According to the lecture, the reward from unselfish attitudes taken by humans like food or organ donations is much more valuable than it is implied in the reading passage. Peer appreciation, social recognition and self-worth feeling are the rewards that trigger these type of acts.
In addition, while the reading passage states that meerkat sentinels stands without food and risk their life to protect the group while they eat, recent studies have shown that they are in fact increasing their chances of surviving.