Why did aboreal apes like Proconsul die out; whereas some terrestrial apes made it?
Late miocene climate change thinned out the forests, so favouring ground apes. That's the usual explanation.
Another theory is that they began to directly compete for resources with the first early monkeys. The arboreal ape species alive today (orangutans, gibbons, chimps) are able to reach fruit and leaves in trees that most monkeys cannot because of the different ways they move.
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