It is not a little remarkable that sympathy with the distresses of others should excite tears more freely than our own distress; and this certainly is the case. Many a man, from whose eyes no sufferings of his own could wring a tear, has shed tears the sufferings of a beloved friend (The Expression of the Emotions in Man and Animals-1872) (Wright 1994). Darwin maybe sensed the weakness of his main theory that dealt with moral sentiments that he threw in a second theory just in case. During human evolution, he wrote in The Descent of Man, "as the reasoning powers and foresight became improved, each man would soon learn from experience that if he aided his fellow-men, he would commonly receive aid in return. From this low motive he might acquire the habit of aiding his fellows; and the habit of performing benevolent actions certainly strengthens the feeling of sympathy, which gives the first impulse to benevolent actions. Habits, moreover, followed during many generations probably tend to be inherited (Wright 1994).".
They say the last sentence of the quote is wrong, because we know that habits are passed from parent to child only by instruction or example. No life experience can affect the genes that are handed down to offspring (Wright 1994). The main thing of Darwin's theory of natural selection was that it did not require the inheritance of acquired traits, as has the previous evolutionary theories, such as Jean-Baptiste de Lemarck's. Darwin saw this beauty which caused him to stress mainly the pure version of his theory. But as he grew older he was willing to us more in doubt mechanisms to solve very issues, such as the origin of the moral sentiments (Wright 1994).
In 1966, George Williams suggested a way to make Darwin's thoughts about the evolutionary value of mutual assistance more useful by taking out the last sentence, and the part about reasoning, foresight, and learning.
