What kingdoms from the three domains haven't evolved something like the reward system in us? Couldn't we feel neutral all the time and undergo an involuntary push towards the right behavior instead, without the need for joy or distress?

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    $\begingroup$ One question at a time, there are at least 4 separate questions here in only three sentences. $\endgroup$
    – John
    Jul 1, 2023 at 22:09
  • $\begingroup$ "involuntary push" towards certain behaviors to satisfy biological needs sounds like a reasonable description of mesolimbic system we do have. Like how else would such drives manifest in cognitive beings? We'd need to retain cognitive mechanisms for prioritizing conflicted drives in real time such that we don't just drop everything when we get a little thirsty or tired, but also so those drives can increase based on the severity of the need. Without varying degrees of discomfort and contentment, what would that even look like? $\endgroup$
    – MikeyC
    Jul 10, 2023 at 21:52

2 Answers 2


Perhaps it's best to equate euphoria with dopamine, because if it can be found to control sex, food choice and foraging of invertebrates, that a major piece of the puzzle:

Dopamine is believed to have evolved around 600-700 million years ago in simple organisms like bacteria. At this stage, dopamine likely had basic functions related to cellular signaling and regulation.

For worms and insects, dopamine played a role in various physiological processes, including locomotion, feeding, and mating behaviors.

In bacteria, it has pretty simple functions in several species like Escherichia coli (E. coli) and Pseudomonas aeruginosa. Although dopamine levels in bacteria are relatively low compared to those in mammalian systems, its presence suggests potential physiological roles.

Bacterial dopamine biosynthesis pathways are similar to those in mammals, involving the conversion of the amino acid tyrosine into dopamine through a series of enzymatic reactions. Key enzymes involved in this process include tyrosine hydroxylase, which converts tyrosine to L-DOPA, and aromatic L-amino acid decarboxylase, which decarboxylates L-DOPA to dopamine.

In E. coli, dopamine is produced in response to oxidative stress caused by exposure to reactive oxygen species (ROS). Dopamine acts as an antioxidant.

Studies have shown that dopamine can enhance the production and stability of the extracellular matrix, promoting biofilm formation in various bacterial species.

Dopamine can modulate flagellar rotation and affect the motility of certain bacteria. In Pseudomonas aeruginosa, dopamine has been shown to enhance twitching motility, a form of surface-associated movement.

in the honeybee (Apis mellifera), dopamine is involved in associative learning and memory formation related to foraging. Dopaminergic pathways are activated when the bee receives a reward, reinforcing behaviors associated with finding food sources.

in insects like fruit flies (Drosophila melanogaster), dopamine is involved in fine-tuning flight behaviors, such as wing movements and flight initiation, and also in arousal.

Dopamine contributes to reproductive behaviors in many invertebrates. It can influence courtship behaviors, mate choice, and mating success. For instance, dopamine affects mating behaviors and receptivity in the nematode Caenorhabditis elegans.

Nematodes are some of the simplest invertebrates, so their use of dopamine for sexual reproduction suggests that the evolution of mammalian euphoria could go back 570 million years ago.


This is kind of a philosophical question in my opinion.
First of all, what is 'right' behaviour?
Something that may be right in one culture may not be right in another.
It highly varies from individual to individual as well.
For example if you think focussed and planned studying is a right behaviour and your brain is caught in some kind of a reward loop in a useless activity like browsing the social media which is causing you distress.
So the question arises that does studying give humans some kind of an evolutionary or biological advantage such that nature may try to evolve our minds in such a way that it is consistently able to focus on studying? I don't believe it does. We are basically same from the survival point of view whether we are browsing social media or studing as your body is surviving and functioning appropriately which is the entire point of evolution itself. If hypothetically studing gave you better survival instincts then maybe evolution could take place in that direction.
However lets take another case;
Lets suppose certain variations exist in genes coding for muscle enzymes and proteins such that some people have better stamina or strength. Over the course of evolution they are likely to be selected as it gives them some kind of an evolutionary advantage.
But the development of the complex human brain is a huge evolutionary accomplishment in itself. Maybe the development of this reward system is itself a beneficial thing and helps us to focus? It basically puts the brain on autopilot mode where we don't have to think much and keep doing things repetitively, it could have evolved to save energy and maybe nowadays we have created things that take advantage of this exact same thing.
It could be that this reward system was actually evolved for our benefit but we humans have themselves learnt to take advantage of this in other humans.

Reward is a natural process during which the brain associates diverse stimuli (substances, situations, events, or activities) with a positive or desirable outcome. This results in adjustments of an individual’s behavior, ultimately leading them to search for that particular positive stimulus. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8992377/#:~:text=Reward%20is%20a%20natural%20process,for%20that%20particular%20positive%20stimulus.

If we follow along the lines of this definiton, then reward sytem development seems highly beneficial from the biological point of view. It readily helps to distinguish between desirable and non-desirable stuff.

I strongly believe that evolutionarily it is in our best interests, it is we who are misusing it. Another remarkable property of our brain is to get conditioned to what can trigger this response and what cannot.

Thank you.

  • $\begingroup$ It's not really philosophical. I wanted to ask what species did emotions like joy, sadness originate with. By "right behavior" I simply meant the things we naturally tend to do or avoid which increase our chance of survival and reproduction. $\endgroup$
    – LLLK7
    Jul 1, 2023 at 10:55
  • $\begingroup$ If you meant that by 'right' things then we are constantly evolving towards it. The development of senses of vision, hearing and smell and the development of reflexes are all directed towards it. Emotions are usually related with the frontal lobe and although other mammalian species and some other chordates feel emotions, humans are the ones with the most complex and complete set of emotions with the required capability and anatomical structures to express them as well. I would suggest you should read the development of frontal lobe, that will really help as well. $\endgroup$ Jul 1, 2023 at 10:58

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