When I was in first grade, I learned that I had something called a blood type and that my blood type was O+. I was initially quite happy with this, as I had interpreted 'O' as standing for 'Outstanding', and the plus meaning I had gone above and beyond outstanding. Of course, oncoming age and knowledge soon robbed me of this silly belief.
When I was in ninth grade, I learned that blood types were defined by a certain protein called an antigen present upon the red blood cell's surface. Karl Landsteiner, in 1900, discovered three such unique types, labelling them with the first three letters of the alphabet; A, B and C (with C soon becoming O). Soon after Landsteiner, scientists discovered a fourth antigen, called AB.
Antigens are present upon the red blood cells much like how houses are present upon a plot of land. First, an H antigen is produced upon the cell surface, before either an A antigen or B antigen is built, depending on the gene that codes for the antigen to be constructed. If the gene codes for an 'A' antigen, then an A-type antigen is built, and if the gene codes for a B-type antigen, a B-type antigen is built. Please note that there isn't much difference between the two, except for their shapes! In an AB-type person, both antigens are present, and in an O-type person (like me!) no antigen is present. Only the first layer is built.
There is, of course, the issue of the Rhesus factor as well- it was discovered in the mid-20th century by Philip Levine, and refers to the production of a separate antigen (labelled Rh) on the surface of the second layer of antigen, be it A, B, AB or simply nonexistent. The Rh factor has become increasingly common and may be a result of a dominant gene.
However, while Landsteiner and Levine (to an extent) have given us what blood types are and how they come about, they haven't quite solved the fundamental question- why do blood types exist? No, seriously, think about it. What sort of an evolutionary advantage does blood type provide?
Of course, there are various structures that have become vestigial and no longer serve any purpose, such as the appendix and our earlobes, but they had had some function in our early evolutionary stages. The appendix helped us digest several tougher fibres in our diet, and our earlobes may have helped us to move our ears more freely to help hunt for food or survive the dangers of hunter-gatherer life, back when it was necessary. What sort of advantage has blood type ever given us? Imagine if everyone was type O! The problem of blood donations would be solved immediately! Death due to blood loss could be immensely reduced.
The answer to the question can only be theorized. Some say it is due to a certain type of diet that blood types have come about, while this theory has more or less been completely rejected due to there being no link between blood type and diet. However, certain evidence has come to light in the discovery of the ABO gene, which is responsible for the second layer of antigen formed over the first. Like I'd mentioned earlier, some genes code for the A antigen, some for the B antigen, and some don't code for any antigen at all, not being able to produce the necessary enzyme (which is like the building block of the antigen) to make it.
It was discovered that almost 3 million years ago, the ABO gene was entirely free from mutation and proto-humans, our ancestors, all had A-type blood. Soon, however, a mutation in the gene came about, causing the antigen structure to be altered slightly into the B antigen. Successive mutations rendered the ABO gene inactive, causing no antigen to be formed, bringing about O-type blood. And then there came AB-type blood, which had both antigens.
Here lies the next question- why did these mutations come about? Again, the answer cannot be proved completely, but it is easy enough to theorize that they had been there from the start! A-type people, for example, were and still are highly susceptible to malaria, while O and B-type people are not. Malaria could have been a selective force that eliminated most A-type people, leaving O and B relatively more prevalent. Initially, some people may have thought that the mutations happened out of a need to resist malaria, but that is incorrect, as mutations do not arrive out of need. They happen randomly and become more prevalent as the commoners are wiped out, so to speak. The same way, B-type and O-type may have appeared out of nowhere and become more common as A-type people became less common.
This, of course, suggests that blood types do, after all, have an evolutionary advantage. However, it isn't a great one. O-type people are more susceptible to diseases such as ulcers, that A-types are not, so if the mutations provide disease resistance, they aren't doing a very good job! So, the only conclusion we can draw is that blood types occurred due to a random mutation in the ABO gene, that changed the blood type of some people and by pure luck, provided an evolutionary advantage and thus became more common.
In short, blood types exist....due to an accident of evolution.
------------------------------
For more math and science-focused articles that will be uploaded frequently, please follow my blog on Blogger.com! It's easy- just create your own account on Blogger, click on 'Reading list', 'edit', then 'add'. Thank you so much for reading!
When I was in ninth grade, I learned that blood types were defined by a certain protein called an antigen present upon the red blood cell's surface. Karl Landsteiner, in 1900, discovered three such unique types, labelling them with the first three letters of the alphabet; A, B and C (with C soon becoming O). Soon after Landsteiner, scientists discovered a fourth antigen, called AB.
Antigens are present upon the red blood cells much like how houses are present upon a plot of land. First, an H antigen is produced upon the cell surface, before either an A antigen or B antigen is built, depending on the gene that codes for the antigen to be constructed. If the gene codes for an 'A' antigen, then an A-type antigen is built, and if the gene codes for a B-type antigen, a B-type antigen is built. Please note that there isn't much difference between the two, except for their shapes! In an AB-type person, both antigens are present, and in an O-type person (like me!) no antigen is present. Only the first layer is built.
There is, of course, the issue of the Rhesus factor as well- it was discovered in the mid-20th century by Philip Levine, and refers to the production of a separate antigen (labelled Rh) on the surface of the second layer of antigen, be it A, B, AB or simply nonexistent. The Rh factor has become increasingly common and may be a result of a dominant gene.
However, while Landsteiner and Levine (to an extent) have given us what blood types are and how they come about, they haven't quite solved the fundamental question- why do blood types exist? No, seriously, think about it. What sort of an evolutionary advantage does blood type provide?
Of course, there are various structures that have become vestigial and no longer serve any purpose, such as the appendix and our earlobes, but they had had some function in our early evolutionary stages. The appendix helped us digest several tougher fibres in our diet, and our earlobes may have helped us to move our ears more freely to help hunt for food or survive the dangers of hunter-gatherer life, back when it was necessary. What sort of advantage has blood type ever given us? Imagine if everyone was type O! The problem of blood donations would be solved immediately! Death due to blood loss could be immensely reduced.
The answer to the question can only be theorized. Some say it is due to a certain type of diet that blood types have come about, while this theory has more or less been completely rejected due to there being no link between blood type and diet. However, certain evidence has come to light in the discovery of the ABO gene, which is responsible for the second layer of antigen formed over the first. Like I'd mentioned earlier, some genes code for the A antigen, some for the B antigen, and some don't code for any antigen at all, not being able to produce the necessary enzyme (which is like the building block of the antigen) to make it.
It was discovered that almost 3 million years ago, the ABO gene was entirely free from mutation and proto-humans, our ancestors, all had A-type blood. Soon, however, a mutation in the gene came about, causing the antigen structure to be altered slightly into the B antigen. Successive mutations rendered the ABO gene inactive, causing no antigen to be formed, bringing about O-type blood. And then there came AB-type blood, which had both antigens.
Here lies the next question- why did these mutations come about? Again, the answer cannot be proved completely, but it is easy enough to theorize that they had been there from the start! A-type people, for example, were and still are highly susceptible to malaria, while O and B-type people are not. Malaria could have been a selective force that eliminated most A-type people, leaving O and B relatively more prevalent. Initially, some people may have thought that the mutations happened out of a need to resist malaria, but that is incorrect, as mutations do not arrive out of need. They happen randomly and become more prevalent as the commoners are wiped out, so to speak. The same way, B-type and O-type may have appeared out of nowhere and become more common as A-type people became less common.
This, of course, suggests that blood types do, after all, have an evolutionary advantage. However, it isn't a great one. O-type people are more susceptible to diseases such as ulcers, that A-types are not, so if the mutations provide disease resistance, they aren't doing a very good job! So, the only conclusion we can draw is that blood types occurred due to a random mutation in the ABO gene, that changed the blood type of some people and by pure luck, provided an evolutionary advantage and thus became more common.
In short, blood types exist....due to an accident of evolution.
------------------------------
For more math and science-focused articles that will be uploaded frequently, please follow my blog on Blogger.com! It's easy- just create your own account on Blogger, click on 'Reading list', 'edit', then 'add'. Thank you so much for reading!
Very nice article ishan. It will be really great if scientists can invent how to produce blood, I guess lot of lives will be saved..!
ReplyDeleteVery well written Ishan.
ReplyDeleteLike you i am also an O type means no antigen present.
Do you think blood type determine personality? This is a very common belief in Japan. What is your opinion about this?
Nice article Ishan. I just read your blog today. Have you heard about golden blood? One of the rarest type...this blood type has a complete absence of any of the Rh antigens. I learnt about it in one of the TV shows and I double checked with my friend who is a cardiologist. Also, if you remember, I had discussed with you about the appendix long time back, you were little then, in 7th grade may be....I explained you how it has become a vestigial organ with no real function tho one theory says, it helps in storing good bacteria.... I always found human biology interesting so I keep reading this stuff and enjoy your blogs too. Keep it up.
ReplyDeleteFrom - Monica Joshi
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