Speciaion in humans

[lucaspa]

According to the above, I'd say they do - or at least, the 'races' we have today developed from three (four?) sub-species.

 

Do any of the "races" have sub-specific names? NO! And the "races" as you listed them don't have allopatric or peripatric distribution. You've tried to make them allopatric, but Negroid is not confined to sub-Saharan Africa. After all, most Melanesians share the same morphological appearance as Negroid but are on the "other side" of both Caucasoid (Persians) and Mongoloid.

 

Also, having "races" develop from sub-species goes against all that we see in evolution. Populations split: you start with a single population and then they split. Not have multiple populations and have them merge.

 

Lucas: "Races" is a meaningless term, as Futuyma (and the Scientific American article) note and demonstrate. "Races" are not the same as biological populations."

 

Agreed

 

Bombus, right here you contradicted your whole argument! If "race" is a meaningless term, then they can't be equated to sub-species OR used as the basis of new speciation! You destroyed your whole position by agreeing with my contrary position! Don't you see that?

 

So, now that you agree with my position -- that races can't be either sub-species or a basis of speciation, let's look at some of the specific statements for accuracy.

 

Agreed, but that doesn't mean a thing. E.g., Humans belong the Genus Homo, but Apes are classed as Pongo, for no specific reason apart from the fact that they are not human!

 

1. That the human "races" have not been classified as a sub-species does mean something. Look at Futuyma again: "A taxonomic term for populations of a species that are distinguishable by one or more characteristics, and are given a subspecific name"

 

2. Your view of classification is mistaken. Apes and humans are classed in the same order Cattaharines. Humans and apes are clased in a different family -- humans in Homonidae and apes in Pongidae. It can be argued that apes and humans should be in the same family. But that is exactly opposite of what you are arguing. You are saying that human races should be split but arguing that humans and apes should be lumped together. Internally inconsistent.

 

However, it is clear that humans do belong in a separate genus from all other apes. Just as chimps, gorillas, and orangutuans all belong in their own genera. The split from common ancestors happened long enough in the past and there have been several speciations since that split. What we have now is just a few survivors of a very rich bush with lots of species. http://pin.primate.wisc.edu/av/slidesets/slides_t/gifs/19a.gif

 

The question was whether different races could develop into different species if isolated. It only takes some members each race (however one defines them) to be isolated for new species to emerge.

 

And I answered that in my first post in the group #13 I suggest you go back and read it. Races are too ill-defined to be a group. There is too much variation of characteristics within races for what you classed as "race" to be a meaningful term. http://www.sciam.com/article.cfm?cha...AA83414B7F0000

 

Populations of humans are smaller and more homogenous. And yes, a few populations are isolated and there is evidence that they are evolving to new species. Again, read my post. Whether they continue to diverge or gene flow merges them back into the main population of H. sapiens remains to be seen.

 

Not according to the Radio 4 program I recently listened to with the guy who mapped the human genome. Anyway, genetic difference is not necessarily relevant.

 

If genetic difference is not relevant, then why bring it up? Also, you have to have genetic difference to express itself in how you decide you have a sub-species. It is also necessary for reproductive isolation to continue. As to genetic diversity, read this article:

7. A Gibbons, Studying humans -- and their cousins and parasites. Science 292:627-629, April 27, 2001.

 

A half-remembered radio program is no substitute for an article in a science journal, Bombus. You need a firmer basis on which to base your ideas. Wikipedia is not an acceptable source, because there is no control over content. Anyone can place whatever nonsense they want on the site.

 

Lucaspa: Each "race" as you defined it consists of dozens/hundreds of populations. "

 

Yes, but that doesn't affect the argument.

Sure it does. If we are looking at the functional unit that becomes a new species, if race is an amalgam of smaller functional units, then it can't be the unit of speciation! Instead, populations are the unit of speciation. Genera can't be the unit of new speciation, either, because they are an amalgam of several different species. So, the "races" as you defined them in post #14 cannot be the source of new species.

 

At one point in biology, "race" = population. But that isn't true in your argument. A population within a "race" could be a source of a new species of Homo.

 

The whole idea of race is based on morphological difference! Let's look at what you wrote again:

 

Bombus: Members of the group are reliably distinguishable from members of other groups. The distinction can be made in any of a wide number of ways, such as: differently shaped leaves, a different number of primary wing feathers, ... relative size of certain bones, different DNA sequences, and so on. There is no set minimum 'amount of difference': the only criterion is that the difference be reliably discernable.

 

"reliably distinguished" is morphology.

So is the idea of sub-species:

 

The quoted source was Wiki, but I was taught it in University. Basically, although human races are not divided into subspecies, if the 'rules' were applied to humans one could quite correctly divide us up into three or four subspecies.

 

1. One unreliable source and one that can't be checked upoon for accuracy!

2. As I have pointed out with reliable sources you can check, your argument is refuted -- as you agreed to! Humans can't be divided up into subspecies at the moment. Even if they could, "races" would not be it. The "races" are not morphologically, genetically, or reproductively enough different to warrant the division. Now, if you want to make an argument that the !Kung are a subspecies, that would be better. However, in light of Futuyma and other textbooks saying that "subspecies" is a meaningless term, even then you won't get far. You can accurately say that the !Kung are a population.

 

Lucaspa: "The phenetic species concept was the one used in Darwin's time and is still applied to fossils. It is NOT the one used between contemporary sexually reproducing species -- such as humans.

 

Maybe, but again, doesn't really affect my argument.

 

Sure it does! Look at what you wrote about how to distinguish a subspecies:

The whole idea of race is based on morphological difference! Let's look at what you wrote again:

 

Bombus: Members of the group are reliably distinguishable from members of other groups. The distinction can be made in any of a wide number of ways, such as: differently shaped leaves, a different number of primary wing feathers, ... relative size of certain bones, different DNA sequences, and so on. There is no set minimum 'amount of difference': the only criterion is that the difference be reliably discernable.

 

"reliably distinguished" is morphology. Of 6 example criteria you proposed, 4 of them are morphological! Which is the phenetic species concept! So you are basing sub-species on the phenetic species concept?

 

Lucaspa "This one doesn't exist. You are misrepresenting the biological species concept. That concept states:

 

Biological species are defined as "different species represent different gene pools, which are goups of interbreeding or potentially interbreeding individuals that do not exchange genes with other such groups." D Futuyma Evolutionary Biology pg 27. Notice how you have changed "do not exchange genes" to "flow of genetic material ... is small". You have warped the terminology to suit your own ends."

 

No idea what your on about there?? Are you on drugs?

 

LOL! Of course you have an idea what I'm talking about. That's why you went to ad hominem. You got caught and now you are trying to distract by insulting me.

 

Sub-species can freely breed with each other and produce fertile offspring. ... The question was whether different races [sub-species] could develop into different species if isolated.

 

Again you destroy your whole agrument! If sub-species are completely interfertile, then there is no basis for speciation! Speciation in sexually reproducing organisms requires reproductive isolation! That's how all the tests on "incipient" speciation are done: looking at reproductive isolation and how far it has gone.

 

You tried to claim reproductive isolation for the races/sub-species: "2. The flow of genetic material between the group and other groups is small and can be expected to remain so because even if the two groups were to be placed together they would not interbreed to any great extent."

 

It's obvious that, when the human "races" are placed together, considerable interbreeding results. Therefore, by your definition, the human races are NOT subspecies.

[bombus]

Lucaspa, you have misunderstood so many of my arguments that i shall just restate it from the start and very clearly for you, else we'll end up going all over the place.

 

I maintain that our current multitude of types of Homo sapiens are developed from a basic stock of humans comprising three (or four) sub-species.

 

These sub-species were/are:

 

1. Caucoisoid (an inaccurate term including modern Europeans, Mediterraneans, Persians, Afghans, Northern Indians, Western Russians etc)

2. Negroid (Sub-saharan Africans)

3. Mongaloid: (Chinese, Japanese, Inuit, ongls, North American and South American 'Indians' etc)

4. Australoid (Veddans, Australian aborigines, Ainu, Uralics) Some class this as a sub-group of 1.

 

There has been much mixing of these basic 'sub-species' producing a multitude of groups that show a range of morphological features. However, the basic sub-species are still around and are readily distinguishable by geographical location.

 

Just so you are absolutely clear, I DO KNOW that humans are not divided in scientific textbooks into sub-species, that's not the point. The point is whether we could (and be scientifically correct) if we chose to do so.

 

One other thing, regarding Apes and Humans, I said Genus but should have said Family. The point was to illustrate that taxonomy is often arbitrary - as is the 'decision' NOT to sub-divide humans into sub-species.

 

Also, Melanesians are not related to Negroid people. They have developed their characteristics independently.

 

I am correct!

[SkepticLance]

To bombus

 

The problem we have here is the lack of clear cut definitions for the taxonomic categories - species, sub-species, and races.

 

I do not think such definitions are impossible, though they will require somewhat arbitrary decisions to be made. They must be based on genetics, not physical characteristic. Imagine brothers. One becomes a tribal warrior. He spends time outdoors and develops a dark tan. He works hard and develops massive muscles. The other becomes tribal shaman, and skulks around in the dark, and fasts often, and never exercises. He becomes pale and puny. Simple physical characteristics might tell you they are unrelated. DNA would tell the truth, though.

 

Thus, to determine if two populations are two different species, different sub-species, different races, or simply different populations of the same group, we need to measure their genetic similarity or difference, and have definitions based on degree of genetic difference.

 

Human 'races' are genetically VERY similar to each other. This to the degree that a white European might be genetically more different from his white neighbour, than he is to an individual of the Zulu tribe. This is why we would not call them different sub-species.

[DeadBeat10]

I like to think of it as the galapagos islands, we just havent been separated long enough yet...

[phylumeister]

To go back to the actual question and not a battle over definitions, the human race currently would not speciate due to our adaptions that become less and less apart of genetics as technology adapts for s. For example, if a group of lets say black labs were released into the arctic, if they manage to survive, they would develop a heavy coat of fur over many generations to adapt, humans however would not do the same, instead a human would build a shelter and obtain warm clothing and thus has a significantly less need to adapt. Due to technology becoming more and more readily available around the world, the need to adapt becomes less and less genetically and so speciation becomes less and less probable. Even if people were sent to an asteroid or something, they would probably just use technology to reconstruct there own environment and thus speciation doesn't appear to be in the future.

[lucaspa]

To go back to the actual question and not a battle over definitions, the human race currently would not speciate due to our adaptions that become less and less apart of genetics as technology adapts for s.

 

That is partly true. Technology does remove a lot of selection pressures for us. But it doesn't remove all the selection pressures.

 

However, in the case of the arctic, humans did adapt to the lower UV irradiation by selection for those individuals with less melanin in their skin.

 

In the case of colonizing an asteroid, technology will not totally compensate for the lower gravity and that becomes a selection pressure.

 

You also need to consider gene flow as another counter to speciation. Even if selection pressures are present in two populations, if there is extensive gene flow between those populations, speciation will still not occur. That's why I emphasized the relative reproductive isolation of the !Kung.

 

As human technology improved transportation, travel became easier and gene flow increased.

 

So you have technology inhibiting human speciation by both altering the environment and shielding us from natural selection and by promoting gene flow by better transportation. It still remains to be seen whether small populations such as the !Kung or Himalayan highlanders can remain isolated enough long enough to give a new species of Homo.

[SkepticLance]

The idea that human evolution has essentially stopped due to technology is a very controversial one. Opinions differ. We have no clear cut scientific data to take one position or the other.

 

Personally, my own humble opinion is that evolution never stops. It may slow down, or speed up, or take a different direction - but never stops.

 

I also think it does not matter. Our new understanding of genetics is leading us inevitably to the capability to change our own genetic make up. While there is a lot of moral outrage at the idea of genetically engineering humans, I think that, with the ability, inevitably we will will do it. Thus, new and genetically different humans will come into being. Some of these changes will be special adaptations. For example : when space travel becomes more common, and more prolonged, we will probably genetically engineer people to be more resistant to the harmful effects of cosmic rays.

 

Evolution of humans in the future will probably be accelerated, and under our own control.

[Paralith]

Actually, some people think we have rather clear evidence that humans are still evolving, and faster than ever. After all, any change in gene frequencies from generation to generation in the human population counts as evolution.

[SkepticLance]

To Paralith

 

I agree that humans are changing. Your reference, though, was referring to changes over the past 5000 years, which does not give data on whether evolution is happening right now.

[iNow]

It doesn't matter. You said that there was controversy over the idea that humans are still (or, have stopped) evolving. Paralith showed one single source (among... I'm sure ... scores she could have) which showed how anybody who claims humans have stopped evolving is either seriously misunderstanding the situation or lying.

 

 

Evolution is always happening.

[Mr Skeptic]

Actually, some people think we have rather clear evidence that humans are still evolving, and faster than ever. After all, any change in gene frequencies from generation to generation in the human population counts as evolution.

 

But is this "forwards" or "backwards" or neutral evolution? Are we better because of it? Would, say, a bacteria exposed to unsustanable amounts of mutagens be considered to be evolving, or dying out (ie, so many mutations that they will eventually die out)?

 

Regardless, I don't think it matters. We humans are impatient, and would never wait thousands or millions of years for evolution to do its thing. We now have the ability to Intelligently Redesign (genetic engineering, new protein design, etc) ourselves, and we will use it. Perhaps we will make ourselves a different species within a few hundred years.

[bombus]

The idea that human evolution has essentially stopped due to technology is a very controversial one. Opinions differ. We have no clear cut scientific data to take one position or the other.

 

Quite right!

 

Humans are still evolving due to sexual selection, which is independant of 'environmental' pressures.

 

As a quick example, the peacocks tail has nothing to do with environmental adaptation, only sexual selection!

 

Our 'tail' is our big brain...

[SkepticLance]

To bombus

 

Nice interesting topic - sexual selection in humans - how much of the physical and behavioural nature of moderns humans came from this kind of evolution?

 

 

I am inclined to think that gender specific behaviour has, to a degree, been selected for by the opposite gender. For example : the human female obsession with her own good looks - hours in beauty parlours, shopping for clothes, applying make-up etc - has been 'programmed' into women by evolution, because males are attracted to good looking females. Thus, a female who takes the time and effort to look good has a better chance of winning a desirable mate.

 

Females have, on the other hand, 'programmed' males into becoming very competitive, because the male who rises above his peers has a better chance of winning a desirable female as his mate.

[Psyber]

When one considers epigenetics as well one must think change continues, even if we do not see it happening. Why should it stop?!

 

Our environment has changed - in the last generation our society has started to favour those who can multitask with their phones and computers, and removed the need for the sustained concentration needed for tasks like reading books and doing calculations in their heads instead of with a machine. Some studies suggest the flashing light of TV sceens and computer monitors may modify EEG detectible electrical patterns towards more short-term focus and more reactivity - ADHD like patterns.

 

For example, the change of style shows up if you compare the new "Dr Who" series with those from the 1970s. The new series is full of noise and frenetic activity/reactivity, but contains less philosphy and consideration.

 

Where may this lead us??

[bombus]

To bombus

 

Nice interesting topic - sexual selection in humans - how much of the physical and behavioural nature of moderns humans came from this kind of evolution?

 

 

I am inclined to think that gender specific behaviour has, to a degree, been selected for by the opposite gender. For example : the human female obsession with her own good looks - hours in beauty parlours, shopping for clothes, applying make-up etc - has been 'programmed' into women by evolution, because males are attracted to good looking females. Thus, a female who takes the time and effort to look good has a better chance of winning a desirable mate.

 

Females have, on the other hand, 'programmed' males into becoming very competitive, because the male who rises above his peers has a better chance of winning a desirable female as his mate.

 

Yes. If you think about what humans find physically attractive (especially males) they all tend to correlate with neotenic (youthful) features. Having a big brain compared to body size is a neotenic feature, so my guess is that we are actually selecting for big brains without really knowing it.

 

We will end up as skinny baby type things with huge heads. Almost exactly like 'grey' aliens. Perhaps they are actually humans from the far future:D

[Daecon]

Are African and Indian Elephants two different species or just two different races?

[Paralith]

Two different species - their geographical distance from each other presents a pretty firm barrier to gene flow between them.

[Mr Skeptic]

Two different species - their geographical distance from each other presents a pretty firm barrier to gene flow between them.

 

And more importantly, it has been so for a very long time.

[bombus]

But the elephants that hannibal used were neither alledgedly, an extinct species (or perhaps sub-species, probably of 'Indian' Elephant).

 

Also, FYI, there was a mammoth alive and well in S. America until 500AD called the Imperial Mammoth. It was hairless though. Hunted to extinction by man presumably.

[dichotomy]

Are Tigers and Lions the same species if they can only produce fertile female offspring, but at the same time produce only infertile male offspring?

 

I think if a species can produce fertile offspring then they are still the same species. Even if the only fertile offspring are either only male, or, only female. What does science think? labels are sometimes futile I suppose?

[Orbital]

I think a lot of this comes down to semantics. I must say I do find it interesting that we, as humans, find it neccessary to create such a word as 'race' which doesn't seem to be applied to any other life form on earth. Sorry, but we are animals and I'm not going to pretend we aren't, and I can't imagine many of you would either. So do we see race in animals? Or do we just see species and subspecies? What is the animal equivelent of race? Is it sub species? Or could it be 'breed', as with domestic animals? I must say I think bombus raises some good points. I guess it is really a difficult problem as there is no scientifically accepted definition of 'species' (and hense 'sub species') and no scientifically accepted definition of 'race'. In fact, the term 'race' is (as previously stated by others in this thread), not really a scientifically based concept, more of a general term used by the lay person.

[Daecon]

Are Tigers and Lions the same species if they can only produce fertile female offspring, but at the same time produce only infertile male offspring?

 

I think if a species can produce fertile offspring then they are still the same species. Even if the only fertile offspring are either only male, or, only female. What does science think? labels are sometimes futile I suppose?

 

So if these females were to produce more offspring with either a Tiger or a Lion, and the offspring was a fertile male, would that [1/4 Tiger & 3/4 Lion] or [1/4 Lion & 3/4 Tiger] male be able to breed with (another) 1/2-1/2 female?

[dichotomy]

So if these females were to produce more offspring with either a Tiger or a Lion, and the offspring was a fertile male, would that [1/4 Tiger & 3/4 Lion] or [1/4 Lion & 3/4 Tiger] male be able to breed with (another) 1/2-1/2 female?

 

I'm not sure. But I think that may be the case. What I know is that Lion and Tiger males breeding with female ligers and tigons do produce fertile offspring of either sex. So it seems that it is possible. Can anyone else help here?

[Paralith]

The offspring of a female lion and a male tiger are called tigons, and the offspring of a male lion and a female tiger are called ligers, and they are the largest cats in the world (siberian tigers are the largest pure cats in the world).

 

Only female tigons and ligers are fertile; males are sterile.

 

The key thing to think about when it comes to defining separate species is a barrier to gene flow. The most obvious barrier is of course physical separation, but behavioral and anatomical barriers can also work just as well. If the males and females of two different species don't give each other the right behavioral mating cues, then they might not ever mate, even if their ranges overlap and they were physically capable of having fertile, hybrid offspring. It's all a moot point if they never mate in the first place.

 

Lion and tiger hybrids have been known to occur in the wild, but very rarely, probably because even when lion and tiger ranges did overlap in the past, the behavioral differences prevented most potential hybrid matings. And what small amount of gene flow that might have come from these very few female hybrids is not anywhere near enough to begin a true hybridization of the two species.