Do we eat shell fish? Or are we the self-ish?

" To put it in a slightly more respectable way, a group, such as a species or a population within a species, whose individual members are prepared to sacrifice themselves for the welfare of the group, may be less likely to go extinct than a rival group whose individual members are place their own selfish interests first. Therefore the world becomes populated mainly by groups consisting of self sacrificing individuals." pg. 7

Since we were little we have been taught to share and not act selfish in any way possible. We learn to depend on one another, work in groups, trust in others, and at times reach our goals by using one an others different abilities. In fact, based on my past knowledge, natural selection and evolution depends on species and their survival. Mutations and adaptations can only be passed on after several generations and several individuals. Sadly, evolution does not depend on one individual only. 

What I am trying to get at is that one individual cannot affect evolution. As if to say, the last phrase "consisting of self sacrificing individuals" contradicts itself, especially when it is related to groups that compete against other groups. If the world is composed of self sacrificing individuals, then we wouldn't be considered a group. But then again we are, we are considered to be a group- humans. I am not going against what the author says. I do believe we are driven by our instinct of survival and therefore enabling our selfishness. Our world is full of selfish people, even though we admire those who put the needs of others before their own, most of us do not have the 'guts' to do this and in a way become selfish. 

Another aspect I would like to mention is the tone of the book. At first, it seems as any ordinary science column in a newspaper. The author talks about Darwin theory and other biological subjects. But as you read, you realize that the author simply uses scientific notations or evidence in this case to confirm his theories on human behavior.