Why Are There Different Blood Types? Image Source: Interactive Biology

Why Are There Different Blood Types?

Do I really need to tell you all what blood is? Well, blood is a body fluid in humans and other animals that deliver necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. Human blood types most likely came to existence to fend off the infectious diseases. The incompatibility of different blood types, however, is just an accident.

Now, let’s get into the blood groups section. There are four main blood types. Blood type A is the most ancient, and it existed before the human species evolved from its hominid ancestors. Type B is believed to have originated some 3.5 million years ago, from a genetic mutation that modified one of the sugars that sit on the surface of red blood cells. The blood group A and B are expressed in many cells and tissues in addition to blood cells and circulate in the plasma as well.

Starting about 2.5 million years ago, mutations occurred that rendered that sugar gene is inactive, creating Type O, which has either the A or B version of the sugar. And then there is Type AB, which is covered with both A and B sugars.

Type O-negative blood is known as the “universal donor” because it lacks the molecules that would provoke that reaction. The term “negative” refers to the blood type which lacks surface molecule, known as the Rh antigen.

The incompatibility in the blood types is not a part of the reason, why are there different blood types, says Harvey Klein, chief of transfusion medicine at the National Institutes of Health Clinical Center. “Blood transfusion is a recent phenomenon (hundreds of years, not millions), and therefore had nothing to do with the evolution of blood groups,” Klein said.

Let’s get back to the main topic, why are there different blood types?

Different Blood Types. Image Source: Canadian Blood Services

Different Blood Types. Image Source: Canadian Blood Services

Scientists estimate that blood types have been around for at least 20 million years. But doctors have only known about them for the last 116 years. Before 1900, countries people died after they were injected with the wrong blood.

But what makes a certain blood type wrong for one person but right for another? Part of the reason has to do with proteins, called Antigens, on the surface of your red blood cells that define your blood type. For example, type A blood contains type A antigens, whereas, type B blood contains type B antigens. But if you mix blood types A and B together, you’ll start an all-out war in the body. Your blood plasma contains antibodies that police the body for anything foreign, including antigens that don’t match your blood type.

When you inject the wrong antigens, antibodies will attack by attaching to them, which then causes the blood to clump. These clumps clog blood vessels, which disrupts circulation, and can prove fatal. It only takes a few milliliters of the wrong blood to cause a serious reaction, so it’s critical that you know your blood type.

There are 35 blood group systems in the world. But yours likely falls under the two most common groups: the ABO group and the Rh group. Together, these groups include the eight blood types that dominate over 90% of the world’s population.

Odds are that you’re either O+ or A+, which account for about 65% of all human blood types. However, blood type can vary from one location to the next. For example, Type O blood is far more common in the western hemisphere while types A and B show up more often in the eastern hemisphere. In India, for instance, your odds of being born B+ are four times greater than in the US. Yet, your chances of developing the rare AB- blood type are less than 2% worldwide.

So, why are there different blood types and where did they come from? Scientists are still trying to find out the mystery. We know that blood types are not unique to humans. Dogs, cats, horses, and other living beings also have them –but animals usually contain different antigens than humans.

There’s also a growing body of research revealing that blood types play a role in our defense against certain diseases. For instance, people with blood type A are at a higher risk for some forms of pancreatic cancer and leukemia as well as smallpox infections, heart disease, and severe malaria. Whereas people with blood type O are far less likely to develop severe malaria, but they’re more prone to ulcers and ruptures Achilles tendons.

So, the next time you give blood, take a few minutes to anticipate just how unusual business it is when the blood eventually enters into another human being.

Which blood group do you fall into? Let us know in the comments below!


Reference: Curiosity