Ape skulls? Human? Hominid?

You also have the sometimes arbitrary division into species in a lineage where the first samples seem quite different but then more specimens are found in between and you have to draw the line somewhere. It gets to the point in the evolution of a species where the difference between specimens close to the dividing point are less than the differences within the species from oldest to youngest.Technically you could take each specimen and define a species by it, and the cut it off where ancestors and descendants are too divergent to interbreed, but each other specimen is also a defining point for a species that would overlap many but not all specimens with the first.

---

we are limited in our ability to understand
by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}