What About the Missing Link?
The concept of a "missing link" between humans and apes arose in the 19th century, when the fossil record was largely incomplete. Large gaps separated species, casting doubt on the theory of evolution. But in the last 130 years, a plethora of fossils have been discovered, greatly narrowing the gaps between species. The Australopithecus afarensis fossil known as "Lucy" is considered to be a key fossil bridging the gap between humans and primitive hominids.
[ References: Wikipedia: Astralopithecus afarensis ]