juan_enriquez's picture
Managing Director, Excel Venture Management; Co-author (with Steve Gullans), Evolving Ourselves

On a brisk May day, in 1967, Tilly Edinger crossed a peaceful, leafy Cambridge, Massachusetts street for the last time. Ironic, given that she survived challenge after challenge. In the 1920s, after becoming a paleontologist against her father’s, and the profession’s, wishes, Edinger and a few others began systematically measuring the fossilized heads of various animals and human ancestors. The idea was to understand the evolution of the cranial cavity and attempt to infer changes in brain anatomy, thus birthing paleoneurology. Then she lost everything, fleeing Frankfurt just after Kristallnacht. As Hitler wiped out most of her relatives, she painstakingly rebuilt her life in the US. Although a lifelong friend and correspondent of Einstein, she led a somewhat reclusive existence, and, as occurred with Rosalind Franklin, she was somewhat underestimated and unappreciated. On May 6th she left Harvard’s Museum of Comparative Zoology and, having lost most of her hearing in her teenage years, she never heard the car coming. Thus ends the first chapter of the field of paleoneurology.

Once the initial, crude skull-measuring methods, such as sand and water displacement, were established, and after a few fossils were measured, there was not a whole lot of rapid progress. Few scholars bet their careers on the new field, ever fewer graduate students signed up. Progress was fitful. Gradually, measurements improved. Liquid latex, Dentsply, and plasticine gave way to exquisite 3D computer scans. But the field remained largely a data desert. One leading scholar, Ralph Holloway, estimated the entire global collection of hominid measurable skulls numbered around 160, about “one brain endocast for every 235,000 years of evolutionary time.”  Lack of data eventually led to a civil war over measurement methods and conclusions between two of the core leaders of paleoneurology, Professors Falk and Holloway.

Nevertheless, the fundamental question paleoneurology seeks to address, “How do brains change over time?” goes straight to the core of why we are human. Now, as various technologies develop, we may be able get a whole lot savvier about how brains changed. Ancient DNA and full genomes are beginning to fill in some gaps. Some even claim you can use genomes to predict faces. Perhaps soon we could get better at partially predicting brain development just from sequence data. And, alongside new instruments, big data emerging from comparative neurology and developmental neurology experiments provide many opportunities to hypothesize answers to some of the most basic lagoons in paleoneurology. Someday we may even revive a Neanderthal and be able to answer why, given their bigger brains and likely at least comparable intelligence, they did not survive.  

There is a second, more fundamental reason why paleoneurology might become a common term; Brains used to change slowly. That is no longer the case. The comparative study of brains over time becomes ever more relevant as we place incredible evolutionary pressures on the most malleable of our organs.

How we live, eat, absorb information, and die are all radically different: a daytime hunter-gatherer species became a mostly dispersed, settled, agricultural species. And then, in a single century, we became a majority urban species. Studying rapid changes in brains animal and human gives us a benchmark to understand how changes occurred over thousands of years, then hundreds of years, and even over the past few decades.

Paleoneurology should retool itself to focus on changes occurring in far shorter timespans, on the rapid rewiring that can result in explosions of autism, on impacts of drastic changes in diet, size, and weight. We need a historic context for the evolution that occurs as our core brain inputs shift from observing nature to reading pages and then digital screens. We have to understand what happens when brains that evolved around contemplation, observation, boredom, interrupted by sudden violence, are now bombarded from every direction as our phones, computers, tablets, TVs, tickers, ads, and masses of humans demand an immediate assessment and response. We are de facto outsourcing and melding parts of our memories with external devices, like our PDAs.

What remains a somewhat sleepy, slow-moving field should take up the challenge of understanding enormous change in short periods of time. It is possible that a 1950s brain, for better and worse, might look Jurassic when compared, on a wiring and chemical level, to a current brain. Same might be true for animals, like the once shy pigeons that migrated from farms into cities and became aggressive pests.

Given that one in five Americans is now taking a mind-altering drug(s), the experiment continues and accelerates. Never mind fields like optogenetics, which alter and reconnect our brains, thoughts, memories, fears using light stimuli projected inside the brain. Eventual implants will radically change brain design, inputs, and outputs. Having a baseline, a good paleoneurological history of brain design, for ourselves and many other basic species, may teach us a lot about what our brains were, where they came from, but even more important, what they are becoming. I bet this is a challenge Tilly Edinger would have relished.