“Mystics exult in mystery and want it to stay mysterious," writes Richard Dawkins. "Scientists exult in mystery for a different reason: It gives them something to do.” This, in a nutshell, is my text for today’s sermon.

Although some people have suggested that we are approaching the “end of science” – that is, a time when all the Big Questions have been answered, leaving only the Small Stuff to be resolved – the reality is otherwise: Our knowledge is still very limited, which leaves the scientific enterprise more incomplete, and thus, more exciting, than ever.

I’m thinking here of just one aspect of science - evolutionary biology - and, moreover, merely one small subset of that large undertaking: The part dealing with our own species, Homo sapiens. The reason, by the way, that our knowledge is more incomplete than ever isn’t because we have somehow been slipping backward, but rather, because the more we learn, the more we discover how much more we have to learn! Newton famously wrote that if he had seen far it was because he stood on the shoulders of giants; by the same token, the farther science sees, the more unknown territory comes into view. That’s the nature, and the excitement, of science itself.

And ironically, we Homo sapiens are both subject and object of much of that unknowing.

“Know Thyself”? Easier said than done, especially since the more we know, the more we discover how much remains to be learned. Far from discouraging, I hope this will be seen as both a reward for past accomplishments and, no less, a challenge to do more. Who wants to read about a topic when science has already “closed the book” on it? Most articles and books about science, however, are just that: Accounts of what has already been learned. This brief blog article and the book from which it derives are different; they’re about mysteries, what we don’t know. Yet.

The Collins Dictionary (2003) defines mystery as “an unexplained or inexplicable event, phenomenon, etc.”, which seems reasonable enough … until you think about it. For an event or phenomenon to be unexplained is one thing, but to be inexplicable is quite another. If something is truly inexplicable, it is beyond the possible reach of human understanding and therefore likely to fit a theological rather than a scientific definition of mystery: Something unknowable except through divine revelation, such as how wine is “mysteriously” turned into the literal blood of Christ during the Eucharist.

Let me lay my cards on the table here and now. I do not believe in theological mysteries, or rather, I believe that they are simply ways of clothing meaninglessness in gobbledygook. At issue, therefore, is not the inexplicable, but rather the unexplained, things about human beings that are currently unknown but that fall within the potential reach of science. After all, the real world poses genuine mysteries aplenty, that is, puzzles that are not yet susceptible to understanding, but that we can be confident will be brought to heel, sometime in the future.

Science, of course, is in the business of doing just this, answering questions about the natural world, Homo sapiens included. And since nature does not disclose her secrets readily, scientists are understandably proud whenever they solve any of her numerous puzzles. As a result, we teach courses, give lectures and occasionally write books whose goal is to share these triumphs. They are, after all, hard-won and often immensely useful. No one, therefore, should begrudge us taking a victory lap now and then.

But just as the race is not always to the swift, nor the battle to the strong (Ecclesiastes 9:11), the cheers of the crowd do not always bespeak that the race is over, or the battle won.

I have been teaching science courses at the college and university level for forty years, and am no less guilty than my colleagues of providing what may well be a misleading perspective on science. Like everyone else, I teach what is known, often at the risk of misleading students into thinking that today’s science is a catalog of established and comprehended facts: this is how cells metabolize carbohydrates, this is how natural selection works, this is how the information encoded in DNA is translated into proteins. The reality, of course, is that we know quite a bit about how cells metabolize carbohydrates, how natural selection works, and so forth. But another, parallel reality is that there is much more that we do not know … and very few courses that talk about this. (One of these days, I will design a course titled something like “What We Don’t Know About Biology,” hoping that my colleagues in chemistry, physics, geology, mathematics, psychology, and the like will join the fun.)

But until then, we must make do. This is precisely what I have attempted in my most recent book, Homo Mysterious: Evolutionary Mysteries of Human Nature, just published by Oxford University Press. Its goal is the same one I urge on my students: Understand what is already known, but not as a static fait accompli. Rather, do it with an eye toward exploring what is not known, those fascinating evolutionary mysteries that remain to be solved. And so, I have attempted to examine the most promising hypotheses surrounding such questions as these:

• Why does homosexuality persist? Given that, on balance, gay people of either sex produce fewer children than straights, this is a first-class evolutionary mystery.

• Why do women menstruate? Some female mammals bleed a little bit in mid-cycle, but not as conspicuously as Homo sapiens.

• Why do women have prominent nonlactating breasts? We are the only species of mammals thus endowed.

• Why do women experience orgasm? Non-orgasmic women are no less successful than their orgasmic counterparts, so what is its fitness payoff?

• Why do men consistently live shorter lives than women? Similarly, why are they more hairy on most of their body, yet less so on the top of their heads?

• Why is it close to a “cross-cultural universal” for women to adorn their bodies more than men? Among most animals, it’s the other way round.

• Why do women undergo menopause? It is exceedingly rare in other animals for females to stop ovulating when they still have much of their lives ahead of them.

• Why is religion found in all human societies? In short, what are the presumed compensations that make up for the personal costs associated with practicing nearly all religions.

• Why do people make art (including music, poetry, stories, visual art, sculpture, dance, and so forth)? Alfred Russel Wallace thought this necessitated divine intervention; Darwin disagreed.

• Why are human beings conscious? After all, it is possible to imagine a world of intelligent robots or zombies, going about their fitness-enhancing business without the slightest self-awareness of what they are doing.

• Why did we evolve such big brains? Was it in the service of communication, tool use, social competition, warlike competition, sexual attraction, etc?

• Did the human species evolve in many different geographic regions and then coalesce, or did we evolve in one place (probably Africa), and subsequently spread out.

• Why did we become bipedal? And similarly, why did we become so (relatively) hairless compared to other mammals?

• Why do we laugh, cry, blush, dream?

• What are the biological sources – if any – of human ethical judgments and rules?

• To what extent are human races biological realities, or social constructs?

This is just a starter list. The greatest evolutionary mysteries, paradoxically, are those that we aren’t currently able to enumerate. Just as some medieval maps used to designate unknown regions with the phrase “hic sunt dragons” (Here there be dragons), a modern map of our own undiscovered lands might conclude “hic sunt mysteria.”

Happy exploring!

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