Today’s factismal: Hominins are humans and their direct ancestors. Hominids are hominins, the other great apes, and their ancestors. And hominoids are hominids and gibbons and their ancestors.
One of the fascinating things to see in science is how terminology changes over time. The carbonic acid in the air of 1897 becomes the carbon dioxide of today. Anthroposcopy (literally, “looking at a man”) becomes physiognomy (“study of features”) becomes obsolete. An accoucheuse becomes a midwife. Priestly’s phlogisticated air becomes Lavoisier‘s azote becomes today’s nitrogen. And Leakey’s hominid becomes today’s hominin.
Usually, the change in terminology comes about as we learn more. For example, we once thought that humans were distinct and completely different from every other species out there. As a result, we gave ourselves a name that showed that distinction; we called all of the humans and their ancestor species “hominids” (“human-ish” in paleontology-speak). But then we learned that humans are very closely related to some great apes and not so closely related to others. Thanks to DNA analysis and fossil interpretation, we found that humans and chimpanzees and gorillas are practically cousins (first and second-degree, respectively) while orangutans are more distant relatives and gibbons are that branch of the family that we never speak of in polite society.
As a result, the term that used to be just for us now includes our cousins; a hominid is any member of the great ape family including humans, both species of chimpanzees, both species of gorilla, and both species of orangutan. Hominoid is even more inclusive and invites the gibbons into the party, where hominin is more restrictive and only allows the humans through the gates.
Though much of the evidence for this comes from comparing the DNA of each species, quite a lot still depends on the fossils that we find. The best fossils for this part of our story are found in the Turkana Basin, which stretches from northern Kenya down into southern Ethiopia. Much of the area is made up of rocks that are 1.4 to 1.8 million years old, which means that they were laid down just about the time that our ancestors laid down for a nap. As a result, they are rich both in hominin fossils and in the fossils that hominins made; things like tools, fish bones, and foot prints. And if you’d like to help find fossils in those rocks, all you have to do is head over to Fossil Finder. There you’ll look at images and point out anything interesting that you see. To learn more, burrow over to: