lets splice in a gene fix for cephalopod senescence and get the invasion over with

I have this headcanon that an ancient ape civilization was at war with cephalopods and they created a weapon of mass destruction that artificially gimped octopus lifespans :'(

There is only one species of octopus that lives socially (LPSO are rare and incredibly intelligent but their lifespans are like 3 years)

Maybe your headcannon should be that apes did a "tower of babel" type thing to make all the octopus individualistic and unable to organize into a civilization

It's more complex than that. The famed octopus city[1] was populated by the gloomy octopus, a species which prior to the discover was believed to have been exclusively solitary.

[1] - https://www.smithsonianmag.com/smart-news/octopus-city-obser...

Well the LPSO is the only consistently social octopus. "Octopus city" was actually 2 cities (the second one being discovered in 2016) and they were groups of about 15 gloomy octopuses. There are a couple of other examples of octopus sociality but on a species-wide level only the LPSO can be comfortably described as social

Almost all octopuses are cannibalistic but Abdopus have also been found living close to and tolerating each other

mutations that occur after reproduction are never weeded out since the genes are passed on already, so natural selection on its own can result in this, just like cancer or lower safeguards against cancer such as short telomeres in humans

This isn’t quite true, is it? A mutation that killed 5 years after childbirth would result in higher mortality rates for the child.

Octopus have extremely high mortality rates and extremely large litters, so there’s that

They don’t raise their offspring

Though FWIW, they do protect their eggs quite well.

Isn't this tied to the senesce? Where their digestive tract has closed and they starve to death at the nest

Ah yeah, I was thinking humans