The famous Flynn effect, of a rise in IQ levels now seems to be reversing across the West:
“The IQ gains of the 20th century have faltered. Losses in Nordic nations after 1995 average at 6.85 IQ points when projected over thirty years. On Piagetian tests, Britain shows decimation among high scorers on three tests and overall losses on one. The US sustained its historic gain (0.3 points per year) through 2014. The Netherlands shows no change in preschoolers, mild losses at high school, and possible gains by adults. Australia and France offer weak evidence of losses at school and by adults respectively. German speakers show verbal gains and spatial losses among adults. South Korea, a latecomer to industrialization, is gaining at twice the historic US rate.
When a later cohort is compared to an earlier cohort, IQ trends vary dramatically by age. Piagetian trends indicate that a decimation of top scores may be accompanied by gains in cognitive ability below the median. They also reveal the existence of factors that have an atypical impact at high levels of cognitive competence. Scandinavian data from conventional tests confirm the decimation of top scorers but not factors of atypical impact. Piagetian tests may be more sensitive to detecting this phenomenon.”
There are many causes of this decline, including one which eugenics writers in the early part of the 20th century predicted, such as by writers like Lothrop Stoddard (The Rising Tide of Color; The Revolt Against Civilization) – the failure of high IQ people to reproduce. This decline alone could well bring down the West and modern civilisation as Madison Grant and Lothrop Stoddard thought. The tree of humanity thus rots from the top down.
We certainly have the toughest battle humanity has ever faced, because the decline in quality has affected our side too: just look at poor James Reed for example!
http://www.sciencedirect.com/science/article/pii/S0160289617302787
https://www.rawstory.com/2018/01/will-natural-genetic-selection-ultimately-make-us-more-dumb/
http://www.amerika.org/social-reality/as-flynn-effect-reverses-cognitive-decline-starts-at-the-top/
http://www.pnas.org/content/114/5/E727.full#sec-2