A micrograph by Thomas Deerinck of the National Center for Microscopy and Imaging Research at UC San Diego reveals the organization of stained glial cells (cyan), neurofilaments (green) and DNA (yellow) in a section of rat hippocampus.
Remembering why we’re so alike
In 1859, not long before Charles Darwin would publish his seminal On the Origin of Species, the renowned British comparative anatomist and paleontologist Sir Richard Owen published a controversial work of his own – an essay contending that humans should be reclassified as distinct and separate from other primates.
Owen was among the scientific greats of his day, a hugely influential figure who was, among other feats, the first to recognize that the fossilized remains being discovered around the world represented a distinct group of prehistoric animals he dubbed “Dinosauria.”
In other words, they weren’t just old, dead reptiles.
But Owen proved to be wrong-headed about other things, most notably his stubborn opposition to Darwin’s theories about evolution and human origins. In his 1859 paper, Owen argued that modern humans represented a singular species based, in part, upon three ostensibly unique neuroanatomical differences in brain structure with nonhuman primates.
In a paper published online this week in PNAS, Larry R. Squire, PhD, professor in the departments of neurosciences, psychiatry and psychology at the UC San Diego School of Medicine and Veteran Affairs San Diego Healthcare System, and Robert E. Clark, PhD, associate professor of psychiatry, recount Owen’s misthinking and go on to explain how memory systems involving the hippocampus are quite similar in form and function in rodents, monkeys and humans.
I won’t go into great detail here about Squire’s and Clark’s observations. They tell a great story, including a brief recounting of patient H.M., who suffered from profound amnesia. Their basic point: There are multiple memory systems among animals, but their differences also highlight their similarities. Rodents, monkeys and other non-humans think a lot like us.
As for Sir Richard, he met up with Thomas Henry Huxley, one of Darwin’s most ardent advocates, a few years later in a famed debate about evolution in general and his notions of brain structure in particular. This debate is not to be confused with Huxley’s 1860 rhetorical romp with the redoubtable Bishop Wilberforce on the merits of evolutionary theory. But like that debate, Huxley easily rebutted all of Owen’s assertions, noting that his three criteria for human uniqueness (one being the existence of a brain region called the hippocampus minor) were found in all primate species. Indeed, in some species the size of the hippocampus minor was larger than in humans.
After Owen’s death in 1892, Huxley reviewed his work, perhaps ungraciously concluding that “hardly any of these speculations and determinations have stood the test of investigation, or, indeed, that any of them were ever widely accepted.”
To be fair, Owen did leave a distinguished scientific legacy, not least of which was the founding of the magnificent British Museum of Natural History. It’s just that in terms of brain anatomy and memory, his ruminations are perhaps better forgotten.