Inheritance of intelligence, gender selection

      - What do you think about the issue?

Inheritance of Intelligence and X chromosome

The inheritance of intelligence is believed to be multifactorial. However, many intelligence genes are located on the X chromosome. The boy only has one X chromosome which comes from his mother. So for men who wants smart sons, you best bet is to marry a smart woman. For ladies, checking out your potential mother-in-law, not your father-in-law, according to Prof. Turner.
Intelligence and the X chromosome by Gillian Turner Lancet 1996; 347; 1814-1815

 Intelligence correlated with semen quality

Higher levels of intelligence are also correlated with higher levels of sperm quality: sperm concentration, sperm count and sperm motility.

Men who scored high on a battery of intelligence tests tended to have higher counts of healthy sperm, while low scorers tended to have fewer and more sickly sperm. 

Commun Integr Biol. 2009 Sep;2(5):385-7.

Birthdate Efficts

For relatively young children that put them at a clear and long-term disadvantage in the educational system.

Birthdate Efficts: A review of the Literature from 1990-on by EDA Sykes; JF Bell; and CV Rodeiro. University of Cambridge, Feb. 2009