# Why do we have different blood types? **URL:** \ **Category:** Factual Questions\ **Created:** [October 10, 2002, 1:04am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610 "2002-10-10T01:04:56Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![Sublight](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@Sublight](https://boards.straightdope.com/u/Sublight)\ **Post date:** [October 11, 2002, 9:20am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/21 "2002-10-11T09:20:36Z")
> [@](#): > > \*Originally posted by Bosda Di’Chi of Tricor \* > \*\*I’m AB Positive. > > I’ve heard that, in Japan, blood types are used for fortunetelling or sexual compatabilty, like horoscopes. > > If any cute Japanese girls are lurking, compatable & interested, e-mail me. 😉 \*\* Indeed it is. Most of the newspapers and morning shows include a blood-type horoscope along with the western birthday-style one. AB types are supposed to be more tempermental and unstable, but also more artistic or creative. ---
**Author:** ![CuriousCanuck](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@CuriousCanuck](https://boards.straightdope.com/u/CuriousCanuck)\ **Post date:** [October 11, 2002, 12:06pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/22 "2002-10-11T12:06:08Z")
I’m AB+ myself. AND I happen to work for Canadian Blood Services. Might I suggest going to www.bloodservices.ca and there are alot of great facts there about blood. And I should also remind everyone that if they can, they should give. Only 3% (5% in the USA) give blood, and over 90% of the population will need it at some point in their lives. I for one would never like to be in a situation where there is no blood for me when I need it. Although, I am AB+ so I am a universal recipient… Another thing about blood types. Certain O- people also have what is called “baby blood”. They lack simply a “virus” attached to their blood cells which allows them and them only to transfer to Newborn babies if necessary. O- makes up 7% of the N. American population, but these special O- people are less than 1%. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [October 11, 2002, 6:16pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/23 "2002-10-11T18:16:56Z")
The genes that determine your blood type code for an enzyme that sits inside your endoplasmic reticulum or Golgi apparatus and modifies sugar molecules attached to membrane proteins that end up on the outside of your cell membrane. Different versions of the enzyme in different combinations give different ABO blood types. As far as I know, there doesn’t **have** to be a big evolutionary advantage for us to have different alleles of this enzyme. If one of our ancestors had a mutation in the gene that caused a slight change like that, and if it didn’t make any difference to your health one way or another, the mutation could have spread through the population by a process called random genetic drift. There’s a whole field of study devoted to the spread of neutral mutations in populations. We have a lot of neutral polymorphisms, but most of them don’t come to our attention the way blood type differences do. By the way, this doesn’t mean that ABO differences **don’t** affect susceptibility to pathogens, just that subtle variations like that don’t **have** to in order to exist. Also, it’s possible, as alluded to above, that a variation like this could start out as an accident and end up having big selective consequences later. There are some people, for example, that have a seemingly neutral polymorphism in lymphocyte surface proteins (I don’t know if any of them are absolutely 100% neutral) that happens to protect them from HIV infection. But that’s not **why** the variations are there. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 12, 2002, 1:35am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/24 "2002-10-12T01:35:05Z")
Darwin’s Finch - great links! A blood type called Duffy! I would never have guessed. But if it’s not called O (pronounced oh) because it’s not A or B, why isn’t it called C? CuriousCanuck - do you know how to get tested for the “baby blood” thing? It seems like it would be a good thing to know. ---
**Author:** ![flertbert](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@flertbert](https://boards.straightdope.com/u/flertbert)\ **Post date:** [October 12, 2002, 1:59am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/25 "2002-10-12T01:59:35Z")
There’s a blood group called “Luthern,” does Garrison Keillor know about this? ---
**Author:** ![Wearia](https://avatars.discourse-cdn.com/v4/letter/w/13edae/32.png) [@Wearia](https://boards.straightdope.com/u/Wearia)\ **Post date:** [October 12, 2002, 5:52am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/26 "2002-10-12T05:52:27Z")
A+ here. So O blood is the least evolved because it lacks some sugar/protein/thingie? Which type is most evolved, AB? (is evolved the right word to use?) What is the rarest blood type? ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [October 12, 2002, 9:36am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/27 "2002-10-12T09:36:12Z")
No, O isn’t less evolved in any way. Just different. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [October 12, 2002, 12:27pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/28 "2002-10-12T12:27:17Z")
Up with the A+'s. That includes me, my wife, my three children and, I think, my four grandchildren (must check that out). I want to correct one common misconception (no pun intended), but it is commonly believed that two type O parents cannot have, say, a type A child. Or two type A’s cannot have a type B. That is almost always true, but not quite always. There’s many a slip 'twixt the cup and the lip and a lot more goes into making one of the A or B antigens that just having the right genotype. So it is possible for a type O to have, say, type A genotype, but not express as a result of another genetic anomoly. His spouse could provide the gene to fix that anomoly, while he provides the A gene and, voila, a type A child. Rare but definitely not impossible. Hope I may have saved a marriage with this information. ---
**Author:** ![Lazlo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lazlo/32/9678_2.png) [@Lazlo](https://boards.straightdope.com/u/Lazlo)\ **Post date:** [October 12, 2002, 2:23pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/29 "2002-10-12T14:23:27Z")
> [@](#): > > \*Originally posted by Sublight \* > \*\*Indeed it is. Most of the newspapers and morning shows include a blood-type horoscope along with the western birthday-style one. AB types are supposed to be more tempermental and unstable, but also more artistic or creative. \*\* Aaaaaaahh… I’ve always wondered why video games such as Resident Evil or Final Fantasy have the character’s blood types (as well as age) listed in their bios. Now I know. Thanks! ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 12, 2002, 9:10pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/30 "2002-10-12T21:10:54Z")
Sublight - Do you have a list of the personality traits of the rest of the blood types? I’m starting to get curious. And is it just ABO or is the Rh factor factored in? O neg, by the way. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [October 12, 2002, 9:46pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/31 "2002-10-12T21:46:02Z")
**Yllaria** , [here](http://www.najaco.com/health/blood_type.htm) is one version. From other sites I’ve found, it looks to be based only on the ABO group. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 12, 2002, 10:27pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/32 "2002-10-12T22:27:09Z")
The frequency of ABO blood types varies drastically between human populations. It is uncertain how much of this is due to gradual spread from a local origin for each of the mutations that gave rise to the different types (or perhaps even multiple origins for some), how much may have been due to genetic drift in small populations that later expanded, and how much might be due to balancing selection due to differing advantages for the different types relative to disease or other selective factors. [This site](http://anthro.palomar.edu/vary/vary_3.htm) shows the global distribution of different blood types. A is most frequent in Europe, B in Asia, and O in Central and South America, but there is a great deal of local variation. Adaptive value for different blood types has been alleged for resistance to various diseases, but this is difficult to distinguish from many other factors. From [here](http://216.239.51.100/search?q=cache:z8wtaKVUmy0C:csbs.csusb.edu/anthro/wesn/anth325/Molnar3.htm+molnar+chapter+3&hl=en&ie=UTF-8): > [@](#): > > 1. Disease Incidence and the ABO Blood Groups > > a) It’s very difficult to prove CAUSAL relationships between blood types and incidence of disease > > i) Environmental factors cannot always be ruled out > > ii) Also, correlation and causation are two different things > > b) Pioneer study in England indicated those with blood type A had highest rates of stomach cancer > > c) Since then, many diseases have been studied (mostly gastrointestinal) > > . . . > e) There are other associations between infectious diseases and ABO blood types > > i) Type O has greater susceptibility to > > (1) Typhoid > > (2) Cholera > > (3) Plague > > (4) Scarlet fever (along with B) > > . . . > > iii) Some disease organisms may be antigenetically similar to ABO blood antigens > > (1) Thus, if a disease causing organism is similar to the H antigen, those with blood type O may not make antibodies against it > > (2) The smallpox virus has been shown to be very similar to the A antigen and blood type A are more susceptible to it > > (3) The same is true of the plague bacillus (similar to the H antigen) > > (a) Given its virulence in 1345 (50% mortality) this may explain why Europe has slightly higher frequencies of A and B alleles > > (b) Also, Asia, India and the Near East have low frequencies of O and they tend to be major plague centers > > (i) So there may be heavy selection against O (plague, cholera) and A (smallpox) > > . . . > > (iv) Insect vectors may also have an influence > > (1) Type O seems to be preferred by blood sucking insects > > a) This may affect the spread of malaria > > . . . > > (f) The bottom line is that we don’t really understand the effects of natural selection on the distribution of ABO alleles > > i) The potential is there- especially because high infant mortality (around 50%) is the rule for most non-industrialized nations > > (1) Especially life threatening are infectious diarrheas (caused by E. coli) > > (2) It was noted that in epidemics in eastern Europe, the bacteria infected those with type O blood the least ---
**Author:** ![Sublight](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@Sublight](https://boards.straightdope.com/u/Sublight)\ **Post date:** [October 13, 2002, 11:30am UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/33 "2002-10-13T11:30:00Z")
Well, like astrology, hundreds of books on correlating blood types with personality have been written, but basically: A - neat, sensitive, serious, but naive B - messy, laid-back, bold, unreliable O - generous, kind AB - creative, but unpredictable Positive and negative don’t seem to matter, but I’m sure some writer somewhere has tried to sell that angle. I don’t actually believe in this, mind you, but at least claiming that the proteins in your blood affect your personality sounds a little more rational than basing it on the alignment of the planets on your birthday. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [October 13, 2002, 2:20pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/34 "2002-10-13T14:20:51Z")
How weird. Those people at the blood bank don’t have the slightest idea what they’re doing! They’re always telling me that I have type O blood, but that list proves I’m actually a B. And don’t even get me started on those fools who put out birth certificates. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 13, 2002, 8:04pm UTC](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610/35 "2002-10-13T20:04:50Z")
Quoth **Bob Scene** : > [@](#): > > There are some people, for example, that have a seemingly neutral polymorphism in lymphocyte surface proteins (I don’t know if any of them are absolutely 100% neutral) that happens to protect them from HIV infection. But that’s not **why** the variations are there. On the other hand: There is currently a very strong selective pressure in favor of that allele. It may be that hundreds of generations down the line, that selective pressure will result in that allele being very common. Should that happen, then it will be fair to say that that allele is there to protect against HIV. [Previous page](https://boards.straightdope.com/t/why-do-we-have-different-blood-types/131610.md?page=1)