Charles Darwin was a very empathic man, who cared a great deal about the suffering of others. And not just "others" as in his peers, but beings all over the globe, from humans in slavery all the way down to birds and insects and even plants.
Charles Darwin was raised in a well-to-do family in Victorian England. This was the time of Jane Austin's works; if you've ever watched a movie adaptation of one of her novels, you know what Darwin's world looked like. And if you've ever read her works, you know how the people of that time thought: everything has it's rightful place, everything is ordained by God and was ordained that way since Creation began; to "rock the boat" of soceity was considered a grave, unspoken cardinal sin.
Yet England, at the time, was in a period of great social upheaval. Famines and disasters pushed more and more people into the city, scrounging for work so their children could eat. The aristocracy of the time had pity on the poor... But not too much pity; that would have been improper. They established a welfare system, but they forced those receiving the welfare into horrible workhouses, where they were seperated by gender and made to work 80 hours or more a week. This was the time of child labor and debtors prisons. It was widely believed, at the time, that such conditions were God's way of encouraging people to not reproduce; a little reminder from on high that God doesn't like sex. (Victorians. Ah, what can ya do with'em?)
The conditions of his fellow man no doubt broke Darwin's heart; this is a man who would berate a perfect stranger for abusing a donkey or a pig, who hated slavery and called it an "abomination" But the attitudes (called Malthusian theory) on how population is kept in check by natural disasters and poverty were to plant the seeds in Darwin's mind for what would become natural selection. He wondered, If things are so bad for we humans, who can choose to excercise self-restraint, how much worse must it be for the lower animals, who always produce more offspring than their natural habitat can sustain?
It was this realization that led Darwin to the conclusion that, in the natural world, where there is only enough food and room to accomodate a fraction of those born, the ones that survived would be the ones who more perfectly fit their niche-- viola, Survival of the Fittest.
Despite this monumental discovery, however, Darwin was hesistant to publish. He knew that the prevailing opinions of his time would be staunchly opposed to his ideas... including the opinions of his beloved wife. He continued collecting evidence and refining his theory for 20 years before he was pushed into publication by the appearance of one Alfred Russel Wallace, who had developed the theory of natural selection himself and was set to publish.
Charles Darwin was a man much concerned with suffering; and not just with the kind caused by clinging, which is what Buddhism mostly concerns itself with, but the general suffering of nature "red in tooth and claw." It led him to question the established ideas of divinely sanctioned order. He could not see how an omniscient and omnipotent creator could devise creatures whose sole means of living was through the painful death of other species (see here, midway down). He had to move his perspective back, zoom out his point of view from the petty English conceits of the time. When he did, he found enlightenment. And through his enlightenment, the world has never been the same.
Happy birthday, Mr. Darwin.