>>593897Stupid leaf, fitness is how adapted an organism is to it's environment. The common ancestor of chimps and humans probably diverged into two separate populations. One evolved further into humans, the other one stayed relatively primitive as chimps.
The reason WE evolved into humans is because the random series of mutations that increased our brain capacity and caused us to walk upright allowed us to exploit our environment better. The chimpanzee population never had a series of mutations like this, so that's why they remain primitive.
