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Create creatures and let them evolve to see how they master various tasks. · By Keiwan

Fitness vs. Task proficiency

A topic by brunoschull created Nov 13, 2018 Views: 153 Replies: 2
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Hi.  I'm a newcomer to the Evolution program.    I am a biology teacher, and I've been exploring the program with students.  It's really powerful and interesting.  Thanks for creating such a great interface!

My question is about how to interpret the progress of the program. 

Once a creature is evolving, you can track its progress with different metrics, such as the fitness score, or its proficiency at a particular task, such as the horizontal distance is has moved from the start (for the running task). 

Is there a difference between these two metrics, fitness and proficiency?  

I ask because the fitness and the task proficiency appear at first glance to be roughly but not perfectly correlated--I might be wrong, maybe they are actually perfectly correlated. 

Is the task performance an absolute measurement, for example, how far the "farthest" joint reached, while the fitness is an average of all the joints/bones/muscles for a particular creature?

Or does fitness measure something else?

In biology "fitness" has a specific meaning related to the contribution of genetic material to the next generation, i.e., to simplify, how many offspring an organism has, and not necessarily how fast it can run, how high it can jump, and so on.  

Is the fitness score in the computer program somehow related to reproduction? 

If the fitness score is not related to reproduction, and the creators would like to make the program as biologically accurate as possible, would it make sense to change the word "fitness" to something else, such as "performance?"

OK, thanks again,



Hi Bruno,  it always makes me really happy to hear that this little simulator is being used for educational purposes, thanks for that!

The "fitness" score in this simulation is perfectly correlated to the creature's proficiency at the task. For example, the fitness score for the running task is computed as the horizontal distance from the start divided by a maximum distance value that a creature would have to reach in order to receive a perfect score of 100%. This maximum distance has been arbitrarily chosen by me. It obviously also scales with the simulation time of each generation, so that increasing that time doesn't make it any easier for the creatures to achieve a higher fitness score.

During the reproduction step, two creatures are selected and their chromosomes are recombined using 1-point crossover, which produces two new offspring. This step is repeated until the new generation has reached the chosen population size. Creatures with a higher fitness score have a higher chance of being selected as parents for reproduction and since the same creature can also be selected multiple times, the fitness score of a creature effectively contributes to the number of offspring that will carry part of the genetic information of this parent creature into the next generation.

I might allow the user to select between different selection and recombination strategies in a future update, in order to offer a few more options for everybody to experiment with.

Best regards, 


Thank you so much for the explanation.  That makes sense.  I just finished some work with students using the simulator, and it was really successful.  Like most good lessons, it only lead to more questions :)  I will make a new post, or contact you directly (if possible) to that this thread does not drift into other topics.  Thanks again--I really appreciate it.