A cornucopia of vertebrate brains: New insights into nature's diversity and how it came to be


Those of us that are evolutionarily minded anatomists spend an inordinate amount of our lives trying to envision how lump A morphed into lump B. We are, if truth be told, a bit obsessed with what we do, and probably appear a tad odd to the noncognoscenti. While my childhood friends were playing stickball or stealing hubcaps (these were the national sports in my home country, Brooklyn), I was sorting bones in the bowels of the American Museum of Natural History. My buddies diligently arranged piles of Topp's baseball cards; I attempted to see which molars belonged with the orangutans and which with the gorillas. Yes, perhaps I seemed a bit odd to some, but it did not faze me in the least. I had a passionate quest, and one that would lead me to approaching hidden secrets that my friends would never know, and never know the pleasure of unveiling.

This same passion and enjoyment for exploration is found in the November 2005 special issue of The Anatomical Record, Part A, entitled “Nature's Experiments in Brain Diversity.” The guest editors for this issue are Lori Marino and Patrick Hof, two dynamic comparative-evolutionary brain morphologists—and frequent coworkers—whose own careers have led them in a hunt to decipher how the brains of big-brained mammals, such as cetaceans and primates, came to be. The issue is partly based on a symposium they organized on the evolution of neurobiological specializations in mammals at the 2005 meetings of the American Association of Anatomists in San Diego.

Marino and Hof have gathered research that demonstrates the remarkable ways that nature and evolutionary history have shaped regions of vertebrate brains. In this compilation of in-depth scholarly reviews and leading-edge science, they have presented a broad spectrum of “answers” to what may have forged the specific gyri, sulci, and nuclei of the brains of living vertebrates. The diversity of groups assessed is most robust. It ranges from some of the largest mammals on the planet—elephants and cetaceans—to diminutive mice and insectivores, and from those molded by demands of the sea to birds and echolocating bats of the air. Our own close relatives, the other primates, receive considerable attention, and the groups studied range from the curious aye-aye (if you have never seen one, this is one odd cousin) to the bouncing tarsier, the ubiquitous (particularly in neuro studies) macaque, to chimpanzees and orangutans.

While the breadth of species studied is impressive, so too is the diversity of brain regions and systems explored. Indeed, it is in the study of these brain “neighborhoods” that one can sense the hidden detective in the researchers as they peer ever closer to assess which nooks and crannies of the brain may have shifted over time, or which regions are homologs to those in other species. Comparative explorations of retinae and photorecptor abilities among mammals (did you ever ponder how these have changed in subterranean species?), the extraordinary sensory specializations in insectivores (I defy anyone not to be fascinated by a star-nosed mole), the changing numbers and distribution of facial muscle controlling motor nuclei (maybe that is why I always lose at poker), or the secrets on the origins of language that may lie in the planum parietale of apes (perhaps our close relatives are talking about us) give wonderful insights into how these systems and regions came to be.

I think that many of the authors in this issue were probably the other kids that worked at the museum with me way back when. As any of us “odd” kids would tell you, having a Mickey Mantle or Willie Mays card is real nice, but it pales in comparison to exploring the brain of a whale or a star-nosed mole. These, as my own kids would say, are “way cool”—as is this most valuable special issue of The Anatomical Record. This issue is available online at http://www3.interscience.wiley.com/cgi-bin/jhome/28243.