Darwin Flashcards
Teleology
An organism or process is teleological if it acts for the sake of a goal, i.e., a telos, Greek word meaning “end” or “purpose”
What did Darwin do for naturalism?
Blew away the last objections against naturalism ‘all the way down’, because he provided the first ‘ultimate cause’ that could plausibly compete with God
What is the Blind Watchmaker problem?
Design implies a designer.
Aha, but what if Natural Selection, was the design?
How was the idea of Evolution around before Darwin?
Many people had been discussing evolution prior to Darwin
Even the ancient Greeks understood the idea of descent with modification [they recognized that children resemble their parents; mottled dogs have mottled pups; diseases run in families]
Kant discussed the idea that similarities between organisms suggested that they had a common ancestor
The great taxonomer Linnaeus (1707-1778) discussed hybridization in plants and how it related to new species
Darwin’s own grandfather, Erasmus, had published on the idea of descent of different species from a common ancestor
Deliberate selective breeding was well-known and widely-practiced by Darwin’s time (and used as one source of evidence for his theory by Darwin)
How was natural selection discovered by Darwin?
Darwin’s book compiled overwhelming evidence for natural selection and discussed the idea in an detailed, systematic way for the first time
Alfred Russel Wallace independently came up with the same idea, but it was not as persuasive.
What is a state space?
State space is a way of representing any particular state as a vector (= a list of numbers)
This corresponds to a single point in a space with as many dimensions as the length of the vector
For example, a person’s height and weight can be specified by two values (Height in cm., Weight in kg): say, (170, 80).
If we graphed the range of weights [x-axis] against the range of weights [y-axis] we would be able to put every person at some exact point in a 2D space (i.e. using vectors of length 2)
What is DNA’s state space? What is its significance?
DNA has an enormous state space: in humans, 4 possible values for each of 220 million base pairs = 4220 million possible values, a massive number (1.236 x 10132453198)
In theory, each point in the very massively dimensional state space of human DNA corresponds to a possible human being
In practice, most of those points (probably almost all) correspond to a non-viable human being
If we wanted to construct a viable (let alone great) human being, a random search through DNA space would be a disaster
The odds would be much much higher that a random point in space defines a non-viable or lousy human being than a great one, and the time cost of search would be insane
What is natural selection in relation to state spaces?
Natural selection is a search algorithm
Natural selection is a way of searching that massive state space in a rational (even ‘brilliant’) way
The idea is: If you want to make a viable/great human being, go to the region of state space that represents another viable/great human being (or two) and search very nearby regions only
In other words: Don’t try to re-invent the wheel every time you want to make a human being
Instead, just make human beings that are only a little different from human beings known to be viable
This means that only a minuscule region of DNA state space is ever searched BUT that region is a ‘hot’ region, that is known to give good results
How does Natural selection, the algorithm, operate?
Step 1: Generate random guesses by slightly changing the value a smallish number of (or mixing up) random base pairs selected from (usually two) viable organisms
Step 2: Pick out the fittest organisms & mate [or mutate] them to generate more guesses (= natural selection or selective breeding)
Step 3: Repeat Step 2
How does searching through DNA state space answer the blind watchmaker problem?
Explains how a search can be conducted that impinges on multiple independent elements simultaneously (the ‘Taoist psychology’ problem)
Describe Richard Dawkins’ analogy to evolution.
Think of a string of letters (traditionally, ‘METHINKS IT IS LIKE A WEASEL’, a line from Hamlet) and assume the keyboard has only capital letters and a space bar (= 27 characters)
Even typing millions of characters per second, it would take more time than the age of the universe to produce the target sentence (13.7 billion years = 4.3 x 1017 seconds)
Instead of randomly typing, start with a wholly random string, copy it (say) 100 times with (say) a 5% chance of mutation at any location, and pick the string closest to the target string for the next ‘parent’
The selection of the next generation parent is the ‘fitness function’: It is unrealistic because it locks in the goal of evolution a priori, and does not use sexual reproduction (which has advantages over mutation)
This algorithm can easily generate the target phrase
In Dawkins’ (1986) book (with underspecified parameters) it took 43 generations (a few seconds on a 1986 computer) to generate it
Generally, it takes at most a few hundred generations with a population size of around 1000
How well does Richard Dawkins’ algorithm work?
This algorithm can easily generate the target phrase
In Dawkins’ (1986) book (with underspecified parameters) it took 43 generations (a few seconds on a 1986 computer) to generate it
Generally, it takes at most a few hundred generations with a population size of around 1000
Note that in real evolution there would not be just one target, but many: a more realistic evolutionary simulation would evolve any acceptable 28 string sentence, and would therefore converge faster
Explain how Physiology and Psychology are related in the sensation of thirst.
For example, thirst reflects:
Detection of decreased blood volume (hypovolaemia)
Detection of decreases in arterial pressure
Changes in osmotic pressure (the pressure needed to halt movement through cell walls)
Decreased salt in the blood
The actual feeling of ‘thirst’ is ‘just’ the body’s way of communicating these physiological states to you, which you experience because creatures who seek water when they experience such states have been more likely to make it to reproduction
Where is thirst ‘really’?: It only exists in psychological space!
How does natural selection answer Plato’s problem?
More generally, the ‘genius’ of natural selection is that it can solve problems simply by having a ‘description’ of the problem (= an environment in which the problem is manifest), some relevant (genetically-specified) operators, and a way of recognizing when you have a solution
It solves Plato’s Problems: How can we recognize what we do not know?
Natural selection recognizes when it has a solution because things work, at least to some degree
Is natural selection True?
Under-educated critics do not seem to understand that the mechanism of natural selection is not open to any possible dispute
Natural selection is just a search algorithm
There is no question that it works!: both by informal and formal analysis, and by thousands of instantiated proofs
Arguing ‘against natural selection’ makes exactly as much sense as arguing ‘against square roots’
