Within the animal kingdom, there are many examples of apparently altruistic or cooperative behaviors in which one animal provides some form of aid to another.

Some examples: Vervet Monkey alarm calls

Allogrooming

Interspecific "cleaning behavior"...

Altruism is defined as an act that confers a benefit to a recipient at some cost to the donor

Given the selfish paradigm of natural selection, true altruism is difficult to explain.

So, how can cooperative behavior be adaptive?

Consider the following five hypotheses to explain cooperation and aid giving; all but one are genetically selfish strategies.

Clearly selfish cooperative behaviors:

Mutualism: both recipient and donor benefit

Phenotypically altruistic behaviors:

Reciprocal altruism: an exchange of altruistic acts, separated by time.

Extortion or manipulation: dominant forcing a subordinate to express cooperative acts because they have no better alternative.

Kin selection: altruism towards relatives

Genetically altruistic behaviors

Group selection (accepting costs for the benefit of the group) the only truly altruistic models of cooperation

Mutualism

Both parties receive benefits simultaneously

Joint participation of two or more individuals must be necessary to increase benefits over what a single individual could achieve

Two animals aiding each other simultaneously are more efficient than one

Here, there are simultaneous benefits and costs to both parties (and B > C)

Participation of all individuals must be necessary in order to benefit, otherwise an opportunity to cheat and get benefit without paying cost

Examples

Pied Wagtails

Group foraging by lions

Communal webs (spiders)

Reciprocal altruism (providing an altruistic act now in the hopes of receiving a similar benefit in the future)

The presence of a time delay between the costly act and the prospective reward is the key feature

Thus, an opportunity arises for the individual receiving the benefit first to leave without repaying the cost.

If an altruist can expect to be reciprocated later, then altruism brings a net long-term gain.

Conditions that would allow reciprocity to evolve

B >> C (The benefit or receiving the altruistic act must be much greater than cost of the act)

Individuals exposed to many altruistic opportunities

Cheaters can be recognized and selectively unaided

Game theory approaches can help understand how this can be stable

Good examples

Coalitions in male baboons

"Tit for Tat" Egg-trading in hermaphroditic fish

Regurgitation in vampire bats

Suspect examples

Food location calls: gulls, vultures, chimps. Broadcast calls must have zero cost to evolve... this is not really altruism

Alarm calls: reciprocal altruism, kin selection, or manipulation?

Extortion (manipulation): Aid givers are making the best of a bad situation

Other examples of apparent aid-giving that are more likely manipulation of subordinates by dominants (i.e. not reciprocal) 

Communal crèche behavior (ostriches, some cichlids)

Communal nesting (Groove billed Anis)

Egg-dumping (Starlings)

Food finding (Striped parrotfish)

As with reciprocity models, high benefit/low cost conditions contribute to stability.

Within "cooperative groups" there is often an unequal division of the benefits in a cooperative system:

Dominants take over resources of subordinates to the point where the subordinate's fitness in the group is just equal to its fitness if it left and lived by itself.

Kin selection (cooperative behavior that increases the fitness of shared genetic material)

Hamilton's notion of inclusive fitness:

Relatives share a known fraction of an individual's genes. Individuals may spread their genes not only by producing offspring but also by spreading a relative's genes, many of which are the same as his own.

Inclusive fitness is an individual's genetic representation in the next generation

equal to its own offspring production plus the summed offspring production of all relatives devalued by r

Thus, a true measure of fitness must include relatives as well as offspring.

The contribution to or from relatives must be devalued by the fraction of genes shared by virtue of common ancestors.

Rules for calculating the coefficient of relatedness for diploid organisms via the path method

Some examples of r for diploid organisms

Some examples for haplo-diploid organisms

Conditions under which altruism will evolve via kin selection

Relatedness is very high (as among sister Hymenoptera.... may also result from limited dispersal)

Benefit to relatives is very high (emergency situations where relative has a great chance of dying if not helped, or many relatives can be helped at one time as in alarm calls)

Cost is very low (donor is young or weak with poor chance of reproducing on its own, or donor is in control of abundant resource).

Ecological conditions that promote kin selection are similar to those that promote reciprocity.....

Assumptions of the kin selection model

Kin selection model is a gene competition model.

Assumes haploid genetic system. More complex models using diploid and haplo-diploid genetic systems generally lead to same conclusion.

Assumes that relatives also possess the altruistic gene. So how does altruismget started? What happens to the first mutant altruist?

Altruism must be facultative initially, and given only to reproductively superior relatives.

Low levels of altruism must develop first (low costs) and the altruist must first spread his genes to his family; an extreme altruist will be selected against in the first generation.

Requires that individuals have some mechanism for recognizing relatives.

Association with a site or nest where relatives generally found (birds)

Familiarity: remembering individuals one grew up with (turkeys, ground squirrels)

Phenotype matching: comparing unknown individuals to a learned template of self or relatives (ground squirrels, bees)

Recognition alleles: perception of true genetic differences (tadpoles?, mice, colonial ascidians)

Intelligence and kinship communication (humans)

Examples of aid-giving to relatives

Communal suckling among female lions

Tasmanian Hen

The Hymenoptera (more later)

The twelve misunderstandings of kin selection (read Dawkins)

Kin selection is a special, complex kind of natural selection.

Kin selection is a form of group selection.

Kin selection requires formidable feats of cognitive reasoning by animals.

It is hard to imagine a gene "for" altruistic behavior.

All species members share the majority of their genes, so selection should favor universal altruism.

Kin selection only works for rare genes.

Altruism is necessarily expected between members of an identical clone.

Sterile workers care for other workers because they are close relatives.

Trivers' theory of parent-offspring conflict does not apply to monogamous species.

Individuals should tend to inbreed, simply because that brings close relatives into the world.

When relatedness is probabilistic rather than exact, altruists will favor relatives of a given type who especially resemble them. Animals are expected to dole out to each relative an amount of altruism proportional to the coefficient of relatedness.

Group selection

Few rigorous models of group selection show an advantage over individual models of selection.

Group selection models that demonstrate that altruism within a group provides an advantage over individual strategies demand restricted environmental and ecological conditions that are not likely to be met in nature.

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