Originally posted to Reddit, moved here for easier access.

Aight here's how it works.

ROCK DECENDENTS!

In essence, a sentient rock (alternatively known as a geobrain) is a naturally formed computer.

How does it happen? Beats me.

Regardless, these computers are surprisingly adaptive in their wiring despite their mostly static nature. If a piece breaks off, it's extremely common (if not standard) for function to actually not be affected at all. This is subject to much study in the Martian Union and our partner states, but, once again, remains a mystery.

Now, you may be piecing things together already. If the bulk of the computer keeps functioning after a breakage, what about the chunk that came off?

Well, here where things get interesting! If that piece is of sufficient size, then it may resume function regardless of the breakage. What's critical here is that being cut off from the main body can cause what could be called a reset, of sorts. In practical terms, this means a new sentient mind has been created. Pieces too small can fail to form the required pathways to support a mind, or can only support a severely inhibited one at most. A gradual change in size over multiple breakages is much more likely to preserve the original mind intact, while sudden shifts may either result in an even more difference mind to the base, or result in a failure entirely. A rock breaking in two can result in the cloning of an identity, creating twins, however margins are slim and this is surprisingly rare.

In a nutshell: A 5-tonne geobrain that loses a 1-gram chip will remain functioning, but it's up in the air if the chip does function. If it does, it's likely either too unintelligent to consider sapient, or has the chance to be Noticibly distinct in personality to its parent body.

The same 5-tonne body, in splitting into a 3 and a 2-tonne body, will likely continue to be sapient, with the 3-tonne body inheriting most of the original identity and personality, with some disruptions unfortunately likely, while the 2-tonne body will very, very likely have significant similarities in personality, but still not sufficiently to retain the full original identity (most of the time). Information, such as knowledge and memories, is rarely passed, at least in forms that aren't extremely broken and disconnected at best.

A 5-gram body splitting off a 1-gram chip is likely to remain sentient, with the 1-gram chip also very possibly becoming sentient, with the potential for similar personality.

In other words, relative size matters.

This process is believed to have been occurring from a single common ancestor, ranging approximately 5000-80,000 tonnes, on each Sentient Populated Body (SPB, a planet, moon, or asteroid with sentient rocks) anywhere between five and two billion years ago. For reasons relating to conditions this is not understood to still be occurring, with the minor planet Rachyito (a dark metallic asteroid undiscovered by humans between the orbits of Jupiter and Saturn, approximately fifteen hundred meters in diameter and remarkably round) being the most recent known instance of this happening independently. Sentient rocks from one ancestry on occasion will end up on another body, most commonly due to impacts, though this, of course, requires that the impact not destroy the rock outright. My ancestors are an example of this, seeing as my family traces their origin to the Canadian Shield hundreds of millions of years ago.

So, I've outlined how this works. How does this work socially?

Dumbing things down, the body in which a chunk breaks off from is considered the mother (regardless of whether the personality has traits that humans would considered traditionally feminine), while the body that broke the piece off, if there was one, is considered the father. Many, many sentient rocks do not have fathers as a result, e.g. if they broke off in a fall. Some SPBs will classify breaks resulting from collisions with non-sentient rocks as Mother-Father parentages, while others will only classify impactors as the Father if the impactor was sentient.

I can trace my ancestry back about fourteen living generations, though I have many cousins and other relatives along this path. My family is known for our small size and unusual composition, having mixed with Martian material through a rare process of surface melting and compression. I am one of the smallest in my family, and of the third most recent generation, breaking off within the last fifty years (I will not specify. I could be four, I could be forty nine. Old enough to drive, not old enough to have committed vehicular manslaughter. Yet). I am near the minimum known size threshold for a sentient rock before breakage, though consider myself lucky to have what is considered a rather stable structure, giving me good clearance in the case of future damage. I consider my Chip Factor (CpF, ratio of current size to theoretical minimum size before total disruption, assuming a reasonable plausible erosion path [note writings on size difference above]) personal and will not be sharing it.

I hope this helped clarify some things!