I was in 4H as a kid and showed my cows at the fair. I was interested in selective breeding to increase the milk production of my cows, but did not fully understand how it all worked. In this blog I will show you how I think it works.
I am going to start out with a group of animals or even humans. The starting distribution is a mix of individuals that can be defined by two factors, median or average and the variance or how distributed it is. If you know anything about math, this will be clear for you. Here are some simple examples that will show you how this works. If we start with the people only of Japan, we will see that they are a little shorter that the people of the USA and that their eyes are shaped differently, but they look much more like each other than do the people in the USA. The conclusion is that Japan has a smaller variance than does the USA. Is that clear? This is a key point that I will use later.
If you would like the people of Japan to become taller, what would you do? How about the USA? Would you do anything different there? Selection breeding is a two step process. One step is to breed up toward the objective and the other is to not breed down against your objective, Now the problem is how do you do that? We know that the off springs tend to be like their parents, not exactly, but close. That means we need to select the parents with the characteristics we want. Now we are getting to the heart of the problem.
How do we select in or out the characteristics that we want or do not want? If the variance of our starting group is small, it is difficult to identify those groups. Look at Japan where the people look very much alike. If we want encourage taller Japanese, we find very few who are much taller than the average. In the USA where there is a wider variance regarding height, it is much easier to find the tall people and the short people and select them in or out of our plan. Not so in Japan.
Are you starting to see that if we could first increase the variance of our group that it would be much easier to change the median by selective breeding. How do we do that? What we need to do is to increase the variance by adding in other races in this case. As I stated in the beginning, the USA already has a wider height variance than Japan even if Japan is shorter. Here is how we use this wider variance. We easily select out the shorter people and discourage their breeding while we do just the opposite with the taller people. If wee keep this up for several generations, the Japanese as well as the USA will get taller or have a taller average. If this sort of thing is kept up for a long period of time the variance will get lower until it becomes more and more difficult to sort out the shorter and taller people.
There are all kinds of factors that impact and skew random selection. I am going to list a few here. Take the border situation here in the USA. It seems that more criminal types are coming in than the starting average here in the USA. This means that the USA will breed toward more criminals. Here is another factor that you might not have thought about. If the criminals breed younger they will have already impacted the population before they go to jail and out of the breeding pool. In the past the crimes were mostly committed by older individuals and they were jailed before getting a chance to breed. Now, we let them out with no bail and allow them to commit more crimes and breed in the same time.
This is just one small thing that is happening, but over time it will have a big impact. That is the reason that we should all be alert to shifts in the breeding pattern of us humans here on Earth. Our individual lives are very short compared to mother nature and how she can change things very significantly over time. Look around and we all know this, but seldom really think about it and realize that we actually have some control over it. If you want the world to not become worse for you grand children, then think about the above and do your share to save the future.
Tj
