Had this theory that the reduction in IQ over the past 100 years could have been engineered with a variety of factors, that caused a cumulative effect. Was trying to compile a possible list:
2 parent families: strong evidence that children from two parent, nuclear families, will be smarter, and have less mental/behavioral issues than those raised by a single parent.
Breastfeeding: strong evidence that children who are breastfed will be smarter than those who arent.
Spanking: strong evidence that children who get spanked have reduced IQ's.
Lead exposure in soil: strong link to reduced IQ.
Fluoride in water: strong link to reduced IQ.
Toxoplasmosis: possible link to reduced IQ.
algae virus, ATCV-1, possible link, debated, to reduced IQ.
birth control in women: possible link to reduced IQ
If you just had one of these the effect would be negligible, but if you are a child of a single parent, who wasn't breast fed, were regularly spanked, regularly played in lead contaminated dirt/sand, who only drank fluoridated water, had a cat or multiple cats, and infected with this algae virus. The odds are your IQ would of been significantly reduced. From lower genius level you would of been reduced to a brainlet. And from brainlet you would of been reduced to mentally handicapped.