Kale
06-18-2014, 04:02 AM
As far as I know, the reasons Out-of-Africa attempts to justify itself is.
1) The most divergent living uni-parental markers are found only in Africa.
2) The earliest modern human remains are found in Africa
3) Modern inhabitants of Europe, Asia, Australia, etc. are less related to the ancient inhabitants of those areas than they are to modern Africans.
Sounds pretty convincing for an out of Africa scenario eh? But what is stopping anyone from using that same line of evidence to argue an INTO Africa migration for modern Africans?
1) The most divergent living uni-parental markers are found only in Africa.
...This speaks not to the greater age of Africans in Africa than Eurasians in Eurasia. If anything it shows that haplogroups are not free to spread around very well, and what is there is likely all that's ever been there. We observe countless migrations through Eurasia in which the haplogroups of the invaders substantially sweep out the haplogroups of the natives, even while often leaving little in the autosomal department. When men conquer a place, it is tradition to take all the females you can...the replacement method here is simple.
- The migration of Eastern people into Finland replaced over half their Y-lineages with N1c.
- We've coaxed y chromosomes out of 7 mesolithic European hunter/gatherers, and discover 1 C1a2. This lineage has only been found a handful of times in modern Europeans. Either we pulled a needle out of an outrageously large haystack, or some serious shit went down in the past few thousand years.
- 3/5 Mesolithic Swedes tested belonged to haplogroup I2a. A marker that is barely existent there today.
- Neolithic people carrying y-dna G2a replace half of the haplogroup I lineages in southern Europe.
- Neolithic/Bronze age people carrying R1b invade Western Europe and overturn 90% of male lineages in parts of Scotland in Ireland.
Enough of Y-dna for now. How about on the mitochondrial side?
- Practically every pre-neolithic sample we have in Europe is of hg U. Haplogroup U among modern Europeans is a mere 10-20%, despite up to 75% of European ancestry deriving from those pre-neolithic inhabitants. Why would there be such a disproportion? Drift could be one explanation, but not across an entire continent, in which different versions of U get replaced in different regions of the continent...This may come down to just basic evolution. Here's something to set up the point I mean. In the animal kingdom we observe the oddity of the liger. Half lion, half tiger, but far bigger than either. What causes this is male lions have y-chromosone genes that strongly promote growth. The biggest male is the dominant male right? But female lions have mt-chromosome genes that, in part, inhibit those of the male to prevent them from growing to the completely impractical and in fact health threatening size of ligers. I can only imagine it is a constant arms race between genders to keep the balance.
Now imagine if this were to occur in humans, but instead of sex-specific genes influencing size, they influenced gender of offspring. Imagine hypothetical 'y-haplogroup 1' exists. Now 'hg-1' branches off into two groups as it inevitably will, 'hg-1a', and 'hg-1b'. Now imagine 'hg-1a' develops a mutation that gives the carrier an increased chance of his offspring being male. Through no selection other than that, 'hg-1a' will slowly outnumber 'hg-1b' and cause it's extinction. This could equally occur with females in mtdna lineages. If this proverbial arms race occurred in isolation, between deciding male and female offspring, everything would likely equal out. But what if a group of people, this arms race already thousands of years in the making, migrate into other group's territory, a group who's sex-chromosomes have no defense against any but their own? The first to establish a dominance would gradually drive out the others.
__________________________________________________ __________________________________________________ _______________
2) The earliest modern human remains are found in Africa
Well, perhaps that shouldn't be plural. All we really have in Africa that is early and at least somewhat modern is Omo 1. Any predecessors in Africa to Omo 1 are non-existent. All we have is Rhodesia, who looks extremely archaic for it's age, like a leftover from an earlier time (or earlier into Africa migration :rolleyes:.). However in Europe and the Middle East, there is a rather fine line between modern human and neanderthal in some cases. And in Asia we have cases of homo erectus that are more modern than Rhodesia, and are 500,000 years earlier. More specifically in China, it seems, they are hoarding quite a nice collection of remains that fit nicely between erectus and modern human, showing some modern characteristics before moderns were 'supposed' to have left Africa.
__________________________________________________ __________________________________________________ ____________________
3) Modern peoples of Europe, Asia, Australia, etc. are less related to the ancient inhabitants of those areas than they are to modern Africans.
If, throughout the vast expanses of Eurasia, groups develop, we should expect them to have plenty of time to diverge. When a gene or technology arises that gives some sort of competitive advantage, these groups could then expand and diffuse across these vast, yet not secluded stretches of land. We would expect groups somewhere in the middle of Eurasia (I'd say somewhere between the Levant to India) would be in the best spot to receive these new genes from all the places they could develop (Europe, East Asia, North Asia, etc.) accelerating their advancement. If one group decided to branch off and bravely explore the jungles of Africa, they would soon expand deeper in and be cut off from the development around them, essentially a snapshot of when they entered. Eurasians would continue to migrate back and forth across the continent, sharing and blending their new genes. When in Africa there might be 5 versions of one gene, each version isolated through time and trees from the others, in Eurasia the one that offers the most advantage will be quickly spread, eliminating the others. Less variation could mean less age, but it could equally mean more selection! After this snapshot in history, the Eurasians would later continue their migrations, absorbing and replacing the earlier inhabitants of these regions; the neanderthals in Europe and central Asia, we might not have absorbed 1-4% neanderthal as homo sapiens, but rather 1-4% since Africans last got their share. Same goes for the Denisovans in Southeast Asia, and probably some more we've yet to discover.
__________________________________________________ __________________________________________________ ______________________
I look forward to discussion, and I look forward to being proven wrong; it's just another way of learning, which is what we are all here to do right? :rolleyes2:
1) The most divergent living uni-parental markers are found only in Africa.
2) The earliest modern human remains are found in Africa
3) Modern inhabitants of Europe, Asia, Australia, etc. are less related to the ancient inhabitants of those areas than they are to modern Africans.
Sounds pretty convincing for an out of Africa scenario eh? But what is stopping anyone from using that same line of evidence to argue an INTO Africa migration for modern Africans?
1) The most divergent living uni-parental markers are found only in Africa.
...This speaks not to the greater age of Africans in Africa than Eurasians in Eurasia. If anything it shows that haplogroups are not free to spread around very well, and what is there is likely all that's ever been there. We observe countless migrations through Eurasia in which the haplogroups of the invaders substantially sweep out the haplogroups of the natives, even while often leaving little in the autosomal department. When men conquer a place, it is tradition to take all the females you can...the replacement method here is simple.
- The migration of Eastern people into Finland replaced over half their Y-lineages with N1c.
- We've coaxed y chromosomes out of 7 mesolithic European hunter/gatherers, and discover 1 C1a2. This lineage has only been found a handful of times in modern Europeans. Either we pulled a needle out of an outrageously large haystack, or some serious shit went down in the past few thousand years.
- 3/5 Mesolithic Swedes tested belonged to haplogroup I2a. A marker that is barely existent there today.
- Neolithic people carrying y-dna G2a replace half of the haplogroup I lineages in southern Europe.
- Neolithic/Bronze age people carrying R1b invade Western Europe and overturn 90% of male lineages in parts of Scotland in Ireland.
Enough of Y-dna for now. How about on the mitochondrial side?
- Practically every pre-neolithic sample we have in Europe is of hg U. Haplogroup U among modern Europeans is a mere 10-20%, despite up to 75% of European ancestry deriving from those pre-neolithic inhabitants. Why would there be such a disproportion? Drift could be one explanation, but not across an entire continent, in which different versions of U get replaced in different regions of the continent...This may come down to just basic evolution. Here's something to set up the point I mean. In the animal kingdom we observe the oddity of the liger. Half lion, half tiger, but far bigger than either. What causes this is male lions have y-chromosone genes that strongly promote growth. The biggest male is the dominant male right? But female lions have mt-chromosome genes that, in part, inhibit those of the male to prevent them from growing to the completely impractical and in fact health threatening size of ligers. I can only imagine it is a constant arms race between genders to keep the balance.
Now imagine if this were to occur in humans, but instead of sex-specific genes influencing size, they influenced gender of offspring. Imagine hypothetical 'y-haplogroup 1' exists. Now 'hg-1' branches off into two groups as it inevitably will, 'hg-1a', and 'hg-1b'. Now imagine 'hg-1a' develops a mutation that gives the carrier an increased chance of his offspring being male. Through no selection other than that, 'hg-1a' will slowly outnumber 'hg-1b' and cause it's extinction. This could equally occur with females in mtdna lineages. If this proverbial arms race occurred in isolation, between deciding male and female offspring, everything would likely equal out. But what if a group of people, this arms race already thousands of years in the making, migrate into other group's territory, a group who's sex-chromosomes have no defense against any but their own? The first to establish a dominance would gradually drive out the others.
__________________________________________________ __________________________________________________ _______________
2) The earliest modern human remains are found in Africa
Well, perhaps that shouldn't be plural. All we really have in Africa that is early and at least somewhat modern is Omo 1. Any predecessors in Africa to Omo 1 are non-existent. All we have is Rhodesia, who looks extremely archaic for it's age, like a leftover from an earlier time (or earlier into Africa migration :rolleyes:.). However in Europe and the Middle East, there is a rather fine line between modern human and neanderthal in some cases. And in Asia we have cases of homo erectus that are more modern than Rhodesia, and are 500,000 years earlier. More specifically in China, it seems, they are hoarding quite a nice collection of remains that fit nicely between erectus and modern human, showing some modern characteristics before moderns were 'supposed' to have left Africa.
__________________________________________________ __________________________________________________ ____________________
3) Modern peoples of Europe, Asia, Australia, etc. are less related to the ancient inhabitants of those areas than they are to modern Africans.
If, throughout the vast expanses of Eurasia, groups develop, we should expect them to have plenty of time to diverge. When a gene or technology arises that gives some sort of competitive advantage, these groups could then expand and diffuse across these vast, yet not secluded stretches of land. We would expect groups somewhere in the middle of Eurasia (I'd say somewhere between the Levant to India) would be in the best spot to receive these new genes from all the places they could develop (Europe, East Asia, North Asia, etc.) accelerating their advancement. If one group decided to branch off and bravely explore the jungles of Africa, they would soon expand deeper in and be cut off from the development around them, essentially a snapshot of when they entered. Eurasians would continue to migrate back and forth across the continent, sharing and blending their new genes. When in Africa there might be 5 versions of one gene, each version isolated through time and trees from the others, in Eurasia the one that offers the most advantage will be quickly spread, eliminating the others. Less variation could mean less age, but it could equally mean more selection! After this snapshot in history, the Eurasians would later continue their migrations, absorbing and replacing the earlier inhabitants of these regions; the neanderthals in Europe and central Asia, we might not have absorbed 1-4% neanderthal as homo sapiens, but rather 1-4% since Africans last got their share. Same goes for the Denisovans in Southeast Asia, and probably some more we've yet to discover.
__________________________________________________ __________________________________________________ ______________________
I look forward to discussion, and I look forward to being proven wrong; it's just another way of learning, which is what we are all here to do right? :rolleyes2: