U am writing up a spec evo about cockroaches gaining sentience after mass extinction of most land vertebrates. I would appreciate feedback, especially from people who study or are interested in entomology, which is why I posted it here in addition to the spec evo sub.
This takes place in a timeline where Nuclear Armageddon happened, leaving much of the northern hemisphere a desolate nuclear wasteland, with the remainder humans plagued by famines, war, and drastic changes in temperature. In addition most other vertebrate species perish due to the radiation and weather changes. Another extinction event like an asteroid hitting the Earth could also happen, cementing the mass extinction of land vertebrates.
The world now belongs exclusively to the arthropods who managed to survive thanks to their exoskeleton and small size.
After several millions of years insects began to evolve and fill the niches of the previous vertebrates, many convergently evolving similar body plans. In particular a clade of Cockroach has gained sapience that is comparable to that of humans thanks to some lucky adaptations.
Why cockroaches? Well for starters they’re known to survive high doses of radiation (Although generally less than many other arthropods). I also personally think they’re neat. But the main reason is that there are several species of Cockroach that exhibit prolonged care for their young. It is very rare for insects to take care of their young, as most are r-selected species, but a few species of cockroach are the exception. The most notable are roaches of the genus Cryptocercus which raise 20 nymphs for 3 or more years (more than many mammals). The adults feed the young through Trophallaxis. The Australian giant burrowing cockroach (Macropanesthia rhinoceros) also takes care of its young for about six months. There is even a species of Cockroach (Perisphaerus) where the mother suckles their young. Cockroaches evolved as an Ootheca, with some even giving live birth.
Overall these cockroaches are the most social insects that aren’t eusocial, and brood care is essential for the majority of species that gain sapience (the octopus being an exception) and necessary to create a civilization.
So let’s take a look at the evolution of our buggy friends
Lungs and Closed Circulatory System
Without any predators, these cockroaches will be able to get bigger as they can consume resources freely. However, their body size is limited thanks to the insect’s spiracles, which are a highly inefficient way of getting oxygen, as well as the fact they have an open circulatory system.
As time goes by, some cockroaches select for stronger muscles at the spiracles which are able to take in more oxygen. As time goes on the Spiracles brachiate forming mini “lungs' ' on the cockroache’s abdomen. In addition, the cockroach gains a closed circulatory system, with their heart pumping blood to the rest of their body. The closed circulatory system has convergently evolved in several invertebrates like worms and cephalopods which is how it happened here. Hemoglobin is also found in some insect species and is a much more efficient way of transporting oxygen, so our roach friends gain this as well.
Their size will still be limited by their exoskeleton, and unless the somehow evolve an internal skeleton they probably won’t be much larger than a coconut crab. I’m not sure how likely it would be for an arthropod to evolve an internal skeleton.
Anyways at this point the roaches’ superior respiratory and circulatory system will allow it to excel further, although it is possible other arthropods will evolve similar structures. I shall be focusing on one particular species of roach even though they will likely be thousands of members in this clade.
Endothermy and Homeothermy
As the Roach gains a larger size and more advanced circulatory system they will also develop the ability to internally regulate their temperature. Their circulatory system can move their blood around. Their antennae also might become feather-like similar to moths, where the increased surface area can help them cool down.
Dexterous hands and forearms
Picking up and carrying things back to one’s nest can be advantageous to the cockroach. Thus several roaches evolved a body similar to a praying mantis (Which has happened before in the extinct cockroach species Manipulator modificaputis). Although specialized in grabbing and carrying things rather than hunting. It is possible they end up living in trees and adopt a diet of nuts and fruit. They also might use their forearms to swing on branches like a monkey.
Vocalization
The cockroach is not alone in this world, and there are many predators like other roaches but others might include wasps, spiders, scorpions, centipedes, and giant crabs. It is possible that many of them co-evolved similar traits allowing them to get larger sizes. (It is also possible that several small species of land vertebrates survived the extinction although lived mostly underground as the world was irradiated and are just now resurfacing.)
While roaches and other insects today communicate through pheromones, sound moves faster than chemicals in air, meaning if the community of roaches are to evade predator attacks, the ability to vocalize will be useful. Madagascar hissing cockroaches have the ability to “hiss” through their spiracles, and since the spiracles for the future roaches .
Their spiracles will gain an organ allowing them to make loud and complex noises, similar to the syrinx of a parrot. This vocalization will also make it more useful to get food and teach their young. They will likely still use pheromones, but rather than complex communication it might be to show their emotions, not unlike body language humans do. As the roaches have exoskeletons they have less facial movements so they can use pheremones sho show their emotion.
Enlarged Brain
Of course the final step of sapience is the requirement for an enlarged brain. As the roach gains a better circulatory system, better ability to gather resources, and the ability to communicate, a large brain that requires a lot of calories can be created. Cockroaches currently have 1 million brain cells, which is rather pitiful, but on the higher end for insects.
As their brains get larger the instincts that drive them to brood care and forming social colonies become more complex into genuine emotions of love and kindness, thus creating stronger social bonds.
Despite being intelligent they will be very different than humans. Perhaps their social bonds will be even stronger, allowing them to form large civilizations with less tribalism.
There are generally 4 checkmarks for an advanced civilization to develop:
Social group Tool use Discovery of Fire Agriculture
Currently, cockroaches are already rather social insects that live in groups, and with more brood care already check that off.
Since the roaches in this timeline have “hands” they are capable of using tools. They will likely start off with crushing nuts with rocks but might form more complex tools as time goes by. Including being able to create fire through rubbing sticks.
As for agriculture, that has already been discovered by some species of termites and ants. In this radioactive world it is possible that radiotrophic fungi have filled the niche of many plants (And are using UV radiation from the sun when the radiation from the nukes ran out) and the roaches grow fungi like their termite cousins. Or simply grow plants.
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source https://www.reddit.com/r/Entomology/comments/l78qut/sapient_cockroackes_speculative_evolution/
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