I will talk about altruism in humans and how it evolved. Altruism in humans can be roughly defined as a selfless act for the welfare of others, at a cost to self. I have read a few theories trying to explain this phenomenon, because an organism incurring a cost to itself only to benefit others defies what we know about genes. Some people say altruism evolved due to kin selection, others say it's due to group selection. I say it's neither. I have come up with my own explanation: altruism evolved in white people (you will soon see why I said white people), because in the kind of environment where their ancestors evolved, being altruistic had survival benefits, not just for others, but for oneself as well. Imagine: A selfless, altruistic person extended a helping hand to others who were in need of help. Those who were altruistically helped tended to feel grateful, and would look for opportunities to repay his kindness. They would be very willing to help and cooperate with the altruistic person, and this benefited the altruist and helped him pass on his genes. Whereas selfish behavior was punished, because people who were on the receiving end of such nasty behavior would hate the selfish person, which meant they would refuse to help or cooperate with him in the future. In other words, the selfish person would be left on his own. This was extremely costly, in the type of environment we are talking about, where people had great trouble surviving without the help of others. As such, selfish, un-altruistic individuals tended to die out, and their genes became lost. And altruistic individuals with their genes survived. Now, I mentioned white people, and it is because altruism is not a human universal. Only (some) white people are capable of altruism. Altruism is not a concept that is ever heard of in other races. Altruism can only evolve in extremely harsh environments where losing the support, help and love of other humans is deadly detrimental. And since only white people evolved under such conditions, only they have evolved to be altruistic. I know that this line of thinking is unthinkable to most biologists. They call this "racist", even though it is the truth. This is a prime case of how political correctness rots the mind. In their effort not to be racist, and to think politically correct thoughts, biologists who are otherwise pre-eminent thinkers fail to see something that is very plain to see. A phenomenon that could have been explained very easily becomes a sphinx' riddle that stumps bright minds for decades. This is both stupid and pathetic. It is also a very good example of how political correctness can interfere with knowledge, and halt the advance of science.
I want to further expound on the spread of altruism in (white) humans. Some of you might say, it's all fine and good that altruism evolved because people loved altruists and would be more willing to cooperate with and help them. But wouldn't this mean that this capacity to feel grateful, and to want to repay kindness, also needs to be present too? Because it could be just as possible that people who were helped by altruists just went on with their lives, never bothering to thank them or help them in the future. This makes sense indeed. And I just want to say, the genes responsible for these behaviors, gratefulness and the tendency to want to return favors, could have spontaneously arisen in the population, just like all the other genes that have ever existed. We are not surprised by this, because we know genes mutate all the time. Somewhere along the timeline of white people's existence, the genes for feeling grateful and wanting to repay kindness must have arisen, we know this because we know such people exist, in our contemporary world. Although I will say that, the genes for altruism necessarily had to have arisen after these gratefulness genes did. For the following reason: If an altruist individual came upon the world, he selflessly helped others at a cost to himself, but there were no others around who would appreciate him and be nice to him back, the altruist would be at a disadvantage and would likely die out. However, if there were already grateful individuals around, then the altruist would do quite well. Genes for the inclination for gratefulness...etc very probably did not produce any physical tangible effects on the person who had them, because they conferred a mental state only. They weren't helpful in helping people survive, but they weren't bad for people, either. So they probably stayed around in white people's ancestors for quite some time, until such a time came when the first altruist person was born, at which point these gratefulness genes could be said to start to have an effect. This is why I think the genes for altruism must have come about later than the genes for gratefulness and for the tendency to return favors.
A word about these genes that give rise to inclinations to be grateful when helped, and to want to return favors. These things aren't physical, as in, they are merely mental or psychological states. They require negligible amounts of energy to produce and maintain, unlike physical things like eyes, heart, arms, muscles...etc., which require quite a bit of energy to produce and maintain. This is why ancient humans could afford to have them essentially sitting around doing pretty much nothing until the first altruist came on the scene. The reason these genes weren't selected out of the gene pool is because, while evolution is quite efficient, it's not 100% efficient. It relentlessly removes deleterious genes from the gene pool and keeps good ones around; however, genes that produce traits that are neither good nor bad don't get removed. As long as they don't actually do anything bad for the person who has them, they stay around. Another related phenomenon is junk DNA. These are DNAs that just sit on chromosomes and do nothing. They don't kill the person who has them, but they do nothing to help him survive and reproduce, either. This is a good example of evolution not being 100% efficient.
Another thing I want to point out. There are many ways to group different kinds of genes. One way I like to do so is to group them into "social" genes, and "non-social" genes. By social genes, I mean the genes whose trait requires a second person in order for them to work. Non-social genes do not. I will give an example for what I mean by each. Imagine the genes for making a person smart. So, basically, genes for intelligence. Intelligence is a non-social gene because it doesn't require a second person to work. An intelligent person might be better at hunting, or at memorizing hunting routes, at making tools, at outsmarting prey animals...etc, and these things produce a positive effect for the individual regardless of whether he is with other people or whether he's completely alone. Now, social genes give rise to traits like beauty, likeable-ness, or in our case, altruism. It is not enough for an individual to be beautiful, there must be another person around to perceive her beauty. There is a social component to it. Beauty gives certain benefits to the person who has it, in the form of preferential treatment from other humans. For example, people might be more inclined to give help or free food to a beautiful person. But no such advantages happen when said beautiful person is on her own, without other humans around her. Without another person to perceive her beauty, it doesn't matter how objectively beautiful she is, it just won't produce any result for her. When an objectively beautiful human goes into the wild, and is starving, the trees won't feel sorry for her and then start dropping apples for her to eat. Because trees aren't humans, and as such, they do not perceive that she is beautiful. Same thing with how she might get eaten by a lion because, again, a lion does not perceive her to be beautiful. She only truly becomes beautiful when there is another human being around to perceive her beauty. This is what I mean by social genes. And altruism is one such kind of genes. It doesn't matter how selflessly altruistic one is, without another human around who possesses the ability to understand, benefit from, appreciate, and then reciprocate back, it doesn't do anything for the person who possess the altruistic traits.