this method to stimulate human evolution would work to cause speciation.
a new society is created. perhaps it's on an island or on another planet. it consists of new born to 30 year olds. only the best and the brightest 500 people from society are picked. intelligence and physical attributes. they do genetic testing on the people to ensure diseases and problems indicated by genes and family history are rooted out.
eighteen to thirty year olds are permitted to breed.
then the population of five hundred would be permitted to expand to five thousand. then by the time it got to five thousand, five hundred of the best are picked out to breed. this method of expansion and retraction would be put on repeat. i'm not expert but i'm assuming these numbers would work. i'm sure the experts can pick ideal numbers to cause this stuff to happen. when a parent shows that it later develops a disease, that can disqualify the offspring as well.
eventually, this would lead to speciation.