Parasites

In this experiment I will be testing a Parasitism behaviour. But first let's introduce the mechanisms of sexual reproduction.

Sexual reproduction

In Evo(rand) there are 2 mechanisms for reproduction:

• Cloning, which has been used in the previous experimeents.
• Mating, which is a reproduction in-between 2 Creatures.

In the Mating relation there are 3 Creatures involved:

• The Father that makes the intended Action to make another Creature pregnant, and once the Father is sufficiently near the other Creature,
• The Mother that is made pregnant by the Father (except if the Mother is already pregnant). The Mother will provide all the Energy of the Child (although this is configurable, but it cannot come from the Father).
• The Child which inherits its DNA from both parents, inherit the Specie from the Father, and any attribute that needs to be conserved (like Energy, Humidity, etc.) from the Mother.

As you can already imagine, the above mechanism can be used for intra-Specie Mating and Inter-Specie parasitism: the Father Specie is using the Energy of another Specie to reproduce itself, similar to a virus.

Configuration

In the below experiment, the simulation is similar to the "Sacrifice" simulation, with the following changes:

• A new attribute Chase is added to the Creature, ranging from 1 to 100, with its value read from the DNA and default to 1 if not found in the DNA:

• The "Kill" action is changed to a "Parasite" Action, with the speed (velocity of turning and moving) equal to Chase. Note that the Mouvement Type is "Chase Target", which means that the Creature will actually move towards its Target (the intended Mother) and follow it till being very near, at which time the Action is actually performed:

• There are only 2 Species.

A few videos

When running the simulation, we do observe the Parasite Action being performed by a substantial proportion of the population. We also observe that:

• When the Parasite Action is developping, the total population is decreasing.
• After the peak, the action is becoming less common (because there are less Creatures of the opposite Specie available), and the population increases again (because Food has been acumulating in the Ground).
• Finally the population returns to its initial size (or slightly higher).

Here are 4 videos:

Note: when a sudden change of Creatures' colour occurs, it is because one of the Species became extinct.

Interesting observation: if we do not add the Chase attribute, and the speed of performing the action remains 1 like the other Actions, the target of the parasite has time to re-act. We can observe this type of self-defense reaction in the Behaviour Rules of the Creatures:

The first rule means: if a living Creature of a different Specie is targeting me, I make myself pregnant by Cloning. This is actually a self-defense mechanism because the parasite cannot make its target pregnant a second time!

Conclusion

What can be concluded from the above experiment? Well, that Parasites can be simulated through artificial simulation. However it also shows flaws in the simulation.

We all know that parasites were present from the very beginning of life on earth. Some say that actually parasites played a crucial part in the evolution, forcing the various forms of life to always evolve in order to compete against their parasites. Some scientists even say that parasites were the main reason for sexual reproduction.

I actually do believe in the above theories.

However, such co-existence does not appear in Evo(rand): either both Species become parasite of the other, or parasites disappear.

It just means that something is missing in Evo(rand), be it allowing a Creature being "pregnant" of multiple Childs, or allowing the parasite to have more control over the DNA mix with the host. Maybe a future version will include those...