The Genetic Legacy of the Indian Ocean Slave Trade

[Angela]

See:
http://www.cell.com/ajhg/fulltext/S0002-9297(17)30394-4

"From the eighth century onward, the Indian Ocean was the scene of extensive trade of sub-Saharan African slaves via sea routes controlled by Muslim Arab and Swahili traders. Several populations in present-day Pakistan and India are thought to be the descendants of such slaves, yet their history of admixture and natural selection remains largely undefined. Here, we studied the genome-wide diversity of the African-descent Makranis, who reside on the Arabian Sea coast of Pakistan, as well that of four neighboring Pakistani populations, to investigate the genetic legacy, population dynamics, and tempo of the Indian Ocean slave trade. We show that the Makranis are the result of an admixture event between local Baluch tribes and Bantu-speaking populations from eastern or southeastern Africa; we dated this event to ∼300 years ago during the Omani Empire domination. Levels of parental relatedness, measured through runs of homozygosity, were found to be similar across Pakistani populations, suggesting that the Makranis rapidly adopted the traditional practice of endogamous marriages. Finally, we searched for signatures of post-admixture selection at traits evolving under positive selection, including skin color, lactase persistence, and resistance to malaria. We demonstrate that the African-specific Duffy-null blood group—believed to confer resistance against Plasmodium vivax infection—was recently introduced to Pakistan through the slave trade and evolved adaptively in this P. vivaxmalaria-endemic region. Our study reconstructs the genetic and adaptive history of a neglected episode of the African Diaspora and illustrates the impact of recent admixture on the diffusion of adaptive traits across human populations."

 

[Ygorcs]

That will be fascinating to know. Still, it doesn't quite solve my persistent doubt about the demographic history of medieval/modern African slaves in the Middle East and South Asia. If the estimates are not being inflated, basically the same amount of Africans who were brought to the Americas was also taken to the Middle East and parts of South Asia. However, even though communities like those of Makrani and Afro-Iraqis do exist, they're usually in the hundreds of thousands, not millions.

One of the best hypotheses is that the Muslims were more willing than Europeans in most colonies to completely mix with and absorb the African (mostly the female) slaves, and that that ethnic mixing had happened much earlier than the recent European colonization in most of the Americas.

I don't know, I'd expect at least dozens or even hundreds of visibly African-admixed people in those regions, and while I do see (and know about) the introgression of African DNA especially in North Africa, this legacy still looks like a diluted minority.

 

[Angela]

I wouldn't think the numbers were the same if we're talking about the actual slave trade. As you say, the slave trade in the Middle East and South Asia was mostly women. The trade in West Africa was also in men, needed for the hard work in the colonies in the New World.

We're able to have some more or less reliable data for this area because we have embarkation lists.

I couldn't find any really hard data about the slave trade to North Africa, or Yemen and parts of Saudi Arabia and the Middle East,or even South Asia. I don't know if this paper has some, because I don't have access.

The slave trade they're talking about here is very recent, of course, but the organized trade for the rest of the areas goes back to before 1000 in North Africa (although there was some SSA even before that, although in very low numbers). In the Yemen, it may go back much, much earlier.

It's impossible to get really accurate numbers for this reason, I think.

I also think there's a clue for the Makrani, at least, when the abstract mentions that the Bakrani were endogamous . In communities divided into castes, introgression may occur, but then it may be contained in those castes rather than spread out throughout the larger community. The same might apply in tribal areas like North Africa, Saudi Arabia, or the Yemen.

In North Africa, the average SSA percentage might be somewhere between 15-20%, but there are some with very little, some, like southern Moroccans, with a lot, and some southern tribes where it is the majority component.
Algerians:

Algerians:

Tuareg

Some Yemeni

 

[Ygorcs]

Yes, you're right. Maybe they had much more time to entirely absorb the DNA of African slaves, and the people whose look now associate with "typical" Yemeni, Moroccan or Egyptian would actually look clearly more African-like than their ancestors 1,500 years ago if we could make such a comparison. I'm pretty sure that ancient DNA will clarify this a bit and allow us to see how much those regions were affected by the influx of slaves.

Also, if Brazil is to be taken as a representative example of the reproductive potential of slaves, unfortunately the conclusion will be quite negative. Brazil is believed to have received 4 million slaves between 1530 and 1850, however by 1850 the entire population of the country was less than 8 million people. Not only that, blacks and African-European mixed people were "only" some 60% of the population by the time slavery ended. That definitely means that the birth rates of Africans were much lower, and the death rates much higher than that of Europeans and mixed African-Europeans or Amerindian-Europeans in Brazil, to the point that now an average Black Brazilian (Black!) has ~40% of non-African ancestry.

I'd expect the same process happened in North Africa and the Middle East, perhaps with even one more caveat that possibly reduced the spread of African DNA there: unlike in the Americas, a shockingly huge proportion of the African male slaves were castrated.

 

[Angela]

Yes, you're right. Maybe they had much more time to entirely absorb the DNA of African slaves, and the people whose look now associate with "typical" Yemeni, Moroccan or Egyptian would actually look clearly more African-like than their ancestors 1,500 years ago if we could make such a comparison. I'm pretty sure that ancient DNA will clarify this a bit and allow us to see how much those regions were affected by the influx of slaves.

Also, if Brazil is to be taken as a representative example of the reproductive potential of slaves, unfortunately the conclusion will be quite negative. Brazil is believed to have received 4 million slaves between 1530 and 1850, however by 1850 the entire population of the country was less than 8 million people. Not only that, blacks and African-European mixed people were "only" some 60% of the population by the time slavery ended. That definitely means that the birth rates of Africans were much lower, and the death rates much higher than that of Europeans and mixed African-Europeans or Amerindian-Europeans in Brazil, to the point that now an average Black Brazilian (Black!) has ~40% of non-African ancestry.

I'd expect the same process happened in North Africa and the Middle East, perhaps with even one more caveat that possibly reduced the spread of African DNA there: unlike in the Americas, a shockingly huge proportion of the African male slaves were castrated.

I think in terms of death rates the same was probably true for Roman slavery. This is what people don't understand, but which you so clearly showed with the example of Brazil. Slaves were fodder, often worked to death. In Brazil, it was largely in the fields, and perhaps mines? In Roman Europe it was agricultural latifundia, the mines, the galleys, various quasi-industrial pursuits, like the making of garum, or dye.

Only educated slaves had it better. Even with women, huge proportions of them were sent to the brothels. The death rate there was high as well, and their children were often aborted or subject to infanticide, as a lot of the graves turning up are showing.

I don't know how much castration took place, although I know that there were slave eunuchs in Roman times. Some of those educated slaves, the ones who were manumitted and came to occupy important positions in the civil service were indeed eunuchs. The Romans probably didn't want intelligent male slaves, perhaps young and good looking some of them, coming into too close contact with their women folk.

I don't think it was as high as in the Near East, though. I've also read that even the offspring of these African women in the Near East were sometimes aborted or killed right after birth. I prefer to think that didn't happen often. I know human beings are capable of horrific things, but those were their children. Still, look at American slave owners who condemned their children to lives of servitude. Of course, with the closing of the slave trade the planters were breeding their own slaves, I guess. In the Near East the attitude might have been that there were always more slaves that could be taken. I don't think slavery was outlawed in Saudi Arabia until the 1960s, and I would bet it still goes on.

What a world.

See the following for the place of eunuchs in the Roman world:
https://www.thoughtco.com/eunuchs-in-the-roman-empire-121003

 

[Ygorcs]

Even with women, huge proportions of them were sent to the brothels. The death rate there was high as well, and their children were often aborted or subject to infanticide, as a lot of the graves turning up are showing. [...]

I don't think it was as high as in the Near East, though. I've also read that even the offspring of these African women in the Near East were sometimes aborted or killed right after birth. I prefer to think that didn't happen often.

Oh God, this is really gross. The indignities of slavery much beyond the "simple" fact of the ownership of a human being never cease to shock me. In Brazil, I think there wasn't a practice of active infanticide of children of slaves, but it is certain (and in some cases documented) that the children of slave women with free whit/caboclo* men and, of course, particularly with their owners were expected to receive a slightly better treatment and be spared the heaviest and most dangerous work. Sometimes the lucky few were even brought into the "grand house", as the master's houses were known.

Meanwhile, an indirect "selection" happened, because those children without a useful "godfather" to protect them (not rarely their own fathers, but nobody needed to mention it aloud) were simply neglected in the unhealthy "senzalas" and worked to death. That's now ingrained in our DNA in a staggering disproportion: while only some ~10% of the Y-DNA lineages are African-like, while ~40% of the Mt-DNA in Brazil comes from Africa. Being a "mulatto/a" was your passport to a less horrible life, perhaps even to freedom ("alforria"). No wonder many poor women were very clear in their preference for a white man. Well, at least apparently they didn't kill their offspring.

 

[Angela]

Oh God, this is really gross. The indignities of slavery much beyond the "simple" fact of the ownership of a human being never cease to shock me. In Brazil, I think there wasn't a practice of active infanticide of children of slaves, but it is certain (and in some cases documented) that the children of slave women with free whit/caboclo* men and, of course, particularly with their owners were expected to receive a slightly better treatment and be spared the heaviest and most dangerous work. Sometimes the lucky few were even brought into the "grand house", as the master's houses were known.

Meanwhile, an indirect "selection" happened, because those children without a useful "godfather" to protect them (not rarely their own fathers, but nobody needed to mention it aloud) were simply neglected in the unhealthy "senzalas" and worked to death. That's now ingrained in our DNA in a staggering disproportion: while only some ~10% of the Y-DNA lineages are African-like, while ~40% of the Mt-DNA in Brazil comes from Africa. Being a "mulatto/a" was your passport to a less horrible life, perhaps even to freedom ("alforria"). No wonder many poor women were very clear in their preference for a white man. Well, at least apparently they didn't kill their offspring.

That could explain what happened in Central and Northern Europe with the Indo-Europeans as well, and the dominance of R1 lineages.

You're right; it's all gross and disgusting. I remember reading about southern planters who, after the slave trade was closed, basically used their female slaves as breeding machines to create their own slave workers. It just doesn't bear thinking about.

It's not all in the past either, and no group is exempt from this horror. About ten years ago, a professional couple who had immigrated here from India was arrested for the treatment they had meted out to their "housekeeper". She was half starved, beaten, virtually tortured. They had her sleeping on a blanket in a closet. Meanwhile they lived in a McMansion and sported thousand dollar outfits. I wanted to beat them black and blue with my own hands, never mind being grateful they could be prosecuted and sent to prison. There are monsters out there hiding behind civilized facades.

 

[bicicleur 2]

That could explain what happened in Central and Northern Europe with the Indo-Europeans as well, and the dominance of R1 lineages.

why do you think so?
subjecting a local population and having many local wives - if that was the case - is a very different situation from importing slaves from another continent and seperating them from their families and tribes

 

[Ygorcs]

why do you think so?
subjecting a local population and having many local wives - if that was the case - is a very different situation from importing slaves from another continent and seperating them from their families and tribes

I'll have to agree with the speculation/hypothesis presented by Angela. I've long been trying to "make peace" with the rapid and overwhelming shift from EEF-dominated to Yamnaya-dominated Central/Northern Europe in the late Neolithic/early Bronze Age.

Tentatively, and of course in an entirely amateur way, I tried to draw some scenarios of fertility rates, average population growth and hypothetical major losses of people in short but destructive demographic disasters that possibly happened when the IE arrived, like plagues and, of course, increased violence and displacement.

To account for that extremely reduced percentage of EEF admixture and, above all, of typical EEF Y-DNA, in a space time of around 400 or 500 years, all but one of the scenarios would have to imply: plague, famine and war casualties of apocalyptical proportions, in the fashion of post-Columbian America (~80% dead); or then an extremely large, epic IE immigration into Central/Northern Europe, which would probably have depopulated the entire Pontic-Caspian steppe, coupled with a "moderate" reductiion of the EEF population (~30%). By Occam's razor, I don't think those were the most probable ones.

We could reach similar results by simply implying a "moderate" initial reduction of the EEF (~30%), though one followed by several generations of increased fertility and lower (especially infant) mortality of IE and EEF/IE admixed people, as well as a clear bias against having children with indigenous (Neolithic) Europeans and taking equally good care of them, not very unlike 18-19th century Brazil (e.g. let's say the EEF men managed to have 3 children surviving childhood on average, but the dominant IE had as much as 6). Nothing very dramatic or apocalyptical, just centuries of social inequality. In just 300 to 400 years, the non-R1 haplogroups would've been reduced to a small fraction, and the autosomal DNA of Yamnaya would be everywhere. Again, not unlike the "weird" case of Brazil even in those regions that received virtually no Euroopean immigration after the 1870s, and still shifted from mainly African+Amerindian to a majority of European autosomal DNA by 2000 AD.

 

[Angela]

why do you think so?
subjecting a local population and having many local wives - if that was the case - is a very different situation from importing slaves from another continent and seperating them from their families and tribes

We see it differently, I guess. The Spaniards came to places like the Caribbean and enslaved the natives, the Amerindians. The Portuguese did the same in Brazil. They both brought slaves from Africa.

Were the living conditions or the treatment meted out to those two groups different in any substantial way? It doesn't seem so to me from my readings. It's true that it seems the Indians in the Caribbean weren't cut out for that kind of work and so most of them died, but women had "mixed" children, enough so that a lot of people in Brazil have Amerindian mtDna. The same is true in the Caribbean.

Or even look at Mexico. That was a densely populated area with a sophisticated culture, yet new diseases decimated them, not to mention guns. Modern Mexicans today predominantly carry European yDna but Amerindian mtDna. Why is that? Did only the men die of the diseases? That doesn't make sense, but Ygorcs scenario does...All the natives became, if not slaves, indentured serfs. The children of the European men and Indian women got better food, probably, better living conditions, lighter work, and so they survived. (The same happened in the American south: the "yellow" and "high yellow" slaves did house work or more skilled labor. The rest worked in the cane and cotton and tobacco fields.) The children of the Indian men didn't, and didn't. In addition, the mixed offspring had some inherited immunity to the diseases.

I think it all makes a great deal of sense.

 

[Sile]

the other previous paper in regards to the same slave trade of the indian ocean was

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0080932

the bulk of the slave traders came from the gulf of persia and the Bay of Bengal

 

[bicicleur 2]

I'll have to agree with the speculation/hypothesis presented by Angela. I've long been trying to "make peace" with the rapid and overwhelming shift from EEF-dominated to Yamnaya-dominated Central/Northern Europe in the late Neolithic/early Bronze Age.

Tentatively, and of course in an entirely amateur way, I tried to draw some scenarios of fertility rates, average population growth and hypothetical major losses of people in short but destructive demographic disasters that possibly happened when the IE arrived, like plagues and, of course, increased violence and displacement.

To account for that extremely reduced percentage of EEF admixture and, above all, of typical EEF Y-DNA, in a space time of around 400 or 500 years, all but one of the scenarios would have to imply: plague, famine and war casualties of apocalyptical proportions, in the fashion of post-Columbian America (~80% dead); or then an extremely large, epic IE immigration into Central/Northern Europe, which would probably have depopulated the entire Pontic-Caspian steppe, coupled with a "moderate" reductiion of the EEF population (~30%). By Occam's razor, I don't think those were the most probable ones.

We could reach similar results by simply implying a "moderate" initial reduction of the EEF (~30%), though one followed by several generations of increased fertility and lower (especially infant) mortality of IE and EEF/IE admixed people, as well as a clear bias against having children with indigenous (Neolithic) Europeans and taking equally good care of them, not very unlike 18-19th century Brazil (e.g. let's say the EEF men managed to have 3 children surviving childhood on average, but the dominant IE had as much as 6). Nothing very dramatic or apocalyptical, just centuries of social inequality. In just 300 to 400 years, the non-R1 haplogroups would've been reduced to a small fraction, and the autosomal DNA of Yamnaya would be everywhere. Again, not unlike the "weird" case of Brazil even in those regions that received virtually no Euroopean immigration after the 1870s, and still shifted from mainly African+Amerindian to a majority of European autosomal DNA by 2000 AD.

how can you know what realy happened?
first it was horses, then it was the plague and now it is slavery

according to this study the neolithic population crashed 700 years before the arrival of corded ware :

https://www.nature.com/articles/ncomms3486#f2

so, what will it be?

it is true that the mtDNA pedigree is very much extended horizontally and that the Y-DNA is much deeper, much more vertical in structure
men outcompeted men and killed each other, while women were kept as breeding machines, it is universal and worldwide
but why specifically extrapolate this to the R1 tribe? is there special evidence to point at them to compare with the slave trade?
there are many areas where certain Y-DNA clades dominated over others in history and even today

 

[Ygorcs]

how can you know what realy happened?
first it was horses, then it was the plague and now it is slavery

but why specifically extrapolate this to the R1 tribe? is there special evidence to point at them to compare with the slave trade?
there are many areas where certain Y-DNA clades dominated over others in history and even today

Of course I can't know, but neither can you, and that is why we are both here in a Forum making hypotheses and arguments about possible explanations. Otherwise, we'd probably be writing our own groundbreaking studies in some great university, don't you think? Hahaha. Also, you mention that certain Y-DNA dominated over others in many areas. Yes, certainly. But at least those events that already happened during written history demonstrably involved some kind of genocide, enslavement, displacement, ethnic seggregation or economic marginalization clearly along ethnic lines. Americas? Check. Canary Islands? Check. Australia and New Zealand? Check. Taiwan? Check. In none of those cases it was all very gradual and "civilized".

Well, let me see... maybe because we have recent and richly documented accounts of how certain new R1b/R1a-majority societies appeared, mainly in the United States, Argentina, Uruguay and Brazil? Considering the usual things we know about the human past and about the increased warfare and population displacement during the Bronze Age, should we really not expect anything even remotely similar to what happened in our "civilized" and prosperous modern times? Doubtful. Also, we are not talking of "R1b tribe" (was there ever such a thing in fact?), but of the incoming peoples who became the new dominant ethnicities in Europe. That includes mainly people with R1b and also R1a, I1, possibly certain specific subclades of I2, and, why not - IE weren't everything in European History -, J2a, J2b and also possibly E-V13.

As for the Neolithic population crashes, yes, I'm considering that, too, in my cenario. There is no way the IE, without modern technology in a tremendously assymetrical relation with primitivenatives, would've accomplished such a thorough population replacement in Northern Europe if they had arrived in a thriving and densely populated region. Just look at their much lesser genetic impact in Southeastern Europe, Iran or South Caucasus (Armenian plateau).

When I hypothesized about those 3 scenarios (apocalyptical population crash; overwhelmingly large IE migration; relatively moderate population decreased coupled with centuries of unequal life conditions and breeding potential), I was considering a lower-ending, though not catastrophic, demographic density for a Neolithic society, ~0.5-0.6 person/km², not 1-2 persons/km², which we know was possible in the most thriving Neollithic societies in the Near East and Southeastern Europe.

Even with that caveat, it'd still mean something like 125,000 EEF people in Brintain. But seriously can anyone expect that the IE-speaking tribes were so, so numerous that they could overwhelm by numbers alone the natives of lands from Ireland to Russia? Again, I maintain that, realistically speaking, I can only imagine a veritable castrophe (Columbian Exchange-like), a horribly genocidal sweep against indigenous males during the conquest, or then the unfortunately quite "familiar" scenario I and Angela have been proposing here, that of slavery/serfdom/racial-ethnic prejudice/race-biased high inequality income and status.

 

[Angela]

how can you know what realy happened?
first it was horses, then it was the plague and now it is slavery

according to this study the neolithic population crashed 700 years before the arrival of corded ware :

https://www.nature.com/articles/ncomms3486#f2

so, what will it be?

it is true that the mtDNA pedigree is very much extended horizontally and that the Y-DNA is much deeper, much more vertical in structure
men outcompeted men and killed each other, while women were kept as breeding machines, it is universal and worldwide
but why specifically extrapolate this to the R1 tribe? is there special evidence to point at them to compare with the slave trade?
there are many areas where certain Y-DNA clades dominated over others in history and even today

Bicicleur,

No one has said this is particular to R1 men. If you want my actual opinion, it's just the nature of men, period. It just happens to be the case that the Indo-Europeans were dominated by the R1 lineages. By extension, the Europeans who went to the New World were also largely R1 men. However, the same phenomenon has indeed played out in other parts of the world where the y lineages were different, as in China, Japan, and Africa with the Bantus and the East African pastoralists.

What happened in central and northern Europe was complicated. The far north-east was practically un-populated until the arrival of the Indo-Europeans. As for central Europe and Britain as well, I've always said there were population crashes there, crashes which might not have occurred or been as frequent or as bad in the south.

In the beginning, I don't think the steppe people had the horse; I don't see much evidence of it in Corded Ware, but it certainly would have been a factor later. Are you starting to doubt they had it or that it was an advantage? That's the whole cornerstone of Anthony's opus, isn't it?

In the beginning their weapons weren't superior. Their metallurgy was poor and derivative for a long time, but it seems now that plague was indeed a factor. We learn new things all the time. I think the latest results from Globular Amphora culture are very suggestive, as is the paper on the plague. It almost seems like GAC was a barrier to further penetration into Europe. Then the flood gates open. Coincidentally or not that's about the time the plague appears.

I don't know why the dynamic about what happens next would be any different in Europe than it was in the New World or Africa or East Asia. The prior population, whether it was lower in absolute numbers already or not, which survived the warfare and the plague was subjugated. If not precisely enslaved, if that bothers you, made into serfs of one kind or another. Goodness, the same thing happened in Italy with the Lombards. That's how unequal mating arises. The other alternative is that the men were just almost all killed off. I don't know, maybe you're right: the Indo-Europeans were homicidal maniacs who practiced genocide.

You're right: no one can absolutely know what happened, but we can make some educated guesses based on the genetics, the archaeology, and the patterns we see in other cultures and times.

It gives me no pleasure to say this, either as a human being or more specifically as a woman, but that seems to be the pattern.

 

[bicicleur 2]

I don't believe much in the horses anymore.
It is very hard to tell if they were ridden or not, and if so, how.
If horseriding was such an advantage, I think it would have been more obvious in the archeological record.
I believe the Mitanni were quite succesfull with trained horses and chariots, later to be picked up by the Hittites, the Egyptians and Asyrians, but all that is later than 3.4 ka, more than 2000 years after the first Yamna folks, and still it were charriots, not warriors on horseback.
I have no clue as for the cause of succes for R1, but I'm confident we'll learn more over the coming years.
That men see each other as a threat and that they were ruthless, I'm sure.
The game men play is the winner takes all, and very often women encourage this, by favoring only winnergenes, whatever that means.

 

[Angela]

I don't believe much in the horses anymore.
It is very hard to tell if they were ridden or not, and if so, how.
If horseriding was such an advantage, I think it would have been more obvious in the archeological record.
I believe the Mitanni were quite succesfull with trained horses and chariots, later to be picked up by the Hittites, the Egyptians and Asyrians, but all that is later than 3.4 ka, more than 2000 years after the first Yamna folks, and still it were charriots, not warriors on horseback.
I have no clue as for the cause of succes for R1, but I'm confident we'll learn more over the coming years.
That men see each other as a threat and that they were ruthless, I'm sure.
The game men play is the winner takes all, and very often women encourage this, by favoring only winnergenes, whatever that means.

I rather agree with you about the horses. They herded them and ate them, yes, perhaps they were even totem animals, but I don't see anything that shows they were a factor in Corded Ware, for example. Later on, even around 2200 BC it's a different story. Later on they also had better metallurgy. Perhaps the plague was also a factor, although of course that wasn't deliberate. Weakness on the part of the farmers because of bad harvests could have been another factor. I guess we'll learn, as you say, more and more. Like the Bronze Age Collapse there were undoubtedly many interlocking factors.

Some women surely do seem to gravitate to wealth and power even today. I don't think it reflects very well on us as a gender, but I'm speaking very much from my own moral code. Although I had choices, I married someone who didn't have the proverbial pot to **** in; he didn't even have parents to help out. However, we both had brains, and education, and determination, and a work ethic, so it all worked out, thank God. In the periods we're discussing, however, a woman's very survival depended totally on men so the imperative was much stronger. Then, a lot of women throughout history have been taken against their will. When a child is involved, even a child of rape, what are you going to do then, whatever your ethical code?

I'm glad I'm living in a place and time where I have the luxury of indulging my strict moral code.