RUBY_VERSION < 1.9

class Parent
end
class Child < Parent
end

puts Child.superclass   #=> Parent
puts Parent.superclass  #=> Object
puts Parent.superclass.superclass  #=> nil

RUBY_VERSION = 1.9

class Parent
end
class Child < Parent
end 

puts Child.superclass   #=> Parent
puts Parent.superclass  #=> Object
puts Parent.superclass.superclass  #=> BasicObject
puts Parent.superclass.superclass.superclass  #=> nil

So now given any class in Ruby, super class will be BasicObject for newer versions.