Apes were the first primates to have the Y-5 molar pattern, characterized by five cusps forming a Y shape on lower molars. This distinguishes them from Old World monkeys, which have a bilophodont pattern with only four cusps. While gibbons are considered lesser apes, they do not have the Y-5 molar pattern and instead have four cusps like monkeys. Apes also have anatomical differences in their shoulders that were advantageous for tree travel.

1. What was the first primate to have Y-5 molar pattern? Gibbons
Solution
Answer- Apes
Description- Apes have five in the Y-5 molar pattern while Old World monkeys have only four
in a bilophodont pattern. Lower molar teeth of apes and humans have five cusps with raised
points on their grinding surfaces is known as a Y-5 pattern because the area between the cusps
roughly is in the shape of the letter Y. Monkeys only have four cusps on their lower molars.
The shoulder anatomy of apes and humans also differs from other primates. This difference and
the advantages it provides for traveling through the trees.
The apes and humans are members of the same superfamily-Hominoidea. It classified into two
families-
1. Hylobatidae- gibbons
2. Hominidae- humans, orangutans, gorillas, chimpanzees, bonobos
Gibbons- Because of their size members of the family Hylobatidae also referred to as the lesser
apes. Long bushy hair on their bodies makes them look stockier. Gibbons have little sexual
dimorphism in body size, with the exception of siamangs. Sexual dimorphism of siamangs is
compared to that of the great apes.