1. The Argument

2. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) The Argument

3. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) The Argument

4. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) (iii)The total success of all females is equal to the total success of all males (Equal Payoff for Sexes) The Argument

5. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) (iii)The total success of all females is equal to the total success of all males (Equal Payoff for Sexes) (iv)‘Individuals’ of the rarer sex are fitter than ‘individuals’ of the common sex (Higher Success for Rarer-Sex Individuals) The Argument

6. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) (iii)The total success of all females is equal to the total success of all males (Equal Payoff for Sexes) (iv)‘Individuals’ of the rarer sex are fitter than ‘individuals’ of the common sex (Higher Success for Rarer-Sex Individuals) (v)Returns from investment into rarer sex higher than from common sex (Higher Returns from Rarer Sex) The Argument

7. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) (iii)The total success of all females is equal to the total success of all males (Equal Payoff for Sexes) (iv)‘Individuals’ of the rarer sex are fitter than ‘individuals’ of the common sex (Higher Success for Rarer-Sex Individuals) (v)Returns from investment into rarer sex higher than from common sex (Higher Returns from Rarer Sex) (vi)Natural selection favours individuals that invest into rarer sex (Best Investment Strategy) The Argument

8. (i)Each offspring derives half its genes from its mother and half from its father (Equal Contribution of Parents) (ii)Each offspring / successful mating gives one ‘credit’ to a female and one ‘credit’ to a male (Equal Payoff for Parents) (iii)The total success of all females is equal to the total success of all males (Equal Payoff for Sexes) (iv)‘Individuals’ of the rarer sex are fitter than ‘individuals’ of the common sex (Higher Success for Rarer-Sex Individuals) (v)Returns from investment into rarer sex higher than from common sex (Higher Returns from Rarer Sex) (vi)Natural selection favours individuals that invest into rarer sex (Best Investment Strategy) (vii)Natural selection neutralises perturbations from equal investment in the sexes (Convergence on Even Sex Ratio) The Argument

9. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio The Argument

10. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871)

11. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871)

12. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871)

13. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871)

14. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871) vii Transmit the tendency to future generations

15. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Darwin (1871) viii Transmit the tendency to future generations

16. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884)

17. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884)

18. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884)

19. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884)

20. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884)

21. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Düsing (1884) ix Behavioural adjustment towards equal sex ratio

22. Gini (1908)

23. “it has all the appearance of being valid, but only the appearance”

24. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914)

25. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914)

26. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914)

27. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914)

28. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914)

29. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914) viii Transmit the tendency to future generations

30. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Cobb (1914) viii Transmit the tendency to future generations

31. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Fisher (1930)

32. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Fisher (1930)

33. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Fisher (1930)

34. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Fisher (1930)

35. i ii iii iv v vi vii Equal contribution of parents Equal payoff for parents Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex Best investment strategy Convergence on even sex ratio Fisher (1930)

36. i ii vi vii Equal contribution of parents Equal payoff for parents Best investment strategy Convergence on even sex ratio Fisher (1930) iii iv v Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex

37. i ii vi vii Equal contribution of parents Equal payoff for parents Best investment strategy Convergence on even sex ratio Fisher (1930) iii iv v Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex

38. i ii iv v vi vii Equal contribution of parents Equal payoff for parents Best investment strategy Convergence on even sex ratio Fisher (1930) viii Transmit the tendency to future generations iii iv v Equal payoff for sexes Higher success of rare sex ‘individuals’ Higher returns from rarer sex