Before we start in with our lecture notes on altruism, take a look at this article which came out in Nature the other Year... is there a gene we can inject via a virus that would make us more altruistic?
Vole story
Viral gene therapy makes males more faithful and friendly.
24 September 2001
ERICA KLARREICH
Vole mates: gene makes males more receptive.
© L. Pitkow et al.
Spells and incantations step aside: scientists have found a genetic elixir of love. It makes males more faithful to females and more friendly to fellow males. It could also shed light on bonding disorders such as autism.
Larry Young of Emory University in Georgia and colleagues used a virus to deliver a gene straight to the part of voles' brains responsible for rewards and addiction, the ventral pallidum. The gene made the animals' brains more receptive to the hormone vasopressin1.
"Something about having more vasopressin receptors makes interacting with another individual more rewarding," says Young. The ventral pallidum, at the bottom front of vole and human brains, is believed to reinforce pleasurable experiences.
Male voles were placed in a cage with a female for 17 hours, then caged with that female and another similar female. Gene-treated voles much preferred the known female. Untreated voles, or those given the gene in a different brain region, showed no preference.
This is the first time a virus carrying a gene to the brain has changed a complex behaviour, says Stafford Lightman, a hormone specialist at Bristol University. "It's quite remarkable, and almost frightening, that you can change bonding behaviour just by changing this one receptor," he says.
Young speculates that a dearth of vasopressin receptors in the ventral pallidum could be a cause of autism, a condition that hampers people from bonding with others. "Problems with this system could be responsible for some of these social deficits," he says.
Addicted to love
Human brain-imaging research has implicated the ventral pallidum in romantic love and in drug addiction. It's not surprising that the same region might be responsible for both, Young says: "People have always thought of love as an addiction."
Experiments show that animals in cages with striped walls injected with cocaine into their ventral pallidum seek out striped walls. They associate the wall pattern with the euphoria of the drug, Young says.
"Perhaps pair bonding is a similar thing," he suggests. "When a vole mates with a female, vasopressin is released in his brain, which stimulates the ventral pallidum. He gets a reward, and associates it with that female."Hormones released when animals are stressed could pave the way for new relationships
Sue Carter, University of Illinois
Vasopressin may also be associated with anxiety. Voles given the vasopressin receptor gene in the ventral pallidum were more anxious than normal: they ventured out into the open less often.
"This helps explain something we already know: that attachments often happen after a stressful experience," says Sue Carter of the University of Illinois, Chicago, who specializes in rodent and human hormones.
"Hormones released when animals are stressed could pave the way for new relationships," she says. "Animals form social bonds when they need them."
References
1. Pitkow, L. et al. Facilitation of affiliation and pair-bond formation by vasopressin receptor gene transfer into the ventral forebrain of a monogamous vole. Journal of Neuroscience, 21(18), 7392 - 7396, (2001). © Nature News Service / Macmillan Magazines Ltd 2001
Altruism & Inclusive fitness
Altruism is any act that reduces the reproductive success of one's self while enhancing that of another individual.
- Examples include sharing of food, territory or sacrifice of one's life.
- Worker female ants don't reproduce themselves but take care of the queen's offspring.
- Being a parent or taking care of offspring
- Warning calls or overt defense.
Hamilton (1964) : Natural selection maximizes the reproductive fitness to maximize the total number of genes going into successive generations whether through one individual or through relatives when,
K > 1/r
where k = recipients benefit / the altruist's cost and
r = coefficient of genetic relatedness
and where we define....Relatedness: possibility that a particular allele present in one individual is also present in other individuals because of descent by a common ancestor
father
mother
sister 1
sister 2... r = 1/2 with mother & sister
nephew 2
nephew 1
r =1/4 with aunt & 1/8 with cousin
Relationship between aunt & child of sister 2 ( aunt/nephew) = 1/2 ( relationship between two sisters x mother and son which is 1/2 ( son gets only half of his genes from his mother ) thus 1/2 x 1/2 = 1/4 of genes held in common.
Between cousins = above relationship X another 1/2 ( genes from aunt or who she's married to ?) = 1/4 x 1/2 = 1/8
Then going back to K > 1/r , for one to be an altruist, either the genetic relationship should be close so 1/r is relatively small or the altruists cost should be low so K takes on a high value.
Who should be an altruist?
- older, less reproductive individuals
- stronger individuals who are less likely to incur personal damage
- individuals with genes which are not overly common or rare in the population
- one who is closely related to a good number of population members
- species with little dispersal- more likely everyone has genes in common
- species in which kin are recognizable- spend time together in tight social structure
Examples:
- food sharing & grooming in monkeys
- warning calls of deer : will snort when in a group of close relatives
- in scrub jay populations, younger members are more likely to help parent rear offspring, generally their younger sibs. In this example however, there are benefits to the 'altruist' - any gain the territory when parents die, gain experience in rearing which will help them in raising their own young, are safer in group setting, gain status important in later mating choices.
Bee, wasps & ants - females take care of young of queen rather than having their own. Why?
Genetic relationship:
- Males are haploid 1N- no fertilization of eggs
- Females are 2N or diploid and are produced only when eggs are fertilized.
Mother to daughter relationships: they receive half their genes from their mother ( 1/2) and 1/2 from their father, so r = 1/2
Sister to sister : since the contribution from their father is 1- their father is only 1N so all his genes are in common but from their mother they may get only 50% of common genes since she is diploid then 1 (father) + 1/2 in common (mother) = (1.5) / 2 = .75
Since their relationship to their mother and their own offspring is 1/2 but to their mothers new offspring ( their new sisters) is 3/4, it makes genetic sense to support the mother's offspring rather than their own.
The population with the blue altruistic bugs, who share their aphids with less lucky individuals will allow a greater proportion of the population to survive, while the first population with everyone for himself will lose a greater part of the population when conditions are bad.
What type of intra-population interactions are most benefical to any organism - self oriented and potentially negative to other members of the population OR in general positive and sharing? What are the costs of either type of interaction?
What might you speculate is a "selfish gene" Might a virus be such an example?
Evolutionarily should altruism be genetically programmed into an indiividual or would it better to make is a conscious choice? Is it possible that individuals such as firemen/women or police have a gene which makes it easier to select their careers? consider given the rules which make altruism make sense ( relatedness, etc)
