(2015-10-13) I wrote this essay in 2014 as part of the Coursera course on “Human Evolution: Past and Future” by Professor John Hawks. Presumably a number of essays would be selected and published in a book. But that final selection fizzled and nothing was ever heard of the book…
This paper shows that the near-term trend of the human evolution will be dominated by seemingly purposeful germline engineering, at the expense of traditional selection pressures that have hitherto acted on the human genome. The shift in the way humans evolve will be unavoidable and unstoppable. It is a consequence of the same old unguided natural selection acting on exogenous, parasitic memes, instead of the human genome.
Human evolution is the change in the genetic makeup of the human population over time. In the past few million years, human evolution was largely driven by natural selection, acting on human genes, shaping and reshaping them in response to changing habitats, resources and competitions, to produce the fittest vehicles (i.e. humans) for perpetuation of genes. These environmental selection pressures acted unprompted and unguided. Their relentless sieving of the human genome sculpted early hominids into us, the modern humans.
In the last few hundred years, changes in social, economical and physical environments have increased exponentially. These would have, in ancient days, triggered heightened and concerted phenotypical changes, as John Hawks detailed for the last 40,000 years in his paper Recent Acceleration of Human Adaptive Evolution (PNAS 2007, PMC 2410101).
By the 21st century, however, most traditional selection pressures on genes are mitigated and rendered effectively irrelevant by the same exponential accelerations in technology, agriculture and medicine. Actual positive selections are few and weak, thus genetic variations are unable to sweep across the population in mere decades before the environment changes yet again. Consequently today’s human genomes disperse in random directions, unrestrained by traditional pressures.
In the near future, only the explicit tinkering of the human germline by humans via genetic engineering can keep pace with the exponential advances in culture. Despite being considered a taboo in the aftermath of Nazi eugenics, germline engineering will eventually become accepted and commonplace. Despite being an artificial, human-directed meddling of the genes, germline engineering actually commands the same universal and lasting power to influence human evolution as natural selection. It will eventually overshadow all traditional selection pressures on genes, adding new alleles to existing loci, new loci to existing chromosomes, and even new microchromosomes where none existed before. International catalogs and standards will enforce compatibility among artificial genomic constructs.
This germline engineering, while appearing to be carried out purposefully by humans, is in fact a phenotypical result of the same old natural selection, now acting on exogenous, parasitic memes that use human brains as hosts, instead of acting directly on human genes. These selection pressures will continue to act unprompted and unguided. Their relentless sieving of memes will fuel the emergence of an evolutionarily stable pairing of pro-germline-engineering memes with germline-engineered human genomes.
Relative Genomic Stagnation
This paper does not argue that the human evolution has stopped. In fact, the human gene pool continued to change under traditional selection pressures in the last 40,000 years (John Hawks, PNAS 2007). This paper, however, argues that the pace of this natural evolution cannot keep up with the exponential progress of the human culture.
Accelerating innovations in agriculture feed orders of magnitude more people, dampening mass starvation and the ensuing selection pressure. Medicine now mitigates effects of diseases, pandemics and bad alleles, making these invisible to selection. Technology and tools allow humans to spread to all corners of the Earth, driving all natural predators to extinction, and subduing the forces of natural selection. Powerful engineering coerces the climate and the landscape to work for humans (wind/hydraulic power) instead of letting them shape us. Human evolution in the 21st century marches in place compared to advances that compress former environmental changes from geological time into mere decades.
There are many ways for this stagnation to end. Man-made greenhouse gasses may trigger irreversible climate changes, displacing and decimating large populations. Unforeseen pandemics may wipe out all but a few isolated populations. An asteroid may exterminate most humans as it did dinosaurs. A nuclear war may kill most people and bring the nuclear winter.
All of these alternative scenarios involve mass mortality and retrograde culture. Natural selection would kick in again in full force. A great number of papers and stories have already been written on these topics.
This paper assumes that human technology, engineering and computing will outsmart all possible disasters in the next one hundred years. It explores the only contender left that can again shepherd the human evolution in the absence of most selection pressures. This paper does not consider extreme alternatives such as the technological singularity with the emergence of a sentient machine, and the immortality of the human race. Consequences of these events are yet unfathomable.
Cells in organisms undergo genetic changes constantly. New alleles, loci and chromosomes arise from natural mutations, mitosis errors, homologous recombination, and infections from bacteria, fungi and viruses. But only those found in germ cells, gametes, or preimplantation embryos leave footprints in the gene pool.
Shortly after the discovery of DNA in 1953, scientists injected new alleles into mice (Jaenisch 1974). New loci were created with gene duplication via PCR (Mullis 1983) and with transgenic injection via plasmid vectors (yeast 1978, mouse 1979). Whole new microchromosomes were created (bacterial 1992, human 1997). Only 47 years after Watson and Crick’s revelation, the Hepatitis C virus was chemically synthesized (Blight 2000). But again, only artificial DNA constructs added to the germline can permanently alter the evolution of an organism (Ruddle/Brinster 1981, mouse embryo). This is exemplified by the Knockout Mice (Capecchi 1989), which already counted thousands of artificial germlines by 2002.
Today we have almost all necessary tools to take the human evolution into our own hands. For genetic engineering on the human germline to be viable, we need more powerful computers and algorithms to model complex in-cell interactions for every genetic change we introduce. We must ensure that germline-engineered people can mate with the rest of population without their offspring losing enhancements or suffering from aneuploidy. We must maintain compatibilities between different germline enhancements when novel parings arise in reproduction between two enhanced individuals.
To this end, an international standards body will arise to catalog and to police germline enhancements. There are precedences for this. In the dawn of the computer age, the American Standard Code for Information Interchange was created (ASCII 1963). This spawned hundreds of derived standards, but continues to serve as the backbone of all text encodings. ARPANET was created in 1963. This TCP/IP-based network became today’s Internet, supporting hundreds of millions of websites via HTTP, HTML and derived standards. Germline engineering standards will usher in the genetic age, enabling human minds to collectively shape humanity’s own evolution at a pace commensurate with cultural changes.
Meddling with the human genome is not something most people approve of, at this time, as was evident in the 1997 film “Gattaca”. But this only reflects the zeitgeist across the globe. It says nothing about the spirit of the time a few decades from now.
Just 150 years ago, black people in the Confederate States were regarded as property. 94 years ago, women could not vote in America. 47 years ago, interracial marriages in many states were prosecutable crimes. And today, homosexual acts are still punishable by law in some states, even as sudden shifts in popular opinion puts the country on the cusp of a sweeping acceptance of homosexual marriages.
The concept of “memes”, as coined by Richard Dawkins in The Selfish Gene (1976) and elaborated in The Extended Phenotype (1982), best explains zeitgeist shifts. A meme is a basic unit upon which natural selection operates, just like a gene is a basic unit. A meme comprising thoughts is replicated and transmitted from person to person in perpetuity, while a gene comprising DNAs is replicated and transmitted from a parent to offspring. A meme encodes phenotypical behaviors in its host, while a gene encodes body parts. Memes are parasites of the human mind, while bacteria and viruses plague the body. All memes in a mind must be compatible and complementary, as bacteria in the gut flora are. Finally, memes undergo natural selection based on the same rules that govern genes.
In light of memetics, it is not hard to see how allele variants of the “human rights” meme, or the “women’s suffrage” meme had been fiercely fighting for a foothold in human minds over the last century, while keeping up with the evolving landscape of their peer memes, under the pressures of natural selection.
In the near future, many single-gene disorders such as Huntington’s disease will be eliminated by widely available germline engineering practices in preimplantation diagnosis. At the same time, genes responsible for the epicanthic fold will be replaced throughout East Asia for cosmetic reasons. Once the world accepts simple allele replacements, new loci and microchromosomes for other genetic enhancements will shortly follow.
Then, the emergence of an evolutionarily stable pairing of pro-germline-engineering memes with germline-engineered human genomes becomes unavoidable.