Final answer:
Non-human apes are still alive because they evolved along their own unique evolutionary paths. Human beings and non-human apes share a common ancestor but are not directly descended from one another. This is reflective of the branching nature of evolutionary processes.
Step-by-step explanation:
The presence of non-human apes alongside humans doesn't contradict the theory of evolution. Rather, it highlights the way in which evolutionary processes work. Human evolution began when our ancestral line diverged from that of other hominids around six million years ago, with humans and chimpanzees sharing a common ancestor. It's important to remember that evolution is not a linear path leading directly from one species to another but is more like a branching tree with various species evolving in different directions.
Species that are today's non-human apes have evolved along their own paths, just as our lineage has led to modern humans. Homo sapiens, while closely related to the great apes, have developed unique traits such as upright posture, a highly complex brain, and opposable thumbs.
Additionally, other hominins like Neanderthals and Denisovans also lived alongside early humans before going extinct. These species, along with the great apes (chimpanzees, gorillas, orangutans) and lesser apes (gibbons and siamangs), evolved from a common ancestor but took different evolutionary routes. This is why we have both human and non-human apes existing today. Each species adapted to their own specific ecological niches over millions of years.