Setting aside the desirability of goal-driven evolution, what should we do with a definition-theory of life that features “Darwinian evolution” so prominently, given the manifest fact that our species is on the verge of improving itself using quite different processes? Must we now modify that definition-theory to read “A self-sustaining chemical system capable of Darwinian or supra-Darwinian evolution”?
Here, we cannot escape the dilemma by claiming that we constructively believe that supra-Darwinian evolution is impossible. On the contrary, many laboratories are working today to develop gene therapy technology to make it so. The elected representatives of the taxpayers are funding this work. We constructively believe that that supra-Darwinian evolution is possible
To save our definition-theory, we might notice that even as we are happily becoming cerebral beings by prospectively altering our personal DNA by design, we still are capable of Darwinian evolution. Last, we might argue that, like an intelligent android, we could not have come into being had our ancestors not first had access to Darwinian evolution.
We are crossing into uncharted philosophical territory here. Philosophers like definitions of natural kinds to consider only the object being defined, not its history. We will have a hard time persuading serious philosophers to accept a system as “life” if, some time in the past (but no longer), it had access to Darwinian evolution.
For astrobiology, we might minimize the dilemma by arguing that supra-Darwinian life is rare. After all, stars like our Sun live for only about 10 billion years. Biology on Earth consumed about half that time to get from the origin of Earth to a form of life that is considering surpassing the constraints of Darwinian evolution. Thus, only around a relatively small proportion of the stars in the Cosmos might orbit supra-Darwinian beings.
Why did it take so long for supra-Darwinian life to emerge on Earth? One hypothesis is that educable toolmakers are hard to get via Darwinian processes. According to this hypothesis, 4.5 billion years were needed to have enough random mutations for genes to arise that allow parents to point at tools and children learn as a consequence. Generalizing this to the Cosmos as a whole, supra-Darwinian systems might be expected to be rare.
Alternatively, supra-Darwinian life may have been slow to emerge on Earth because environments where tool-making was useful generally come along only infrequently. After all, in a static environment, Darwinian evolution prefers specialists, species that do just one thing and do it well. A tool-making species is a generalist, and generalists have advantages over specialists only when the environment is diverse and, especially, changing. Tools and education are necessary in a rapidly changing environment, as DNA cannot keep up without having so many mutations that create too much genetic disease.
At least this is so with Homo sapiens. Because we make tools, we can survive in a huge variety of environments, more than any other species. Further, we can survive when our environment changes rapidly, far better than if we needed to rely on Darwinian mechanisms to adapt.
Dramatically changing environments are rare in the history of Earth. Yet, recently, after the onset of the ice ages, they became the rule. Under this model, the ice ages selected for human toolmakers by creating an environment where a generalist lifestyle based on toolmaking was fitter than a specialist lifestyle based on conventional (but slow) optimization of DNA sequences. In this view, without the ice ages, humans and the type of intelligence valued by humans would likely not have emerged, even on Earth. And if the exceptionality of ice age–like climate change on a planet is universal, then supra-Darwinian life should also be exceptional universally.
With these thoughts in mind, we can ask whether the life that we are most likely to encounter in the Cosmos has evolved supra-Darwinian approaches to fitness? This would seem to depend on whether we find that life or whether that life finds us.
Consider an a fortiori argument. Homo sapiens is now much closer to doing directed genetic therapy than it is to doing interstellar travel. Extracting a universal law from this, we might propose that, in the natural progression of biological evolution, species learn how to prevent their children from dying of genetic diseases (and how to drive their own evolution) before they learn to be interstellar space travelers.
This a fortiori argument has some practical consequences. If you have been abducted by an alien from another star system, your abductor was probably not “life” according to the NASA definition-theory. The technology that he, she, or it used to come to Earth to abduct was, a fortiori, developed after technology that allowed his, her, or its DNA to be prospectively engineered by his, her, or its parents. That engineering might even have been done specifically to allow him, her, or it to travel between stars.
However, if we encounter life in our Solar System, it is not likely to be as intelligent as we are (as it has not yet encountered us). Thus, the life that we find will not yet have developed either space travel or gene therapy. Thus, the NASA definition-theory of life is likely to be useful.