Altruism is defined as unselfishly helping others at personal cost (or no benefit) to yourself. An example of altruism would be opening the door for someone or contributing to charity. Jesus is undoubtedly our greatest role model for altruism.
"Our early human ancestors were frequently altruistic," says a study published in the February 2006 edition of Current Anthropology. "Reciprocity is arguably the foundational basis of cooperation in humans," writes University of California – Santa Barbara's Michael Gurven.
According to evolutionary psychologist Nigel Barber, "reciprocal altruism colors much of human emotion and social behavior." Barber writes in his book Kindness in a Cruel World: The Evolution of Altruism (ISBN 978-1591022282) that the concept of survival of the fittest needs to be modified to fit observed behavior, such as the cooperative behavior of bees, vampire bats or ants.
Scientists in the journal Current Biology performed experiments with students which implied that the desire for a reputation of doing good deeds (which would cause others to hold a more favorable opinion of such a reputation) may drive the desire for altruistic behavior. This was cited as an example of indirect reciprocity. However, this also operates on a desire for future gain, and does not explain why individuals might consider altruistic behavior more favorable.
The question thus remains, can a deed performed with the expectation of future benefit can properly be classified as unselfish or altruistic? In all of the examples above, scientists seem to think so. But this still does not explain sacrifice without personal gain or with personal harm. Altruism by definition is a deed performed without expected gain, so a good deed performed with the hope of future reciprocity clearly does not fall under that definition.
Evolution and Altruism
In January of 2007, Private Ross McGinnis was operating a .50-caliber machine gun mounted on the military Humvee he was riding while on patrol in Iraq. When an enemy soldier threw a grenade into the vehicle, Private McGinnis threw his body onto the grenade. The device exploded, killing the soldier instantly. Four of his friends escaped injury because of Private McGinnis's sacrifice.
Evolution is left wholly without an explanation when it comes to examples of unselfish sacrifice. Evolution states that an organism will seek its own personal betterment, protection and benefit in all it does. Thus to survive, thus to fulfill the ultimate goal of reproduction and propagation of the species. In The Origin of Species, during Charles Darwin's enumeration on natural selection and objections to evolution, he writes: "Natural selection will never produce in a being anything injurious to itself, for natural selection acts solely by and for the good of each."
According to NewScientist (a pro-evolution science publication), "The origin of human altruism has puzzled evolutionary biologists for many years" and "[altruism] has been a stubborn thorn in the side of evolutionary biologists." Evolutionists are not certain what caused humans to begin behaving unselfishly, but in general, agree that in the end, any altruistic behavior achieves some goal desirable to that individual. (Survival of the species as a whole, or alleviating guilt, or a personal feeling of satisfaction.)
Why would any person sacrifice their own comfort, or even their life, for the betterment of another? This is a question evolution struggles with.
Origination of Altruism
According to evolutionists, altruism is an "almost uniquely human trait." This is supported by research published in the journal Nature which found that "chimpanzees are indifferent about doing their neighbor a good deed, even if it causes them no inconvenience." Evolutionists even predicted that chimpanzees would be spiteful, rather than altruistic, but found that the primates are actually indifferent, suggesting that spite (egoism) also originated with humans. 
Biological or Genetic Explanations
Scientists seeking to explain altruism according to evolution have proposed a theory of "hitchhiking" - the idea that genes programming for costly behavior were selected because they were companion to genes which coded for fitter genes chosen by natural selection. Also proposed is the kinship theory, which states that close relatives also carry the gene for altruism, which is essentially reciprocated benefit. As stated above, reciprocated benefit cannot necessarily be qualified as genuine altruism. Further, these two theories don't explain where the altruistic inclination originated to begin with.
According to Northern Illinois University's Professor David Buller, however, kin selection is not reflected in observation. Buller asserts that according to kin selection, the more distant a relative becomes, the more likely they are to be abusive. In studying the issue, Buller concludes "There is no substantial difference between the rates of severe violence committed by genetic parents and by stepparents."
Emory University researchers suggested that there is a biological basis for unrewarded altruism. Scientists said MRI-based experiments for brain activity found that "social cooperation is intrinsically rewarding to the human brain" and that "the altruistic drive to cooperate is biologically embedded - either genetically programmed or acquired through socialization during childhood and adolescence." Once again however, this is altruism with expected future utility.
Also, if there are genetic and/or biological explanations for selfless deeds, then neither credit nor blame can be assigned to a person for those deeds, as they are but the product of chemical reactions, not personal initiative or benevolence on the part of an individual.
Within the framework of Biblical Christianity, human behavior makes sense. In the Bible, John 15:13, Jesus explains "Greater love has no one than this, that he lay down his life for his friends." While it is written in Jeremiah that "The heart is deceitful above all things and beyond cure," the Bible also tells us in Romans 2:15 that the law of God is written on the hearts of all men, and that their consciences also bear witness.
Thus, altruism can be explained as a moral standard written in the hearts of men, which the evil of the heart wars against daily.
- UCLA study points to evolutionary roots of altruism, moral outrage November 24, 2004
- Nice guys do finish first in lizards' evolutionary race, says MSU professor May 2, 2006
- Evolutionary Psych May Not Help Explain Our Behavior After All April 29, 2005
- Wikipedia Article on Kin Selection
- Wikipedia Article on Altruism