Humans don't just descend from apes; we are apes. Humans are part of the great ape family, and our evolutionary brothers and sisters -- chimpanzees, bonobos, orangutans and gorillas -- haven't exactly been feeling the love from humanity. In most places, they're legally treated as things, not beings, but the great ape personhood movement challenges that long-held assumption.
1. Great apes are our closest relatives
Humans share a majority of our genetic material with chimpanzees (the precise numbers are highly disputed, from 70 to 99 percent similarity). Yet great apes are regularly hunted, kept as pets or showpieces, and used in research labs for humankind's benefit and entertainment. Other great apes living in the wild, like the orangutan above, are often naturally curious about noninvasive human visitors, such as the scientists and students living at Camp Leakey, a research facility and refuge nestled in the Tanjung Puting National Park in Borneo. This orangutan has learned to wash its "clothes," body, and face merely by watching and copying the human residents -- further evidence of these great apes' capacity for experimentation and innovation.
2. They use and understand complex languages
Captive and rescued great apes have learned sign language, used keyboards and computers and mastered sequences. In the wild, they have their own language of gestures, similar to sign language or body language, indicating that they can attach meaning to symbols on their own. Researchers have compared other apes' language abilities to those of human children, and they can pick up language just like human children do: by watching, listening and trying it out for themselves.
3. Great apes experience emotions and desires