Marmosets are New World monkeys. Most marmosets are tiny and just about 20 cm long.
Only recently studies have become possible with marmoset, thanks to successfully controlling a specific intestinal parasite. 1 marmoset year is approximately 10 years. so lifespan experiments still have a reasonable time frame. Following human years would correspond to following a marmoset 3-4 month; measurements in the ongoing project are done every three months so that a matching window could be selected.
The Marmoset has been studied regarding body growth and development.
There is an ongoing project on age-related data in the Marmoset with preliminary results . If the exact same measurements that are done in the marmoset project would also been done in humans, then it would be possible to start projections and learn a lot from this model.