Trivially primitive simulation of survival (or not) of lineages

gistfile1.rb

class Male
  @@lineage = 1
  def initialize
    @lineage = @@lineage
    @@lineage += 1
  end

  def inspect; "<#{@lineage}>"; end

  attr_reader :lineage
end

popsize = 1000
generations = 100

# Percentage of the population we consider rich
rich_pct = 0.1
# Integer factor of how many more children the rich part of the popopulation gets
factor = 2
# Percent of "children" that die before their generation reproduce
death_pct = 0.09

tribe  = Array.new(popsize) { Male.new }

(1..generations).each do |gen|
  pivot = (tribe.size * rich_pct).to_i
  rich = tribe[0.. pivot-1]
  poor = tribe[pivot..-1]

  # The new generation consists of <factor> times children of
  # each rich male, and 1 child of each poor male.
  tribe = rich * factor + poor

  # We're not taking into account transfer of wealth at all.
  # In this primitive simulation, every member of the new generation
  # gets an equal chance of being rich.
  tribe = tribe.shuffle

  puts "Generation #{gen}"
  puts "   #{tribe.size} people after reproduction"

  culling = (tribe.size * death_pct).to_i
  puts "   Culling #{culling} people"
  tribe.slice!(tribe.size-culling,culling)
  puts "   #{tribe.size} people after deaths"

  puts "   There are #{tribe.collect(&:lineage).uniq.count} lineages left"
end