John Gribbin makes a number of excellent arguments for humans being the only intelligent life in the galaxy in “Alone in the Milky Way” [“Beyond Us,” Part 3 of our single-topic issue, A Singular Species: The Science of Being Human]. But the same processes that eventually allowed intelligent life to emerge on our planet are still in play. As our galaxy continues to evolve, we might expect increasing opportunities for this situation to be repeated.

GREG KONESKY Hampton Bays, N.Y.

Gribbin's assumptions are preposterous. The galaxy is 100,000 light-years across. We sent our first radio transmissions around 120 years ago, so a response from beings a mere 65 light-years away would still have a distance to travel to us. And how far would our own transmissions go before they became so faint and dispersed as to become unrecognizable?

ART CASSEL Riverside, Calif.

The accompanying graphic “Chain of Improbable Coincidences” lacks one component: at the moment of the big bang, all the laws of nature happened to exist from the get-go. Science proposes the possibility of innumerable other universes. If true, it's important that ours was just right from the start for these events to even occur.

MICHAEL TYLER Rochester, Mich.

GRIBBIN REPLIES: Konesky is correct that we may be the first, rather than the only, technological civilization in the Milky Way. But will we still be here when others arise?

Cassel makes the common assumption that radio or other electromagnetic waves would provide the first signs of other civilizations in our galaxy. In fact, the best way to explore the Milky Way would be to build a few self-replicating probes called von Neumann machines, which could travel to nearby stars and make copies of themselves from the raw materials that surround them. With the exponential growth in the number of probes, they would be able to visit every star in the galaxy in a few million years. The cost would be about the same as that of an instrument such as the James Webb Space Telescope because after the first few, the rest come free. So the Fermi paradox (If there are other civilizations in our galaxy, why haven't they come here?) is as forceful as ever.

Tyler makes an excellent point, which I did not have room to go into. The question of why “our” universe is “just right” is indeed a puzzle for theorists and is a theme of my 2009 book In Search of the Multiverse.


I applaud Pedro Domingos for rejecting the sentient-AI-will-enslave-us narrative in “Our Digital Doubles” [“Beyond Us,” Part 3]. But in his enthusiasm for anticipated uses of supposedly smart tech, he overlooks how overuse could be harmful.

For example, he envisions a digital double going on millions of virtual dates and living countless probable lives so that it can deliver you the optimal romantic partner and life. But life and romance are not algorithmic optimization problems comprehensible in the language of computation. What if the costs of going on some bad dates let you to learn something about yourself and others? How will you know what you want without any experiences?

Domingos assumes technology necessarily extends human capabilities. As Evan Selinger and I explore in our 2018 book Re-Engineering Humanity, this is a significant mistake. For millennia, humans have gained and lost capabilities as they developed and used tools. Take what might be our most fundamental capability—free will—which depends on our built sociotechnical environment. Like romance and even our humanity, free will can be lost in a world managed by AI.

BRETT M. FRISCHMANN Charles Widger Endowed University Professor in Law, Business and Economics, Villanova University


In “The Hardest Problem” [“Why Us?”, Part 1], Susan Blackmore explores the debate over the nature of human consciousness and how it might differ from the experiences of other animals.

It is difficult not to anthropomorphize nonhuman behavior when observing what appears to be creative activity among some nonhuman primates and perhaps other species. It might be worth hypothesizing that creativity may be an observable marker for consciousness, if only because the animal displaying it must have some capacity for self-reflection and interpretation of its environment and its place in it.

ROBERT RODGERS Emeritus professor, College of Pharmacy, University of Rhode Island

Blackmore says that animals do not share the sense of a conscious “I” that humans have. If so, how can we account for the planning shown by some animals, such as squirrels gathering nuts for the winter or dogs burying bones? Both require the sense of a persistent “I” that will be around, and hungry, in the future.

JOHN ORLANDO via e-mail

BLACKMORE REPLIES: In answer to Rodgers: Creativity might be a marker for consciousness, which makes intuitive sense when applied to toolmaking crows or orangutan artists. But what about bowerbirds, which instinctively decorate elaborate constructions, or deep-learning algorithms that write articles? The suggestion that creativity requires a capacity for self-reflection thus fails; deep-learning algorithms are surely not indulging in it.

Orlando claims that squirrels need “the sense of a persistent ‘I'” to store nuts. While this may be true of us storing food in the freezer, squirrels’ nut-hiding ability is inherited, and they need have no idea why they are doing it.

Many of us are led astray by powerful but false intuitions about the self. Our self is one of the brain's many constructions, not its controller.


Menno Schilthuizen's article “Darwin in the City” [“Beyond Us,” Part 3] discusses how several species have evolved to adapt to urban environments. It made me wonder what we are doing to ourselves. Are modern medicine and the engineering of our living environments causing us to evolve into a species with low disease resistance and weaker ability to cope with different climates?

ED HERMAN Utica, Mich.


In asking the question of how human beings became “a different kind of animal” in “An Evolved Uniqueness” [“Why Us?”, Part 1], Kevin Laland emphasizes copying and social learning.

Are these really the primary factors in shaping the difference between humans and other species? How do we use a communal store of experience to devise novel solutions to life's challenges? Someone has to think of the novel solution for the first time. The primary difference for human beings, I would suggest, is that we can imagine future possibilities, beyond what we can see or touch now.

KEVIN LOUGHRAN Belfast, Northern Ireland

Laland soft-pedals the essential role the invention of writing played in making humanity unique. Prior to that development, knowledge had to be stored in a brain and conveyed directly from one individual to another. It was thus susceptible to alteration and vulnerable to annihilation. Writing untied knowledge from the limitations of time and place and raised it to a level that made possible a pervasive, interactive, ever growing culture.

PETER GELFAN via e-mail