Recently, prominent theoretical physicist Michio Kaku (pictured) told media that reaching out to extraterrestrials is a “terrible idea.” Kaku, author of The God Equation: The Quest for a Theory of Everything (2021). So long SETI, after all these years? Well, not quite. He explains,

Soon we’ll have the Webb telescope up in orbit and we’ll have thousands of planets to look at, and that’s why I think the chances are quite high that we may make contact with an alien civilisation. There are some colleagues of mine that believe we should reach out to them. I think that’s a terrible idea. We all know what happened to Montezuma when he met Cortés in Mexico so many hundreds of years ago. Now, personally, I think that aliens out there would be friendly but we can’t gamble on it. So I think we will make contact but we should do it very carefully.

Andrew Anthony, “String theorist Michio Kaku: ‘Reaching out to aliens is a terrible idea’” at The Guardian (April 3, 2021)

When Montezuma met Cortés from Spain in Mexico in 1519, things went badly at first for Montezuma’s civilization.

Kaku isn’t alone with his concerns. Astrobiologist Dirk Schulze-Makuch worries that there may be a Great Filter, by which alien life forms flourished and then were killed off by their own technology before we ever reached that point:

Thus, if Perseverance or other follow-up missions discover evidence of alien life on Mars, this implies that the Great Filter happens at the point where humans became technologically advanced, or that it lies in our future. If the former is true, that makes our species truly special. Could we really be that unique? I have my doubts when I see other intelligent species on our planet, some of which, such as octopi, apes, and crows, could be said to be in a kind of pre-technological stage. On the other hand, in writing the book The Cosmic Zoo with William, I couldn’t escape the feeling (yes, I know, scientists and feelings) that there is something very special about us humans.

But if the latter is true, and we technological humans are not incredibly rare in the galaxy, the outlook for our species, and indeed for life everywhere, is very gloomy. We’re talking about an existential threat—bigger than Coronavirus or even climate change—that could set us back decades, or even hundreds of years. It would be something capable of taking out all (or nearly all) technologically advanced species. This is why Bostrom hopes we don’t find alien life on Mars, or anywhere else. It would mean we’ve already made it through the Great Filter—perhaps when life first arose on our planet, against great odds.

But that would also leave us in a barren, almost lifeless universe.

Dirk Schulze-Makuch, “We May Never Find Life on Mars—And That Could Be a Good Thing” at Air & Space (March 12, 2021)

The problem the Great Filter Hypothesis raises is that, if we are not special in some way, we are threatened. If we are special, we may be alone. We might be best off alone. Schulze-Makuch hopes there is some other reason why we don’t see ET.

Philosopher Nick Bostrom, whom Schulze-Makuch mentions, put it like this in an influential paper in 2008, expressing the hope that we would find nothing on Mars because “we would have some grounds for hope that all or most of the Great Filter is in our past if Mars is indeed found to be barren. In that case, we may have a significant chance of one day growing into something almost unimaginably greater than we are today.”

Schulze-Makuch thinks that the aliens would necessarily share some behavior patterns with us:

To start with, any intelligent alien species would likely have predatory roots, because the evolutionary trait of intelligence is promoted if you have to hunt for your food. A lion has to be smarter than a grazing antelope. A wolf has to be smarter than a mountain lion—because it’s not as strong, it has to anticipate the prey’s next move and communicate with other wolves in the pack. At some point, a predatory species has to learn to hunt sustainably, otherwise prey—and eventually predator—become extinct. More likely, they would come to rely on additional food sources, more predictable and long-term, as humans did when they developed agriculture. This requires even more social structure and communication.

Dirk Schulze-Makuch, “The Science of Aliens, Part I: Would They Be Friendly, or Threatening?” at Air & Space (April 6, 2021)

But, of course, we don’t know what the ecology would be like on exoplanets. High intelligence evidently originates in factors other than a struggle for food because many life forms struggle for food but only a few have high intelligence. We also don’t really know that there can’t be high intelligence apart from a struggle for food. There are other struggles in life.

We could also turn the topic around: What if the risk is on the other side, that the ETs can’t afford to take chances with us? That’s the basis of the Dark Forest Hypothesis. Of course, the ETs may have been destroyed by their smart machines (the Berserker Hypothesis) or hiding out from the environment effects of their own technology (the Aestivation Hypothesis).

So far, all we know is that we have not found a fossil bacterium on Mars. But no one thinks we should stop looking.

Here’s a thought: Today, many thinkers worry about what happens when the extraterrestrials land. But will they feel worse if ET never lands? Maybe being alone is the greatest fear. People who believe in God don’t have quite the same problem because in many ways, science points to God, and it matters less whether ET does or doesn’t exist.

In any event, we shall see.

Note: Here’s a free excerpt of Michiko Kaku’s new book, The God Equation.

You may also wish to read: Does science fiction hint that we are actually doomed? That’s the implication of an influential theory, the Great Filter hypothesis, as to why we never see extraterrestrials. Depending how we read the Kardashev scale, civilizations disappear somewhere between where we are now and the advanced state needed for intergalactic travel.

and

Tales of an invented god