Why does a soldier throw himself on a hand grenade to save the lives of a half-dozen unrelated fellow soldiers? Why does someone run into a burning building they happen to be passing to save a child they don’t know? From a Darwinian perspective these seem to be enigmatic behaviors that would “select against” such individuals (or more properly, select against the heritable component of this behavior).

There are several possible explanations for this. The most important one might be that this sort of behavior doesn’t really happen very often. It is so rare that it can be ignored and written off as irrelevant in the light of overwhelming evidence that humans usually act selfishly. There are billions of people in this world, but we can name the top altruists. We can’t name all the selfish people.

But if we want to provide a hypothesis that could explain non-kin based altruism that should be kin-based altruism, there is one.

We don’t need to explain altruism as kin-based. One person can do something “altruistic” for another person because they expect (and usually get) a return, like in that move that I haven’t seen “Pay it forward” or that insurance company commercial that I’ve seen too many times (not the cavemen or the gecko, but the one where the lady stops the man from getting run over, etc.). More likely, such forms of reciprocal altruism are more direct. I scratch your back, and in the not too distant future, you scratch my back (not someone else’s back).

We may also expect “altruistic acts” to occur as a means of showing off.

But the burning baby and hand grenade scenarios don’t involve a payoff if, at the end, you are dead. So, these behaviors have to be either truly dumb from a Darwinian perspective, or something else.

This is where Ultimate vs. Proximate explanations or mechanisms for behavior come in. Simply put, an organism may be selected by Darwinian processes to tend towards a particular behavior, and in the context of this behavior’s evolution, it makes sense to implement this behavior under certain conditions. But then the conditions change. When the conditions change, evolution may eventually cause a change in how this behavior works, but in the meantime the behavior becomes (at least some times) “inappropriate.”

Since there is a difference between the ultimate (evolutionary) fitness-related reasons for the behaviors existence and the specific neurological or hormonal mechanism for the behavior’s implementation, the former can make sense in the large view, and the latter often not make sense in the immediate instance.

In the so-called “environment of evolutionary adaptiveness” men are usually with other men who are their close relatives. In humans, it is more often than not the female who moves out of her natal (birth) group to join her new mate in his natal group. Thus, a given man is related to the other men in his group. The other men may include his father, uncles, brothers, and sons. Children in the group are all his children, his siblings children, or otherwise related. Thus, at any one moment in time, if you can give up your life to save every single person in you group, you might be doing something that makes sens in an evolutionary framework. At the very least, there should evolve a mechanism that allows for the option of suicidal altruism.

The guy in the army is not hanging around with his relatives. He is unrelated to his fellow soldiers. But in the evolution of this trait, there did not develop a mechanism to assess this degree of relatedness to group members. The degree of relatedness was an already extant, expected, reliable thing that made up part of the context in which suicidal altruism might evolve. Perhaps all it takes is a sense of “brotherhood” to cause a male’s brain to shift into “might-have-to-die-to-save-genes” mode. Certanily, training, living, and fighting together could facilitate this sense of brotherhood among men in the military, and it is clear (and this has been studied) that there are training techniques and other aspects of military life that enhance this phenomenon.

Thus, evolved traits including behaviors always have to be understood … explained … at multiple levels. One way to do this is to separately consider the ultimate (evolved, fitness-related) and the proximate (mechanistic … how does the trait actually work) levels as separate. (There are other levels but that is for another time.) The proximate mechanisms can be very powerful. Hunger and sex drive. Say no more.

This way of thinking helps to explain the very interesting behavior recently exhibited by a pair of gay flamingos. (Thanks to CMF for bringing this to my attention.) Gay flamingos may seem odd, but there are gay couples (both males and females) in all thus-far studies species of pair bonding birds.

Here’s the story:

LONDON (AFP) - A pair of gay flamingos have adopted an abandoned chick, becoming parents after being together for six years, a British conservation organisation said Monday.

Carlos and Fernando had been desperate to start a family, even chasing other flamingos from their nests to take over their eggs at the Wildfowl and Wetlands Trust (WWT) in Slimbridge near Bristol.
But their egg-sitting prowess made them the top choice for taking an unhatched egg under their wings when one of the Greater Flamingo nests was abandoned.

The couple, together for six years, can feed chicks by producing milk in their throats.
Fernando and Carlos are a same sex couple who have been known to steal other flamingos’ eggs by chasing them off their nest because they wanted to rear them themselves,” said WWT spokeswoman Jane Waghorn.

“They were rather good at sitting on eggs and hatching them so last week, when a nest was abandoned, it seemed like a good idea to make them surrogate parents.”
Gay flamingos are not uncommon, she added.

“If there aren’t enough females or they don’t hit it off with them, they will pair off with other males,” she said.

Both male and female birds in pair bonding species tend to have strong nesting and off-spring care drives. These drives are hormonally driven (that’s the proximate mechanism) and serve to enhance individual fitness by enhancing reproductive success (that’s the ultimate explanation). It has been noted that gay male couples seem to do a much better job at raising young than heterosexual couples (and possibly gay female couples) in birds. I suspect there could be two reasons for this, if it is true. First, males may need extra doses of offspring care hormonally mediated drives in order to get them to do the right thing (instead of acting like guys). Second, they may be engaged in less intrasexual competition, and thus have more energy and time for offspring care.

(By the way, there is a famous pair of gay male eagles at the US National Zoo that has raised many offspring from eggs laid by hetero-birds.)

It probably helps that in Flamingos and many other birds, males can “lactate.”