If you’re a long-time reader of this site, you doubtless share my fascination with the missions that are defining our summer — Dawn at Ceres, Rosetta at comet 67P/Churyumov-Gerasimenko, and in the coming week particularly, New Horizons at Pluto. But have you ever wondered why the fascination is there? Because get beyond the sustaining network of space professionals and enthusiasts and it’s relatively routine to find the basic premise questioned. Human curiosity seems unquenchable but it’s often under assault.

‘Why spend millions on another space rock?’ was the most recent question I’ve received to this effect, but beyond the economics, there’s an underlying theme: Why leave one place to go to another, when soon enough you’ll just want to go to still another place even more distant? The impulse to explore runs throughout human history, but it’s shared at different levels of intensity within the population. I find that intriguing in itself and wonder how it plays out in past events. The impulse is often cited as a driving motif that has pushed human culture into every corner of the planet, but it comes in waves and can lie fallow until new discoveries bring it to the fore.

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Back when I was writing Centauri Dreams (the book), I looked at the Conference on Interstellar Migration, which was held in 1983 at Los Alamos. This was a multidisciplinary gathering including biologists and humanists along with physicists and economists, and a key paper there was the synergistic work of Ben Finney (an anthropologist) and Eric M. Jones (an astrophysicist). Called “The Exploring Animal,” the paper argued that evolution has produced an exploratory urge driven by innate curiosity. The authors considered this the root of science itself.

It was probably the Los Alamos conference that introduced the theme of Polynesia into interstellar studies, the idea being to relate the settlement of the far-flung islands of the Pacific to future missions into the interstellar ocean. From Fiji, Tonga and Samoa and then, in another great wave, to the Marquesas, Hawaii and New Zealand, using double-hulled dugout canoes with outrigger floats, these explorers pushed out, navigating by ocean swells, the stars, and the flight of birds. Finney and Jones call this the outstanding achievement of the Stone Age.

Here’s an excerpt that puts the view succinctly:

The whole history of Hominidae has been one of expansion from an East African homeland over the globe and of developing technological means to spread into habitats for which we are not biologically adapted. Various peoples in successive epochs have taken the lead on this expansion, among them the Polynesians and their ancestors. During successive bursts lasting a few hundred years, punctuated by long pauses of a thousand or more years, these seafarers seem to have become intoxicated with the discovery of new lands, with using a voyaging technology they alone possessed to sail where no one had ever been before.

And to me, this resonates when you see something like this:

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Image: This map of Pluto, made from images taken by the LORRI instrument aboard New Horizons, shows a wide array of bright and dark markings of varying sizes and shapes. Perhaps most intriguing is the fact that all of the darkest material on the surface lies along Pluto’s equator. The color version was created from lower-resolution color data from the spacecraft’s Ralph instrument. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Are Finney and Jones right that there is an ‘intoxication’ in the discovery of new lands? It’s certainly a sense I have, and most of the people I deal with in aerospace clearly have it. But note as well the fact that these bursts of expansion into the Pacific were also marked by long pauses, thousand-year breaks from the outward movement. We can see this as a process of consolidation, I suppose, or maybe a broader cultural fatigue with the demands of exploration. Are we entering a similar era in space, a time of reflection and retrenching before the next great push? If so, we have no good guidelines on how long that period may last.

In his new book Beyond: Our Future in Space (W.W. Norton, 2015), Chris Impey likewise speculates on the urge to explore. Humans do it differently from animals, after all — we are the only species that moves over large distances with a sense of purpose and organization, sometimes for reasons that have little to do with the availability of resources. Like Finney, Impey cites the Polynesian example, seeing it as driven by a mixture of culture and genetics.

Are there specific genes that come into play in at least parts of the population to make this happen? Because we all know that for some people, exploration is not an option — not even an interest. Most of Europe stayed home when the ships that would open up the Pacific and the Orient to western trade and expansion set sail, and remained at home while emigrants took to the seas to settle elsewhere. Even so, in every era, the exploratory impulse seems firmly planted, which is why even dangerous missions always find no lack of volunteers.

Impey is interested in certain developmental genes that he believes give us advantages over other hominids. In particular, he focuses on a gene called DRD4, which controls dopamine and thus has influence on human motivation and behavior. A variant of this gene known as 7R produces people more likely to take risks, seek new places and explore what is around them. About one person in five carries DRD4 in its 7R form. Impey notes that the 7R mutation occurred first about 40,000 years ago as humans began to spread across Asia and Europe.

Impey doesn’t go so far as to call this an ‘exploration gene,’ but he does think that carriers of 7R are more comfortable with change and are better problem solvers. From the book:

Even if they’re only present in a fraction of the population, the traits that favor adventurousness are self-reinforcing. If the 7R mutation has slightly higher frequency in a population that migrates, that frequency will increase in a finite gene pool. Mobility and dexterity are enhanced as they are expressed. The most successful nomads will encounter new sources of food and new possibilities for enhancing their lifestyle. The best users and makers of tools will be spurred to come up with new tools and novel applications of existing tools. The fulcrum of this feedback loop is our one attribute that’s unparalleled: a big brain.

Is DRD4 7R the source of the internal fire that drives our explorations? It’s a pleasing thought, for it implies that despite periods of pullback, the exploratory impulse is ever outward, for it exists as part of the template of our species. I doubt we can pin curiosity and migration down to this one salient, but our past does imply there is something within us that accounts for our restlessness. Whatever that something is, we find it reinforced in the great explorations of our time. And it seems to be strong enough to survive the periods of retrenchment and apathy that sometimes punctuate our efforts, and that tend to get lost in the big picture of history.

Yesterday’s post asked whether we were nearing the end of an era with the flyby of the last of the ‘classical’ planets. The answer is yes, but the beauty of eras ending is that they have successors, and our inherent human curiosity is not something that can be long suppressed. The Voyagers have already begun the bridge between the interplanetary era and the interstellar, and New Horizons will soon enough follow. Keep in mind the words of Andre Gide when New Horizons swings about to take images of Pluto and Charon receding in the night: “Man cannot discover new oceans unless he has the courage to lose sight of the shore.”

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