Apart from cleaning, caring and cuddling, mothers provide another very important function. Some say that they are the primary genetic influence on the next generations inteeligence.

Some breakthrough research has suggested that imprinted genes have an
integral role in the inheritance of intelligence. The investigation suggests that the "mother's genes play the dominant role in the development of the parts of her offsprings' brains that are responsible for intelligence. The father's genes, on the other hand, may shape ... the parts of their brains that influence emotional make-up". Although research continues to find out more about the imprinted genes that influence intelligence, one preliminary hypothesis is that the "mother's genes make the biggest contribution to the part of the brain that society values most - the cortex", which is the portion of the brain that is responsible for intellectual skills such as language and the ability to plan ahead.

for more information, see the articles at:

www2.cedarcrest.edu/academic/writing/intelligence/nempage1.htm