I think such an alien adversary would have been more than capable of wiping out humans long ago if they already had the capabilities to direct asteroids toward us. (And also travel the very vast distance to get to us.)

I could maybe believe it if they were throwing them for fun / to study how we react. Which might go in line with the theories that many "UFOlogists" espouse: that sightings are sporadic and rare because aliens are basically pranksters trolling us all. (For the record, I find this pretty contrived, and I believe the far more likely explanation is that there haven't ever been any visitations.)

If you assume that berserkers are difficult to produce and disperse throughout the galaxy, then you might conclude that they have limited capabilities.

Perhaps after detecting intelligent life and reporting it, perhaps it attached itself to the largest convenient asteroid/comet, and altered it's orbit just so to stunt human development just enough to allow for a more complete extermination ship to be dispatched.

Like a galactic immune system - suicide berserkers designed to signal the human infection, and then suicide themselves to slow the disease evolution.

The galaxy is many billions of years old. I would not rule out the development of such a system.

The fact that the galaxy is billions of years old is one part of what would lead me to think that such an immune system would destroy the entire planet, or at least kill all life on it, with the very first projectile/attack.

sounds like a scenario of Starship troopers rather than a food for thought.

Not really. People at this time lived with a much lower population density. Our modern cities that can house millions of people within a few square miles are only possible because of advanced infrastructure for transporting water, food, and waste, and only desirable because of our industrial society where all these people can work in close proximity.

In ancient times, people were much more limited by the distribution of resources, so rather than one big city, they'd have lots of smaller settlements. Note that most ancient "cities" would be small towns by modern standards - Jerusalem for example had a population of around 5000 inhabitants around 1000 BCE. Pretty much every place where there could be such a settlement, there would be.

Thus in that period, if you picked a random spot on earth, the odds that there would be a (by the standards of the day) dense population center in close proximity would be much higher than today.

> ...food for thought.

Is it though? Isn't food for thought something you're supposed to think about? I'm not going to spend much time pondering a petulant alien overlord scenario, especially considering that humanity would probably qualify for a rock or two from such a being as of late and none have been forthcoming.