Introduction to genetic algorithms (serialization II)

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(Serialization II)
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From <artificial intelligence technology in game programming> Chapter 3

Tsinghua University Press

(Translated by zzwu)

 

However, some readers may already think that if this is the only thing that happens in the organism during the breeding period, even after thousands of generations, the eyes of the most adaptable members can only be as big as those of the initial population. According to our observation of the natural world, we found that human or animal eyes are actually larger than one generation. This happens because when genes are transmitted to future generations, there is a low probability of errors, which leads to minor changes in genes. This is somewhat like the old Chinese whispering games: one message is sent one by one among a team; the first person Gently tells a story to the second person's ears, the second person gently transmits the story to the third person, and waits until the last person finally tells the story. Usually, this will make a lot of jokes: The last person tells the story and the first one is completely beyond sight. In fact, this type of error occurs when information is transmitted from one system to another. A column of pictures shown in Figure 3.2 is a surprising example. This is the result of a test: the first person draws a map of a bird (see the upper left corner)
The second person will be handed over to the second person. After seeing the second person, he will redraw another person for him. In this way, the figure drawn by the second person will be significantly 'alienated '. If you have the opportunity to gather with more than a dozen friends, I suggest you do this small experiment, because it seems incredible that the original pictures can be changed so much.

Interesting fact Ancient Coins are prone to loss errors of this type of information. The coins used by early erliterts and Stantons were heavily counterfeited; an emperor's portrait was found on the original coins (which were already used for payment in many cities and towns) then it becomes the shape of a horse or a bowl of fruit. You can see at a glance that the counterfeit currency was used at that time, without using any high-tech ultraviolet equipment for detection!

 

Figure 3.2 A test of information transfer. (Fantasy graphics provided by Thames and Hudson)

You can say that the plot or story has changed (or mutation) from one person to another ), the same variation occurs in their genes during biological reproduction. The probability of mutation is usually very small, but after a large number of generations, the mutation will look very impressive. Some variations will be detrimental to organisms
(This has the greatest possibility), while some may have no impact on the Adaptability of organisms, but some may bring obvious benefits to organisms, so that it can surpass its similar creature. In the previous example, the genetic mutation that causes an animal's eye diameter to become larger is a favorable mutation that will compare the animal with other animals in the population, it seems like a super fashionable model. This trend that increases the size of the eyes requires genetic involvement. When the Evolution goes through thousands of generations, it will make animals grow a pair of eyes as big as a dish! See the Figure 3.3.

Figure 3.3 evolution of an Adonis

In addition to improving existing features, Evolutionary mechanisms can also generate a variety of new features. Let's take the evolution of our eyes as an example.

It can be imagined that animals had no eyes at all in a period of time. At that time, animals sailed in their environments completely by the smell and touch to escape the animals that prey on them. They are also very good at doing this, because they have already experienced thousands of generations. At that time, male with big noses and long hands and feet were welcomed by female children. However, one day, when two animals are paired, a genetic mutation occurs on a blueprint provided for skin cells. This mutation allows its offspring to develop a very photosensitive cell on their head, so that its offspring can identify whether the surrounding environment is bright or dark. This gives him a small advantage, because if a kind of meatFoodAn animal, for example, an e, comes within a certain range, then it will block the light, then the animal will feel it, you can quickly go to a hidden place to hide. In addition, this skin cell can also indicate that it is now at night or during the day, or tell him that it is on or under the ground, and this information can be used to facilitate both prey and nutrition. As you can see, this new skin cell will give this animal a little more advantage than the rest of the population, and thus have more opportunities to survive and multiply. After a while, due to the evolutionary mechanism, genes with photosensitive skin cells may appear in the chromosomes of many animals.

Now, if you want to push it out and imagine that this photosensitive cell gene has a more favorable mutation, you can see that after many generations, photosensitive cells form a region after differentiation. This region continues to grow and produces some more definite features, such as forming a crystal or producing visual cells that can distinguish colors. You can also imagine that, A mutation changes an animal from a photosensitive area to two photosensitive areas, thus giving the animal a stereoscopic vision. Stereoscopic Vision is a huge improvement for an organism because it precisely tells him how far the target has left him. Of course, you can also mount mutations that adversely affect your eyes into the same genes. But the important thing here is that future generations will not be as successful as those who already have improved eyes, and they will eventually become extinct. Only Successful genes can be inherited. You can observe any characteristics in the natural world to find that their evolution is developed by countless small changes, and they are beneficial to the owner. Unbelievable, right?

These restructuring and mutation mechanisms demonstrate how evolution is done. I hope you now understand how organisms gradually form different types of features to help them achieve greater success in their living environment.

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