Spider monkeys have long, thin arms with hook-like hands that allow them to swing through the trees, and they don’t have opposable thumbs either. However, as climate change progresses over 1000’s of years, there would most likely be almost nil trees, so their arms may shrink and fingers and toes may develop claws, as they may have to turn carnivorous due to the lack of sufficient vegetation. Their snouts and mouths would probably be bigger and grow sharper teeth for the same reason. To deal with the tree shortage, their tail might contract, similar to our tail bones. Besides this, they would shed fur during summer and grow much during winter to survive the extreme weather. As for the inevitable reign of humans, as spider monkeys have more intellect than other creatures, they could start evolving like humans, such as building houses, or using basic technology. They'd be different!
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