.L. 333-8) and Au. sediba (MH2) fall outside the human range of variation.

Indeed it is interesting, but probably less interesting than your fertile imagination driven by ideological supposition believes.

Did you see the title of Figure 3?

Figure 3: Orientation of the sustentaculum tali relative to the mediolateral axis of the calcaneal tuberosity.

Want to explain that, do you?

Wortfish wrote:

felltoearth wrote:

Wortfish wrote:This is interesting: https://www.nature.com/articles/ncomms9432

Fig. 3: There is clear separation between African apes and H. sapiens. Dinaledi, along with Au. afarensis (A.L. 333-8) and Au. sediba (MH2) fall outside the human range of variation.

There’s also a clear separation between reality and your cognitive abilities, so what of it?

Explain. I don't see how an ape with so many arboreal features can be called a member of the Homo genus.

No, you explain without appealing to your incredulity.

How many 'arboreal features' does naledi possess?

How many 'arboreal features' is a species permitted to possess for it to remain a member of Homo?

Going to pretend to expertise in comparative primate anatomy now, Wortfish? You are a busy man considering your only interest is in undermining scientific knowledge in favour of your antiquated mythology.

Wortfish never retracted the LIE about what the researcher “wanted”. Quote mined in another thread, recently. IMO sanctions should follow. Lesser trolls have been banned for less. Do we need chew toys so desperately? I think not.

RS