Is Evolution a "posthuman" concept?

[mzungu]

Good idea. Do we ever see a new dog species showed up?
Why can dog have new species and human can not?

all dogs can interbreed and therefore they are one species.

Read this article on the Galapagos Finches and you will understand what I mean: "Instant" Evolution Seen in Darwin's Finches, Study Says

I know that you have a closed mind and no amount of evidence will convince you but I have only two choices here: To debate the issue with you or to ignore you totally. This is a debate forum and so far you have brought forth nothing of substance that can give credence to your dismissal of ToE.

All scientists dream of refuting any scientific theory yet ToE stands. Do you honestly think this is a worldwide conspiracy? Anyone who can refute ToE will not only win the Nobel but will become the most famous scientist of all time.

 

[sfs]

So, what is the nature of the genetic "difference". Be mercy on my ignorance to genetics. Thanks.

Several million genetic variants are at different frequencies in the two populations. Several more million rare variants are present in one population but not the other. For some pairs of populations, there are a small number of genetic variants that are at 100% in one population and 0% in the other, but it's only a tiny fraction. Almost all differences between human populations are a matter of how common a variant is.

 

[sfs]

Why does it stop at the Homo erectus? Was the interbreeding frequent enough then to stop the evolution?

As has already been explained to you several times in this very thread, evolution didn't stop. Geographically separated human populations became different genetically; that's evolution, and that's why different groups of people look different. (Remember when we just discussed this?) Had it kept going ten times as long, perhaps a really isolated group would have formed a different species. Perhaps not.

In a populated country such as India or China, the majority of people do not interbreed for many thousands of years (they still don't today). Would that create some genetic differences among those populations?

That would create small genetic differences, as indeed it has. There is far too much gene flow between India and China for it to lead to speciation, almost certainly.

 

[sfs]

We do have example of fast speciation which took place in hundreds of years (those are used to argue for evolution). We have also seen something did not evolve at all over millions of years.

Yes. Speciation rates vary a lot. Obviously, speciation is likely to occur faster in a species that has twenty generations in a year than in one that goes 25 years between generations like humans.

If human race is an indication of human evolution, then how fast did it happen?

We don't have a complete enough record, but in our immediate lineage speciation might occur once or twice in a given line in a million years. No reason this should be a constant rate, since it depends not only on the rate of evolution but on whether the species splits geographically or not.

 

[sfs]

So are the genetic differences between the average Indian people (as a group, because most of them "intra-breed" even today) and average Chinese people (same situation) become bigger and bigger? If not, why not?

They're getting smaller (as I already said previously) because there is too much interbreeding.

You may choose groups of small population to answer this question. But I do not know the name of the group which has small population and is not interbreeding. I am sure there are many. For example, a small tribe in a remote area of some isolated place. That is why I used Eskimos.

There are virtually no such groups with zero outbreeding over many generations. The best candidates I can think of are the Jarawa and Sentinelese of the Andaman Islands.

 

[sfs]

So, why don't we have a new human species?

Because all humans can still interbreed with other humans.

Are you a new species since your y-chromosome is different from your ancestor 1000 years ago?

No. The genetic differences involved do not split humans into reproductively isolated groups.

Which one of the two is called human? If both are, then why is the change meaningful?

"Meaningful" is in the eye of the beholder. It's a change, and that makes evolution. Whether it's meaningful depends on what kind of change you're interested in.

 

[juvenissun]

all dogs can interbreed and therefore they are one species.

All humans can interbreed. Then why are races the sign of evolution?

Don't bother to answer. I am just giving you a little hard time based on the logic of your comment.

 

[juvenissun]

As has already been explained to you several times in this very thread, evolution didn't stop. Geographically separated human populations became different genetically; that's evolution, and that's why different groups of people look different. (Remember when we just discussed this?) Had it kept going ten times as long, perhaps a really isolated group would have formed a different species. Perhaps not.


That would create small genetic differences, as indeed it has. There is far too much gene flow between India and China for it to lead to speciation, almost certainly.

How do you figure that? I thought there has been very little gene flow between the two. Is there a BIG mountain which separates the two? Plus they both have huge amount of population.

 

[sandwiches]

All humans can interbreed. Then why are races the sign of evolution?

Don't bother to answer. I am just giving you a little hard time based on the logic of your comment.

The reason you're struggling with such a simple concept, Juvy, is because you fail (refuse?) to understand that evolution does not always lead to different species.

Tell you what: Make some nice chamomile tea. Read a few articles on the subject. Think about it calmly. Maybe light a candle for relaxation, then come back and see if it's clear to you, then.

 

[sfs]

All humans can interbreed. Then why are races the sign of evolution?

Don't bother to answer. I am just giving you a little hard time based on the logic of your comment.

But you're not giving him a hard time based on the logic of his comment. Your response makes no sense at all, given what the word "evolution" means.

 

[juvenissun]

Because all humans can still interbreed with other humans.


No. The genetic differences involved do not split humans into reproductively isolated groups.


"Meaningful" is in the eye of the beholder. It's a change, and that makes evolution. Whether it's meaningful depends on what kind of change you're interested in.

This is well said. I hate paleontology. And I think I hate anthropology too.

Your definition of evolution is the most basic and the most generous one. Yet you can not specify the conditions for the emergence of a new human species (regardless of population). To the past (vanished) human species, all you can say is that we do not know why did they appear and why did they disappear (except a few general principles which are theoretical). By your definition, human certainly evolves today. But most likely, we will not see any visible changes. To me, that means no evolution based on a more meaningful definition to me. As a consequence, the genetic difference among races is a result of evolution to you, but since they are still all humans, it is not a feature of evolution to me.

Side point: If the most modern life form such as human is so hard to pinpoint the track of its evolution, how can anyone be sure on anything based only on fossil record? That is why I can not accept the traditional idea of evolution. It is simply a giant myth, when compared with your studies on humans.

 

[sfs]

How do you figure that? I thought there has been very little gene flow between the two. Is there a BIG mountain which separates the two? Plus they both have huge amount of population.

But it takes very little gene flow to maintain similarity between two populations. Unless a particular variant is being directly selected for in one of the populations, the differences grow because of genetic drift. To set the scale, consider a genetic variant that has an allele frequency of 50% in a population of size 100,000,000 individuals. Each generation the allele's frequency will change randomly by ~7000 copies, out of the 100,000,000 copies in the population. Migrants from another population with the same allele frequency will have a larger effect on the frequency if they number ~14,000 individuals per generation. That means the two populations will not drift apart if there are ~560 migrants per year, which is much smaller than the actual number of people that effectively migrate.

 

[sfs]

Your definition of evolution is the most basic and the most generous one. Yet you can not specify the conditions for the emergence of a new human species (regardless of population). To the past (vanished) human species, all you can say is that we do not know why did they appear and why did they disappear (except a few general principles which are theoretical). By your definition, human certainly evolves today. But most likely, we will not see any visible changes. To me, that means no evolution based on a more meaningful definition to me. As a consequence, the genetic difference among races is a result of evolution to you, but since they are still all humans, it is not a feature of evolution to me.

I care about the definition of "evolution" used by biologists. You can define "evolution" to mean "buttermilk pancakes" -- use whatever language you like. What the scientists are talking about, however, is what I'm talking about.

Side point: If the most modern life form such as human is so hard to pinpoint the track of its evolution, how can anyone be sure on anything based only on fossil record?

We can't be sure about the precise historical track of the evolution of most species, in the sense that we don't know which fossils represent ancestral species and which represent closely related side branches. We don't know why species split, but we still know they're related. We don't know exactly when or why Neandertals and modern humans diverged, but we know they're closely related, because we can look at their genes. We know that chimpanzees and humans are more closely related than either is to gorillas, again because we have looked at their DNA.

That is why I can not accept the traditional idea of evolution. It is simply a giant myth, when compared with your studies on humans.

That's not a reason, at least not a rational one. I don't know anything about the precise historical track of your ancestry; you probably don't know much either, past a few generations. Does that mean we should consider your ancestry a myth? Of course not. Given a sample of your DNA (and maybe fifty bucks) I could tell you in great detail what fraction of your ancestors came from which continents.

 

[juvenissun]

But it takes very little gene flow to maintain similarity between two populations. Unless a particular variant is being directly selected for in one of the populations, the differences grow because of genetic drift. To set the scale, consider a genetic variant that has an allele frequency of 50% in a population of size 100,000,000 individuals. Each generation the allele's frequency will change randomly by ~7000 copies, out of the 100,000,000 copies in the population. Migrants from another population with the same allele frequency will have a larger effect on the frequency if they number ~14,000 individuals per generation. That means the two populations will not drift apart if there are ~560 migrants per year, which is much smaller than the actual number of people that effectively migrate.

What a wonderful calculation. I have to admit that I don't have the knowledge base to argue about it.

But, could this be proportional? Would 1 migrant affect the gene homogenization in a group of 200,000 population? It is very hard to imagine that it will.

 

[juvenissun]

I care about the definition of "evolution" used by biologists. You can define "evolution" to mean "buttermilk pancakes" -- use whatever language you like. What the scientists are talking about, however, is what I'm talking about.


We can't be sure about the precise historical track of the evolution of most species, in the sense that we don't know which fossils represent ancestral species and which represent closely related side branches. We don't know why species split, but we still know they're related. We don't know exactly when or why Neandertals and modern humans diverged, but we know they're closely related, because we can look at their genes. We know that chimpanzees and humans are more closely related than either is to gorillas, again because we have looked at their DNA.

That's not a reason, at least not a rational one. I don't know anything about the precise historical track of your ancestry; you probably don't know much either, past a few generations. Does that mean we should consider your ancestry a myth? Of course not. Given a sample of your DNA (and maybe fifty bucks) I could tell you in great detail what fraction of your ancestors came from which continents.

So, according to you, what would be the most favorable conditions for the appearance of another human species?

*population size ?
*degree of isolation ? (? migrant/yr)
*time interval ?
*Pressure of change ? (biological or non-biological, low, medium or high)

Let's assume I give the above items some optimum values, would you still say that you are not sure that there will be a new species come up?

 

[mzungu]

So, according to you, what would be the most favorable conditions for the appearance of another human species?

*population size ?
*degree of isolation ? (? migrant/yr)
*time interval ?
*Pressure of change ? (biological or non-biological, low, medium or high)

Let's assume I give the above items some optimum values, would you still say that you are not sure that there will be a new species come up?

Consider this:

You have a 1968 Mustang in mint condition. You decide to move to Europe and take your car with you. In Europe Mustang parts are hard to come by and when your alternator packs up you decide to replace it with an European one of approximately the same same characteristics.

Your car now is not 100% the same as it was before but in all respects it is still a Mustang.

Slowly as time goes by you keep replacing small parts like bulbs, fan belts, brake pads tires etc. So far it is still considered a Mustang. Now you decide to move to Mongolia where parts are not available. With every breakdown you take it to the workshop and the mechanics replace the engine and gearbox with such from other vehicles made in China and they need to modify the engine mounts and gearbox mounts of the Mustang to fit the foreign engine and gearbox.

Now you still have a Mustang but it cannot be considered a mustang as the main components (engine and gearbox) of original Mustangs will no longer fit directly into your Mustang. It is a Hybrid "Mule". Part Mustang part Chinese.

Then you do the same with all the mechanical component bar the body. Now you have a car that resembles a mustang but is not a Mustang. It belongs to the family: Automobiles

of the type: Family car

of the model: "Mustangchina" which for all intents and purposes cannot be defined as a Mustang but be as a new type of car "New species"

As you can see the different stages of evolution of your car at some point ended up creating a new species but was not so when the changes were small.

If you cannot understand this analogy then May I recommend you indulge in something new like "Ham slicing with lasers". Very handy if you ever join the crew of the SS Enterprise!

 

[juvenissun]

Consider this:

You have a 1968 Mustang in mint condition. You decide to move to Europe and take your car with you. In Europe Mustang parts are hard to come by and when your alternator packs up you decide to replace it with an European one of approximately the same same characteristics.

Your car now is not 100% the same as it was before but in all respects it is still a Mustang.

Slowly as time goes by you keep replacing small parts like bulbs, fan belts, brake pads tires etc. So far it is still considered a Mustang. Now you decide to move to Mongolia where parts are not available. With every breakdown you take it to the workshop and the mechanics replace the engine and gearbox with such from other vehicles made in China and they need to modify the engine mounts and gearbox mounts of the Mustang to fit the foreign engine and gearbox.

Now you still have a Mustang but it cannot be considered a mustang as the main components (engine and gearbox) of original Mustangs will no longer fit directly into your Mustang. It is a Hybrid "Mule". Part Mustang part Chinese.

Then you do the same with all the mechanical component bar the body. Now you have a car that resembles a mustang but is not a Mustang. It belongs to the family: Automobiles

of the type: Family car

of the model: "Mustangchina" which for all intents and purposes cannot be defined as a Mustang but be as a new type of car "New species"

As you can see the different stages of evolution of your car at some point ended up creating a new species but was not so when the changes were small.

If you cannot understand this analogy then May I recommend you indulge in something new like "Ham slicing with lasers". Very handy if you ever join the crew of the SS Enterprise!

It still looks like a Mustang. At normal speed, it runs like a Mustang. It then, still is a Mustang.

Use it as an analogy to human race. Even it does not look like the original Mustang anymore (painted with a different color), it is still a Mustang.

 

[mzungu]

It still looks like a Mustang. At normal speed, it runs like a Mustang. It then, still is a Mustang.

Use it as an analogy to human race. Even it does not look like the original Mustang anymore (painted with a different color), it is still a Mustang.

No it is not a Mustang when all the parts are not Mustang parts.

Remember that the hummingbird moth looks and flies like a hummingbird but they are totally different animals.

Sorry Juve but I think you are purposely being dismissive and are not in the least interested in learning anything.

BYE

 

[sfs]

What a wonderful calculation. I have to admit that I don't have the knowledge base to argue about it.

But, could this be proportional? Would 1 migrant affect the gene homogenization in a group of 200,000 population? It is very hard to imagine that it will.

No, 1 migrant would have little effect. Genetic drift increase as the square-root of the population size (it's just binomial sampling error), so starting with a population of 100,000, the equivalent number of migrants needed would be ~25/year.

 

[sfs]

So, according to you, what would be the most favorable conditions for the appearance of another human species?

*population size ?
*degree of isolation ? (? migrant/yr)
*time interval ?
*Pressure of change ? (biological or non-biological, low, medium or high)

Let's assume I give the above items some optimum values, would you still say that you are not sure that there will be a new species come up?

There are no precise numbers to offer: speciation has not been observed many times, and reconstruction of past speciation has too many uncertainties. The general rules are clear: The smaller the population size (as long as it is large enough to be sustainable), the greater the isolation and the longer the time, the higher the probability of speciation. Degree of selective pressure matters a great deal if the pressure is on a trait that directly or indirectly affects reproductive compatibility, e.g. pressure for two populations of plants to flower at different times of the year would make them speciate very quickly. Strong selection on a trait that isn't related to compatibility but that is highly polygenic (affected by many genes) might have a modest effect, while selection on an unrelated single-trait locus should have very little effect.