Watch out, your human exceptionalism is misleading you. Plenty of animals have a sense of morality (https://pmc.ncbi.nlm.nih.gov/articles/PMC6404642/).

For social animals (humans included) behaving morally can be adaptive behaviour. Your fitness is increased by group fitness.

Animals learn - bite the owner, or overstep the e-fence, and you'll be punished for it and not do it again. LLMs don't learn, and anyways don't feel punishment.

Animals, humans included, don't really have "morals" - they have survival instincts that result in behavior that may be viewed as moral, but whose origin is indeed survival of the fittest and millions of years of co-evolution.

e.g. Males don't typically fight to the death over territory or females, but this isn't because they have some morality code over unnecessary death - it's because death-match fighting endangers themself just as much as the other guy, and so evolution has selected against that level of uncontrolled aggression.

Evolution is also (really primarily) selecting for things that help the survival of the species, not the individual, and much of what you may think of as "morality" comes from that - avoidance of behavior that is detrimental to the social group/species, not just the individual.

Morality in animals is pretty well documented. Key point - humans are animals and very little separates our abilities from other animals.

A starting source- https://pmc.ncbi.nlm.nih.gov/articles/PMC6404642/