Selfless part-time
Selfless behavior in the family group in order to promote one's own genes in a roundabout way is a phenomenon that has now been proven all over the country. But why does an individual sacrifice himself for others with whom he has no blood ties?
For a long time, altruism and cooperation in the animal kingdom were considered a mystery: What sense should it make to put one's own reproductive success, which is the measure of all things from a biological point of view, behind in favor of others and to support their offspring? What reward could tempt one to settle for a governess post? If you only took care of yourself and your own offspring, the success rate would be significantly higher. Quite apart from the problem of parasites, who quickly show up as soon as someone else is willing to invest more than usual. How to protect yourself?
The solution in the cases known so far was that it was not just anyone who enjoyed the self-sacrificing initiative, but relatives. Accordingly, the reward for the altruist was that he did not promote his own genes directly, but the genes of his clan. And as numerous experiments show, the question of exploitation regulates itself: If everyone involved switched to egotistical thinking, this soon destroyed the entire community to the detriment of everyone - in this respect, freeloaders do appear again and again, but a wide variety of ways and means have developed to keep them in check hold.
So is altruism a family affair? That's what it looked like-until Barry Sinervo of the University of California at Santa Cruz and his colleagues stumbled upon an example that somehow didn't fit the bill: the side-spotted iguana (Uta stansburiana). Here, as the researchers discovered three years ago, males who are not related to each other at all behave cooperatively. The highlight of the matter, however, is that the animals that work together and defend their territory against conspecifics are genetically very similar. And the researchers took a closer look at this aspect.
Cooperations only occur with the blue-throated color variants, which are characterized in their behavior above all by the fact that they take care of their females intensively. They have to defend themselves against orange-throated neighbors who are constantly trying to expand their territory aggressively and mostly successfully. These usurpers are only harmed by yellow-throated conspecifics that do not have their own territory, but instead mate with the females behind the males' backs on a campaign of conquest. With regard to reproductive success, in this three-way system each participant is superior to the other and inferior to the last one, like in the children's game rock-paper-scissors: one has the upper hand for a certain time, then it's another's turn.
The different throat colors are controlled by one gene. And when the researchers looked at the genome of fathers and their offspring as well as the overall reproductive success, they found the solution to the riddle: selflessness only takes place part-time. In phases in which the pressure from orange-throated neighbors is particularly great, a male involved puts his own interests aside completely and acts as a buffer against the power-hungry would-be invaders. His alliance partner can devote himself entirely to promoting young talent.
In the long run, however, the relationship is more like mutualism - a mutually beneficial relationship. Because when it comes to the number of offspring, both partners do well in those times when the orange-colored conspecifics are rarer. Above all, they produce more offspring than like-minded blue people who prefer to go through life as loners (the respective behavior pattern is inherited): Although their balance sheet looks better than that of the part-time altruists, it is significantly worse than that of the beneficiaries in hard times. And in a long-term comparison, they are also surpassed by the cooperating partners.
Here the genetic basis of the lifestyle became apparent: If the recognition of the blue throat color alone was decisive for the cooperation, this should be developed across the board by the carriers of this color variant. However, the blue loners revealed some differences in their hereditary disposition – the scientists determined that at least three other genetic factors are therefore necessary for an animal to be willing to cooperate.
It is the long-term benefit that keeps the altruism alive, which could otherwise end up being phased out, Sinervo and his colleagues conclude. After all, the partners would still have the option of going their own way again in unfavorable times - the animals rarely live longer than one breeding season, so why do they care about the consequences of the next few years? But faced with this choice, none of the iguanas in the experiment turned out to be wimps: once they had entered into a partnership, they also stood by it.
However, how the Bluethroat recognize potential cooperation partners remains unclear. The genes linked to this may influence other behaviors, such as the rhythm of head nodding, or physical characteristics such as smell. Only one thing seems certain: cooperation in real life appears to be based on some kind of cooperation at the gene level.
