Genetics: What does your blood type say about your ancestry?

For some reason I have always been interested in blood types. Maybe it's because my grandma always had this gigantic looking book in her living room called "Eat Right 4 your type" or maybe it is because my own blood type is O negative, which makes me a universal blood donor. Whatever the reason, my fascination with blood types led me towards a little research that relates blood types to ancestry. 

A Brief Science Lesson

Have you ever donated or received blood? Chances are you have discovered your own blood type based on one of those transactions. The reason being that doctors have to ascertain your blood type before giving your donated blood to someone else or before you receive blood to ensure compatibility between the two blood types. 

From a simplistic point of view, there are four blood types: A, B, AB, and O. Your blood type depends on the antigens that are present in your red blood cells and the types of antibodies that your blood makes. For example, those with type A blood have red blood cells with A antigens present and their blood makes antibodies that fight type B antigens. Those with type B are the opposite. Type AB individuals, therefore, have both sets of antigens in their red blood cells and produce no antibodies; type Os have no antigens and produce antibodies that fight both types of antigens. Here's a chart that is probably easier to understand:

Blood Types and Ancient Humans

That's nice. But this is a genealogy blog, so what the science lesson? It turns out that your blood type is inherited from your parents, and that means it has been passed down through the generations, perhaps for tens of thousands of years. That's pretty cool (or maybe it's not cool and I'm a bigger nerd than I thought)! 

The evolution of blood types throughout human history can be broken down into a few categories, which I will call: Hunter-Gatherers, Nomads, Agrarians, and Collection. Please keep in mind that I have read several articles and am condensing that information into a few paragraphs. Lots of other folks on the web, especially nutritionists and dietitians, have explained each blood type and their origins more thoroughly than I have. 

Enjoy!

Type O: The Hunter-Gatherers

If you have Type O blood, congratulations. You possess the most ancient of modern blood types. It is also the most common blood type: 37% of Americans have type O+ and 6% have O- blood type. Cro-Magnon, or Early Modern Humans are our first direct ancestor. They ate a protein-rich diet and began hunting big game with tools and weapons. Their O blood type supported this hunter-gatherer lifestyle and people today with type O blood often secrete more stomach acid and have an easier time metabolizing animal proteins. 

Since I am type O, I can attest that for a six month period I became a vegetarian and suffered from anemia, general fatigue, and I was hungry all the time no matter how much non-animal protein I consumed. I finally broke that diet and am now omnivorous and happy. I also have the stomach problems associated with the blood type and have acid re-flux disease, am prone to ulcers, and must, must, must exercise at least 5 times per week to counteract a lot of those symptoms. The more I run, the better I feel!

Type A: The Agrarians

At the beginning of the Neolithic Period, about 30,000 BCE, people began to domesticate animals and created farming communities. The move from hunter-gatherers to farmers also saw the beginning of a new ABO blood type, A, in Caucasian people between 25,000 and 15,000 BCE.  The new blood type group evolved from a new diet based on plants rather than meats.  About 13,000 years later, the Indo-Europeans carried the A blood type into populations in Russia and Eastern Europe. My daughter is type A and she prefers a diet of fruits, vegetables, and a little grain and protein.

Type B: The Nomads

The end of the Neolithic Period, about 10,000 BCE, saw the emergence of yet another blood type: B. This blood type originated in parts of India, Pakistan, and southwestern Asia. And, as the Mongolians moved throughout Eurasia, the B blood type became firmly established throughout the region as well. Because these peoples depended on domesticated livestock, type Bs can more easily digest animal proteins and lactose: type Bs are the only blood types that can easily digest dairy products after the age of 2 years old. They are also more likely to be adaptable and malleable. 

Type AB: The Collective
AB is the rarest and newest of all four blood types--it is only about 1000-1200 years old! Type A and B are co-dominant and result from a mixed inheritance of A and B alleles, unlike all of the other blood types that evolved from environmental aspects over thousands of years. Type ABs can take on either or both traits of type A and B, sometimes creating health problems such as weight gain. For example, type AB may have the ability to digest meats because of its nomadic type B blood, but lack the stomach acid to properly break down and process those meats, thus rendering most of the protein into fat rather than metabolizing it. 
I am married to an AB type and he can and will eat just about anything! This characteristic reflects the mixed inheritance of the co-dominant alleles that evolved under very different circumstances. 

Conclusions
No matter what your blood type, you inherited those alleles from your ancestors. It is also nice to reflect upon the evolutionary circumstances that surrounded the appearance of different genes. To learn more about the evolution of the four blood types see the links above or check out the following: 

A brief history of human blood types National Library of Medicine

Why do we have blood types? Carl Zimmerman for BBC Future

This answer to a forum question on Standford at The Tech's website contradicts the theory of O as the first blood type. 

And here is an article from the Institute for Creation Research that argues all the blood types were introduced into the genome at essentially the same time (when Adam and Eve were created).