Origin of Modern Humans: Out of Africa or Otherwise

[Ibrahim]

The bottleneck theory is the only reason why the OAT, can not work. Too bad they put that in, otherwise it would have made a great story. Plus the Homo sapiens you provide are actually classified as archaic humans not modern humans. The surviving nasal anatomy of archaic humans and neanderthals is not the same as that found in modern humans, neither is the internal structure of their bones. In other words, there is a reason the bone densities differ, and there is a reason there is a bottleneck. And, by nasal anatomy we're talking about both internal and external structures.

Omo I is not an "archaic" homo sapiens (at least according to from lucy to language, and the picures I observed). his features are too advanced (at least those we have to look at). also, there is no evidence of nasal organs found for either Omo I or Omo II, as Omo I was composed of a mandible, the forhead section. cheeks, and maxilla, and occipitals-all fragmentary. Omo II is a skullcap (literally that). Omo II is definitely Archaic though, I do agree with ye on that. and while you are right that dali and idaltu are different from modern Homo sapiens in nasal anatomy (and are more robust), and are archaic in features, Its worth pointing out that I never said they were ancestral: I said dali's face was flattened a bit by eons in rock (the face in life wouldn't have been proper homo sapiens-too prognathic IMO), and idaltu was a subspecies that lived 165,000 years ago. Also, you are ignoring the fact that there is a shocking lack of fossilized evidence for Homo sapiens before 50,000 BP. the samples of humans we have from before that time period are limited in nature, localized, and from very short time periods. Its possible that the modern nasal anatomy evolved already, but that we have yet to find them, or worse still, they have yet to fossilize. paleontology (and especially paleoanthropology), are both hit and miss sciences in that regard. hence we cannot say that the Omo's, idaltu, or any fossil group from the timperiod is representative of the whole species; only of smaples of those species.


also, I'm not surprised that densities in bone are thicker in ancient man, as apposed to modern man; we as a species, having embraced all sorts of bone lightening techniques (i.e technology), have no need for the dense bones of ancient man. Its also worth pointing out that the 1st 160,000 years of documented Homo sapiens (archaic or otherwise) shows no signs of the culture or sofistication we recognize today, but rather typical mousterian artifacts and culture similar to neanderthal culture. this is also shown in the fossil evidence: compare skhull or Omo I and II's anatomies to those of modern humans, you will see that thier bones are proportionally thicker (just like ye said). now, compare a post 50,000 year old human (cro magnon I), and you will see that the bone structure and density is almost identical to ours (a little thicker). in fact, there isn't really a difference whatsoever. (N.B: our stature and brain size as a pecies has been declining over the last 10,000 years as per evidence in farmers vs. hunter gatherers bones.

So basically, one might say that any given creature evolving in a subtropical or arid-subtropical environmental setting would require no additional biological adaptation in order to thrive within a temperate, subarctic, or arctic zone? Or do we really mean, without a couple of quick genetic alterations, making it a new and improved genus, would we soon see an old-school species as a side order, in some evolutionary carrion-to-do menu?

I never said that nasal and stature evidence was the only evidence that we as a species originated from a tropical environment(In fact I specifically said: Arid or semi Arid); they are simply the only ones that are viewable to us from the fossils, as skin does not normally fossilize (I know of no mummy from before 10,000 BP). Skin will indicate the environment as well, as increased melanin is evidence of increased UV (i.e sunlight and heat), but alas, we have no mummies from that long ago. I also gave climatic evidence for why a modern human would evolve his nose in Africa (hot, and drier than today). I also do not consider its implications to the survival of neanderthals, homo heidelburgensis, or Archaic homo sapiens, as their extinction is not the topic of this debate. (this is in response to the carrion to do part). also, I read the posts you have about the nasals, and I'm well aware of the internal and external nasal adaptations

Also genetic studies alone can simply not determine age, and given the bottleneck theory wouldn't the higher degree of variation within the African sample actually indicate that this region was not the source area? Otherwise would modern humans found in the outlaying regions also display the same type of variation? On top of this, these studies never actually provide details about the nature of the African sample. For example does it include individuals found in rural area, or does it include urban elements associated with colonial populations from Asia and Europe? As well, I didn't understand those link's relevance to archaic or modern human nasal anatomy?

CmacQ

I never said genetic studies showed any age; merely that the most diversity was from Africa, and least outside it. also, If you want to know just where they sampled the Africans from, the answer is 121 Africans from six subsaharan regions out of 189 individuals (this is the second study out of that LA team that started this; IIRC, it does include the San*; the first study came from Urban bases of population, so yes the first time it was flawed). so yes, the Africans were sampled from Urban and rural surroundings, even nomadic, and yes the researchers do cite the nature of the population. All you have to do to get the info is read the papers they wrote-they have them there. also, I must point out that the mitochondrion of every African population available has been sampled repeatedly, for the human genome project, as well as the from urban, rural, and nomadic bases (otherwise, we wouldn't know that the San were of a particular Mitochindrial group (A something).). these repeated tests have shown that our origions are recent (comparatively minimal variation in genomes), and that the most variation is in Africa (i.e Africans are the oldest). I do understand your concerns, but I can tell ye, if it is repeateable ad consistant, regardless of technique (sampling population, size, etc), then I have very good cause to believe this. and frankly there is no other way to explain this genetic factor IMHO. also, the fact that non Africans have less variation than Africans (again, regardless of sampling) shows a recent origin, from a very small population, somewhere over 250, from the main african populations, and that those in turn were older, but still recent). bear in mind. fossil evidence again shows that we as a species spent most of our history in Africa, and only left for good around +80,000 years ago (otherwise mungo man, from Australia wouldn't be 50,000 years old; it would have taken thousands of years to spread that far). there is also no evidence that the khavseh cave people got any furthur than the area of the holy land...

also, the nasal evidence is actually supportive of some sort of bottle neck, as in order for this feature to become prevalent in our species, we would have to have this feature dessiminate over a very small population. I do not see how this, the mitochondrial evidence, or the bottleneck theory, or any other, are conflicting as you say they do. and didn't I mention the stature differences between neanderthals and even archaic homo sapiens? I did didn't I?

I didn't understand those link's relevance to archaic or modern human nasal anatomy?

I didn't say those were for the nasal or not nasal, did I?

those sources were for where I got the info for Omo I, idaltu, Dali, and all the other fossils I mentioned: I figured you fellows wanted to take a look at those, as I am certain someone will argue about them. besides, when presenting a scientific argument, you are supposed to cite your research (though I admit, I tend to forget that myself).


*San=for those of you who don't know, they are often called Bushmen. I mention them due to their namadism and distance from the urban centers, which minimized contact between them and outsiders.

[cmacq]

Good points.

Omo I is not an "archaic" homo sapiens (at least according to from lucy to language, and the picures I observed). his features are too advanced (at least those we have to look at). also, there is no evidence of nasal organs found for either Omo I or Omo II, as Omo I was composed of a mandible, the forhead section. cheeks, and maxilla, and occipitals-all fragmentary. Omo II is a skullcap (literally that). Omo II is definitely Archaic though, I do agree with ye on that. and while you are right that dali and idaltu are different from modern Homo sapiens in nasal anatomy (and are more robust), and are archaic in features, Its worth pointing out that I never said they were ancestral: I said dali's face was flattened a bit by eons in rock (the face in life wouldn't have been proper homo sapiens-too prognathic IMO), and idaltu was a subspecies that lived 165,000 years ago.

Point well taken

Also, you are ignoring the fact that there is a shocking lack of fossilized evidence for Homo sapiens before 50,000 BP. the samples of humans we have from before that time period are limited in nature, localized, and from very short time periods. Its possible that the modern nasal anatomy evolved already, but that we have yet to find them, or worse still, they have yet to fossilize. paleontology (and especially paleoanthropology), are both hit and miss sciences in that regard. hence we cannot say that the Omo's, idaltu, or any fossil group from the time period is representative of the whole species; only of smaples of those species.

Good point about the 50,000 date. Now how can we fit this into a bottleneck?

also, I'm not surprised that densities in bone are thicker in ancient man, as apposed to modern man; we as a species, having embraced all sorts of bone lightening techniques (i.e technology), have no need for the dense bones of ancient man. Its also worth pointing out that the 1st 160,000 years of documented Homo sapiens (archaic or otherwise) shows no signs of the culture or sofistication we recognize today, but rather typical mousterian artifacts and culture similar to neanderthal culture. this is also shown in the fossil evidence: compare skhull or Omo I and II's anatomies to those of modern humans, you will see that thier bones are proportionally thicker (just like ye said). now, compare a post 50,000 year old human (cro magnon I), and you will see that the bone structure and density is almost identical to ours (a little thicker). in fact, there isn't really a difference whatsoever. (N.B: our stature and brain size as a pecies has been declining over the last 10,000 years as per evidence in farmers vs. hunter gatherers bones.

Ok we aren't surprised about the difference in bone densities, because from our advanced vantage point we can see the stages in the progression and the end result, so we naturally assume cause (stress) and effect (culture). But, for a moment lets pretend we're blind to the outcome, and ask why are the bones of modern humans less-dense and lighter; or in other words what precisely was replacing the bone to make them lighter and how would that be associated with comparable adaptation in the nasal anatomy, 50,000 years ago, and a bottleneck?

I never said that nasal and stature evidence was the only evidence that we as a species originated from a tropical environment(In fact I specifically said: Arid or semi Arid); they are simply the only ones that are viewable to us from the fossils, as skin does not normally fossilize (I know of no mummy from before 10,000 BP). Skin will indicate the environment as well, as increased melanin is evidence of increased UV (i.e sunlight and heat), but alas, we have no mummies from that long ago. I also gave climatic evidence for why a modern human would evolve his nose in Africa (hot, and drier than today). I also do not consider its implications to the survival of neanderthals, homo heidelburgensis, or Archaic homo sapiens, as their extinction is not the topic of this debate. (this is in response to the carrion to do part). also, I read the posts you have about the nasals, and I'm well aware of the internal and external nasal adaptations.

Very interesting point; Arid or semi Arid. Right, I would agree with that, however that may include a wider spectrum than one might first suspect. As arid or semi-arid was used to support the OAT, I naturally assumed Africa was intended. Indeed, I would also agree that the basic nasal adaptations likely occurred there. These would of course focus on heat dispersal and humidification. However, in order to successively exploit the more marginal and extreme environments offered by the semi-arid and arid environs associated with subarctic and arctic settings; wouldn’t another set of biological adaptations be needed? Of course these would focus on heat conservation and modification of humidification that substantially insulated the process. So would this bring us back to an Ice Age, 50,000, a bottleneck, and why the OAT can't work; or what?

I'm still thinking southwest asia?




CmacQ

[Ibrahim]

Good point about the 50,000 date. Now how can we fit this into a bottleneck?

we don't-simple. the 50,000 year marker is the first time (roughly), that we see evidence of a more sofisticated, and rapidly evolving culture (such as mungo man, from Australia). I was just illustrating tyhe lack of fossil evidence, prior to then, which i do agree is odd.

Ok we aren't surprised about the difference in bone densities, because from our advanced vantage point we can see the stages in the progression and the end result, so we naturally assume cause (stress) and effect (culture). But, for a moment lets pretend we're blind to the outcome, and ask why are the bones of modern humans less-dense and lighter; or in other words what precisely was replacing the bone to make them lighter and how would that be associated with comparable adaptation in the nasal anatomy, 50,000 years ago, and a bottleneck?

you are overanalysing the problem. there is no other thing that replaced our need for muscle but our dependance on culture more sophisticated than mousterian levels (i.e, advanced technology). physiologically, the bones became thinner in width as well as cross-section, and our stature decreased. It also doesn't necessarily have association with the nasal anatomy, which as i pointed out, must have occured prior to when our ancestors supposedly left Africa, +80,000 years ago, and hence, prior to our bone density decrease. simply put, the two (nasal changes and bone density changes), have about as much relation to each other as a dinosaurs feathers and hollow bone: they evolved in the same animal, but have nothing else to do with the evolving of these features mutually. they only became truly interelated when the dinosaurs took to flying (i.e, birds).

Very interesting point; Arid or semi Arid. Right, I would agree with that, however that may include a wider spectrum than one might first suspect. As arid or semi-arid was used to support the OAT, I naturally assumed Africa was intended. Indeed, I would also agree that the basic nasal adaptations likely occurred there. These would of course focus on heat dispersal and humidification. However, in order to successively exploit the more marginal and extreme environments offered by the semi-arid and arid environs associated with subarctic and arctic settings; wouldn’t another set of biological adaptations be needed? Of course these would focus on heat conservation and modification of humidification that substantially insulated the process. So would this bring us back to an Ice Age, 50,000, a bottleneck, and why the OAT can't work; or what?

I'm still thinking southwest asia?




CmacQ

its unlikely we came from southwest Asia: it was the exact opposite of today back in the ice age (i.e more subtropical). this is particularly true of the coastal areas, such as yemen, the gulf area (which was a river valley then), and the holy land. odd, but true. the interior would have just been too dry, however.

as for the bottle neck: I shamefully forgot to mention that the bottle neck refers not to our origins as a species (otherwise even African mtDNA would be monotonous), but rather to the people leaving Africa, who due to their small numbers (outside Africa), would have shrunk the mitochondrial strands into a single mtDNA lineage more or less. It is used to account for the comparative lack of mtDNA diversity outside of Africa. It has two causes: 1) a small population base out of Africa (definitely the main one) and 2) it was punctuated by the Mt.Toba eruption (supposedly), further shrinking the population.

as for where all this leads us: It leads us to what is simply put: the Ice age. the ice age created drier, more difficult conditions for life in Africa, life in Africa (people included) got changed, man developed bigger brains and wierd nasals, consolidated them selves in Africa, then a certain segment (minimum, of c.250) left Africa (via Yemen rather than the holy land), traveled, and spread themselves throughout the world. I actually suspect culture as we know it was a response to the conditions much different to Africa's, as well as changes in Africa itself (even drier conditions), which forced a change not in physical, but social terms, and this later manifested itself physically (i.e, thinner bones, smaller stature, etc). I am certain our story as a species was actually more complicated than this, but so far, the evidence as seen here so far leads only in one direction: OAT.

lastly, please bear in ming: 50,000 years BP is an approximate marker: its possible culture more sofisticated than moustrian culture existed prior to this date, but there is almost no evidence in that timeperiod. thre is a gap from 90,000-70,000 years ago, during which only a few scraps of evidence exists.

[cmacq]

I'm sorry there is so much here I'll have to get back to you. But again think Neanderthal. I have to run for now.


CmacQ

[Ibrahim]

I also forgot: we humans have physiologically adapted to the colder climes, but not in the same fashion as neanderthals: the inuit have evolved short and stocky limbs and stature (not nearly to the extreme of neanderthal however, as their chest and nose are still modern human in appearence), and the skin color has lightened up to a coppery color.

that said, we did not evolve the features of the neanderthal nose, due to the fact that we do not need it, a point many do not realize: A neanderthal didn't really posses the same level of technological sophistication as post 50,000 year modern man, who invented tailored clothes, and needle, in order to take the furs and hides and cloth, and make pants, shirts, tunics, etc. you already observed the effect cultural evolution had on our bones and stature, and in this regard the inuit's changes are no different: they can partially control their own evolution seperately from what nature says. there again is also not enough time to evolve such sweeping changes (less than 80,000 years)