About Luca

What is Luca?

Luca is a philosophical thought experiment.

The question being asked in this experiment is: if many random sequences are produced and continuously changed, could one of them ever encode a functional message?

Luca is designed to produce many random binary sequences (i.e. strings of 0 and 1). When you spawn an Organism on this website, a collection of binary sequences (Chromosomes) is produced. Every time you refresh the page of your Organism or a friend opens the link that you send them, one of the Chromosomes is randomly mutated, and the new sequence is saved in Luca’s database.

What can a Luca Organism do?

The binary sequences are then converted to the very same characters on your keyboard (ASCII printable characters). When your web browser loads the page for an Organism, it reads through each string of characters generated by the random binary sequences. If it so happens that the right characters are placed in the right order, the generated string of characters could potentially be meaningful. You might see words on your screen like “Hello, world!” or a question like “Who would have thought?”.

It is possible that the message produced isn’t meaningful to you, but is meaningful to your web browser. A binary sequence could translate to something that looks like this: “<style> blah blah blah </style>“. This is called an HTML element. If, instead of “blah blah blah”, a valid block of styling information was provided between the opening and closing tags, something could be changed on the page that you see. Perhaps the color of the navigation bar at the top will change, or the size of the title, or the background image. If a different element is used, like <form>, the page you see could show a form that you can interact with. You can find a list of all valid HTML elements here.

If an Organism happens to produce a valid <script> element, your browser can do so much more than just change the size of some text. Whatever message is passed between the opening and closing “script” tags is interpreted using your browser’s JavaScript engine. If the message happens to be valid JavaScript code, then your browser will run it. It can define variables, perform mathematical operations, redirect your browser to a different website, move things on the page, open a new window, or even offer you a file to download (not that you should accept it).

So a Luca Organism can do anything that your browser is capable of doing. In theory, one Organism might recreate everything you see on this page here. After all, there is a unique set of 0’s and 1’s underlying the contents of this page.

Where does the DNA come in?

This experiment is inspired by the information-carrying molecule of life: deoxyribonucleic acid (DNA). The program underlying Luca simulates a double-stranded DNA molecule, thus a Chromosome. Every Organism carries at least one Chromosome. Each strand of a Chromosome is a sequence of ‘A‘s, ‘C‘s, ‘G‘s, and ‘T‘s (bases). The two strands are converted to binary sequences according to an arbitrary key (A: 00, C: 01, G: 10, T: 11).

Each binary sequence is then scanned for all possible “genes“. A gene, here, is defined as any string of ‘0’s and ‘1’s with a length that is a multiple of 8. Genes are then “transcribed” by converting each set of 8 digits to a corresponding printable character.

The mutation process is also designed to resemble DNA mutation mechanisms. For now, four mechanisms are possible: insertions, deletions, substitutions, and double-stranded breaks. More mechanisms will be added over time.

When an insertion occurs, up to 100 random bases are consecutively inserted at a random location on a random chromosome. When a deletion occurs, up to 100 consecutive bases are deleted. A substitution involves up to 100 consecutive bases being replaced by new ones. And a double-stranded break causes one Chromosome to become two separate Chromosomes.

How does the population evolve?

The Organisms on Luca “live” in the web browser that accesses it. If an Organism is no longer visited by anyone, it will not be alive anymore, as its genome will not be transcribed anymore. So, the Organisms which are most frequently accessed will be selected for, and the others selected against. It can be expected, then, that the population will evolve in favor of the more frequently visited Organisms. The mantra here would be “survival of the popular“.