Final answer:
Phylogenies based only on anatomical traits can be incorrect. The presence/absence of the frontal sinus can provide the correct answer for the evolutionary relatedness between orangutans, gorillas, chimpanzees, and humans.
Step-by-step explanation:
Phylogenies based only on anatomical traits can sometimes be incorrect because morphological characteristics can evolve multiple times and independently throughout evolutionary history. This means that organisms may appear similar based on their anatomy, but their underlying genetic relatedness may be different. The advancements in molecular technologies have allowed scientists to use genetic and molecular analyses in addition to morphological traits to construct more accurate phylogenies.
The trait that gives the correct answer for the evolutionary relatedness between orangutans, gorillas, chimpanzees, and humans is the presence/absence of the frontal sinus. This trait can provide information about the shared ancestry and genetic relatedness between these species.