The Problem Of Altruism In Evolutionary Biology And Its Most Famous Proposed Solutions
When Charles Darwin published On the Origin of Species in 1859, he proposed a revolutionary new way of thinking about the natural world. Darwin insisted that nature's remarkable beauty and diversity is not a static creation. Rather, it is the result of hundreds of millions of years of slow, small changes called evolution.
At the heart of Darwin's theory is the process of natural selection . The rules of natural selection are simple: survival and reproduction. While this may be easy enough for humans - even the foolish ones among us - the natural world is much more selective.
There is a reason why plants and animals reproduce in far greater numbers than is necessary to maintain their populations: Most of these seeds, eggs, and young children do not survive. When resources—food, light, water, companions—are scarce, the slightest physical advantage may be the difference between life and death, between extinction or reproduction.
In his comprehensive studies of diverse species from pigeons to barnacles, Darwin recognized that variation was the driver of evolution. Even when the same animals mate, their offspring show marked variations in size, color, and other physical traits.
If one of these random differences improves a plant or animal's chance of survival — sharper teeth or longer claws — that trait is more likely to be passed on to the next generation. Likewise, if random variation improves the chance of successful mating and breeding—such as colored feathers to attract mates—the genes for that trait are more likely to be passed down.
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In this way, evolution is the sum of billions of “choices.” These choices are logical, but they are tough - staying fit.
Evolutionary biologists measure an organism's "fitness" by its ability to reproduce. An individual who passes his genetic material to 20 offspring during his lifetime is more suitable for reproduction than another individual of the same species that produces only 13 offspring. By this logic, an individual without offspring has a fitness level of zero - congratulations, you have been kicked out of the genetic pool.
Or maybe not. What if there was a mechanism within natural selection that rewards not only the strongest, the smartest, the fastest, but also the most helpful and altruistic? Keep reading to explore the fascinating and controversial theory about kin selection.
altruism problem
Competition is key to Darwin's theory of natural selection. In nature, members of the same species compete ruthlessly for limited resources. Without competition, the genetically weak would have the same chance of survival and reproduction as the strong, and evolution would stop. For evolution to work—for organisms to become increasingly fitter over time—there must be winners and losers.
but there is a problem. In nature, there are some species that refuse to play the game of competition. Instead of fighting teeth and nails to survive and reproduce, these animals dedicate their lives to helping others survive and reproduce. In evolutionary biology, this behavior is called biological altruism.
What do we think of a worker bee who spends every moment of her short life gathering nectar to feed the beehive without ever mating? Or a bachelor who volunteers to help build nests and protect the young of other birds, without ever having his own family?
Altruism in nature seems to contradict basic principles of natural selection—how are genes for altruistic behavior passed from one generation to the next if these altruistic individuals do not produce offspring of their own? The so-called “altruism problem” baffled scientists for a century after Darwin.
The pioneering solution, pioneered in the 1960s by an obscure graduate student named William Hamilton, is called Kin Selection. Hamilton suggested that altruistic behavior in the natural world was not random. The helper bird does not randomly choose two strangers and protects their young. Instead, altruistic behavior is more likely to be expressed in animals towards kin, blood related organisms.
By helping one-blood relatives. An altruistic organism ensures that at least some of the shared genetic material will be passed on to the next generation. According to Hamilton's rule, the altruistic cost of not having children is more than offset by the clan's increased reproductive success. Altruism genes are transmitted because they improve the overall fitness of the group.
This is what Hamilton's rule looks like mathematically:
where c is the cost to the giver of the altruistic behavior, b is the benefit enjoyed by others and r is the “relationship coefficient”, where higher values of this coefficient indicate closer blood ties between organisms.
Confused? Perhaps it would be useful if we looked at some specific examples of altruistic behavior in animals. And how this behavior is stimulated through the election of relatives.
Examples of kin selection
There are many examples in nature of altruistic behavior. But only a few seem obvious examples of what evolutionary biologists have called kin selection.
The Florida scrub is one of the best-studied examples of an organism that clearly prefers its blood relatives when exhibiting altruistic behavior. The Florida peeled jay is one of several species of birds in which some members of the social group work as helpers during the breeding season. Instead of mating with their mates, the helpers give up their personal breeding. They help other pairs gather food and protect the nest from predators.
When a herd of flaked florida jays has been identified and monitored over several generations. The researchers found a high preference for helping relationships among close family members. Of the 74 helping relationships observed, 48 helped their biological parents, 16 helped a biological father, seven helped a brother, two helped a mother, and only one helped an unrelated stranger.
Large colonies of some ants, bees and wasps are other common examples of kin selection. In many of these colonies, the queen is the only female that reproduces. Almost every other task in the colony is taken over by hordes of sterile workers. From foraging and gathering food, to building a nest or hive, and raising young. Since successive generations of these insects are born from the same mother, these generations are linked by brotherhood. This motive may explain the workers' keenness to feed and protect the young (bringing them) at the expense of their personal reproduction.
Warning signals are another common example of altruistic behavior motivated by kin selection. In certain groups of closely related animals, such as squirrels and monkeys, clan members will sound an alarm when a predator is ready to pounce. This warning signal allows family members to escape from danger, with the potential to draw dangerous attention to the sender of the warning signal itself, and thus this is considered altruistic behavior.
Despite its logical and emotional appeal, the choice of relatives has its critics. Next we'll look at some of the strongest criticisms of kin selection, including one from a leading evolutionary biologist.
Arguments against kin selection.
On the surface, the theory of kin selection makes a lot of sense. If natural selection is designed to exclude traits that reduce reproductive success, how do we explain the existence of altruistic traits that reduce reproductive fitness to zero? Kin selection shows that these traits are passed on through relatives who share much of the same genetic material and have more children with the help of their altruistic givers.
But what if we focus too much on the individual? Sure, altruistic behavior such as guarding another bird's nest or gathering food for the queen may reduce the reproductive fitness of an individual bird or bee to zero, but what if it increases the net fitness of the entire
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Darwin himself, in 1871 in his book The Descent of Man, first postulated the idea of group selection. Under this theory, altruistic traits are passed on if the group's reproductive capacity is increased. Blood relations have nothing to do with it. Darwin explained this using the concept of self-sacrifice. Monkey tribes that display selfless behavior and sacrifice the whole self will defeat rival groups that only care about themselves, thus passing on those “noble” genes.
In fact, group selection was the dominant solution to the altruistic problem before kin selection came. It turns out that the strength of the kin selection argument is not theoretical but mathematical. Using complex mathematical simulations, Hamilton and his colleague Maynard Smith demonstrated that mass selection does not have the evolutionary force that perpetuates altruistic behavior from generation to generation.
The argument is further complicated by the fact that in nature, many tight-knit social groups also consist of close relatives. Where does kin selection end and collective selection begin? The debate is heating up today. Distinguished Harvard biologist Edward Wilson, one of the early proponents of kin selection, co-authored an article in Nature in 2011 claiming that kin selection was nonsense and that he had the math to prove it.
(Wilson encountered evidence that made him suspicious of the relationship between degree of kinship and altruism. Researchers were finding insect species that shared a lot of genetic material with each other but did not act altruistically, and other species that shared little and did so, proposing an alternative theory that the origins of Altruism and teamwork have nothing to do with kinship or degree of attachment between individuals.The key to the puzzle is the group: under certain conditions, groups of cooperators can outperform groups of non-cooperators, thus ensuring that their genes—including those that predispose them to cooperate—are passed on to the The next generations). He went on to say that collective selection occurs in humans.
The 85-year-old Wilson has been criticized by his peers (mass selection, fiercely opposed by many evolutionary biologists who argue that natural selection works at the level of an individual's genes rather than a group), but his assertive stance is evidence that Darwin's revolutionary ideas are still Conflicts occur after more than 150 years.
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