What most people “know” about human evolution is wrong, or at least isn’t quite right. The image showing people moving from chimpanzee to modern human, slowly becoming taller and more erect at various stages is wrong. It’s a good way to sort-of understand the concept of evolution but it doesn’t cover the twists and turns of human ancestry, or the gaps. It also does a disservice by starting with chimpanzees because humans were never chimps. We share a common ancestor with chimpanzees but split about 7 million years ago. Millions of years of evolution means that chimps are also very different from that common ancestor.
The split that separated us from the chimps is also not an isolated event. Over millions of years there have been other splits, some of which resulted in dead ends. That means there are human-like ape skeletons out there which are only distantly related to us and are not our ancestors at all. There is even at least one branch, neanderthals, which our ancestors split from, then mated with before they died out. That means that we split and then our branches fused back together again millions of years later.
In this video from It’s ok to be smart, host Joe Hanson, Ph.D. describes evolution as a scraggly bush full of tangles rather than a tree. To me, trying to put together our evolutionary tree is more like a complicated piece of Ikea furniture (say a bookshelf with drawers) – except that when you open the box someone has taken away part of the instruction manual, thrown away some of the parts and added a bunch of other parts which may or may not go with what you’re trying to assemble.