Tag Archives: evolution

Evolving adaptable adaptability

If the environment changes, then there is a fitness benefit to being an adaptable organism. On the other hand, adaptability is costly (bigger brain for adjusting behaviour, various backup systems in the body like the camel’s hump need to be carried around). So adaptability gives a net benefit if the environment changes sufficiently rapidly.
If periods of change alternate with periods of constant environment, then it would be useful to have the ability to switch adaptability off for a while. This is adaptable adaptability. The ability to switch adaptability off is in turn costly. It is useful to have if periods of environmental change alternate with periods of stability sufficiently rapidly. It would be good to have an ability to switch off the ability to switch adaptability off if changes and stability alternate with different frequency over time. Even more complex patterns may necessitate the ability to switch the ability to switch the ability to switch adaptability, etc. Hierarchies of abilities controlling abilities arise.
Perhaps after an infinite hierarchy, there is some meta-ability that can switch all lower order abilities. Self-awareness or something similar.

Sexual signals are similar to money

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Ronald Fisher analyzed signalling in biology through traits that do not confer direct fitness advantage (higher survival or fecundity), but are desired by the opposite sex. This attraction is an equilibrium in a coordination game – if a potential mate has traits desired by the opposite sex, then the offspring with that mate are likely to have these traits as well and succeed in attracting the opposite sex. The traits confer a mating advantage, which is part of a fitness advantage, justifying the desirability of the traits.
It is a coordination game, because in a different equilibrium, traits without a direct fitness advantage are not desired. Then these traits do not give a mating advantage to the offspring and therefore do not have an indirect fitness advantage either. Then it is not fitness-enhancing to desire them. In summary, if a trait is expected to be desirable in the future, then it is desirable now, and if a trait is expected to be neutral or undesirable, then it is neutral or undesirable now.
Fiat money is inherently worthless, but in one equilibrium of the money game, has positive value in terms of other goods. If everyone expects that others will accept money in return for goods in the future, then it is useful to obtain money now. So everyone is happy to deliver goods in return for (a sufficient sum of) money now. The money game is a coordination game, because if everyone expects money not to be accepted in the future, then they do not give goods for money now. If money is expected to be worthless, then it is worthless, and if money is expected to be valuable, then it is valuable.
An overview of signalling in biology is at http://en.wikipedia.org/wiki/Signalling_theory and Fisher’s theory at http://en.wikipedia.org/wiki/Fisherian_runaway
The coordination game of money is studied by Kiyotaki and Wright (1989, 1993): http://www.jstor.org/stable/1832197 http://www.jstor.org/stable/2117496 and more simply explained in van der Lecq “Money, coordination and prices” https://books.google.com.au/books?id=r1r40SB0Wn8C&pg=PA29&lpg=PA29&dq=fiat+money+coordination&source=bl&ots=iI0M96m-qz&sig=lRHBAWIXYZs2V5S-iNFeH-2yar8&hl=et&sa=X&ei=d3lqVeneJ8TvmAX4vIGgDg&ved=0CEoQ6AEwBw#v=onepage&q=fiat%20money%20coordination&f=false

Of beauty

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What is beauty in human beings? Poets have written a lot about it. I will take a different approach. Beauty is the traits that humans have evolved consider attractive. The characteristics of a good mate, in other words. A good mate is someone with whom one would expect to have numerous fit offspring. A healthy and fertile person. Beauty consists of the outward signs of health and fertility.
Health signals are similar for men and women – good posture, energetic movement, strength and speed, neither excessive fat nor skeletal thinness, smooth skin without patches of different colour, clear voice, bright eyes, no strange smells, thick lustrous hair etc. Posture, movement and strength signal that there is no internal disease that causes weakness or fatigue. Excessive fat or thinness suggest metabolic problems or malnutrition. Skin diseases manifest as roughness and redness. Clear voice signals absence of throat or lung diseases, bright eyes show no eye infection etc.
Fertility signals differ somewhat across genders. Youth and health are associated with fertility in both genders, but a masculine or feminine figure is a fertility signal only for the appropriate gender. Broad shoulders, big muscles, wide angular face and hairyness are all caused by high testosterone levels. These suggest a fertile male, but if observed in a female, are signs of some endocrine disease. Smooth curves, large breasts, narrow waist and wide hips are signs of high oestrogen levels and a fertile female. The narrow waist further suggests the woman is not pregnant already (pregnancy means current sex is unlikely to lead to offspring, which can be interpreted as temporary infertility as far as the current partner is concerned).

Recursive definition of fitness

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Evolutionary theory predicts fitness maximization by organisms over a large enough number of generations. Fitness is described as the ability to survive and reproduce given the environment, but I have not seen a formal definition of fitness even in mathematical models of adaptation.

A direct definition of fitness is difficult to give. Fitness is not the number of offspring, because then a fitness-maximizing organism would accept the following trade: add one child and remove the reproductive ability of all your children. Similarly, fitness is not the number of grandchildren or grand-to-the-n-children, because if it was, the reproductive ability of the grandchildren would be traded away for one more grandchild. If fitness was the number of fertile offspring surviving to adulthood, this trade could be shifted by one generation: add one adult fertile child and remove the reproductive ability of grandchildren or all descendants in a more distant generation. Clearly one has to take into account all descendants in the infinite future in some way.

Fitness can be defined recursively: it is the sum of the fitnesses of the offspring (multiplied by some positive constant). The fitness of each child in turn is the sum of the fitnesses of that child’s offspring, their fitnesses are the sums of the fitnesses of their offspring, and so on to infinity.

Under this definition, the trade described initially would not be made: changing the fitnesses of all descendants in some generation to zero would not be accepted, no matter what is offered in return (increasing the fitness of more distant descendants cannot be part of the same trade). Increasing the summary fitness of descendants in some more distant generation, other things equal, is inconsistent with reducing the fitness of descendants in a nearer generation. This is because if the fitness of an organism increases, other things equal, then the fitness of all that organism’s ancestors increases.

Under multilevel selection, as in Reeve and Holldöbler 2007, there is more than one fitness concept. There is individual fitness and group fitness, if both individuals and groups reproduce. The definitions of these fitnesses are also recursive, but more complicated, since fitness at one level of reproduction will interact with the fitness at another.