The Fossil Chronicles: How Two Controversial Discoveries Changed Our View of Human Evolution is by a scientist Dean Falk, who has contributed significantly to the study of evolution of the human brain, and who has been directly involved in some of the more interesting controversies in 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.