Brain tissue is energetically expensive. A decrease in brain volume may be advantageous to an animal’s survival under the environmental conditions associated with islands. ~ English paleontologists Eleanor Weston & Adrian Lister
H. floresiensis (~0.9–0.05 MYA) is one of the last known hominin species to become extinct. Specimens were first found on the small Indonesian island of Flores in 2003.
While H. floresiensis clearly belongs in the human family as a distinct species, their skeletons are like no other. Nicknamed the Hobbit because its small size, these folk were 1.0–1.2 meters tall, with brains roughly the size of modern guerillas (420 cm2).
Homo erectus reached Flores about 1 million years ago. The hominid population there evolved to be smaller, as is common with island mammal species, owing to limited food resources and other factors.
Small brains were of no consequence mentally. Hobbits made tools as sophisticated as their contemporaries.
H. floresiensis was far from unique. Pygmies in Africa are a similar adaptation. Such small stature in hominins has arisen independently a few times. Like H. floresiensis, H. luzonensis was a hominin that adapted to living on Luzon, a Philippine island, via downsizing. Among the adaptations was better ability to climb trees: a physiological and lifestyle reversion not seen since australopiths.