Blending Theory of Inheritance Explained


Although it is sometimes referred to as a scientific theory, the blending theory of inheritance was more of an early hypothesis regarding the transmission of biological data. It is an idea that was never formally published, ascribed to a specific person, or presented in any way.

The idea of blending inheritance is that inherited traits are determined randomly by nature. The genetic data from the mother mixes with the genetic data of the father to create offspring that is determined from a range that is bound by their homologous traits.

Take height as an example. If a child has one parent that is tall and the other is quite short, then the blending theory of inheritance suggests that the child’s height will be somewhere between the height of the father and mother. This would become a limiting boundary for future offspring, which would then affect the rest of the lineage.

Over time, the potential for variation would continue to narrow in regards to each trait. Given enough time, everyone would eventually be the same height because there would no longer be a lengthy range for randomness to operate.

Why Was the Blending Theory of Inheritance Accepted?

We have only recently begun to discover the truth about genetics. In the past, there were many attempts offered to explain how all the children in one family could have blue eyes, but in another family they would have all brown eyes. The blending theory of inheritance seemed like a reasonable compromise between all of the ideas that were being proposed at the time.

By offering a bit of randomness to the idea of a genetic transfer when having offspring, it also created a certain sense of equality. Everyone would be somewhat random in their creation.

Yet this theory was not fully accepted by the scientific community, even if it was widely believed to be true within the general population. The blending theory cannot account for the reason why genetic traits can reassert themselves within a lineage after being gone for several generations. A family might not have anyone with blue eyes for several generations, yet then two parents with brown eyes could give birth to a baby that had blue eyes.

If the blending theory of inheritance were indeed true, then the reestablishment of genetic traits could not occur, but it does.

Darwinism and the Blending Theory of Inheritance

Charles Darwin is credited as being one of the first to suggest that a form of evolution is responsible for life as we know it in our present day. The publication of On the Origin of Species in 1859 was contrary to what many scientists, who were highly religious, believed to be fact in regards to how life was created.

In the minds of the scientific community at the time, Darwin’s work was dangerous. He was upsetting the status quo because evolution, in their minds, was a direct challenge to God. With the need to defend their structures of belief, a number of “arm chair” theories were promoted as a way to counter what Darwin published in Origin.

The blending theory of inheritance happened to be one of them. It was an idea that became popular because it directly countered what Darwin was proposing. As one critic, Fleeming Jenkin, noted in a critique that was published in 1867, it would be impossible for an idea like the “survival of the fittest” to be true. The superior traits would be blended away over time through inheritance, making it impossible for that theory to work.

Gregor Mendel and the Blending Theory of Inheritance

Gregor Mendel offered a counter-theory to the popularized blending theory of inheritance in 1865. Through his experimentation with plant hybridization, he proposed that particulate inheritance was the means of genetic transfer, not blending. Mendel’s work reinforced Darwin’s work at the time and it is still used to this day as the basis of the inheritance model.

So what can we learn from the blending theory of inheritance?

We must be able to distinguish between facts and alternative facts. Every idea deserves to be considered, but those ideas must also be questioned. We must probe every idea, even popularly held beliefs, to see if there are foundational truths present. We must be willing to ask tough questions instead of blindly accept what someone offers as a universal truth.

Through testing and questioning, we further our knowledge. This process proved that the blending theory was incorrect through experimentation and testing. We can still do the same thing today.