The Fossil Chronicles: How Two Controversial Discoveries Changed Our View of Human Evolution

Back when I was a graduate student I was assigned by my advisor a set of literature to absorb and comment on. The mix of published and soon to be published papers included a series of papers written by Ralph Holloway and Dean Falk. These represented a fight over the interpretation of early hominid brains as studied through endocasts. Endocasts are fossilized casts of the inside of an animal’s brain case or the artificially produced version made of casting material poured into a skull. Either way, you get a roundish blob that resembles the exterior of the original brain. Endocasts are of limited value, as layers of tissue in a living mammal separate the brain from the skull, attenuating detail. As Falk point out in her book, endocasts are a rather “surficial” view of a brain, but are not without their uses.

Fossil endocasts are compared to endocasts made from the skulls of “living” primates and humans, which in turn are understood via other forms of neuroanatomy and, of course behavioral observation. We can look at brain scans during activities of a primate or a human to see that a certain area of the brain does a certain kind of task. If this region is larger in humans than in monkeys, and has to do with something more relevant to human behavior than to monkey behavior, we might infer that this region enlarged in the endocast of an extinct hominin indicates human-like behavior, or the lack of enlargement indicates a lack thereof.

These Holloway and Falk papers represented a real academic fight typical of the day. The fact that Dean Falk was a woman working in a largely male field was not lost on us young graduate students, as we wondered if she was being marginalized for her gender. Holloway was fond of pointing out that Falk was wrong in part because a lot of very smart and well established people said things contrary to her findings. Both researchers, it seemed, had valid points, but not all of the arguing was about the science.

Parallel arguments emerged at the time in the study of growth rates, teeth, and other features of various hominin remains, and related to what I view as one of the central questions of human evolution: Childhood. Modern humans have a different timing of growth and development from our nearest living relatives, the non-human apes, and a large part of this has to do with the insertion of an extended period of development we call childhood, in the human’s lifespan. Along with this goes an extended period of neural development during which our brains take on all those human-like characteristics that make us distinct form the other apes. The Holloway-Falk argument was whether or not the brains of Australopithecines were ape-like or human-like, and this is exactly the same argument that was central to the Taung-Piltdown comparison of previous decades and to Raymond Dart’s research. The argument is nuanced and complex. You’ll need to read the book to find out how it goes. We now think that Australopiths were mostly ape-like but not entirely, and unambiguous members of the genus Homo such as Homo erectus are human-like in many ways. Falk’s book would be worth the read just to get her perspective on this historically important debate. But wait, there’s more.

The Hobbit is no longer just a story by Tolkien!

Did you know that the use of the phrase “The Hobbit” to describe that Indonesian fossil, Homo floresiensis, has been “banned” by the people making the movie “The Hobbit”? I won’t do that here, of course.

Anyway, the second, and main, theme in Falk’s book is the interpretation and meaning of the fossil hominin known as The Hobbit, but which shall hereafter be called “the Hobbit,” found in 2003 on the island of Flores, in Indonesia. This is one of the most important finds of the last hundred years. The Hobbit is a small brained hominin that made rather advanced stone tools and otherwise lived like any other pre-modern hominin may have, hunting, scavenging, and gathering. Nothing like this newly discovered species was thought to exist: There are no small brained bipedal apes any time anywhere over the last 1.5 million years, but the Hobbit appears to have lived between 94,000 and 12,000 years ago. The world of the Hobbit is a little like a quaint historical neighborhood left alone by modern development because it found itself off the beaten track on the edge of some large city. One wonders, given the reality of the Flores find, if the world was once (partly) populated by others as different from the main line of human evolution, briefly, early, and displaced quickly and completely enough that we happen to not have run into it elsewhere.

Falk investigated the artificial endocasts of the Flores the Hobbits. One fossil in particular, a female known as “Flo” provided the skull. Since Flo and her fellow the Hobbits were so unusual, numerous explanations appealing to disease or abnormality have been made and continue to be made. Microcephaly, a condition occasionally found in humans, predominated but is not the only explanation offered. The preponderance of evidence, including Falk’s work, rules out all of these explanations. This Hobbit thingie, known officially as Homo floresiensis, is normal, if very different than expected, like Taung was different than expected. And it that is how the stories chronicled by Meredith and Falk fold into each other: The history of the study of human evolution is not just about fossils, it is about surprises and how those surprises make well educated otherwise rational people act in that period of time before everyone eventually settles on a new view.

I’m not sure if you need to read this book before you see the movie “The Hobbit (TM)” … probably you should read this one instead … but at some point you’ll have a chance to enjoy Dean Falk’s rather unique volume.

Meredith starts out with an examination of the Taung fossil, its discoverer, anatomy, and associated controversy. As you probably know, Taung was brought light by anatomist Raymond Dart, and had its initial impact on human evolutionary studies in the 1920s when the British Piltdown fossils, now known as forgeries, held sway as the archetype of early human ancestors. At that time, there was a concept of what a human ancestor would look like (large human-like brain, ape-like teeth and in-between body) and lo and behold, a fossil fitting this description was found and immediately established as physical dogma, despite the presence of what we now regard as obvious indicators that it was a fake. Taung has more of an ape-like brain and ape-like teeth but a more human-like body in that it walked upright, and depending on one’s view, could be regarded as somewhat human-like in other details. Britain was a, if not the, center of the world of Anthropology (and many other disciplines) and already had a very nice human ancestor, thank you very much. Dart’s work was thus sidelined, ignored, or even ridiculed. By the mid to late 1940s, as is well chronicled by Meredeth, Piltdown was uncovered as a hoax, and Taung and other materials from South Africa vindicated, just in time for two major events to occur: The de-centralization of human origins study so other people could play too, including South Africans, the French and even the Americans; and the start of discovery (in the 1950s) of what would eventually be regarded as several key fossils from Tanzania, Kenya and Ethiopia.

Meredeth’s chronicle then moves on to the days of Mary and Louis Leakey, and their real and intellectual heirs, Richard and Meave Leakey, the Berkeley group the most famous of which are Donald Johanson and Tim White, and the increasingly internationalized and nondisciplinary teams of researchers addressing finer and finer questions about human evolution. His telling of the story is rich in detail. I thought I had heard all of the scuttlebutt, but Meredith had a few tidbits new to me, and most of the … interesting moments … that he leaves out have more to do with the archaeological research than the fossil research.

The take-home message of Meredith’s Born in Africa: The Quest for the Origins of Human Life is that conflict in personality, national interest, and access to resources is more interesting than the story of human evolution itself, mainly because there is more flesh on it. We can name the actors in the drama, and we can feel their joys and their heartaches. We can relate to the underdogs and be very annoyed at the coyotes. Meredith does not ignore the human evolutionary story itself: You get that too. But as a comedian once said of baby races: The real reason you are interested is to see the crashes.

(This is a modified version of a review originally published here.)

Well, it’s here, in American Scientist!

Yes, I know, that’s an internet thing, but it is the internet version of the print thing. Please have a look, and leave a nice comment! Or a mean comment, whatever.