We can pretty much all agree that there are a few animals on Earth that have achieved a level of cognition that sets them well above the rest. Whales, for example, are known for their intelligence and communication skills, and dogs have evolved to be remarkably in tune with our emotions and expressions.  

That makes us feel, if anything, more connected to them than other creatures, which why we generally think it's wrong to kill them.

Then, on the other hand, there are creatures so alien and different from us that it's hard to care for them at all, even if they play a vital role in the world's ecosystem. This is the fate of many insects - especially the ones that invade our households, which we swat and squish without a second thought. Well, those days may be over, because researchers have found evidence that suggests insects are, in fact, conscious and egocentric.

Yup, those flies you murdered last week had feelings… sort of.

According to a team of researchers from Macquarie University in Australia, flies and fleas are able to have "subjective experiences", which is one of the most basic forms of consciousness.

"When you and I are hungry, we don't just move towards food; our hunger also has a particular feeling associated with it," researcher Colin Klein told Discovery News. "An organism has subjective experience if its mental states feel like something when they happen."

To come to this conclusion, the team studied scans of fly brains, taken in the midbrain region that's nestled inside the folds of the cortex. Using these images, they compared the fly's brain to other animals, and found that fly brains have similar structures to human brains that allow them to model the world the same way we do.

"In humans and other vertebrates [animals with a backbone and/or spinal column] there is good evidence that the midbrain is responsible for the basic capacity for subjective experience," Klein told Discovery News. "The cortex determines much about what we are aware of, but the midbrain is what makes us capable of being aware in the first place. It does so, very crudely, by forming a single integrated picture of the world from a single point of view."

Since they model the world in this way, Klein and his team say flies are also egocentric because they selectively pay attention to certain things over others in order to survive.

The researchers now want to investigate further to try and figure out how consciousness arose evolutionarily in all creatures. Right now, evidence suggests that organisms became conscious when they started to prioritise needs and gained the ability to move freely about the world.

The best way to think about this is to consider jellyfish - creatures that don't appear to possess consciousness. Jellyfish do not move freely around the oceans - instead, they ride the waves in hopes that they don't land on a beach. If they gained mobility, they would eventually need to make choices as to which direction they should go to fulfil their needs, and from this, consciousness might evolve.

There's still a lot to learn, but the team's findings are paving the way forward by understanding how insects - a creature we generally feel indifferent towards - gained a basic form of consciousness.

The team's findings were published in Proceedings of the National Academy of Sciences.