Life Evolves. Can Attempts to Create ‘Artificial Life’ Evolve, Too? – Scientific American

What is life? Like most great questions, this one is easy to ask but difficult to answer. Scientists have been trying for centuries, and philosophers have done so for millennia. Today our knowledge is so advanced that we can precisely manipulate life’s building blocks—DNA, RNA and proteins—to build biological machines and engineer new genomes. Yet despite all we know, no universal consensus currently exists on life’s fundamental definition.

The reason life’s definition still eludes us is simple: we know of just one type of life—the kind that exists on Earth—and it’s challenging to do science with a sample size of one. This is the so-called N = 1 problem (wherein “N” denotes the number of eligible candidates that scientists can study). No matter how ingenious researchers may be in divining life’s general principles from the single instance of which they’re sure, they have no way of confirming whether they’ve done so successfully until N increases. Searching for another instance of life—whether it’s found right here on Earth, elsewhere in the solar system or beyond—is one way to expand N. The search has scarcely begun, but it has already consumed billions of dollars and countless hours of labor, even though there is no guarantee that a discovery will ever come.

There is, however, another potential way to solve the N = 1 problem: instead of finding some second genesis for life, some scientists are seeking to create one. The field of artificial life—called ALife for short—is the systematic attempt to spell out life’s fundamental principles, either by studying lifeless natural systems that exhibit lifelike behavior or by building artificial systems to compare against nature’s creations. Many of these practitioners, so-called ALifers, think that somehow making life from scratch is the surest way to really understand what life is—an approach perhaps best summarized as “build first, explain later.”

Spoiler alert: so far no one in this nascent domain has convincingly made artificial life—though not for any lack of trying. This demonstrably dismal track record makes ALife a ripe target for criticism that ranges from accusations of “playing God” to declarations of the field’s dubious scientific value.

Takashi Ikegami, a complexity scientist at the University of Tokyo, is tired of such complaints. His field is just like any other basic science that seeks knowledge for knowledge’s sake, so asking about “the point” of ALife might be, well, missing the point entirely, he says.

“The existence of a living system is not about the utility of anything,” Ikegami says. “Some people ask me, ‘So what’s the merit of artificial life?’ Do you ever think, ‘What is the merit of your grandmother? What is the merit of your dog?’”

Endless Evolution

As much as many ALifers detest emphasizing their research’s applications, the quest to create artificial life could have practical payoffs, too. Artificial intelligence may be considered ALife’s more glamorous cousin in that researchers in both fields are enamored by a concept called open-ended evolution. This is the capacity for a system to create essentially endless complexity, to be a sort of “novelty generator.” The only system known to exhibit this is Earth’s biosphere—an ongoing, multibillion-year evolutionary explosion of biodiversity that ultimately traces back to simple, single-celled ancestral organisms. If—or when—the field of ALife manages to replicate life’s inexhaustible “creativity” in some virtual model, presumably those same principles could give rise to truly inventive machines.

Currently, in AI, “you can build these monstrous deep-learning systems, but at some point, these systems can’t learn anymore,” says Steen Rasmussen, an ALife researcher and physicist at the University of Southern Denmark. “What does it take for a system to continue to learn? Nobody knows.”

Compared with the developments of AI, advances in ALife are harder to recognize. One reason for the discrepancy is that ALife is a field in which the central concept—life itself—is vexingly undefined. The lack of consensus among ALifers doesn’t help either—there isn’t a set of shared tenets to guide their collective work, let alone standards to evaluate it. The result is a diverse but meandering array of projects that each advance haphazardly along their unique paths. For better or worse, ALife mirrors the very subject it studies. Its muddled progression is a striking parallel to the eons-spanning evolutionary struggles that have so profoundly shaped Earth’s biosphere.

Assembling ALife

ALife’s unofficial kickoff came in 1987 at the first Interdisciplinary Workshop on the Synthesis and Simulation of Living Systems at Los Alamos National Laboratory, where the field gained the legitimacy of a name. Coined by computer scientist Christopher Langton, the term “artificial life” provided a unifying label for the scattered interdisciplinary studies of scientific misfits and vagabonds pondering lifelike behavior. Rasmussen was one of the workshop’s attendees 36 years ago. He recalls feeling like he was “coming home.”

Some ALife ideas date further back. In 1948 mathematicians John von Neumann and Stanislaw Ulam set out to formulate how machines could, in theory, self-replicate—a trait that ALifers later targeted as a hallmark for life. Applying pen to paper, the mathematicians constructed the concept of cellular automata, dynamical entities made up of shaded or unshaded cells skipping across a two-dimensional grid. In von Neumann and Ulam’s formulation, each individual cell blinks on or off based on simple relationship rules with its neighbors. Depending on the initial placement of the constituent cells, their clusters can showcase surprisingly complex behaviors such as self-replication ad infinitum. The mathematicians’ work with cellular automata helped them realize that replicating living cells must be able to somehow internalize and record information about their environment—an insight prescient to the then-growing recognition of DNA’s role as earthly life’s information-storage molecule.

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