Here's why:
* Evolutionary Lineage: Apes and monkeys belong to different branches of the primate family tree. Apes are more closely related to humans and have undergone a longer evolutionary process of brain development.
* Brain-to-Body Ratio: While apes have larger brains overall, they also tend to be larger animals. When comparing brain size to body size, some monkey species have a higher brain-to-body ratio.
* Species Variation: It's important to note that there's a huge variety within both the monkey and ape families. Some monkey species, like the capuchin, have relatively large brains for their size. Similarly, smaller ape species like gibbons have smaller brains than larger species like gorillas.
Here's a simplified comparison:
* Apes: Larger brains overall (gorillas, orangutans, chimpanzees, bonobos)
* Monkeys: Smaller brains overall, but some species have larger brains relative to their body size (macaques, baboons, capuchins)
In conclusion: While there are exceptions, it's generally true that apes have larger brains than monkeys.