Why is European Blood So Unique Rh Negative Explained and More

Does the blood running through your veins reveal something about your ancestry? Why is blood type O so common in Ireland and the Atlantic fringe, Rh negative so elevated in Europe, while type B is dominant in parts of Asia? Well, in this video, we'll uncover the hidden links between blood type and ancestry. But before we look at why there is such variation in blood types across the world, let's quickly get an overview of the main blood types. Now the ABO system classifies blood into four main groups, A, B, AB and O. This is based on whether red blood cells carry A antigens, B antigens, both or neither, as this breakdown shows. And let me know what your blood type is in the comments below, and where you are watching this video from. Now your blood group is determined by the genes you inherit from your parents. And on top of the ABO classification, there is the Rh system, more commonly referring to the RhD antigen. If you have the RhD protein on your red cells, you are Rh positive. If you lack it, you are Rh negative. Now look at this table. You can see how rare Rh negative is around the world, at only 6% or so. Yet it is elevated in Europe, or in places with a lot of European ancestry, such as the United States. But why is this? Well we'll explore this connection between Rh negative and European ancestry later in the video. Now each of the four blood types can be Rh positive or Rh negative, which means in total, there are eight total blood types. And if you look at this table, you can see that O positive is the most common blood type in the world, found in around 42% of people. AB negative is the least common of the main eight types, on the other hand. There is also an extremely rare blood type that is often forgotten, called Rh null, or nicknamed golden blood. Fewer than 100 people have ever been documented with this since its discovery in 1961, which lacks all Rh antigens. But how do blood types vary by populations in Europe and across the world? Well if we start with Europe, two broad trends stand out. The first is that group O reaches very high frequencies in parts of the Atlantic fringe, especially in Ireland and some regions of Iberia. And secondly, Rh negative frequencies are unusually high in Europe compared to the rest of the world, especially in the Basque country. Now Ireland is one of the clearest examples. If you look at this table, you can see that around 55% of the population belongs to blood group O. 47% are O positive and around 8% O negative. Rh negativity rates in general sit in the mid to high teens. These figures make Ireland one of the most O-heavy populations in Europe, with the European average of type O only around 45%. But why is type O so high in Ireland? Well a key factor is thought to be Ireland's geographical isolation and the ancestral genetic signature of the early hunter-gatherers who first settled at Ireland. An interesting paper from 2017 was written by the population geneticist E. Matheson, who looked at blood groups in ancient Europe, and his results suggested that around 65% of Mesolithic hunter-gatherers would have belonged to blood type O. Over millennia as well, a founder effect in genetic drift could have been at play, amplifying type O's rate in Ireland. We also see that people with Irish ancestry around the world often have elevated levels of type O as well due to this. Now another region in Europe that is often discussed in blood type debates is the Basque Country, spanning parts of northern Spain and south-western France. This is because they have the highest rates of Rh negative in the world, at between 21 and 36%. Some theories claim that high Rh negativity in the Basque people point to mysterious or ancient origins. However, this high level was thought mainly due to the long-term geographical isolation in the Pyrenees. This allowed older genetic patterns and genetic drift to shape frequencies. Now when it comes to Europe overall, blood types O and A are by far the most common. As we've previously noted, blood type O is very common in western Europe, whereas type A becomes more common in parts of northern and central Europe. And if you look at this table that's been sorted for type A blood, you can see that the likes of Norway is one of the highest in the world, with many other European countries listed as well. And when we sort the table for A negative, it's mostly European countries at the top, with the UK actually the highest. Now Mongolia also shows up in some of these tables, and this actually has one of the most distinctive blood type profiles in East Asia. This is largely because it sits at a historical crossroads between East Asia and the Eurasian steppe. But what about North America? While blood type A reflects a mixture of European ancestry combined with African and indigenous contributions, blood type O remains the most common in general, at roughly 44-45% of the population, followed by type A at around 40%. Rh negative blood occurs in roughly 12-15% of the population, closer to European levels. Now among indigenous populations of the Americas, type O reaches extremely high levels, often between 70% and nearly 100% in some groups. Rh negative blood, on the other hand, is very rare. Much different to Europe. Now these strikingly high levels of O in indigenous peoples of the Americas are widely attributed to founder effects. When small ancestral populations migrated from Siberia into the Americas during the last ice age, they likely carried a limited range of ABO variation. Over time, genetic drift in relatively isolated populations likely amplified the dominance of type O. And if you look at this table, sorted for O positive rates around the world, it's South American countries like Ecuador and Peru that top the list. But if we sort the table for O negative, you can see that it's a different story. But what about Asia? Well when it comes to Southern Asia, type B dominates this region, and is very common in countries like Pakistan and India. If you look at this table sorted for B+, for instance, you can see that Southern and Southeastern Asian countries top the list. Rh negative in these regions is relatively uncommon though, typically between 3 and 8%. In East Asia, the most common blood types are either type O or type A, depending on the country. If we look at China, O, A and B are all common, while Japan and Korea tend to show particularly high frequencies of type A. Rh negative blood is extremely rare across this region though, often occurring in less than 1% of the population. Now Central Asia is more of a mixed zone. Type O, A and B are found here in good levels, with Rh negative somewhere between 2 and 8%. When it comes to Australia and New Zealand, type O typically makes up around 45 to 50% of the population, followed by type A at roughly 35 to 40%. B and AB are much less frequent. Rh negative levels are relatively high by global standards, around 15 to 17%, again reflecting strong British and Irish ancestry in the population. Indigenous Australians and the Maori peoples generally have very high type O frequencies, and very low Rh negative levels. Now if we turn to Sub-Saharan Africa, type O is the dominant blood group across much of West, Central and East Africa. Rh negative blood, however, is far less common than in Europe, typically ranging between 1% and 5%. The high frequency of type O in parts of Africa may partly be influenced by natural selection, as certain studies suggest that type O may offer some protection against severe malaria. Across the Middle East and North Africa, type O is again the most common blood group. Rh negative frequencies are moderate, usually between 5 and 10%. Higher than in most of Asia or Sub-Saharan Africa, but lower than in Europe. These distributions reflect the region's long history as a crossroads between Africa, Europe and Asia. So the global dominance of type O, the concentration of type B in South Asia, and the higher Rh negative frequencies in Europe all reflect deep population history. And the Rh factor in particular adds another layer of intrigue. But why is Rh negative blood so common in Europeans? Well the reasons are debated. Some people point to a potential Neanderthal link, whereas others focus on genetic drift and founder effects in ancestral European populations. If we turn back to this 2017 paper on the blood groups in ancient Europe however, another potential explanation emerges. Now the author Matheson analysed the rates of Rh negative blood types in ancient populations that make up the foundational genetics of most Europeans, i.e. hunter-gatherers, early European farmers, and then steppe ancestry. And his results suggested that steppe ancestry individuals had the highest levels of Rh negative blood, at around 40%. Compared to around 24% in hunter-gatherers, and only 4% in early farmers. So perhaps the high levels of steppe ancestry in Europeans is one driver of these Rh negative levels. Yet this also raises more questions in and of itself, as in why did these people have such high levels in the first place? That's something I might explore in a future video, and please let me know if you would like to see that in the comments below. So what does this all mean for ancestry? Well, blood groups do reflect deep human history. They reveal echoes of Ice Age refugees, ocean crossings, migrations, isolation, epidemics, and demographic bottlenecks. Yet the limits are equally important. Two populations can share identical blood type distributions, yet have very different histories. Conversely, individuals within the same family can have different blood types. Blood type can thus hint at broad ancestral patterns, but is only one variable in a much more complex picture. But what are the hidden links between eye colour and ancestry? Well, to find out, please click here. Thanks for watching, please subscribe and hit the bell, and let me know your thoughts in the comments below, and please become a member if you're interested in member-only videos. Top link in the video description below. But yeah, thank you for watching, and I'll see you next time.