An interesting article on the "negative bias":
https://www.verywellmind.com/negative-bias-4589618
Earlier in human history, paying attention to bad, dangerous, and negative threats in the world was literally a matter of life and death. Those who were more attuned to danger and who paid more attention to the bad things around them were more likely to survive.
This meant they were also more likely to hand down the genes that made them more attentive to danger.
Research suggests that this negativity bias starts to emerge in infancy. Very young infants tend to pay greater attention to positive facial expression and tone of voice, but this begins to shift as they near one year of age.
Brain studies indicate that around this time, babies begin to experience greater brain responses to negative stimuli. This suggests that the brain's negative bias emerges during the latter half of a child’s first year of life. There is some evidence that the bias may actually start even earlier in development.