It's something that many of us reckon with: the sense that we're not quite as sharp as we once were.
I recently turned 42. Having lost my grandfather to Alzheimer's, and with my mom suffering from a similar neurodegenerative disease, I'm very aware of what pathologies might lurk beneath my cranium.
In the absence of a cure for Alzheimer's and other forms of dementia, the most important interventions for upholding brain function are preventive — those that help maintain our most marvelous, mysterious organ.
Based on the science, I take fish oil and broil salmon. I exercise. I try to challenge my cortex to the unfamiliar.
As I wrote my recent book, A History of the Human Brain, which recounts the evolutionary tale of how our brain got here, I began to realize that so many of the same influences that shaped our brain evolution in the first place reflect the very measures we use to preserve our cognitive function today.
These traits and behaviors help retrace our past, and, I believe, were instrumental in why we remain on the planet today.
And they all were, at least in part, enabled by our brain.
Social smart alecks finish first
The human saga is riddled with extinctions.
By "human," I don't just mean Homo sapiens, the species we belong to, but any member of the genus Homo. We've gotten used to being the only human species on Earth, but in our not so distant past — probably a few hundred thousand years ago – there were at least nine of us running around.
But with the exception of Homo sapiens, they're all gone. And there's a good chance it was our fault.
Humans were never the fastest lot on the African plains, and far from the strongest. Cheetahs, leopards and lions held those distinctions. In our lineage, natural selection instead favored wits and wiliness.
Plenty of us became cat food, but those with a slight cognitive edge — especially Homo sapiens — lived on. In our ilk, smarts overcame strength and speed in enabling survival.
Ecology, climate, location and just sheer luck would've played important roles in who persisted or perished as well, as they do for most living beings. But the evolutionary pressure for more complex mental abilities would lead to a massive expansion in our brain's size and neurocircuitry that is surely the paramount reason we dominate the planet like no other species ever has.
Much of this "success," if you can call it that, was due to our social lives.
Primates are communal creatures. Our close monkey and ape cousins are incredibly interactive, grooming each other for hours a day to maintain bonds and relationships. Throw in a few hoots and hollers and you have a pretty complex community of communicating simians.
An active social life is now a known preserver of brain function.
Research shows that social isolation worsens cognitive decline (not to mention mental health, as many of us experienced this past year). Larger social networks and regular social activities are associated with mental preservation and slowed dementia progression.
Entwined in this new social life was an evolutionary pressure that favored innovation. Our eventual ability to generate completely novel thoughts and ideas, and to share those ideas, came to define our genus.
As we hunted and foraged together, and honed stones into hand axes, there was a collective creativity at work that gave us better weapons and tools that enabled more effective food sourcing, and, later, butchering and fire. Effectively sharing these innovations with our peers allowed information to spread faster than ever before - a seed for the larger communities and civilizations to come.
Challenging ourselves to new pursuits and mastering new skills can not only impress peers and ingratiate us to our group, but literally help preserve our brain. New hobbies. New conversations. Learning the banjo. Even playing certain video games and simply driving a new route home from work each day, as neuroscientist David Eagleman does, can keep our function high.
Whether it's honing ancient stone or taking up Sudoku, any pursuit novel and mentally challenging may help keep the neural circuits firing.
We really are what we eat
All the while, as we hunted and crafted in new and communal ways, we had to eat. And we did so with an uniquely adventurous palette.
Homo sapiens is among the most omnivorous species on the planet. Within reason we eat just about anything. Whether it's leaves, meat, fungus, or fruit, we don't discriminate. At some point, one of us even thought it might be a good idea to try the glistening, grey blobs that are oysters - and shellfish are, it turns out, among the healthiest foods for our brain.
The varied human diet is an integral part of our story. As was the near constant physicality required to source it.
On multiple occasions over the past 1 to 2 million years climate changes dried out the African landscape, forcing our ancestors out of the lush forest onto the dangerous, wide-open grasslands. As evolution pressured us to create and commune to help us survive, a diverse diet also supported our eventual global takeover.
Our arboreal past left us forever craving the dangling fruits of the forest, a supreme source of high-calorie sugars that ensured survival. Back then we didn't live long enough to suffer from Type 2 diabetes: if you encountered sweets, you ate them. And today we're stuck with a taste for cookies and candy that, given our longer lifespans, can take its toll on the body and brain.
But humans were just as amenable to dining on the bulbs, rhizomes and tubers of the savanna, especially once fire came along. We eventually became adept scavengers of meat and marrow, the spoils left behind by the big cats, who preferred more nutritive organ meat.
As our whittling improved we developed spears, and learned to trap and hunt the beasts of the plains ourselves. There is also evidence that we learned to access shellfish beds along the African coast and incorporate brain-healthy seafood into our diet.
Studying the health effects of the modern diet is tricky. Dietary studies are notoriously dubious, and often involve countless lifestyle variables that are hard to untangle.
Take blueberries. Multiple studies have linked their consumption with improved brain health. But, presumably, the berry-prone among us are also more likely to eat healthy all around, exercise, and make it to level 5 on their meditation app.
Which is why so many researchers, nutritionists, and nutritional psychiatrists now focus on dietary patterns, like those akin to Mediterranean culinary customs, rather than specific ingredients. Adhering to a Mediterranean diet is linked with preserved cognition; and multiple randomized-controlled trials suggest doing so can lower depression risk.
A similar diversity in our ancestral diet helped early humans endure an ever-shifting climate and times of scarcity. We evolved to subsist and thrive on a wide range of foods, in part because our clever brains allowed us access to them. In turn, a similarly-varied diet (minus submitting to our innate sugar craving of course) is among the best strategies to maintain brain health.
All of our hunting, and foraging, and running away from predators would have required intense physical exertion. This was certainly not unique to humans, but we can't ignore the fact that regular exercise is another effective means of preserving brain health.
Finding food was as social an endeavor as it was mental and physical. Our creative brains harnessed information; gossiping, innovating, and cooking our spoils around the campfire.
Researchers are beginning to piece together the complex pathology behind the inevitable decline of the human brain, and despite a parade of failed clinical trials in dementia, there should be promising treatments ahead.
Until then, in thinking about preserving the conscious experience of our world and relationships — and living our longest, happiest lives — look to our past.
Bret Stetka is a writer based in New York and an editorial director at Medscape. His work has appeared in Wired, Scientific American, and on The Atlantic.com. His new book, A History of the Human Brain, is out from Timber/Workman Press. He's also on Twitter: @BretStetka.