Homo naledi is only 250,000 years old

The accumulation of small heritable changes within populations over time.

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Re: Homo naledi is only 250,000 years old

#101  Postby monkeyboy » Jun 08, 2017 10:31 pm

Why is this all so complicated for some people?

My 8yr old is able to look at the pic of the colour change from blue to red and see that it goes blue, darker blue, purply blue, more purple than blue, purple, sort of dark purply red, purply red, dark red, red.

If you set a sort of bracketing system into this and say that within say a limit of 3-4 colour shades (or wider brackets over many more colour shades if you include shades like Amethyst, Fuchsia, Lavender, Lilac, Magenta, Mauve, Orchid, Thistle and Violetand other shades that only girls with huge shoe and make up collections know the names of), mating could successfully occur but beyond that it couldn't, that would be representative of a species evolving down one evolutionary trail.

Now if someone could draw this for me, I lack the requisite skill, Start with the blue in a nice wide block. On the left, follow the same path through purple to red. On the right with a small gap, follow a similar pattern through green to yellow. This would be divergence. The red can't breed with blue. The yellow can't either and the yellow definitely can't with the red because they're only related a long ways back when both species were blue, their common ancestor.

It's why our closest relations, the apes share a common ancestor with us but neither they nor us are still that unchanged common ancestor, we both evolved down divergent paths to be entirley different species, lots of similarities but different enough. We know some points (shades) that have occured along those evolutionary trails. We don't have the full colour chart yet with every single shade filled in but we have enough, way plenty to demonstrate a consistent theme supporting the TOE, not just the fossil record backed up with scietific dating techniques (which the creotards will or won't respect depending on how dates work out for their arguments) but DNA too. And it's all consistent, supporting the TOE.
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Re: Homo naledi is only 250,000 years old

#102  Postby Shrunk » Jun 09, 2017 12:33 am

Wortfish wrote:Where you have two diverging populations, isolated from each other, there will come a point when individuals from both populations may not be able to interbreed with each other. However, they can interbreed with members of the same population. That would be called speciation. But if you have just a single evolving population or lineage, then speciation can only happen if parents give birth to offspring who are of a different species and cannot (hypothetically) interbreed with them.


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Re: Homo naledi is only 250,000 years old

#103  Postby Shrunk » Jun 09, 2017 12:36 am

DavidMcC wrote:
Shrunk wrote:
Wortfish wrote:
Thommo wrote:
Ok, so this is very important. You have acknowledged here that it is not true that speciation is impossible under the conditions you specified.


I can understand speciation occurring as a result of two isolated populations diverging apart without violating Dawkin's condition. In that scenario, it is the accumulated differences between the populations that matter, not between parent and offspring.


I see. So differences are accumulating between the two parallel lines, but within the lines (both of which begin with a single common ancestor) nothing is changing. :picard:

That isn't what he said. Lines can diverge from each other without becoming internally more divergent.


How so?
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Re: Homo naledi is only 250,000 years old

#104  Postby DavidMcC » Jun 13, 2017 1:39 pm

Shrunk wrote:
DavidMcC wrote:
Shrunk wrote:
Wortfish wrote:

I can understand speciation occurring as a result of two isolated populations diverging apart without violating Dawkin's condition. In that scenario, it is the accumulated differences between the populations that matter, not between parent and offspring.


I see. So differences are accumulating between the two parallel lines, but within the lines (both of which begin with a single common ancestor) nothing is changing. :picard:

That isn't what he said. Lines can diverge from each other without becoming internally more divergent.


How so?

Simple: within a given species, there is the possibility of any two individuals of opposite sex mating, and this prevents their offspring from becoming too genetically diverse, whereas between different, non-interbreeding lines, any amount of genetic diversity can occur, without causing a problem with infertility.
PS, sorry about the late reply - I haven't been browsing this site for a while.
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Re: Homo naledi is only 250,000 years old

#105  Postby Shrunk » Jun 14, 2017 12:34 am

No problem. TBH, I don't see how that relates to what Wortfish wrote, but it's probably not worth pursuing further. There's nothing to be learnt.
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Re: Homo naledi is only 250,000 years old

#106  Postby DavidMcC » Jun 14, 2017 11:44 am

Shrunk wrote:No problem. TBH, I don't see how that relates to what Wortfish wrote, ...

It relates to what YOU wrote. Wortfish doesn't have a complete monopoly on incorrect posts, you know!

LATE EDIT: Also, AFAIK, we are not entirely restricted to commenting on the OP!
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Re: Homo naledi is only 250,000 years old

#107  Postby Shrunk » Jun 14, 2017 2:22 pm

DavidMcC wrote:
Shrunk wrote:No problem. TBH, I don't see how that relates to what Wortfish wrote, ...

It relates to what YOU wrote. Wortfish doesn't have a complete monopoly on incorrect posts, you know!

LATE EDIT: Also, AFAIK, we are not entirely restricted to commenting on the OP!


OK, I see the confusion. My statement was a sarcastic rewording of what Wortfish had said. IOW, what I wrote was knowingly and intentionally incorrect. Sorry if that wasn't clear.
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Re: Homo naledi is only 250,000 years old

#108  Postby DavidMcC » Jun 14, 2017 3:35 pm

Shrunk wrote:
DavidMcC wrote:
Shrunk wrote:No problem. TBH, I don't see how that relates to what Wortfish wrote, ...

It relates to what YOU wrote. Wortfish doesn't have a complete monopoly on incorrect posts, you know!

LATE EDIT: Also, AFAIK, we are not entirely restricted to commenting on the OP!


OK, I see the confusion. My statement was a sarcastic rewording of what Wortfish had said. IOW, what I wrote was knowingly and intentionally incorrect. Sorry if that wasn't clear.

Oh, I see. I didn't spot that. Sorry! I should have realised that you would know better than that!
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Re: Homo naledi is only 250,000 years old

#109  Postby Wortfish » Jun 15, 2017 2:00 am

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.
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Re: Homo naledi is only 250,000 years old

#110  Postby Thommo » Jun 15, 2017 2:20 am

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?


The exact same way that whole numbers only ever differ by one from their neighbour, yet any number has a number that is a million greater than it.

That's notwithstanding that this isn't how speciation occurs, as was already covered. And it's through speciation that new species emerge.
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Re: Homo naledi is only 250,000 years old

#111  Postby Wortfish » Jun 15, 2017 2:39 am

Thommo wrote:
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?


The exact same way that whole numbers only ever differ by one from their neighbour, yet any number has a number that is a million greater than it.

That's notwithstanding that this isn't how speciation occurs, as was already covered. And it's through speciation that new species emerge.


To use your analogy, the difference between 1 and -1 is the same as the difference between 10 and 12. But 1 and -1 are different types of signed integers whereas 10 and 12 are of the same positive type. You can't really escape the problem that - for a new species to emerge - offspring must be produced that are of that new species and not of their parents' species.

Another example would be 99 and 100. The former is two digits and the latter is three. But they are as apart as 6 and 7.
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Re: Homo naledi is only 250,000 years old

#112  Postby Cito di Pense » Jun 15, 2017 3:19 am

Wortfish wrote:
To use your analogy, the difference between 1 and -1 is the same as the difference between 10 and 12. But 1 and -1 are different types of signed integers whereas 10 and 12 are of the same positive type. You can't really escape the problem that - for a new species to emerge - offspring must be produced that are of that new species and not of their parents' species.


No, organisms have to be produced which are sufficiently different to their cousins in the next county, but don't take these terms too literally. I don't think you appreciate the magnitudes of time and distance that are involved. It means that the populations are separated by physical barriers that don't get crossed. Think of the situation of gastropods, for example, who don't travel far in their lifetimes.

Wortfish wrote: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.


But NineBerry's point is that it involves groups of organisms separated in space and not just in time.

Anyway, organisms are not integers, and have subsystems. You are losing the battle to understand biology on many fronts. It might not be fair to say that, if in fact you are simply abandoning the battle. It's not that abstruse, but you do have to be able to abandon analogy and keep three or four direct concepts active for the duration of the period that you're trying to write a sentence or two about evolution. That is, you have to be able to think about a species of organisms that have subsystems, and so on, subsystems that make up the phenotype expressing the genome. And you have to think about the separation in space as giving organisms different sets of problems to solve in living. That way you can begin to understand genetic drift in separate populations, because different environments do impose different sets of constraints on individual organisms that are geographically separated. This is what you would use to try to understand that different sets of organisms will survive in each separate range and that the sets will diverge if given enough time, not least because (given enough time) the habitats in separate ranges keep diverging, too, considering that habitats are never monospecific: everyone has to eat. Not only is the species in question changing, the species in its menu are changing, too. This divergence means that eventually all the individuals of one population will be incapable of interbreeding with any of the individuals of the other population.
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Re: Homo naledi is only 250,000 years old

#113  Postby Thommo » Jun 15, 2017 4:03 am

Wortfish wrote:
Thommo wrote:
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?


The exact same way that whole numbers only ever differ by one from their neighbour, yet any number has a number that is a million greater than it.

That's notwithstanding that this isn't how speciation occurs, as was already covered. And it's through speciation that new species emerge.


To use your analogy, the difference between 1 and -1 is the same as the difference between 10 and 12. But 1 and -1 are different types of signed integers whereas 10 and 12 are of the same positive type. You can't really escape the problem that - for a new species to emerge - offspring must be produced that are of that new species and not of their parents' species.


Not only can I escape it, but you already conceded the point in its entirety:
Wortfish wrote:
Thommo wrote:
What remains? We now have two populations which cannot interbreed and are thus different species yet we have not violated the parent-child interfertility condition.


Yep, understood. But looking at our own lineage, we know that we have ancestors that were not members of our species. How did these ancestors produce direct descendants that are not of their own species if Dawkins is to be believed?

There is no problem for species emerging.

Wortfish wrote:Another example would be 99 and 100. The former is two digits and the latter is three. But they are as apart as 6 and 7.


Umm, exactly. You have an arbitrary division (the number of digits in base 10, these numbers have the same number of digits in base 9 and 11) and you can get there with "parent numbers" that are no more different than any other set of "parents".

In addition to this analogy it has been explained directly already too:-
http://www.rationalskepticism.org/evolu ... l#p2558660

So to recap:
- You have agreed that there is no barrier to new species emerging (this is known as speciation).
- You have not challenged that large differences of any magnitude can accumulate by incremental small steps.
- You are still puzzled by the arbitrary way species get named and distinguished into categories historically.

The thing you're puzzled over doesn't matter though, it's purely conventional, and that convention is (roughly speaking) that we refer to ancestors of a population as being of a "different species" if their genome would not allow them to directly interbreed with the descendant population if both populations were alive today.
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Re: Homo naledi is only 250,000 years old

#114  Postby Wortfish » Jun 15, 2017 11:51 am

Thommo wrote:
Umm, exactly. You have an arbitrary division (the number of digits in base 10, these numbers have the same number of digits in base 9 and 11) and you can get there with "parent numbers" that are no more different than any other set of "parents".


The point is that, at least in base 10, there is a difference between 99 and 100 which is more than just a small increment. The latter has three digits whereas the former only two. A threshold has been crossed even though it took 90 increments.

So to recap:
- You have agreed that there is no barrier to new species emerging (this is known as speciation).
- You have not challenged that large differences of any magnitude can accumulate by incremental small steps.
- You are still puzzled by the arbitrary way species get named and distinguished into categories historically.


All I am saying is that a new species can only emerge if the parents of one species give birth to offspring of another species at some point - or else the same species remains. There may well be a gradual process leading up to this, but the change has to occur if a new species is to arise. If we were to trace your ancestors far back enough, one of them would eventually not meet all of the criteria for being an anatomically modern human and so would have to be categorised as a different species. However, its immediate descendant would (just) be sufficiently modern to be part of our species, thereby refuting Dawkins.

The thing you're puzzled over doesn't matter though, it's purely conventional, and that convention is (roughly speaking) that we refer to ancestors of a population as being of a "different species" if their genome would not allow them to directly interbreed with the descendant population if both populations were alive today.


Got that. But it's not just a case of historical retrospection and interpretation. As I mentioned, the ancestor with the fused chromosomes, 2a and 2b, may have been reproductively isolate from its parents. The loss of the baculum (penile bone) could have happened within a single generation, and this could have caused issues with interbreeding.
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Re: Homo naledi is only 250,000 years old

#115  Postby Thommo » Jun 15, 2017 12:09 pm

Wortfish wrote:
Thommo wrote:
Umm, exactly. You have an arbitrary division (the number of digits in base 10, these numbers have the same number of digits in base 9 and 11) and you can get there with "parent numbers" that are no more different than any other set of "parents".


The point is that, at least in base 10, there is a difference between 99 and 100 which is more than just a small increment.


If that's the point it's equally wrong in both cases. 100 is 1 more than 99, and we are only one generation removed from our parents.

This does not mean that 100 cannot be 99 more than 1, or that we cannot be 99 times more genetically distant from our ancestors of 100 generations ago.

Just because every generation may be able to interbreed with its predecessor and successor that does not mean it must be able to interbreed with its 99th degree predecessor or its 9999th. The intermediate generations have long since passed away, closing down the pathway through which genetic information once flowed in exactly the same way as geographical isolation.

Wortfish wrote:All I am saying is that a new species can only emerge if the parents of one species give birth to offspring of another species at some point - or else the same species remains.


And all you're saying is wrong. Repetition isn't required. The explanation is the same as it was on the previous occasions.

Wortfish wrote:There may well be a gradual process leading up to this, but the change has to occur if a new species is to arise. If we were to trace your ancestors far back enough, one of them would eventually not meet all of the criteria for being an anatomically modern human and so would have to be categorised as a different species. However, its immediate descendant would (just) be sufficiently modern to be part of our species, thereby refuting Dawkins.


No, because species is a concept relating to multiple populations alive at the same time. Borrowing that concept for a different situation doesn't directly translate like that.

Wortfish wrote:Got that. But it's not just a case of historical retrospection and interpretation.


It is. It is purely a matter of convention.

Wortfish wrote:As I mentioned, the ancestor with the fused chromosomes, 2a and 2b, may have been reproductively isolate from its parents.


Maybe, maybe not. Wouldn't matter either way in terms of a general principle though. If (as you repeatedly suggested) it's impossible for speciation to occur without such a quantum leap then you're about 4 billion examples short.
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Re: Homo naledi is only 250,000 years old

#116  Postby DavidMcC » Jun 15, 2017 12:11 pm

Wortfish wrote:... You can't really escape the problem that - for a new species to emerge - offspring must be produced that are of that new species and not of their parents' species.

Another example would be 99 and 100. The former is two digits and the latter is three. But they are as apart as 6 and 7.

In the case of the hominid line, a chromosome fusion event occurred, probably about 6 MYr ago, that split the human from the chimp line:

https://en.wikipedia.org/wiki/Chromosome_2_(human)
Evolution

Further information: Chimpanzee genome project

All members of Hominidae except humans, Neanderthals, and Denisovans have 24 pairs of chromosomes.[10] Humans have only 23 pairs of chromosomes. Human chromosome 2 is a result of an end-to-end fusion of two ancestral chromosomes.[11][12]

The evidence for this includes:
The correspondence of chromosome 2 to two ape chromosomes. The closest human relative, the chimpanzee, has near-identical DNA sequences to human chromosome 2, but they are found in two separate chromosomes. The same is true of the more distant gorilla and orangutan.[13][14]
The presence of a vestigial centromere. Normally a chromosome has just one centromere, but in chromosome 2 there are remnants of a second centromere in the q21.3–q22.1 region.[15]
The presence of vestigial telomeres. These are normally found only at the ends of a chromosome, but in chromosome 2 there are additional telomere sequences in the q13 band, far from either end of the chromosome.[16]

According to researcher J. W. IJdo, "We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2." [16]

(The references can be found on the linked Wiki page.)
Of course, this is not typical of speciations in general, in which a string of mutations in the germ line cells of a sub-population occurs, leading to reproductive isolation of one sub-population from athe others, and hence the splitting of one species into two.
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Re: Homo naledi is only 250,000 years old

#117  Postby DavidMcC » Jun 15, 2017 12:18 pm

... The chromosome fusion causes some genes to have a changed chemical environment, so that gene expression may change without a change in the actual gene. At the same time, breeding with unaltered karyotype becomes less successful, leading to partial genetic isolation. In the case of the human-chimp line divergence, the event occurred within a very small, physically isolated population in NE Africa.
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Re: Homo naledi is only 250,000 years old

#118  Postby Wortfish » Jun 15, 2017 1:11 pm

Thommo wrote:
Just because every generation may be able to interbreed with its predecessor and successor that does not mean it must be able to interbreed with its 99th degree predecessor or its 9999th. The intermediate generations have long since passed away, closing down the pathway through which genetic information once flowed in exactly the same way as geographical isolation.


Let's play along with this. So your argument is that interbreeding is possible for the immediate predecessors/successors but that if we go back 100 genertions or so, interbreeding might not be possible. OK. But in the gradual model you espouse, there has to be a point at which, if we did have the two generations separated by time living contemporaneously, interbreeding wouldn't work out. Thus, the parents of the offspring of generation Y might just about be able to interbreed with their ancestors of generation X, but the offspring, repesenting generation Z, might not be able to because a threshold has now been crossed and the cumulative number of incremental changes means a new species has now arisen.

No, because species is a concept relating to multiple populations alive at the same time. Borrowing that concept for a different situation doesn't directly translate like that.


Well, Homo erectus and Homo sapiens were contemporaries and yet the former was also ancestral to the latter.

It is. It is purely a matter of convention.


It is also a matter of definition in terms of reproductive compatibility.

Maybe, maybe not. Wouldn't matter either way in terms of a general principle though. If (as you repeatedly suggested) it's impossible for speciation to occur without such a quantum leap then you're about 4 billion examples short.


Well, at least in plants, whole genome duplications can easily result in a new species suddenly appearing as Dawkins admits. That isn't a quantum leap though.
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Re: Homo naledi is only 250,000 years old

#119  Postby Thommo » Jun 15, 2017 1:20 pm

Wortfish wrote:
Thommo wrote:
Just because every generation may be able to interbreed with its predecessor and successor that does not mean it must be able to interbreed with its 99th degree predecessor or its 9999th. The intermediate generations have long since passed away, closing down the pathway through which genetic information once flowed in exactly the same way as geographical isolation.


Let's play along with this. So your argument is that interbreeding is possible for the immediate predecessors/successors but that if we go back 100 genertions or so, interbreeding might not be possible. OK. But in the gradual model you espouse, there has to be a point at which, if we did have the two generations separated by time living contemporaneously, interbreeding wouldn't work out. Thus, the parents of the offspring of generation Y might just about be able to interbreed with their ancestors of generation X, but the offspring, repesenting generation Z, might not be able to because a threshold has now been crossed and the cumulative number of incremental changes means a new species has now arisen.


Sort of, but not really. Because that's not how a species is defined.

In particular in terms of the way you conceptualized it:
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...

it doesn't follow.

There's no transitive property of direct reproductive compatibility here. Just because the 100th generation descendant is reproductively incompatible with the ancestor doesn't mean the 50th is.

Wortfish wrote:
It is. It is purely a matter of convention.


It is also a matter of definition in terms of reproductive compatibility.


For species alive at the same time. Which isn't the case in your situation.

Wortfish wrote:
Maybe, maybe not. Wouldn't matter either way in terms of a general principle though. If (as you repeatedly suggested) it's impossible for speciation to occur without such a quantum leap then you're about 4 billion examples short.


Well, at least in plants, whole genome duplications can easily result in a new species suddenly appearing as Dawkins admits. That isn't a quantum leap though.


That doesn't seem relevant.
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Re: Homo naledi is only 250,000 years old

#120  Postby Cito di Pense » Jun 15, 2017 1:37 pm

Thommo wrote:The explanation is the same as it was on the previous occasions.


The Bard of Hibbing, recent Nobel laureate in literature, wrote:

And me, I sit so patiently, waiting to find out what price
You have to pay to get out of going through all these things twice.
Хлопнут без некролога. -- Серге́й Па́влович Королёв

Translation by Elbert Hubbard: Do not take life too seriously. You're not going to get out of it alive.
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