The next time a creationist spouts some nonsense about how the lack of a fossil record undermines the theory of evolution, direct them to the hominid family tree. If you haven't read much about human origins lately, it might come as a surprise that so many species have been identified (and more all the time).
One of the most important fossils, and one that marked an important turning point in paleoanthropology, was discovered 50 years ago this month by Mary Leakey. She (and her husband; I suppose we must mention him) spent decades looking for fossil hominids in Kenya's Olduvai Gorge before finding their first: a skull of Australopithecus boisei, a.k.a. Paranthropus boisei, a.k.a. Zinjanthropus boisei, a.k.a. "Nutcracker Man," which lived about 1.8 million years ago.
As the list of possible names suggests, paleonthropologists have argued quite a bit about exactly how to classify the various hominids. But this fossil clarified one important point. Before Mary Leakey's discovery, many experts thought that hominids evolved in Asia. After her discovery, it was clear that hominids evolved in Africa. The newfound skull also showed that other poorly understood fossils, such as the Australopithecus africanus that had been discovered earlier in South Africa, were part of our own distinguished lineage rather than merely ancestors of apes.
Smithsonian ran a story a few years ago about the absurdly paleoanthropologically prolific Leakey family, including son Richard who grew up digging for bones. It helps explain why it's easier to find a photo of Louis showing off the Nutcracker skull than Mary:
Although Louis grabbed the headlines, it was his second wife, Mary, an archaeologist, who made many of the actual finds associated with the Leakey name. Until later in their relationship, when their marital ties all but snapped for both personal and professional reasons, she let her husband bask in the limelight while she conducted her beloved fieldwork....
Then, in 1959, came the now-famous discovery, in Olduvai, of a 1.75-million-year-old skull that Leakey named Zinjanthropus boisei, and which he asserted was the “connecting link between the South African near-men . . . and true man as we know him.” The skull was similar to those of the robust ape-man creatures that had been found in South Africa, but differed from them in having heavier bones and bigger teeth. Nearly three decades of work had at last been rewarded, it seemed, and the huge publicity surrounding the find propelled the Leakeys—particularly Louis, though Mary had actually discovered the skull—to still greater fame.
Here's to the next 50 years of discoveries about human origins.