Biologists define members of the same species as organisms that can mate to produce fertile offspring. With fossils we cannot do that, so we have rely on what they look like. Because appearance can be a matter of opinion, there have been many disputes about classification of hominids (a hominid is all human relatives including chimps and gorillas whereas hominin refers to those organisms in the lineage following the split from chimps about 6 MYA).
If we use what something looks like as our species definition then we might put males and females, or young and old individuals into different species. So, as biologists, we need to know something about the variation in a population to give us more confidence in our allocation of organisms into different species.
The aim of this practical is to: