My baby fingers grasp my fisher price animals.
A New World monkey doesn’t use her thumbs. Unlike humans and most Old World monkeys, their thumbs are not opposable.
A human baby would eat from her fingers. The thumbs show up after she mastered eating with her fingers.
New world monkeys
Thumb orientation lies in line with other digits. Opposes the next digit in a scissors-like grip
(Spider monkeys have lost their thumbs)
Fingernails = some species have fingernails on big toe
Old world monkeys
Thumbs are rotated and more opposable, more like ours (Hanuman langurs, baboons)
(Thumbs reduced or absent among colobine monkeys of Africa)
Fingernails and toenails are present on all digits