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Posted: 02 February 2008 10:52 PM   [ Ignore ]
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How certain are we that all the Hominidae alive today are either chimps, gorillas, orangutans, bonobos, and homo sapiens? Is it possible that there could be another hominoid species alive (I presume somewhere in Africa) that looks very much like us but genetically would be classified as a different species (different enough for our two species not being able to produce an offspring)? How great is our knowledge of the African continent? It could be a small tribe of a few individuals, a group of “people” (?) that has been separated from the rest of everybody else for many thousands of years.

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Posted: 03 February 2008 08:32 AM   [ Ignore ]   [ # 1 ]
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Correct me if I’m wrong, but I think that the African continent is pretty well explored and, indeed, inhabited. The chances of us finding any new human-sized creatures there is de minimus. What brought this up?

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Posted: 03 February 2008 12:19 PM   [ Ignore ]   [ # 2 ]
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dougsmith - 03 February 2008 08:32 AM

Correct me if I’m wrong, but I think that the African continent is pretty well explored and, indeed, inhabited. The chances of us finding any new human-sized creatures there is de minimus. What brought this up?

George, you’re not asking about an african bigfoot tribe - you’re suggesting that there’s a tribe, or a group of isolated tribes who don’t amrry outside their limited group. AND, while they look just like any human, they have deep enough genetic differences that they’d be technically classed a separate species of *Homo*. Right?

That seems pretty unlikely, too, but a rather cool speculation. I’m not sure how you’d ‘bust’ a myth like that, except to show that every tribe in africa (or other remote areas of the world, like Papua New Guinea) has reliably married and had healthy, normal children outside their tribe or local group.

I think you’d be surprised how much even people on foot travel around and get chances to exchange genes with the local folk.

Kirk

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Posted: 03 February 2008 01:52 PM   [ Ignore ]   [ # 3 ]
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George - 02 February 2008 10:52 PM

How certain are we that all the Hominidae alive today are either chimps, gorillas, orangutans, bonobos, and homo sapiens? Is it possible that there could be another hominoid species alive (I presume somewhere in Africa) that looks very much like us but genetically would be classified as a different species (different enough for our two species not being able to produce an offspring)? How great is our knowledge of the African continent? It could be a small tribe of a few individuals, a group of “people” (?) that has been separated from the rest of everybody else for many thousands of years.

This raises another question, since the original migration of Indians ‘out of Africa’, over the Bering Strait (or an ice age land bridge), down into the Americas,  yields population groups separated by “many thousands of years”.  And yet the Olivia Judson NYT article this week notes evolutionary divergence of sticklebacks separate in ponds after the last ice age…

http://judson.blogs.nytimes.com/2008/01/29/the-repeater/index.html?8ty&emc=ty


So while I would not think a tribe could keep separate as you describe,  I’m interested in the question of to what extent animals on separate continents (including humans) do not diverge into separate species.

It might be that the gene pool has to be small—and if there were a small pocket of homonids like George describes they might diverge.

I don’t know the literature to give a reference.

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Posted: 03 February 2008 02:30 PM   [ Ignore ]   [ # 4 ]
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As I understand, there is very little genetic diversity among human populations compared to similarly distributed populations of other mammals, with the hypothetical explanation of a genetic bottleneck from the oruginal migration out of Africa. Given this, one would expect founder effects and genetic drift to have less impact on isolated poipulations, with these populations retaining similarities and interbreeding capacity longer than those of a species with greater initial genetic diversity. The Genographic Project is an ongoing project to assess the migration patterns of humans from the point of view of genetic variation among geopgraphically-separated populations.

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Posted: 03 February 2008 02:56 PM   [ Ignore ]   [ # 5 ]
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mckenzievmd - 03 February 2008 02:30 PM

As I understand, there is very little genetic diversity among human populations compared to similarly distributed populations of other mammals, with the hypothetical explanation of a genetic bottleneck from the oruginal migration out of Africa. Given this, one would expect founder effects and genetic drift to have less impact on isolated poipulations, with these populations retaining similarities and interbreeding capacity longer than those of a species with greater initial genetic diversity. The Genographic Project is an ongoing project to assess the migration patterns of humans from the point of view of genetic variation among geopgraphically-separated populations.


Thanks!
I hadn’t heard that term
[genetic bottleneck]
Thanks.
It seems like this is a natural enough question when approached from the right direction that it would have been looked into.

It’s the “converse” of George’s question—- why can all humans interbreed, if they were separated by continents for 5-10-20K years (?)

Article from Atlantic in 2004
http://www.theatlantic.com/issues/2001/04/olson-p3.htm

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Posted: 03 February 2008 03:21 PM   [ Ignore ]   [ # 6 ]
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This is an area thoroughly out of my expertise, but I’ve never let ignorance stop me from postulating. LOL

Many species are quite specialized to fit their environment.  Only a small enviromental change will have a major effect on their survival so positive mutations are quickly absorbed into and become dominant in their population.  It doesn’t take too many of these for them to diverge from their parent species.  Other species have generalized characteristics.  That is, they can’t excel in any given situation to the extent that the specialists can, but they can deal with a great many situations moderately well.  I believe primates fit this generalized category.  As such, they wouldn’t have the strong response to a change in environment, and mutations wouldn’t be as likely to replace the former population. 

If this is the case, primates, or at least, hominids, wouldn’t tend to generate new species very rapidly.  I don’t know how to include Neanderthals in this scenario, but I didn’t claim it was perfect.

Occam

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Posted: 03 February 2008 06:50 PM   [ Ignore ]   [ # 7 ]
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Thanks for your responses, everybody. There are many reasons why I have been wondering about this for some time now. I remember reading an article (can’t remember where) about a hill, somewhere in California, inhabited by three different species of salamanders. What is interesting about them is that the species located in the middle of the hill can interbreed with both (the bottom and the upper) species, but the upper and the lower species don’t (cannot?) interbreed between them. It is probably a waste of a time for a layperson like myself to speculate about any of this, but I was just curious what the chances are for something similar happening to us.

And then there were the posts by Mr. Tweedy. What would it take for Mr. Tweedy—or the guy who debated PZ Myers the other day; I’m sure you have all probably heard this on Dawkins’s site by now—to accept the theory of evolution as a fact? It is as easy not to pay attention to evolving salamanders, as it would be difficult to ignore evolving humans. That’s all.

I’ll read your links and see if I can get any more confused. Thanks again.

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Posted: 03 February 2008 07:18 PM   [ Ignore ]   [ # 8 ]
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Occam - 03 February 2008 03:21 PM

Many species are quite specialized to fit their environment.  Only a small enviromental change will have a major effect on their survival so positive mutations are quickly absorbed into and become dominant in their population.  It doesn’t take too many of these for them to diverge from their parent species.  Other species have generalized characteristics.  That is, they can’t excel in any given situation to the extent that the specialists can, but they can deal with a great many situations moderately well.  I believe primates fit this generalized category.  As such, they wouldn’t have the strong response to a change in environment, and mutations wouldn’t be as likely to replace the former population.

This seems logical, Occam. It’s been also said many times that very soon we will be in charge of our own evolving, or better “not evolving”, since we will be able to “help” the ones with genetic disorders. It kind of makes you think that homo sapiens is as good as it gets. Well, for awhile at least…

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Posted: 03 February 2008 07:38 PM   [ Ignore ]   [ # 9 ]
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inthegobi - 03 February 2008 12:19 PM

That seems pretty unlikely, too, but a rather cool speculation. I’m not sure how you’d ‘bust’ a myth like that, except to show that every tribe in africa (or other remote areas of the world, like Papua New Guinea) has reliably married and had healthy, normal children outside their tribe or local group.

I once heard that some scientists were observing a group of chimps where some of the females would sneak out (the scientists never caught them!) to a neighbouring tribe to get pregnant. They have no idea why they would do this. Perhaps an instinct to help to introduce new genes (for health reasons?) into the home tribe? You see? Even cheating can be a good thing. grin

Maybe this is also the reason why we find babies of mixed races “so cute”? It probably is a good thing to mix up the genes once in a while…

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Posted: 04 February 2008 10:37 AM   [ Ignore ]   [ # 10 ]
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Occam, look at this:

Just because modern humans are able to manipulate their environment, says University of Toronto molecular anthropologist Esteban Parra, “doesn’t mean biological evolution has stopped. It has increased.”

Interesting article. You can read it on Dawkins’s website.

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Posted: 04 February 2008 06:03 PM   [ Ignore ]   [ # 11 ]
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OK. you’re dragging up memories from my Zoo 1A and 1B classes in 1949-50.  As I recall, and I’m sure Brennen can be much more accurate, what your salamanders were involved in was a Rosenkreist (?).  The example given in my class was of a series of bird subspecies around a mountain.  Each could mate with those subspecies adjacent to it, but by the time they had expanded their areas and gone completely around the mountain, the birds who then connected were entirely different species.

I think selection will continue, but not be “natural”.  People will decide what they want for their kids and have the genes in a sperm and an ovum modified to accomplish it.  The problem is that often people don’t know what’s really better for increased probability of survival.  I can imagine asking for increased intelligence, more resistance to cancer and diseases, avoidance of allergies and defects.  However, a great many people will be having their kids modified for things like blond hair, bigger muscles, increased height, and of course, much larger primary and secondary genetalia.  What they won’t know is how the changed genes will interact in succeeding generations.  If religions are still around, the leaders will probably try to have all their members have kids who are more compliant; dictators will push for better soldiers, etc.  I would guess that at some point there would be problems with interbreeding, thus developing different species.

Occam
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Posted: 04 February 2008 07:40 PM   [ Ignore ]   [ # 12 ]
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I think if we were ever to reach the capability to steer our evolution in a desired direction, the impact on the ecosystem would be probably devastating. Look only at the invention of penicillin. Thanks to Fleming the seas are running out of fish. Every time we help our species, we are hurting the planet.

Also, I don’t know if you read the article I provided above, but it says the better off we are, the more numerous our species becomes, and all this actually results in speeding up the process of natural selection. Who knows…

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Posted: 04 February 2008 08:47 PM   [ Ignore ]   [ # 13 ]
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George - 04 February 2008 07:40 PM

... the more numerous our species becomes, and all this actually results in speeding up the process of natural selection…

I don’t believe this can be true. Natural selection creates wider morphological differences with small (bottlenecked) populations. The larger the population and the wider the genetic mixing, the more likely any genetic difference is to be swamped. Homo sapiens is now at stasis, basically, and going by past species that have reached large populations (dinosaurs, trilobites, etc.), we could remain essentially the same for literally hundreds of millions of years. That is, except for the possibility of artificial selection or manipulation, which is an entirely different phenomenon.

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Posted: 04 February 2008 09:01 PM   [ Ignore ]   [ # 14 ]
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Did you read the article from Dawkins’s site, Doug? I know it was written by a journalist but she does quote professors from McGill and UofT. There are many examples in the article that seem to indicate that the human evolution is indeed speeding up.

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Posted: 05 February 2008 05:16 AM   [ Ignore ]   [ # 15 ]
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George - 04 February 2008 09:01 PM

Did you read the article from Dawkins’s site, Doug? I know it was written by a journalist but she does quote professors from McGill and UofT. There are many examples in the article that seem to indicate that the human evolution is indeed speeding up.

Actually that’s not quite what it says. It quotes a number of eminent scientists disagreeing with the hypothesis (let’s keep their opinions in mind as well), and says that there’s some evidence of genetic alterations in the past 5,000 years. So, most likely we’d be talking about genetic changes in small isolated populations of hunter-gatherers around 3,000 BCE. OK, but that has absolutely no bearing whatever about there being ongoing important genetic changes, much less about evolution “speeding up”. The massive increases in population I was mentioning happened in the past couple of thousand years. 5,000 years ago was just outside that window, or at any rate on the border.

I should add that it does make the point about some genetic changes in the last thousand years being due to disease pressure: to that extent, yes, there will always be some pressure for genetic change on a species-wide basis. Those who survive a disease tend to have some genetic difference that allows them to do so. And to the extent that increased population leads to increased disease pressure, there is at least a small amount of “speeding up” in that sort of genetic change. But we aren’t talking, e.g., about changes in morphology. We’re talking about minor changes at the cellular level that allow us to fight particular sorts of parasites, infections or viruses. And to the extent that now disease tends to be fought by scientific means, this sort of evolutionary pressure may lessen as well.

[ Edited: 05 February 2008 05:24 AM by dougsmith ]
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