Have trouble sleeping at night?  DON'T read this.  You never know what awaits you at your desktop computer. I created them. I can destroy them, and I can bring them back. - Thomas S. Ray Thomas is an evolutionary biologist, who has created an electronic world named Tierra, which is populated with self-replicating digital organisms that EVOLVE as they compete for computer time and memory. Ray's Tierra (Spanish for Earth) organisms do not actually live (keep in mind that scientists don't have a definitive definition for life), they are merely computer programs that continuously make copies of themselves.  The goal is to learn about evolution by watching their behavior. Tierra is a world where life, death, competition and reproduction are represented in computer terms.  Thomas uses an ALmond( Artificial Life Monitor) to observe the shifting patterns of colored rods on the screen.   These colored rods represent computer programs that are replicating and trying to populate the screen with their offspring (innate instinct?). (Plague in a glass bottle)  Ray used a program that simulates a second computer.  This was necessary to prevent his creations from getting loose and wreaking havoc like computer viruses.  This virtual computer (the program) includes a block of memory the creator calls the soup (primordial).  He unleashed his organisms (programs) there.  To add authenticity to his creations, he developed a unique computer language in order to write these self-replicating programs.  To mimic the size of the human genetic code, he limited the number of distinct instructions to 32 to control all operations within Tierra.  He added a feature of molecular biology, which he calls the address by template .  This means that the organism (ex. 1100) cannot reproduce until it finds a complement (0011) somewhere in the soup (memory).  All of this would not truly mimic evolutionary theory unless he allowed for mutations. He did this by having the bits in the memory soup to randomly flip from 1 to 0 or vice versa an average on once every 10,000 executed instructions.  The other means for mutation occurs when programs attempting to copy themselves make an error during replication, producing an inexact copy. Tierra also has a grim reaper.  It is in the form of a monitoring program that eliminates the oldest creatures and the most defective ones - those that erred most often in executing their instructions.  When the population reaches a certain level (ex. 80%) the reaper is unleashed in a night of terror and death visits the elderly and the lame.  There is no immortality.  An organism eventually ages or mutates to death.  The reaper keeps a list.  Aging moves an organism up on his wishlist.  Errors in execution also moves a program up one notch on death row.  There is no way to escape death, but there is a way to delay it - the Fountain of Youth.  It consists of two difficult sets of instructions.  If an organism executes them correctly, it moves down a spot on the hit list. During Tierra's first run, Ray's lone 80-instruction organism quickly reproduced and diversified into a variety of different creatures. His most optimistic expectations had led him to hope that the offspring would be more efficient at reproduction.  He guessed that the offspring program would consist of less instructions - 76.  BUT Tierran evolution produced a speedy creature that was only 22 instructions long and could reproduce six times as fast as the ancestor.  In contrast to this pint-sized speed demon, mammoth creatures emerged, some with 23,000 instructions.  They could not compete with the smaller organisms and like the dinosaurs, they died off.   Parasites emerged, which mimicked real-life viruses that invade a cell and use its ribosomes to make copies of themselves.  These computer parasites don't have the genes for the copy procedure, so some of them invaded the ancestor program and used its copying instructions to reproduce.  A decendant of the ancestor program was produced which was immune to the parasites, but then another parasite was born which could bypass that immunity.  These were all SIMPLE tricks. Organisms called hyperparasites invented tricks for competing for computer time (the equivalent of energy).  Computer time is allotted equally to all programs.  Some creatures developed an ability to steal extra time for reproducing.  When a normal parasite invades a hyperparasite and attempt to reproduce itself using the host's copy procedure, the hyperparasite substitutes its own code for the unsuspecting program to replicate throughout its life.  By doing this the hyperparasite reproduces more often without being charged for extra access time. To REALLY complicate things, I'll tell you this.  After the hyperparasites drove the parasites to extinction, they formed a community of hyperparasites and cooperated with each other for reproductive purposes.  This made them vulnerable.  They were invaded by a hyper-hyperparasite known as a cheater. It snuck into their community and stole the energy source (access time) that the hyperparasites pass among each other. LYING, too, can pay off in Tierra.  When time was allotted to programs for reproduction _base_d on their size, some organisms told it, they contained more instructions than they did, gaining more time for reproduction. Tierran evolution is also marked by punctuated equilibrium.   Another twist, the reaper was removed.  This resulted in overpopulation, causing the memory to fill up.  In order to reproduce, the organism would have to free up memory by killing another creature. Tierra offers skeptics dramatic proof that random chance can produce systems of great complexity.  (but Someone still created it.) I have pictures of these life forms.  They look like a lot of multicolored horizontal lines of varying length on a screen.  One day, Marylynn nearly tripped over some type of cord leading to the computer at the front of the classroom. Anyone who saw the projection on the screen would have described the image as distortion.  But surprisingly, it looked a lot like these pictures, except that the lines were not multicolored! (life forms not self-aware?) Says Langston, The time will come, when computer-dwelling artificial creatures will become curious about their origin (just like us), and will discover that the human creatures peering at them through the other side of the monitor had something to do with it.

Hey Micheal, like Stevie Ray Vaughn is on my computer.