The problem of Evil is a moot problem.
If there were no God, then suffering is exactly what we would expect from a blind, indifferent universe: accidents, disease, cruelty, and unequal pain all happen because nature has no moral aim. But if an all-powerful, all-knowing, perfectly good God exists, then the distribution of suffering still raises a serious question: why is any of it necessary at all?
If some people live almost entirely sheltered lives while others endure torture, abuse, disease, war, or extreme poverty, then suffering is not being handed out by any obvious moral principle. It looks random, not purposeful. That is hard to reconcile with the idea of a perfectly good God. A good God would not create a world where one child is surrounded by safety and another is condemned to agony for no clear reason. The fact that many people go through life with very little direct evil, while others are crushed by it, suggests that suffering is not a targeted moral tool from a loving creator. It looks more like the outcome of blind natural processes, social inequality, and chance.
If God were truly omnipotent, omniscient, and perfectly benevolent, then pain would not seem scattered by blind chance, virtue would not so often be crushed while cruelty prospers, and extreme suffering would not so frequently fall on the innocent.
The problem is not merely that suffering exists, but that it does not seem to fit any obvious morally coherent plan, which makes the world look less like the creation of a righteous divine mind and more like the product of impersonal forces operating without concern for moral outcomes.
About the sin of humanity:
From an atheist point of view, pediatric cancer is one of the most devastating reasons the “sin of humanity” explanation collapses under its own cruelty, because nothing about a child being born into a body that turns against itself looks like justice, moral correction, or meaningful punishment; it looks like raw, obscene indifference. The idea that children are somehow “paying” for humanity’s failures by suffering horrifically in hospitals, losing their hair, vomiting from treatment, being cut open, weakened, terrified, and sometimes dying anyway is not moral order, it is moral outrage dressed up as theology.
Evil existed before humans:
Humans belong to Synapsida (the lineage leading to mammals). Dinosaurs belong to Sauropsida (the reptile lineage, including birds). So the last common ancestor of humans and dinosaurs was the last common ancestor of Synapsids and Sauropsids — an early amniote.
The earth back then was obviously full of nefarious things just like nowadays. Being eaten alive, dying of thirst or hunger, gruesome diseases etc.